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The NIST ATM Network Simulator Operation and Programming

1. ABR Poisson ABR Batch TCP IP ABORT Creation of an Application component results in the appearance of this menu window since there are several types of such components Selection of a type will result in the appearance of one the information windows shown below 46 For these information windows the shaded line is not an output parameter it is the name of the ATM Application at the other end of the route The name is filled in automatically when the route is created All ATM Applications have an input parameter labeled Start Time This is the number of microseconds after the program starts that the Application will begin generating cells By setting the start time to a different value for each Application the user can ensure that they all do not start at once Constant Bit Rate CBR Information Window Name Bit Rate Mbits sec 0 Start time usec 0 Number of Mbits to be sent 0 Other End Connection Name Cells are generated at a constant rate for the duration of the simulation Variable Bit Rate VBR Poisson Information Window Name Bit Rate Mbits s 0 Mean Burst Length usecs 0 Mean Interval Between Bursts usecs 0 Start Time usecs 0 Number of Mbits to be sent 0 Other End Connection Name Traffic is generated as an ON OFF source Cells are generated at the specified bit rate
2. and free calls However no real speed advantage was noted This module is still useful though because it makes it possible to free all allocated memory chunks with one call Cells and events are allocated using this module and of course anyone else may use it as well The functions of the mempool module are relatively easy to understand and are described at the beginning of mempool c 2 5 3 Debugging There are several ways to do debugging There are two ways that are convenient to use with the simulator Include additional code for debugging which is enclosed between ifdef DEBUG endif DEBUG define the flag DEBUG for the C compiler and set the debug level by dbg_set_level DBG_ERR or dbg_set_level DBG_INFO to trace certain actions The arrival of cells at a certain component can be recorded by calling log_a_cell c p ce defined in log c In order to properly print the contents of a cell it might be necessary to modify this function according to the type of cell that is displayed 39 40 2 6 Creating New Versions To create a new version of the simulator by adding your own component to it all you need is libsim a any simulator header files that your new component needs comptypes c and the source to your component In brief you must take the following steps to create a new type of component It is assumed that you have already built the simulator library libsim a and the executable with the distributed comp
3. A box outline will appear which can be resized by moving the mouse with the button still depressed When the box outline is the desired shape and size release the mouse button and the window will be resized It is also possible to resize the entire simulator window Its initial size is the full size of the screen To change the size or location of the window use the standard X Window manager uwm You must have the line resizerelative in your uwmrc file for this to work however 1 6 3 4 Resizing Information Windows Clicking and holding the middle mouse button anywhere inside the information window will cause its dimensions and text to get larger To return to the normal size the information window must be closed and reopened 1 6 4 Saving a Network Configuration There are two ways to save a network configuration The SAVE command allows the user to save the present network configuration Clicking on the SAVE control button causes the program to prompt the user for a filename under which to save the configuration The SNAP command does the same thing as SAVE except that it also saves the present arrangement of meters and information windows on the display The SNAP command saves the temporary values of the components parameters A detailed description of the formats of both these file types is given in Appendix C 1 6 5 Post Simulation Analysis using the Log File In many cases the user will find it desirable to have data on one or m
4. meter type if so desired To do this click the middle mouse button on the Meter Type line at this point the meter select window shown will appear Click the middle mouse button on the desired line to select the type The most desirable meter type will depend on the parameter that is to be monitored For example a binary meter is best for a congestion flag a bar graph for percentage of link utilization Time History A for packets in an output queue etc See Meter Types in Appendix B for a full description of available meters 14 To delete a meter click the middle mouse button on the box in the component information window used to create the meter The meter will disappear and the box will revert to its normal color Meters are not cleared at the restart of a simulation To start with a clear meter delete it and create a new one 1 6 1 3 Logging Data Data logging is a method of recording the values of a parameter while the simulation is running Logging for a parameter is toggled on and off by clicking the middle mouse button on the right hand box on the information window line for that parameter When logging for a particular parameter is turned on its box in the information window becomes white and every new value of that parameter with a corresponding time stamp is saved in a file The file is created in the current directory with the name sim_log xxxx where xxxx is the process ID of the simulator The file created by this process
5. Network Window If the program is started with no configfile this area is blank The network is represented as a collection of components connected to each other in the desired configurations ATM switches and broadband terminals B TEs are represented by rectangular boxes while ATM Applications are represented by ellipses both shapes contain the name of the component ATM switches and B TEs are interconnected by Physical Links The Links are also considered components and are identified by name but they are represented on the figure by straight lines The connection between a B TE and an ATM Application is also represented by a line but is not considered a component i e it is not a physical entity and has no associated parameters Other information not shown on the figure is displayed in the Network Window as required When creating or modifying a component an information window appears beside its symbol displaying the component s parameters When a virtual connection is established between ATM applications a dotted line appears denoting the path of the information flow When a simulation is running one or more meters may appear on the screen to display information about selected parameters 1 4 2 The Text Window The text window appears as a bar at the bottom of the screen The text window allows the program to present various messages to the user In addition any keyboard input is displayed in the text window The cursor does not need t
6. This meter consists of a horizontal bar whose length is proportional to the parameter value This type is most useful for parameters that are expressed as a percentage of some maximum value The Y axis scale setting applies to the horizontal dimension in this case In the example shown if the Y axis scale is 100 then the value indicated is approximately 40 The X axis scale for this meter is undefined and cannot be set This reversal of axes is unintended it will be corrected in future versions LOG BAR GRAPH TIME HISTORY A The log meter type is like the bar graph except that the horizontal scale is logarithmic Like the bar graph the Y axis scale setting applies to the horizontal dimension In the example shown if the Y axis scale is 10 the value indicated is approximately 5 The X axis scale is undefined and cannot be set The TIME HISTORY A meter displays parameter values that have been averaged over an interval of time When setting the X axis scale the user is asked to enter a sampling interval in microseconds This is the minimum interval between lines drawn on the screen i e the minimum update interval The meter will not be updated unless the parameter value is changing When an update does occur the value is the average value since the last update The Y axis scale is set by the user but the full scale range will be adjusted by the program as necessary For example if th
7. X I O routines to allow the user to build only legal connections The X routines know that a component of type ATM Application must be at the beginning of a virtual channel When the user picks an ATM Application the X routine calls that component action routine with this command to find out which components are allowed to be next on the path As the user picks more components the process continues until he she picks another ATM Application to end the path EV MAKE ROUTE This command is a no op for some components like physical links ATM Applications and B TEs use it to store the route number in the VCI field of their component structures The ATM Switch component creates a local routing table and stores the previous and next component and the VCI number of the route 2 3 2 Regular Events EV CLASS EVENT The following events are those which are directly involved in the running of the simulation It is necessary to have a set of regular events that are understood by all components in order to facilitate global communication within the simulator Additional regular events may be defined if needed To define a new event just put a new define statement into the eventdefs h file EV RECEIVE Receive a cell event EV READY Component ready signal EV BUSY Component busy signal 32 2 3 3 Private Events Private events are events that have only local significance i e they are defined within action routine for use by that routine only Priva
8. a fraction of the total transmission size Transmitter s State A TRUE FALSE control If FALSE no transmission will take place but the Application can still receive Start Time When this is a positive number it is the number of microseconds after the program starts that the Application will begin to generate traffic If a negative value is placed here the Random Start feature will be activated see below Random Start Period If Start Time is negative the value entered here is the mean for a random start time Transmission Size The total number of data bytes payload to be sent Mean Packet Processing Time The mean delay to process the packet 49 Packet Processing Time Variation A computation based on a random perturbation in the processing delay in the range Packet Processing Time Variation Packet Processing Time Variation Maximum Segment Size The maximum size of the TCP IP packet whether it is being sent or being received My Receive Window Size This number determines how many packets are going to be sent without waiting for an acknowledgment Output Parameters Number of Bytes Unsent This is the number of bytes remaining from the total specified under Transmission Size Every TCP IP packet has a sequence number including the ACK packets The following three parameters let the user enable the logging of these numbers as the packets are sent or received Note that only the logging function applies
9. of the meter box can be modified by the user See 1 6 3 3 Resizing Windows below When a meter has been created clicking on the meter symbol with the middle button will cause the following meter setup window to appear Meter name Select the desired line in the window by Component name clicking on it with the middle button then make the desired entry from the keyboard Meter type The meter name may be anything the user Y axis scale desires The component name is entered X axis scale microseconds automatically it is always the name of the component selected for monitoring but it may Display meter name yes be changed The X and Y axis scales may or Display scale no may not be adjustable depending on the meter type The Histogram type meter Histogram Min 0 requires some additional entries See Meter Histogram Max 0 Types in Appendix B Display meter name Histogram Cells 0 and Display scale are options that may be toggled on or off by a click on the line Histogram Samples 0 When Display scale is on horizontal lines will appear on the meter as the program BINARY METER BAR GRAPH LOG TIME HISTORY A TIME HISTORY D DELTA METER HISTOGRAM adjusts the Y axis scale When a meter is created a type considered to be appropriate will be selected by default The user may however change the
10. or variable bit rate The user specifies the bit rate for constant bit rate CBR applications For variable bit rate VBR applications the user sets the burst length interval between bursts and the mean rate For lower priority traffic the user may create an available bit rate ABR application For all of the application types the user sets the start time and the number of megabytes to be sent Other application types that can be simulated include TCP IP applications 1 2 4 Physical Link This component simulates the physical medium copper wire or optical fiber on which cells are transmitted The user may choose the link speed from a list of several different standard rates The user also specifies the length of the link The output parameter reported by the simulator is link utilization in terms of bit rate Mbits s 1 3 Executing the Program To execute the ATM Network Simulator the following is typed at the command line where X configfile stoptime sim x s seed configfile stoptime Used for running the simulator in background mode With this option the simulator will not use X Windows it will run on a machine that does not have X Windows When using this option a configfile must be specified otherwise the simulator will have no network to simulate and will produce no meaningful results Also the configfile specified should be a snapshot that has some parameters logged to disk so that the simulator run prod
11. parameter The rest of the line gives the component name and parameter name respectively 15 All lines following the ones marked with are the actual data recorded during the simulation The first column is the parameter ID the second column is the time in ticks and the third column is the value of the parameter at that time A slightly different format is used for the case where the data logged represents cell arrival at a switch or B TE component This is the logging enabled with the box on the component s name line In this case the third column is the name of the component on which the data is collected switch3 in the example The fourth column is the name of the link from where the cell arrived link 22 and the fifth column is the route number 1 6 2 Making Modifications 1 6 2 1 Modifying Components After it is created a component can be modified by editing its input parameters To edit a parameter pop up the component s information window by clicking on the symbol with the middle mouse button then click on the parameter to be edited A prompt will appear in the text window at which time the new value of the parameter can be entered 1 6 2 2 Deleting Components Deleting components is done with the KILL control button After clicking on KILL any component that the user clicks on is deleted When finished deleting components the user clicks on QUIT to get out of this mode CAUTION Failing to click on QUIT after deleting ca
12. switchl SWITCH 417 341 param switchl switch param 0 Delay to process a cell uSec 0 param 155 Switching Slot time Mbit s 155 param 10000 Output q size cells 1 inf 10000 param 550 High Threshold for Q Congestion Flag 550 param 450 Low Threshold for Q Congestion Flag 450 param Logging every ticks e g 1 100 1 35 component hostl BTE 331 452 param hostl hostl param 50 Max Output Queue Size 1 inf 50 param Logging every ticks e g 1 100 1 neighbor switchl link1 neighborl switchl link2 neighbor hostl tcp1 routel tcpl hostl link1 switchl link2 host2 tcp2 C 2 Format of the SNAP File The SNAP file contains all the configuration information of a SAVE file plus additional information that reveals the status of the simulated network at a particular point in time i e when a snapshot of the simulation has been made At the top of the file are two lines starting with the pound sign The first line records the seed used for that particular simulation run This line will not be loaded or used if the file is used as a configuration file The second line records the time in ticks when the snapshot was taken Following the two lines starting with the pound sign is a listing of all the components in the network The format of the component listing is the same as for the SAVE file but with some additions If component ha
13. to analyze the behavior of ATM networks without the expense of building a real network There are two major uses for the simulator as a tool for 1A Heybey The Network Simulator Laboratory of Computer Science Massachusetts Institute of Technology October 1989 ATM network planning and as a tool for ATM protocol performance analysis As a planning tool a network planner can run the simulator with various network configurations and traffic loads to obtain statistics such as utilization of network links and throughput rates of virtual circuits It could be used to answer questions such as where will be the bottlenecks in the planned network what is the effect of changing the speed of a link will adding a new application cause congestion etc Statistics are reported directly to the screen or logged in a data file for further processing As a protocol analysis tool a researcher or protocol designer could study the total system effect of a particular protocol For example one could investigate the effectiveness of various flow control mechanisms for ATM networks and address such issues as mechanisms for fair bandwidth allocation protocol overhead bandwidth utilization etc In order to conduct experiments an investigator must first change or add additional codes to implement the protocol to be studied The simulator is designed in such a way that modules simulating components of an ATM network can be easily changed added or deleted Activ
14. usec 0 Start time usec 0 Number of Mbits to be sent 0 Other End Connection Name 48 TCP IP Information Window Name Bit Rate Mbits sec 0 Buffer Size bytes 0 Transmitter s State FALSE Start Time usec 0 Start Random Period sec 0 Transmission Size bytes 0 Number of bytes unsent 0 Sender sequence number logging Sender ACK sequence number logging Receiver sequence number logging Mean packet processing time usec 0 Packet processing time variation usec 0 TCP open time usec 0 TCP close time usec 0 Connection Busy FALSE Packet input queue has 0 pkts Max segment size octets 0 My Receive Window size octets 0 Peer Receive Window size octets 0 RTT usecs 0 RTO usecs 0 RTO current 0 Average throughput bytes sec 0 Retransmission percentage 0 Other end connection Name The TCP IP Application sends data in large packets These packets must be segmented to fit into the ATM cell structure before being put on the network A rather extensive set of parameters are provided that give the user flexibility in controlling and monitoring this type of application Input Parameters Bit Rate The bit rate for the cells on the ATM route Buffer Size The size of the user s buffer large enough to hold many packets but
15. ELTA or HISTOGRAM Obviously if the CanHaveMeterMask flag is not set no value needs to be put into this element 25 p_flags p_scale Contains flags that control the display The constants masks are defined in the file simx h with the following names InputMask When set the simulator will call the function pointed to by p_input Parameters that have this flag set will also have their values saved using the p_make_short_text routine when the configuration of the simulator is saved CanHaveMeterMask When set the parameter can be displayed in a graphic meter using values pointed to by p_calc_val DisplayMask When this flag is set the parameter will be displayed in the information window infowindow that appears when the user clicks on a component The text displayed is pointed to by p_make_text CanHaveLogMask If the parameter has this flag set the user can cause the parameter values to be written to a file on the disk as the values change To update screen displays either meters or infowindows or to cause data to be logged to a disk file the action routine for the parameter must call log param c p every time the value changes The variables c and p are pointers to the component and parameter respectively The log param function is found in the log c file This is a scaling factor for the meter If p scale gt 0 the value returned by p calc val is multiplied by this number The scale factor is disabled mul
16. NISTIR 5703 The NIST ATM Network Simulator Operation and Programming Version 1 0 Nada Golmie Alfred Koenig David Su U S DEPARTMENT OF COMMERCE Technology Administration National Institute of Standards and Technology Computer Systems Laboratory Advanced Systems Division Gaithersburg MD 20899 August 1995 TABLE OF CONTENTS Introduction tias EE RAS Re AAS eR CES BOS 1 Purpose vsu ue E Rowley wie ERG Pe ELA E DAA ie 1 Terminology an this Manual amp 3 2 a dale tek ae ae x REA E SER ER Re 2 PART 1 User s M nudl tan eee Ave oras abans 3 1 1 Objectives and Overview sa ed ad 3 1 2 Component Descriptions 2 6644 ges poe oe ee lp ee ed eq 5 1 2 T ATM Switch oae ni ia ee ee eee eed REG eee ws 5 1 2 2 Broadband Terminal Equipment B TE 5 1 2 3 ATM Application 4 425442 deo o Seb beh heh eed 5 124 Physical Link o e acs alee ate Sp ule ea X ER 5 13 Executing the Prostate dod ERE OR Ee t 6 1 4 The Display iu s aod Reid 2 eta Rm ERE ERESGNS 7 1 4 1 The Network Window eee 7 1 4 2 The Text Window vols das EE E Ede EE E A 7 14 3 The Control Panel visa no irste p eeu rele EX XAR MEER 7 1 4 3 1 Analog Clock s sa usse REGE ORE e 8 1432 Digital Clock eta Oe Ge C x PCR COSA 8 1 4 3 3 Control Buttons verruga 9 1 5 Operating the Simulator 2 we os oe ee et ee oe ack xe ae RA Ra E URS 11 1 5 1 Loading a Network Configuration llle 11 1 5 2 Creating a Network Confi
17. able buffer space for each type of queue CBR VBR or ABR If any queue exceeds the set limit cells are dropped and this is recorded as a percentage of the total number of cells received by the switch Also there is a per port cell drop parameter recorded for each queue 1 7 3 Broadband Terminal Equipment B TE The B TE component simulates a Broadband ISDN node e g a host computer workstation etc A B TE has one or more ATM Applications at the user side and a physical link on the network 19 side Cells received from the Application side are forwarded to the physical link If no slot is available for immediate transmission a cell queued in one of two queues a VBR CBR queue or an ABR queue The user can specify the maximum output queue size if either queue exceeds this limit cells will be dropped The parameters that can be monitored for a B TE are the number of cells in an output queue and the number of cells dropped at each queue Also the total number of cells received from the network may be monitored 1 7 4 ATM Applications The ATM application at the end point of a link is a traffic generator The traffic source emulated by this component may be a constant bit rate CBR source or a variable bit rate VBR source Either source type may generated at one of two priority levels a CBR VBR level highest priority or the Available Bit Rate ABR level where cells are sent on the transmission bandwidth that is available after the highe
18. alc val p make text This element points to a routine that is called to produce a value to be displayed in a meter Each unit of this number represents one division on the scale of the displayed meter For example the function for a cell queue length parameter might return the length of the queue divided by ten so that each division of the displayed meter represents ten cells in the queue Used to generate text for parameter display this element returns a pointer to a string The string is expected to contain some meaningful human readable representation i e with some sort of label of the value of the parameter p make short text Also returns a pointer to a string but the string contains only the value of p input the parameter no labels Used primarily for logging data to disk Points to a function that will read an input string from either the keyboard or from afile This routine will convert the string to an appropriate value and store it into the parameter This is used for the initialization of values that affect the operation of the component and that can vary from one instance of the component to another For example hosts have a Processing delay parameter that is the time needed to process a cell p display type This element sets the default meter type for the display of parameter values The constants are defined in simx h currently the possibilities are BAR GRAPH BINARY LOG TIME HISTORY TIME HISTORY D D
19. ammer s Guide 000 002 eee eee 21 2 L Objectives ANd OVerview css ates ASE E EE ee aS Bok pubs eas 21 2 ASOMMPONE MUS td OG ER e e dete d ee CAE Ree RC Kran SUN 22 2 21 Classes and TYp S esos ede Ro o 22 2 22 Component Data Structures 2l iA e poe de 23 2 2 3 Parameters ost Mace techn ipte Ihm qoe dO ot eov S Ioa 23 224 Neighbors zd e suci ead pe Rete Ee oh ba e dede 27 2 2 5 Relationship of Data Structures 24 4 0 were AG Pees 28 2 2 5 CHO ISOUEITIES 1 Ge meh Ga cou hy ax Gu tse Pe ices sah cba Roda code quis hte ee oe a 20 Li MAM CUES A ARO CURE MOR as ia RR 31 2 3 1 Command Set EV CLASS CMD 0005 31 2 3 2 Regular Events EV CLASS EVENT 32 2 3 S Privat Events os cr Slaw a SCR ME Res fa Ue tl OCC AER We BA 33 2 34 The Event Manager emir desarro PR REPE RE 33 2 4 ATM Network Related Issues a v wg nannaa 35 2 4 1 ATM Cell Definition 227 o Suse canard ado oo NoD wk os 35 2 4 2 Setting Up the ATM Virtual Channel llle 36 73 A does stes rore S Bc cM agio eL Mo Ma at ed ec eM Coat qu 37 2 51 Lasts and Queues ud ot uo ex ee eR toss Pad es 37 2 9 2 ME TOS sonos Robes der eS S amm Sp boa ada edes perd 39 2 5 3 DebUSEIIP ies S com Eco NUR RR eid ced sui fud ER dire 39 2 6 Creatine New Versions crue ed eae cech eos See Re yoy aed SUR Rn 41 APPENDIX A Parameter Information o o oooooooooo o o 43 Ad GASES Witches S tc Are e ER
20. any components this will be a no op 31 EV_NEIGHBOR Attach another component as a new neighbor The component to be made a neighbor is pointed to by arg A component should only allow legal neighbors For example an ATM Application will not allow an ATM Switch to be attached as a neighbor the ATM Application can only be connected to a B TE Broadband ISDN Terminal EV_UNEIGHBOR Remove the neighbor pointed to by arg from the list of neighbors and free any memory used to keep track of the neighbor such as a cell queue and the neighbor structure itself If there is a parameter associated with this neighbor it must be removed from the queue of parameters and freed This is a no op if the component is not a neighbor EV_LEGAL_NEXT_HOPS arg points to an list see the section 2 5 1 Lists and Queues for an explanation of an list that contains a virtual channel connection being constructed not including comp The list contains only the components in the path so far comp is the component being considered as the next step in the connection The action routine must return a new list of the components that are legal in the path after comp A NULL list indicates an error an empty list means that comp is not legal for the virtual channel connection so far that there is no legal next virtual channel link or that comp is the end of the channel The caller will Iq delete the returned list after it is done with it This command is used by the
21. at a component needs to know about is ev_enqueue This function creates a new event and places it in the event queue to be fired at the proper time ev_enqueue returns a pointer to the newly created event The arguments correspond to the ones passed to the action routine that will receive the event The syntax of ev_enqueue is as follows Event ev_enqueue type src dest time rtn ce vpi arg int type Type of event e g EV RECEIVE EV CREATE etc Component src Component which issues this command Component dest Component on which command applies tick t time Time at which the event should be scheduled PFP rtn The action routine of the destination component Cel ce Pointer to a cell VPI vpi Route number if a cell is passed caddr t arg Can be anything Note PFP is a Pointer to a Function that returns a Pointer and is defined in component h rtn is therefore the action routine to call when the event is fired The arguments ce and arg are optional they may be replaced by NULL if no cell is being sent and no information needs to be passed 33 You may schedule events at the current time or at any future time Scheduling events for the past is considered illogical There is no control over the order e g FIFO or LIFO of execution of events that are scheduled to fire at the same time Hence events scheduled at the same time are not guaranteed to fire in any particular orde
22. button toggles between two modes When the simulation is running the word PAUSE will be displayed Clicking on the button will then stop all activity with all parameter and time information held in place With the simulation stopped the button label will change to RUN clicking on it will cause the simulation to resume running with current settings This button allows the user to slow down the simulation by setting a delay between each event firing The text window will appear asking for the desired delay in microseconds Clicking on this button will toggle screen updating on or off The simulation will run faster with screen updating turned off The clock will continue to be displayed with updating turned off Clicking on a component while updating is off will cause the parameter window for that component to appear with current data Clicking on the component a second time will make the window disappear This button may be used to stop a simulation in progress or to eliminate components Clicking on the KILL button while a simulation is in progress stops all activity If a simulation is not running clicking on a component after KILL has been clicked will delete that component In either case the QUIT button must be used to leave the KILL mode This button allows the user to load a network configuration The text window appears asking for the name of the file to be loaded Note that this erases whatever configuration was being displayed on th
23. cate a list and a queue respectively and any other arguments are elements on which to operate Here is a summary of the available list and queue commands 37 l create Kej_addh l elt l e _addt l elt l e remh l l e remt I Kej_adda l prev new l e del l elt find elt Iq delete l Iq_clear l l obliterate Create a new empty list and return it Returns NULL on error Add elt to the head of the list 1 The le version does not return anything it is a macro the 1 type returns NULL on error couldn t allocate memory to hold the pointers non NULL otherwise As above but add elt to the tail of the list I Remove the item at the head of the list and return it Remove the item at the tail of the list and return it Add new to the list after prev which must already be in the list Again the le is a macro that doesn t return anything and 1 adda returns NULL on error Delete elt from the list I Search for elt in the list Returns a pointer to the 1 elt that contains elt An elt is the structure that contains the pointers used to add something to an list See list h for the definition This function works for both lists and queues It also works for both flavors of each although the effect is slightly different For le lists Iq delete frees the list and the elements that were stored in the list For l lists the function does not free the items stored in the list just the l
24. ct to be displayed on screen list co neighbors Points to a list of neighbors of this component Parameters data that will be displayed on the screen short co menu up If true then text window is up queue co params Variable length queue of parameters Any other info that a component needs to keep will vary Component 2 2 3 Parameters Any information about a component that needs to be displayed on the screen logged to disk or saved in a configuration file must be stored in a parameter A parameter is a data structure that besides storing a value stores information needed to display save or load the parameter The 23 information stored includes pointers to functions to convert the parameter to and from a string the name of the parameter and flags describing how to save and or display the parameter The Param structure is defined in component h for the readers convenience it is listed below typedef struct Param struct Param p_next p_prev So that these can be put in a queue char p name 40 Name of this parameter for display PFD p calc val Computes a value to be displayed in a meter PFP p make text Makes a string containing the current value PFP p make short text As above but only the value no text PFI p input Routine to input this parameter GRAF OBJECT p my picture The graphics object to display this int p display type Type
25. ctives and Overview This part of the document provides information for the simulator user to create network topologies using simulated ATM switches terminal equipment and physical links The manual includes instructions for display manipulation component linking and routing parameter setting data logging and post simulation analyses The user may select from a variety of applications the behavior of which will determine the kind of traffic generated for transmission through the network The user may control the parameters associated with these components define the routes and specify many details concerning the logging and display of performance data The primary user interface to the simulator is through an X Windows display screen The screen simultaneously displays the network configuration a control panel for running the simulation and parameter information The display contains a text window for user prompts which also provides a place for parameter data entry Output parameter values may be be displayed in numerical form in information windows or as graphical meters Output parameter values may also be tagged for logging to a file the data logging frequency is determined by the user 1 2 Component Descriptions The following are brief general descriptions of the major building blocks of the simulated ATM Network For more detailed functional descriptions see 1 7 Simulator Concepts and 2 2 Components A complete list of input an
26. d an open information window when the snapshot was taken the keyword infowindow appears immediately after the line with the component keyword Next comes the input parameter listing each line beginning with the word param and followed immediately with a number indicating the parameter s value Following the value are two other numbers The first number indicates whether or not the log box is active any number between 0 41 means it is inactive 42 77 indicates an active log box For input parameters an active log box means that the parameter line will be recorded once in the log file The box can only be activated by changing this number in the SNAP file not by clicking on the box in the window The final number on these lines is unused and is always a zero 56 Following the param lines is a list of all output parameters each line beginning with the keyword pflags The text on each of these lines following the pound sign is a comment that contains the parameter description and value Output parameter values are not used when the SNAP file is used as a configuration file On each output parameter line following the pflags keyword there is a 2 or a 4 with the letter a or b appended This is a code that reveals whether the output parameter has its data logging box in the active mode and or its meter window open The different combinations are as follows 2a the log box is not active the meter window is closed 2b the log box i
27. d output parameters available for each component can be found in Appendix A 1 2 1 ATM Switch This is the component used to switch or route cells over several virtual channel links When a switch accepts an incoming cell from a Physical Link it looks in its routing table to determine which outgoing link should send it If the outgoing link is busy the switch will queue the cells destined for that link and not send them until free cell slots are available for transmission The user may specify the processing delay time maximum output queue size and queue size thresholds The parameters that can be monitored for a switch include the number of cells received number of cells in an output queue number of cells dropped and the status of congestion flags 1 2 2 Broadband Terminal Equipment B TE This is a component to simulate a broadband ISDN node e g host computer workstation etc A B TE component has one or more ATM Applications on one side and a physical link on the other side Cells received from the Application side are forwarded to the physical link if the link is busy the cells go into a queue The user can specify the maximum output queue size The parameters that can be monitored are the number of cells in an output queue and the number of cells dropped 1 2 3 ATM Application This is a component to emulate the behavior of an ATM application at the end point of a link It can be considered as a traffic generator either with a constant
28. during a burst Mean burst length and mean interval between bursts are user specified but the actual periods of both are drawn from an exponential distribution Variable Bit Rate VBR Batch Information Window Name Mean Number of cells generated 0 Mean Interval Between Bursts usec 0 Start time usec 0 Number of Mbits to be sent 0 Other End Connection Name 47 The user specifies a mean number of cells that are to be sent in each burst and the mean interval between bursts the actual numbers are drawn from an exponential distribution Bit rate is not an input the number of cells to be transmitted are ready to be sent as a patch by the time burst interval begins The input parameters for the Available Bit Rate Applications are exactly like their CBR VBR counterparts Available Bit Rate ABR Constant Information Window Name Bit Rate Mbits sec 0 Start time usec 0 Number of Mbits to be sent 0 Other End Connection Name Available Bit Rate ABR Poisson Information Window Name Bit Rate Mbits s 0 Mean Burst Length usecs 0 Mean Interval Between Bursts usecs 0 Start Time usecs 0 Number of Mbits to be sent 0 Other End Connection Name Available Bit Rate ABR Batch Information Window Name Mean Number of cells generated 0 Mean Interval Between Bursts
29. e screen at the time The SAVE control button allows the user to save the present configuration in a specially formatted text file which is readable by the simulator at LOAD time The text window appears asking for a filename under which to save the configuration Present values of the components parameters are not saved This is similar to SAVE but in addition it saves the present arrangement of meters and information windows on the display The text window PRINT QUIT appears asking for a filename under which to save the configuration Present values of the components parameters are saved Prints out the network topology into a postscript file This is the normal exit from the simulator program Note that clicking on the QUIT button while in KILL mode merely causes an exit from that mode it does not cause an exit from the program 10 1 5 Operating the Simulator 1 5 1 Loading a Network Configuration There are three ways to specify a network configuration for the program to simulate l Specify the name of a configfile describing the network on the command line This network will be automatically loaded when the programs begins Use the LOAD command while in the simulator program This is accomplished by clicking on the LOAD control button a prompt will then appear in the text window asking for a file name After the user enters the name of the file the network configuration is loaded Note that this erases whateve
30. e user sets the Y scale to 1000 and the parameter values begin to exceed 1000 the full scale range will be doubled to 2000 A horizontal line will be drawn at the midpoint of the meter to indicate the scale change This process of doubling the range will be repeated as often as necessary resulting in many horizontal lines on the face of the meter The vertical distance between these lines will always represent the Y axis value set by the user 99 The TIME HISTORY D meter is similar to the A type but the update of the meter occurs every time the parameter value changes The value displayed is the actual value of the parameter and not an average Since X dimension of the meter is dependent on the rate of change of the parameter the X axis scale cannot be set by the user The Y axis scale behavior is the same as for the TIME HISTORY A meter TIME HISTORY D The Delta meter type indicates the absolute value of the change in the value of a parameter The meter is updated every time a change occurs Since the X dimension of the meter is dependent on the rate of change of the parameter the X axis scale cannot be set by the user In this example the Y axis scale is 5 the II parameter value changes by an increment of one several times then two several times then three etc The Y axis scale DELTA behavior is the same as for the TIME HISTORY A meter To use the Histogram meter the us
31. ebore Mee es ee Ne MR SUR Rd at 43 A 2 Broadband Terminal Equipment B TE 00 0005 45 NO ATM Applications i o aoo Spo FOL Ead ug he edad AMEN Bea haere ek Qe pott 46 Constant Bit Rate CBR Information Window 4 47 Variable Bit Rate VBR Poisson Information Window 47 Variable Bit Rate VBR Batch Information Window 47 Available Bit Rate ABR Constant Information Window 48 Available Bit Rate ABR Poisson Information Window 48 Available Bit Rate ABR Batch Information Window 48 TCP IP Information Window 526 eod ce uy esc qr nuUa Rae See o UN e o 49 AA Link Components me cana uec e UR QE AEN da nS ra Re weed dam Ret 51 ii APPENDIX B Meter Types APPENDIX C Configuration File Formats C 1 Format of the SAVE file C 2 Format of the SNAP File iii The NIST ATM Network Simulator Operation and Programming Version 1 0 ABSTRACT An Asynchronous Transfer Mode ATM network simulator has been developed to provide a means for researchers and network planners to analyze the behavior of ATM networks without the expense of building a real network The simulator is a tool that gives the user an interactive modeling environment with a graphical user interface With this tool the user may create different network topologies control component parameters measure network activity and log data from simulati
32. ell Drop 0 pflags 2a 4 Cells in VBR Q to link1 0 pflags 2a 4 Cells dropped in VBR Q to link1 0 pflags 2a 4 Cells in ABR Q to link1 0 pflags 2a 4 Cells Dropped in ABR Q to link1 0 pflags 2a 1 Congestion for Link link1 FALSE pflags 2a 4 Cells in VBR Q to link2 0 pflags 2a 4 Cells dropped in VBR Q to link2 0 pflags 2a 4 Cells in ABR Q to link2 0 pflags 2a 4 Cells Dropped in ABR Q to link2 0 pflags 2a 1 Congestion for Link link2 FALSE component host2 BTE 562 460 param host2 32 0 host2 param 50 120 Max Output Queue Size 1 inf 50 param 1 120 Logging every ticks e g 1 100 1 pflags 2b 4 562 424 159 93 Cells Received 0 pflags 2a 4 Cells in VBR Q to link2 0 pflags 2a 4 Cells dropped in VBR Q to link2 0 pflags 2a 4 Cells in ABR Q to link2 0 pflags 4b 1 446 547 130 55 Cells Dropped in ABR Q to link2 58
33. er must make four entries in the meter setup window Histogram Min Histogram Max Histogram Cells Histogram Samples Histogram Min and Max define the X axis range of the meter The value of Histogram Cells determines how many cells or HISTOGRAM classes the histogram will have The total number of samples to be included in the figure is entered in Histogram Samples The Y axis represents the number of occurances of the parameter value in the specified range For example if Min 0 Max 100 Histogram Cells 4 and Histogram Samples 50 then the meter is divided into four cells representing value ranges of 1 25 26 50 51 75 and 76 100 Occurances of 10 20 5 and 15 in these ranges respectively will result in a figure like that shown The total Y axis scale is 50 the same as the total number of samples included 54 APPENDIX C Configuration File Formats Network configurations that have been created with the simulator program may be saved in files for future use The SAVE and SNAP commands described briefly in sections 4 3 3 and 6 4 are used to create these files This appendix gives a detailed description of the file formats C 1 Format of the SAVE file The SAVE file conserves information about the components including their screen position the values of their input parameters their interconnection with neighboring components and the established routes virtual circuits Note that it does not preserve values o
34. es that the item being placed on the list contain the pointers needed to link it into the list This means that no extra memory is needed to put the new item into the list However this also means that the item being placed on the list must include room for one or two pointers at the beginning and it can only be on one list at a time Since the item itself contains the pointers the pointers for the first list will be overwritten when it is placed on a second list This type of list we have chosen to call an e list or a qe queue The le stands for list element and it means that the items being placed in the list already have the pointers for a list element built in As an example the global list of components is an le list and the component structure contains two pointers the structure elements co next and co prev The other kind of list allocates a small area of memory in which to store the pointers every time a new element is added to a list This means that adding and removing items from the list is slower but any type of data structure even ones that don t have pointers at the beginning can be placed on any number of lists any number of times This type of list is called an list or a q queue Functions and macros that start with le and qe are the faster routines and the ones that start with 1l and q are the more general ones With one exception l create serves both types of list In the arguments to the functions l and q indi
35. f output parameters status of information windows meters or data logging instructions for these features use the SNAP file described below The listing below is an example of a SAVE file There are three distinct types of information in the file component descriptions linkages and route definitions The component descriptions come first The first line of each description begins with the keyword component followed by the component s name in single quotes then the component type in capital letters and finally the x and y coordinates of the screen position of the component The lines immediately following are a listing of the input parameters and their values Any text on a line after a pound sign is a comment the comment identifies the parameter Following all the component descriptions are the linkages Each line of this group begins with the keyword neighbor1 followed by a component s name in single quotes and then either a physical link name or another component name in single quotes In the example switchl has two physical links attached while the B TE named host1 is connected to the ATM Application named tcpl The last group of lines in the file is the route listing Each line begins with the keyword routel which is followed by the names of all components in the route Each component name is in quotes The component list always begins and ends with an ATM Application component Sample SAVE file component
36. guration llle 11 1 5 2 1 Creating Components 1 51 ola toes OE 3 11 1 5 2 3 Linking Components 4 2 2192 ERR Re ES 12 1 523 Creating ROUES valio pier XA DK S CEN EACH 12 1 6 Operational Features 2 22556 6401442 pea S RE TA veg eee E xL 15 1 6 1 Displaying Information about the Network 13 1 6 1 1 Component Information Windows 13 LOLI Meta od Et be ets eif ae a 14 161 3 Logesmg Data A Ve bo IAEA T e es 15 LO 124 Log File Format DS Lie eh Se EUER aeg 15 1 6 2 Making Modifications S 24 5 bU he eed Ey Cee Rae eee 16 1 6 2 1 Modifying Components 00 0008 16 1 6 2 2 Deleting Components ot postu fo dh P48 Ga BS rd 16 1 6 3 Manipulating the Network Display ooooo 16 1 6 3 1 Raising Lowering Windows 2 0 5 16 1 5 5 2 Moving WIDOOWS 2 2 2d Sia a qiu E aa 16 1 6 3 3 Resizing Windows lees 17 1 6 3 4 Resizing Information Windows l l 17 1 6 4 Saving a Network Configuration llle 17 1 6 5 Post Simulation Analysis using the Log File 17 157 eStulator Concepts Laa eese trt nbn Lett s ad ed eto eM aatia 19 ARS A tg x RE NUN ReLoS Ra eres 19 1 2 ATM SWIC Side 3 3 ds a Boa A 19 1 7 3 Broadband Terminal Equipment B TE 19 1174 ATM Applhations reges opes cR ee Sle Mopac Rent 20 1 7 5 Link Components ii p eR S Xu OE VER UR ee 20 PART 2 Progr
37. he component that contains the parameter The I O routines read and change the value only by calling one of the functions pointed to in the parameter structure A parameter is initialized by calling param_init with arguments containing values for various fields in the parameter structure The values for the arguments calc_val make_text make_short_text and input are pointers to predefined functions in subr c which consists of a set of routines that calculate the parameter s value display it etc for a variety of types of the 24 parameter such as int double boolean and more The following is a listing of the param_init routine Param param_init c name calc_val make_text make_short_text input display_type flags scale Component c Pointer to the component char name Name of parameter PFD calc_val Function to update the parameter value for display PFP make_text make_short_text Function to convert value to a string PFI input Function to read input string and convert into param value int display_type Type of display bar graph histogram etc int flags How to display look below for details double scale Scale for meter The names of arguments listed below correspond to fields in the parameter which in most cases have the same name beginning with the prefix p_ For example the argument calc_val is for p calc val flags is for p flags etc p c
38. he window that appears when a component is first created does not necessarily have any of the output parameters that are shown here these are added automatically when the components are all linked together in a network A 1 ATM Switches Delay to process a cell An increment of time N A 2 EET after the arrival of a cell at the switch before Delay to process a cell usec 0 the switch places the cell on the outgoing Slot time Mbits sec 0 link Output queue size cells 1 inf 0 Slot time The rate at which cells are High Threshold Q cong flag cells 0 switched from an input port to an output port The program calculates the cell slot time from the bit rate entered The actual switching of Logging every n ticks e g 1 100 0 a cell from input port to output port occurs at the beginning of a slot period Low Threshold Q cong flag cells 0 Cells received 0 Percent cell drop 0 Output queue size Available buffer space for Cells in VBR Q to link n 0 a queue the same value is used for every queue in the switch When a cell is ready for transmission but a slot on that link is not Cells in ABR Q to link n 0 available it waits in a queue at that port Cells dropped in VBR Q to link n 0 Cells dropped in ABR Q to link n 0 High Threshold Q congestion flag If the Congestion for link n FALSE number of cells in any queue exceeds this value the congestion flag is se
39. his process is explained in more detail in the Events section of this document A module to handle the allocation and deallocation of cells is provided in the package The module keeps track of all the cells so that when the simulator is reset all cells can be freed in one step cell alloc returns a new cell cell free frees a cell and cell free all frees all cells The simulator obeys the convention that all components must dispose of all cells that they receive in one way or another In other words a component that receives a cell must either call cell free on the cell or send the cell to someone else but not both Furthermore a component that sends a cell to someone else should no longer refer to that cell If it wants to save the cell 35 for some reason if the cell might be retransmitted for example the component must call cell_allocQ and make a copy of the cell 2 4 2 Setting Up the ATM Virtual Channel The simulator implements static connections An ATM channel begins and ends with a component of the type ATM APPLICATION A particular Application can have a route to only one other Application When the user clicks on an ATM Application that is at the other end of the virtual channel this is done while making the route the routing table at each ATM Switch is updated and information about the next link and the next ATM Switch found on the path is stored The file route c contains a couple of functions to manipulate con
40. ifdef DEBUG dbg_write debug_log DBG_info Component b started a no op endif break case EV_RECEIVE result b_receive b src cell break case EV_READY result b_ready b src break default break Y end switch statement 30 2 3 Events The simulator is event driven the event queue is a queue of events kept sorted by time To fire an event the first event in the queue is removed the global time is set to the time of that event and the action routine pointed to in the event structure is called When the user clicks on the START button each component is sent a reset command followed by a start command then the simulator enters a loop The loop processes any X events updates the display then fires all the events at the head of the event queue that have the same time Currently there are three classes of events commands regular events and private events Commands and regular events are defined in eventdefs h Commands are those events which perform some action such as reset start create etc while regular events are those which are concerned with the actual running of the simulation e g receive ready busy Private events are events that components send to themselves therefore they are defined in the source files of the components rather than in a central location 2 3 1 Command Set EV_CLASS_CMD All components must accept the following commands The component need not actually use the com
41. ing with ATM Applications To create a Route hold the shift key down and click the left mouse button on each component in the route A message will appear briefly in the text window after each click to affirm or reject the addition of the component to the route The first and last components in this process must be ATM Applications When the user clicks on the final Application on the path the route is created Only one route going out of an ATM Application is assumed although multiple routes may be coming in Performing a shift left click on anything other than a component aborts route creation However any other commands or button clicks that are not shift left clicks can take place at any time in the route creation process If the user attempts to include a component in the route which cannot be included perhaps because it is not a neighbor it will not be included but the route creation process will not be aborted To abort an incomplete route creation process and start over shift left click twice on the window background Once routes have been created they cannot be deleted All desired routes should be created at one session i e do not try to add routes to a loaded file that has been previously configured and contains routes CAUTION Any attempt to start or run a simulation before routes have been created will cause a program crash 12 1 6 Operational Features The simulator provides several features which may be used to enha
42. is part of the document briefly describes the ATM Network Simulator Software and the procedures necessary to make user modifications such as the creation of new components or to change the behavior of existing components It is assumed that the reader is familiar with C Language programming techniques conventions and notations and has the source code of the ATM Network Simulator available for reference The simulator can simulate anything that can be modeled by a network of components that send messages to one another The components schedule events for one another to cause things to happen The model being simulated and the action of the components is entirely determined by the code controlling the components not by the framework of the simulator The person who implements the components can decide how they will go about having components send messages to one another the simulator framework only provides the means to schedule events and to communicate with the user The simulator program includes a graphical user interface which provides the user with a means to display the topology of the network define the parameters and connectivity of the network log data and to save and load the network configuration In addition to the user interface the simulator has an event manager I O routines and various tools that can be used to build components 21 2 2 Components The component is the basic building block of the simulator There are differen
43. ist and associated extra garbage As with Iq delete this function works for both lists and queues This function removes all the items from a list or queue If itisa le list or qe queue the memory for the items is also freed otherwise they are merely removed from the list or queue This function is only for I lists It frees the list the 1_elts used by the list and the data blocks which must have been allocated using malloc or calloc The following functions perform the same actions on queues as the similarly named functions for lists q create q e _addh q elt 38 q e _addt q elt q e _adda q prev new q e _del q elt q find q elt Finally queues have the following operations of their own q e _deq q Removes and returns the item at the head of the queue qe_find q qe Looks for the item qe in the queue Returns qe if found NULL otherwise qe_dela q prev Removes the element after prev in q This operation is O unlike q e _del which is O n 2 5 2 Other Tools In addition to lists and queues the simulator includes a hash table module and a module to control allocation of fixed size memory blocks The functions for these modules are contained in hash c hash h mempool c and mempool h The hash table is fairly straight forward Its functions are described in comments at the beginning of hash c The mempool was originally written to try to speed up the simulator by avoiding calloc
44. ities can be recorded on a cell by cell basis for subsequent analysis Terminology in this Manual The network to be simulated consists of several components sending messages to one another The components available include ATM Switches Broadband Terminal Equipment B TE and ATM Applications Switches and B TE components are interconnected with Physical Links a Physical Link is also considered a component The ATM Applications are logical entities that run on B TE hosts The Applications may be considered as traffic generators that are capable of emulating variable or constant bit rate traffic sources ATM Applications are connected to each other over a route that uses a selected list of adjacent components to form an end to end virtual connection All components are characterized by one or more parameters Parameters fall into two categories input and output both kinds are listed in information windows which appear next to the applicable component when the user so desires All input parameters may be specified by the user at the time of component creation or they may be modified later Network activity may be observed by opening meter windows to display selected parameters There are various types of meter windows available and they can be placed anywhere on the screen Parameter information may also be logged i e stored on disk in a file named sim_log xxxx where xxxx is the process ID of the simulator PART 1 User s Manual 1 1 Obje
45. k 1 output and data logging selected for Number of cells dropped Both box types are valid only for output parameters clicking on either box for any other parameter will have no effect When defining a component for the first time a prompt will appear in the text window automatically asking for the required information Each entry is terminated by a RETURN No other action is possible until all requested information has been entered To modify a parameter at any other time click the middle mouse button on the desired line Once again the prompt will appear in the text window and the value may be entered terminated by a RETURN A RETURN with no entry will accept the current value To remove the information window from the screen click the middle button on the component s symbol and the information window will disappear 13 1 6 1 2 Meters To display information about a parameter in graphical form a meter is created for that parameter To create a meter for a particular parameter of a component click the middle button of the mouse on the left most box next to the parameter on the component s information window This box will become white and the meter will be created This meter will remain on the screen even if the component s information window is not displayed Meters are stacked below the component box whose parameters values they display They consist of rectangular boxes of varying lengths and heights The location and size
46. l be created The information window also has elements that control data display and recording these will be discussed below 11 1 5 2 3 Linking Components After the ATM switches and B TE components have been created they are connected into a network by creating physical links A physical link is also considered to be a network component and has a name and parameters associated with it A link may connect any two ATM switches or one switch and one B TE The procedure for creating a link is as follows Select the first component to be linked by clicking on it with the middle mouse button while holding down the shift key Select the second component to be linked by the same method At this point a line will appear and the physical link component will be created As with other components an information window will appear and the user will be prompted to enter a name and some input parameters To complete the linking process the ATM Application components must be connected to the B TE components The process is like creating the physical link shift click middle button on component but in this case only a line linking the components will appear no information window This is because this type of connection is not considered a component 1 5 2 3 Creating Routes A Route is an ATM Permanent Virtual Connection a path over which the cells travel through the network In the simulator a Route is a list of adjacent components beginning and end
47. logy e g link1 bb1 switch2 ABR2 etc in addition to what we see in Figure 3 b a Sample Network Switch2 Switch 1 b Relationship of Component Parameter and Neighbor Structures list of components Component Component Component Figure 3 Creation of a Component 28 2 2 6 Action Routines As previously stated every component contains an action routine This routine is called for each event that happens to a component Events are explained in a later section of this document The action routine is called usually not by the event manager but rather by the action routine that scheduled the event to execute a set of commands that will give the component its unique behavior The writer of a component can create components with any sort of behavior Components can send any type of events to one another However in order to allow the simulator to do various housekeeping functions every action routine must respond to a minimum fixed set of commands A synopsis of the action routine and the commands it is expected to perform is as follows All of these include files may not be needed but they are the common ones include lt sys types h gt include lt stdio h gt include sim h include log h include q h include list h include simx h X window stuff amp also component h include comptypes h The types of components include cell h include even
48. ltiple Applications are queued in one of two priority queues if no link slot is available for transmission If either queue exceeds its size limit cells will be dropped Name Max Output Queue Size 1 inf 0 Logging every n ticks e g 1 100 0 Cells Received 0 Cells in VBR Q to link n 0 Cells dropped in VBR Q to link n 0 Cells in ABR Q to link n 0 Cells dropped in ABR Q to link n 0 Maximum Output Queue Size Available buffer space for each type of queue Logging every n ticks If n is set to 1 data will be logged for a parameter anytime there is a change in its value Potentially this could occur at every tick Since this may result in an extremely large data file it may be desirable to set n to a larger number For example if n 100 logging will occur only if a change occurred and 100 ticks had gone by since the last logging activity Cells Received Total number of cells received by the B TE Cells in xBR Q to link n Cells awaiting transmission in a given priority queue There are two types of queues a CBR VBR queue and an ABR queue Cells in the CBR VBR queue have top priority a cell from the ABR queue will be sent only if the CBR VBR queue is empty Cells dropped in xBR Q to link n Cells dropped at the network port when a queue exceeds its maximum size 45 A 3 ATM Applications CBR VBR Poisson VBR Batch ABR Constant
49. mand but should respond in an orderly and predictable way when the command is received When used in an action routine the action routine should return NULL if an error occurs during a command and something that is non NULL otherwise EV_CREATE Create a new instance of a component The comp variable must be NULL arg points to the name of the new component and the action routine returns either a pointer to a new data structure or NULL for error The action routine must allocate the correct amount of memory for the new component s data structure create its empty neighbor list create the queue of parameters create any cell queues etc This command must also initialize all the private data in the component as necessary The only information that need not be initialized are any parameters with the InputMask flag set They will be initialized by the simulator as specified in the Parameters section of this document EV_DEL Delete an instance of component This command will detach the component from any neighbors it has free any storage associated with the component including its data structure and perform any other necessary clean up EV_RESET Reset the state of the component clear out any cell queues forget about any cells being processed etc When the START button of the simulator is hit EV_RESET is called first for all components and then EV_START EV_START Start operations for example start a cell generator sending cells For m
50. mation associated with the neighbor that must be displayed a parameter structure must be allocated initialized appropriately and added to the queue of parameters in the component structure See the function b_neighbor in bte c for an example of usage The following is defined in subr c and can be used when writing a new routine to give it the capability to add neighbors Neighbor add neighbor c neighc max num neighbors num classes Component c Comp to add neighbor to Component neighc New neighbor int max num neighbors Max number neighbors allowed 0 infinite int num classes How many classes follow Similarly the following is also defined in subr c and can be used to provide a routine with the capability to remove neighbors remove neighbor c neighc Component c neighc 27 2 2 5 Relationship of Data Structures Figure 3 shows the data structures that are formed when a component is created As stated in the preceding sections the component data structure contains the doubly linked parameter list and a set of pointers that point to the individual components When a neighbor is added the component creates a neighbor structure and puts it on its neighbors list Each neighbor structure then contains a pointer to a neighboring component When all of the components in the network are created and linked together then list of components will be completed and will include all elements in the network topo
51. missions as a percentage of total packets sent A 4 Link Components Name Link Speed Mbits sec 0 STS 1 51 840 Mbits sec STS 3C 155 520 Mbits sec STS 12C 622 080 Mbits sec STS 24C 1244 160 Mbits sec DS 3 44 736 Mbits sec ATM F Multimode Fiber 100 Mbits sec Distance km 0 Link Rate Mbits sec to Switch n 0 Link Rate Mbits sec to B TE n 0 51 There are only two input parameters for a Physical Link link speed and distance The link speeds shown in the window are not selectable with the mouse the desired speed in Mbits s must be typed into the text window However the bit rate typed in need not be exact the software will accept a round number near the standard rate and make the necessary adjustment The bit rates shown include overhead bits The simulator maps the entry into the correct payload rate when doing calculations for bits transmitted One exception if the entry is less than 40 Mbits s the entered rate is accepted directly with no mapping The link output parameter is link utilization in each direction in terms of bit rate Mbits s 32 NE BINARY METERS BAR GRAPH APPENDIX B Meter Types The Binary meter type is most useful for true false indicators such as flags If assigned to a parameter with numerical values the rectangle will be shaded with one of five colors to differentiate it from a binary parameter
52. n be harmful to your configuration inadvertent deletion of components may result if the middle button is used for selection without QUITing the delete mode Also note that clicking on QUIT while in KILL mode does not cause an exit from the simulator program but a second click on QUIT will end the session It is not possible to delete components once they have been placed in a route an ATM Virtual channel Furthermore it is not possible to delete a route thus the user should make every effort to insure that the configuration is constructed as desired before creating the routes 1 6 3 Manipulating the Network Display 1 6 3 1 Raising Lowering Windows Clicking the right mouse button on a window will raise bring forward that window so that nothing else on the display will obscure that window Clicking the left mouse button on a window will lower push back that window so that it does not obscure any other windows 1 6 3 2 Moving Windows Any of the windows in the network display may be repositioned including components meters and information windows Even the control buttons and clock may be moved but only as a group To accomplish a move click and hold the right mouse button on the window drag the box outline which appears to the new location for the window and release the mouse button 16 1 6 3 3 Resizing Windows It is possible to resize meter windows To do this click and hold the middle mouse button on one corner of the window
53. nce the display of information modify the network that was created save existing configurations and log data from the simulation runs 1 6 1 Displaying Information about the Network 1 6 1 1 Component Information Windows These are the same windows that appear when a component is created They are used during the process of setting values of input parameters but may also be used to modify those values display output parameter values and to control data logging The figure below is an example of an information window The first line shows the component name the second line an input parameter The two shaded blocks are output parameters with current parameter values displayed Note This shading does not appear on the screen switch Max Output Queue Size 1 inf 1 Link 1 output queue has 25 cells Number of cells dropped on route 0 To bring the information window onto the screen click the middle mouse button on the component s symbol a window similar to the one above will appear To the left of each parameter s information line are two small boxes Clicking the middle mouse button on the left hand box toggles a meter display on and off for that parameter clicking on the right hand box toggles data logging on and off for the parameter The box will become white when its function is turned on and revert back to its background color when it is toggled off The example above shows a meter created for Lin
54. nections To determine where to route a cell next the function Route_info rt_lookup some arguments ieee can be called from an ATM Switch action routine this should return the next link and next switch The routing process starts when io within IO c calls make_route_event_handler bevent which is found in route c The routing process involves creating a route_list which is a list of components When finally the user clicks on a component of type ATM APPLICATION which is at the end of a route all switches found in route_list call their respective action_routines to update their local routing modules 36 2 5 Tools 2 5 1 Lists and Queues Lists doubly linked lists and queues singly linked lists are used extensively throughout the simulator Lists and queues contain variables to store the current maximum and minimum length of the list queue A list has the following structure typedef struct list list header lelt l_head first element in list l elt L tail last element in list int len number of elements in queue int max maximum length int min minimum length list An element in the list 1 elt has the following structure typedef struct l elt list element struct l elt le next le prev Links caddr t le data 1 elt Because both lists that were efficient and lists that were flexible were needed there are two kinds of lists One kind requir
55. no metering is possible Sender Sequence Number Logging Sender ACK Sequence Number Logging Receiver Sequence Number Logging TCP Open Time The time that the first TCP packet was sent TCP Close Time The end of the TCP transmission all bytes have been sent Connection Busy Activity flag for TCP processing TRUE busy FALSE not busy Packet input queue has n packets This queue contains packets waiting for TCP processing both for transmission before segmentation and for reception after reassembly Peer Receive Window Size This is the other end companion to My Receive Window Size RTT Round Trip Time time from packet sent to ACK received This is set to a default value at the beginning of a simulation run then actual measurements are made and Jacobson s algorithm is used to smooth the result Jacobson V Congestion Avoidance and Control Proceedings of the ACM SIGCOMM 68 August 1988 50 RTO Retransmission Time Out the time interval to wait before deciding an unacknowledged packet has been lost At the start of a simulation this is set equal to RTT a default value then as measurements of RTT are accumulated Karn s exponential backoff multiplier is incorporated to calculate this parameter RTO current This is the Retransmission Time Out interval currently being used Average Throughput This is based on the average number of packets successfully transmitted Retransmission Percentage Retrans
56. ny types these are defined as follows Constant Bit Rate CBRCONNECTION Variable Bit Rate Poisson VBRCONNECTION 22 Variable Bit Rate Batch BATCHCONNECTION Available Bit Rate Constant ABRCONNECTIONI Available Bit Rate Poisson ABRCONNECTION2 Available Bit Rate Batch ABRCONNECTION3 TCP IP Application TCPCONNECTION When creating a new type of component comptypes c and comptypes h must be modified to contain a new constant for the new component type and a new entry must be made in the comp types array 2 2 2 Component Data Structures Each instance of a component has a data structure that is used to store any information needed by the component as well as standard information needed by the simulator for every component Component structures are kept in a list the order of the list depends on the order of creation of the component Each different type of component has its own structure which is defined in the header h file for that type but the beginning of every component structure is the same This generic structure is as follows actual listing can be found in component h typedef struct Component struct Component co next co prev Links to other components in list short co class Class of component short co type Type of component char co name 40 Name to appear on screen PFP co action Main function called with each event COMP OBJECT co picture Graphics obje
57. o be in the text window when entering information with the keyboard When entering information using the keyboard pressing Return without entering any text will tell the program to accept a default value or to abort that operation 1 4 3 The Control Panel 0 000 Milliseconds Link lik Figure 1 Typical Simulator Screen The control panel appears on the right hand portion of the screen It contains an analog clock a digital clock and an array of control buttons 1 4 3 1 Analog Clock The analog clock indicates the passage of simulator time in a graphic style The intent is not a precise timer but to give the user an indication of how busy the simulator is A tick is a movement of 6 degrees around the circle Each tick of the big hand represents 1 millisecond Each tick of the small hand represents one revolution of the big hand 60 milliseconds 1 4 3 2 Digital Clock The digital clock provides a display of current simulator time accurate to the nearest 10 nanoseconds 1 4 3 3 Control Buttons The following is a description of the function of each control button All of the functions are initiated by clicking with the middle mouse button START PAUSE RUN DELAY UPDATE KILL LOAD SAVE SNAP Clicking on this button will start the simulation with simulated time initialized to zero The simulation can be restarted as many times as the user wishes each click on the button will initialize the simulation This
58. o change the shape of the component one needs to write the routine that will draw the component for example see pop comp window in components c Change the Makefile to make sure the new components are compiled and linked into the simulator For a simple component it should suffice to add newcomp o to the ADDLOBJS macro in the makefile In fact the following command line should be able to build a new simulator without modifying the Makefile make ADDLOBJS newcomp c custom sim If you want dependencies on header files and or any special rules for making your new component you will have to change the makefile 41 42 APPENDIX A Parameter Information The purpose of this appendix is to present detailed information about ATM system parameters that the user is required to define as inputs or monitor as simulator outputs In all the information windows name appears on the first line The user may choose any name desired for the component but it is helpful if the name has some relation to the component type e g linkl bte2 etc As soon as the name is entered it will appear on the first line of the information window and inside the component symbol The figures in this appendix designate output parameters by shading this shading does not appear on the actual screen It is not possible to enter information on the lines that are designated for outputs Similarly it is not possible to select an input for metering or data logging T
59. of meter for display int p log Integer associated with this param for logging double p scale Scale to use for meters struct Structure to store data in int i Commonly used value types int vpi Only need to use one of these types double d caddr t p struct Structure describing parameter value if needed caddr t p int vpi int i pi tick t sample Keeps track of time parameter value was updated u This structure is used and maintained by the simulator Param A component may have as many parameters as needed They are stored in a doubly linked list pointed to by co_params The I O routines iterate through this list to display the parameters as described below The action routine may reference the parameters any way it wants In addition to the linked parameter list there is a set of pointers in the component that point to the individual parameters As the parameter is initialized and added to the list the pointer is set to point to it Then the action routine can use a named variable to refer to the parameter rather than trying to search through the list The actual value of a parameter is stored in a structure at the end of the Param structure Currently the structure has room for an integer a double or a pointer A new value type can be added just by changing the definition of the structure This value is not used by any part of the simulator except for the action routine of t
60. on runs Part 1 of this document is the user s manual for the simulator it includes instructions for creating network configurations specifying component parameters manipulating the display logging and saving measurements and post processing of data Part 2 has been prepared as a guide for the user who wishes to modify the simulator software to accommodate network components not previously defined or to change the behavior of components already defined Introduction The ATM Network Simulator was developed at the National Institute of Standards and Technology NIST to provide a flexible testbed for studying and evaluating the performance of ATM networks The simulator is a tool that gives the user an interactive modeling environment with a graphical user interface NIST has developed this tool using both C language and the X Window System running on a UNIX platform This tool is based on a network simulator developed at MIT that provides support for discrete event simulation techniques and has graphic user interface GUI representation capabilities The ATM Network Simulator allows the user to create different network topologies set the parameters of component operation and save load the different simulated configurations While the simulation is running various instantaneous performance measures can be displayed in graphical text form on the screen or saved to files for subsequent analysis Purpose The ATM network simulator is a tool
61. onents to make sure that it all works l Modify comptypes c and comptypes h to contain a new constant for the new type of component a new entry in the component_types array and a declaration of the action routine Create a new component structure putting it in its own h file say newcomp h The easiest way to do this is to look at one of the existing component structures and modify it as necessary Be sure to read component h for a description of the common component structure that all simulator components must share This shared part of the structure must exist and be the same for all components Parameters and the private part of the structure can be modified as desired Create an action routine for the component Again the easiest way to do this is to use the code from an existing component as a model Also see the descriptions in this document of the various commands that an action routine must perform If the new component will interact with the components that are already written it must deal with the events that they will send it and it must send them events that they are expecting Otherwise it can act in whatever way it wants Add an object picture or choose one from among the object pictures provided When a component is created the routine create_component found in edit c is called from IO c This routine given the type of component to be created will call the appropriate routine to draw the component on the screen T
62. ore network components plotted or otherwise presented for further analysis One way of doing this is to parse the sim_log file in order to get a data file with two columns X Y that can be fed into any datasheet program such as Lotus 1 2 3 GnuPlot etc A filter program is provided with the simulator package for this purpose The usage for the filter is as follows filter sim log xxxx component name parameter name 2 Trade names mentioned in the text are meant only to identify typical products Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology nor does it imply the products are necessarily the best availble for the purpose 17 The above line will send the filter output to the standard output device to redirect the output to a file type filter sim log xxxx component name parameter name gt output file The filter program can be easily modified to do other post processing tasks such as to change the time from ticks to milliseconds or to obtain a throughput rate from the cell arrival data The figure below is an example of a parameter plot obtained by post processing a sim log file This figure represents the throughput rate for a particular route that has a VBR traffic source The measurement of interest in this case is the virtual circuit VC rate at the switch at the receiving end of the route on a particular link and identified with a particular route This info
63. poses an ATM switch reads off the route number found in the cell then looks up its routing table to forward the cell via the next link to the next switch or to the next B TE if at the end of a connection The cell data structure is not constrained to be any particular format Of course if you are only modifying some existing components you should not remove any elements from the structure but if you are writing a set of components from scratch a cell can contain anything To change the contents of a cell just change the definition in cell h and recompile The following is a simple example of a cell structure typedef struct_Cell Define cell structure struct _Cell cell_next Pointer for use by the queue the cells will be stored in VPI vpi Route number virtual path identifier PTI pti Payload type identifier struct cell_payload Structure for the payload portion Packet tcp ip info The payload will AALS Trailer len be any one of RM rm these three types u Structure Cell An event may include a cell and most simulation events as opposed to housekeeping commands do so Normally cells are transmitted from one component to another by having the transmitting component call a routine ev_enqueue which creates a new event and places it in a queue to be fired at the appropriate time The receiving component must be able to process the event in order to receive the cell T
64. r There also exists a function to unschedule events 1 e remove events from the queue Selection of events to be removed may be done according to source and destination components and type or according to a particular event expiration time void ev_dequeue_by_comp_and_type src dest type Component src dest Evtype type Remove from the queue any subset of events with particular source and destination components and type A NULL source or destination matches all components void ev_dequeue_by_time t tick_t t Remove from the queue all events due to expire at a particular time t Again it should be noted that the designer of components for the simulator is free to use whatever convention he she desires for communication between components The simulator just provides the ability to send events what the events mean is up to you See the section on Components for the conventions now used 34 2 4 ATM Network Related Issues 2 4 1 ATM Cell Definition Since the simulator is designed to simulate ATM networks a cell data type has been defined A cell constitutes a very important data type in the simulator because it contains the route number needed for routing by ATM switches A cell is a data structure defined in the file cell h The structure may contain different elements to tailor the cell for different applications but must always contain the route number For switching or routing pur
65. r configuration was being displayed on the screen at the time Create a network while in the simulator program using the tools the program provides Using this process the user decides on the appropriate components their characteristics and interconnections 1 5 2 Creating a Network Configuration The process of creating a network for simulation starts with the creation of components 1 5 2 1 Creating Components Creating components except for links is achieved by holding the shift key down and clicking the right mouse button on the background The initial location of the component will be the location of the mouse when the right button is released Components may be repositioned after they are created see 1 6 3 2 Moving Windows below After the right button is released a menu of component types will appear this menu contains the items shown After the user clicks on the desired component type a ie component information window will appear on the background B TE The user will be prompted in the text window to enter certain information about the component The first item requested is ATM APPLICATION always the component s name Next the user is prompted to ABORT enter values for input parameters i e the parameters that will define the component s behavior in the network For a comprehensive list of these parameters see Appendix A After all the required parameter values are entered the component wil
66. r level traffic has been sent At each priority level there are three types of traffic generators 1 A constant rate traffic where the user specifies the bit rate Cells will be generated at the specified rate for the duration of the simulation 2 Variable Bit Rate Poisson This type of traffic has an ON OFF source Both the burst period ON and the silence period OFF are drawn from an exponential distribution The user specifies the mean burst length the mean interval between bursts and the bit rate at which cells are generated during the ON period 3 Variable Bit Rate Batch For this traffic source the user specifies the mean number of cells generated during a burst and the mean interval between bursts For all of the traffic types the user specifies the start time and the number of megabits to be sent Another ATM Application type that can be simulated is a TCP IP application See Appendix A for a list of input and output parameters 1 7 5 Link Components This component simulates the physical medium copper wire or optical fiber on which cells are transmitted The user may choose the link speed from a list of several different standard rates The user also specifies the length of the link The output parameter reported by the simulator is link utilization in terms of bit rate Mbits s The measurement of link rate is averaged over a period of 10 cells 20 PART 2 Programmer s Guide 2 1 Objectives and Overview Th
67. rmation was parsed out of the sim log file and the number of such cells arriving was counted for a particular period of time The count per unit time was then translated into Mbits s by a simple calculation and the result plotted as shown Per VC Throughput T 200 T T VCVBR 150 2 2 5 eo 5 100 o gt D n 50 A p eet eec teme et p nee ede eme 4 0 i i i i 0 20 40 60 80 100 Simulation Time in milliseconds Figure 2 Sample Parameter Plot 18 1 7 Simulator Concepts 1 7 1 Simulation Clock The simulator is event driven Components send each other events in order to communicate and send cells through the network The software contains an event manager which provides a general facility to schedule and send or fire an event An event queue is maintained in which events are kept sorted by time To fire an event the first event in the queue is removed the global time is set to the time of that event and any action scheduled to take place is undertaken Events can be scheduled at the current time or at any time in the future Scheduling events for the past is considered illogical Events scheduled at the same time are not guaranteed to fire in any particular order Simulator time is maintained by the event manager in units of ticks The time is maintained as an unsigned 32 bit value The simulator time represented by one tick can be changed by software modification see section 2 3 4 but not by the sim
68. s active the meter window is closed 4a the log box is inactive the meter window is open 4b the log box is active the meter window in open Following the above is another entry consisting of a single digit with the value of 1 through 7 This digit represents the type of meter used for the graphical display The types are identified as follows 1 Binary meter 2 Bar graph 3 Log graph 4 time history A 5 time history D 6 Delta meter 7 Histogram If the meter window for an output parameter is open the coordinates of its position on the screen and its dimensions are given immediately following the meter type entry For example for the line pflags 2b 4 562 424 159 93 the x and y coordinates of the window are 562 and 424 and 159 and 93 are the height and width respectively The remainder of the SNAP file contains linkage and route definition these are in a format identical to the SAVE file Sample SNAP file Seed 776093072 Time of snapshot ticks 0 component switchl SWITCH 417 341 infowindow param switchl 320 switchl param 0 120 Delay to process a cell uSec 0 57 param 155 12 0 Switching Slot time Mbit s 155 param 10000 12 0 Output q size cells 1 inf 10000 param 550 12 0 High Threshold for Q Congestion Flag 550 param 450 12 0 Low Threshold for Q Congestion Flag 450 param 1 120 Logging every ticks e g 1 100 1 pflags 2a 4 Cells Received 0 pflags 2a 4 C
69. t Low Theshold Q congestion flag The congestion flag is cleared when the number of cells in all queues fall below this value 43 Logging every n ticks If n is set to 1 data will be logged for a parameter anytime there is a change in its value Potentially this could occur at every tick Since this may result in an extremely large data file it may be desirable to set n to a larger number For example if n 100 logging will occur only if a change occurred and 100 ticks had gone by since the last logging activity Cells Received Total number of cells received by the switch Percent cell drop Number of cells dropped by the switch as a percentage of the total cells received Cells in xBR Q to link n Cells awaiting transmission in a given priority queue There are two types of queues for each port a CBR VBR queue and an ABR queue Cells in the CBR VBR queue have top priority a cell from the ABR queue will be sent only if the CBR VBR queue is empty Cells dropped in xBR Q to link n Cells dropped at a port when a queue exceeds its maximum size Congestion for link n There is one congestion flag for each port The flag is set when a queue exceeds its High Threshold value cleared when both queues fall below the Low Threshold 44 A 2 Broadband Terminal Equipment B TE Unlike a switch there can be only one physical link attached to a B TE component Cells received from the Application side there may be mu
70. t classes of components examples are switches physical links terminal equipment and ATM applications Some classes allow different types within the class in order to accommodate the simulation of a variety of implementations For example an ATM application may generate traffic at a constant bit rate or a variable bit rate that is governed by some particular distribution function Every component consists of an action routine and a data structure All components of the same type share the same action routine this routine is called for each event that happens to a component Each instance of a component has its own data structure which is used to store information that characterizes the component plus some standard information required by the simulator for every component 2 2 1 Classes and Types Every component has a class and a type A particular class of component may contain several different types of components The following are the different classes of components currently defined and in parentheses the way the names appear in the source file comptypes h Links LINK CLASS ATM Switches SWITCH CLASS Broadband Terminal Equipment BTE CLASS ATM Applications CONNECTION CLASS For now the Link Switch and B TE classes contain only one type each Respectively they are as defined in comptypes c and comptypes h Physical Link ATMLINK ATM Switch SWITCH B TE BTE The ATM Applications class however contains ma
71. tdefs h Types of events amp commands defined here include event h include this component type h E Definition of some Local Events if needed caddr_t action src comp type cell vpi arg Component src Component that sent this event Null for cmds Component comp Component to which this event cmd applies int type Type of event or cmd that is happening Cell cell A cell VPI vpi VPI number of data cell wherever it is applicable caddr_t arg Whatever Usually a large switch statement on the event type j An example of the large switch statement referred to in the last comment line above is shown in the code below which is extracted from the action routine for BTE bte c The switch statement contains a case for every type of event to which the component is expected to respond These include the events for component creation routing and initialization as well as the basic function of giving the component the ability to pass cells The example demonstrates the usual way to transmit a cell that is to pass it with an EV RECEIVE event to another component The transmitting component calls ev enqueue EV RECEIVE src dest time rtn ce arg which has as one of its parameters a pointer to the cell ce When the resulting event after being queued in the event list gets fired the action routine of the destination component 29 is called and
72. te events are the means by which an action routine can send events to itself 2 3 4 The Event Manager Components send each other events in order to communicate and send cells through the network The event manager provides a general facility to schedule and send events The primary functions of this facility are the maintenance of simulator time and the control of event queueing Simulator time is maintained by the event manager in units of ticks Currently ONE tick is 10 nanoseconds Once a tick is defined in microseconds or in nanoseconds it is easy to convert this value to seconds milliseconds etc To convert from ticks to microseconds use the TICKS_TO_USECS macro defined in sim h To convert from microseconds to ticks use USECS_TO_TICKS Analogous macros exist for nanoseconds and full seconds represented as doubles The current time in ticks is returned by the function ev_now The time is maintained as an unsigned 32 bit value so at 10 nanoseconds per tick a total of 42 seconds of simulated time is available for one run of the program If longer simulation runs are required the tick definition may be changed At ten microseconds per tick for example the simulator can run for almost 12 hours of simulated time In sim h there is a typedef called tick_t which has the tick definition in microseconds For the current definition of 10 nanoseconds the definition line is define USECS_PER_TICK 0 01 The only other event related function th
73. the pointer to the cell structure is passed as an argument in that call The destination action routine executes the portion of the code that describes the behavior of the destination component when it receives a cell The above is still true even when no cells are passed and the component is merely sending events to itself of various housekeeping tasks switch type case EV_RESET Case for receiving the command EV_RESET result b_reset b Call the routine b reset break case LINK SLOT Case for receiving the private event LINK SLOT result b ready b src Call the routine b ready break case EV CREATE Case for receiving the command EV CREATE result b create char arg Call the routine b create break case EV DEL NOTE result b delete b This pattern of calling a routine for each break case of an event received continues for all case EV_NEIGHBOR of the switch statement When a routine is result b_neighbor b Component arg break called the portion of the code that defines case EV_UNEIGHBOR the behavior of the BTE for that event is executed result b_uneighbor b Component arg break case EV_LEGAL_NEXT_HOPS result b_hops b list arg break case EV_MAKE_ROUTE ifdef DEBUG dbg_write debug_log DBG_INFO Component b processed EV MAKE ROUTE event endif result b_route b list arg vpi break case EV_START
74. tiplier 1 if p scale is zero 26 2 2 4 Neighbors Neighbors are stored as a list of Neighbor structures this list is pointed to from component structures Each neighbor structure contains a pointer to the neighboring component a queue in which to store cells if needed a busy flag and a pointer to a parameter to display anything that might be associated with the neighbor The definition of the Neighbor structure is listed below it can be also be found in component h typedef struct_Neighbor struct_Neighbor n_next n_prev Links for the list Component n c Pointer to the neighboring component The next values will vary from network to network and from component to component For example only switches and hosts have queues in the current application queue n pq Queue of packets to be sent short n busy True if neighbor is busy double n prev sample Previous sample time used for utilization calculation in links Param n p Index of parameter to display whatever Param n pp Index of parameter to display whatever Param n ppp list n vpi List of parameters related to vpi number of the different routes caddr t n data If a component wants to store arbitrary data for each neighbor put it here Neighbor When a neighbor is added the component must create and initialize a neighbor structure and put it on its neighbors list If there is some piece of infor
75. uces some results Allows the user to specify the seed for the random number generator If this option is omitted the current time in UNIX format is used as the seed The seed actually used is printed at the beginning of each simulator run and is saved as a comment in any log files produced by the simulator Specifying a particular seed is useful if identical results are expected from successive simulator runs A file describing the configuration of the network to simulate Such a file is produced by the SAVE and SNAP commands in the simulator Length of time in microseconds of simulated time for the simulator to run Most useful when running non interactively with the x option When the simulator stops it will automatically produce a snap file of its current state 1 4 The Display The display is composed of three major parts A network window to display ATM network configurations This window is used both while creating the configurations and to show network activity while the simulation is running A text window for messages that will prompt the user and to provide a place for the user to input text or parameter values A control panel that consists of a clock and several control buttons such as START QUIT etc 1 4 1 The Network Window Figure 1 is an example of the simulator screen seen by the user once a network configuration has been created The entire area not otherwise occupied by clock and control buttons is the
76. ulator user For the present a tick represents 10 nanoseconds With that value a total of 42 seconds of simulated time is available for one run of the program 1 7 2 ATM Switch The switch is the component that switches or routes cells over several virtual channel links A local routing table is provided for each switch This table contains a route number that is read from incoming cell structure and is the equivalent of the cell s virtual channel identifier a next link entry and a next switch next B TE entry Let s consider a cell arriving at the switch from a physical link At the next switching slot time after some delay set by user the switch looks in its local routing table to determine which outgoing link it should redirect the cell to At this point if the link has an empty slot available the switch puts the cell on the link If a link slot is not available the cell awaits transmission in one of the priority queues namely the CBR VBR queue or the ABR queue depending on the type of service provided by this virtual channel Cells in the CBR VBR queue have priority over cells in the ABR queue i e it is only when the CBR VBR queue is empty that the ABR traffic is sent If either queue exceeds a High Threshold value set by the user a congestion flag for that port is set to True Both queues must be below a Low Threshold value for the congestion flag to be reset to False The Output Queue Size set by the user determines the avail
77. will contain an entry for every value change of every parameter that was tagged for data logging Every entry will consist of parameter number time tick and parameter value at that tick The parameter number will be identified by name in the file header For Switch and B TE components clicking on the right hand box next to the component name in an information window results in the arrival of each cell on n cells into that component being logged into the sim log file For these components there is an input parameter Logging every n ticks that lets the user decide on the frequency of the data logging When operating without X Windows x switch on in addition to the sim log file a file named sim snap xxxx is created when the simulation is finished This file is actually a snapshot file containing the component status and parameter values at the time the simulation stopped 1 6 1 4 Log File Format The following brief example shows the format of a sim log file 1 switch3 Name 2 switch2 Cells in VBR Q to link22 3 switch2 Cells dropped in VBR Q to link22 2 3003 1 2 3003 2 2 3043 3 1 3277 switch3 link22 4 2 4095 3 34175 1 The lines at the head of the file starting with pound sign are a listing of all of the parameters that were marked for data logging when the simulator was running The number immediately following the is the ID number that will be used in the remainder of the file to identify the

The NIST ATM Network Simulator Operation and Programming

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