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1. 5 I Taylor B Adamson I Downard and J Macker AgentJ Enabling Java Ns 2 simulations for large scale distributed multimedia applications 2006 RR n 7075 24 U Herberg A Sample Tcl File set opt chan Channel WirelessChannel channel type set opt prop Propagation TwoRayGround radio propagation model set opt netif Phy WirelessPhy network interface type set opt mac Mac 802_11 MAC type set opt ifq Queue DropTail PriQueue interface queue type set opt 11 LL link layer type set opt ant Antenna OmniAntenna antenna model set opt x 1000 X dimension of the topography set opt y 1000 Y dimension of the topography set opt ifqlen 50 max packet in ifq set opt nn 5 number of nodes set opt lm true log movement set opt stop 30 simulation time set opt rp Agent J Routing Protocol LL set mindelay_ 50us LL set delay_ 25us LL set bandwidth O not used Agent Null set sport_ 0 Agent Null set dport_ 0 Queue DropTail PriQueue set Prefer_Routing_Protocols 1 unity gain omni directional antennas set up the antennas to be centered in the node and 1 5 meters above itAntenna OmniAntenna set X_ 0 Antenna OmniAntenna set Y_ 0 Antenna OmniAntenna set Z_ 1 5 Antenna OmniAntenna set Gt_ 1 0 Antenna OmniAntenna set Gr_ 1 0 Mac 802_11 set CWMin_ 15 Mac 802_11 set CWMax_ 1023 Mac 802_11 set ShortRetryLimit_ 7 Mac 802_11 set LongRetryLimit_ 4 Mac 802_11 set RTST2. e setNativeRouterPort This call will be forwarded to the AgentJRouter object to set the UDP port number it is listening to for control traffic Incoming packets that have a destination port equal to the port number stored in Agent JRouter will be treated as control traffic and forwarded to the Java routing pro tocol Other packets are treated as data packets and forwarded to the demultiplexer of the NS2 node e router All arguments of this command will be forwarded to the Agent JRouter and executed as commands on that object e drop target This sets the drop target of Agentj but also of AgentJRouter This is necessary in order to trace dropped packets in the trace file e log target This sets the log target of Agentj but also of AgentJRouter This is necessary in order to trace any events such as sent or received packets in the trace file In addition to the changes in the command function of Agentj a new function recv was added recv represents the Packet Entry as depicted in figure 3 Any packet that arrives on the RTR layer will be delivered to the recv method As the Agentj object is inserted as a routing agent in NS2 but the forwarding decision is taken in the Agent JRouter object this function just forwards the packet to the Agent JRouter object RR n 7075 20 U Herberg 6 2 2 AgentJRouter Class Agent JRouter is responsible for deciding how to process an incoming control or data packet as described i
3. Copyright c 2008 All rights reserved include MyRouter h static class MyRouterInstantiator public TclClass public MyRouterInstantiator TclClass Agent AgentJRouter MyRouter TclObject create int argc const char const argv INRIA Integrating Java Support for Routing Protocols in NS2 29 return new MyRouter protean_olsrv2_router MyRouter MyRouter AgentJRouter PLOG PL_INFO MyRouter starting up n MyRouter MyRouter bool MyRouter ProcessCommands int argc const chart const argv if strcmp argv 0 reset do nothing for the moment return true return false void MyRouter receivePacket Packet p Handler handle PLOG PL_TRACE entering MyRouter receivePacket n struct hdr_cmn ch HDR_CMN p struct hdr_ip ih HDR_IP p nsaddr_t saddr ih gt src_ addr_ nsaddr_t daddr ih gt daddr PLOG PL_TRACE f MyRouter receivePacket at d Packet received from kd to hd port Ha forwards d n Scheduler instance clock agentjref_ gt addr saddr ih gt daddr ih gt dport ch gt num_forwards if ih gt dport routingProtocolPort_ ch gt ptype_ PT_AGENTJ set the packet type if ih gt dport routingProtocolPort_ kk saddr agent jref_ gt addr amp amp ch gt num_forwards 1 send on up to Agent ih sttl 1 PLOG PL_TRACE f MyRouter receivePacket is a control packet n
4. Scheduler instance clock Tcl amp tcl Tcl instance tcl evalf s ks kd agentjref_ gt getTclNodeName agent routingProtocolPort const charx tclResult tcl result Agent theAgent Agent Tcl0bject lookup tclResult if theAgent theAgent gt recv p 0 else Packet free p PLOG PL_TRACE MyRouter receivePacket theAgent is NULL n RR n 7075 30 U Herberg return else send packet back out interface PLOG PL_TRACE MyRouter is sending packet back out interface n check ttl if ih gt ttl_ 0 PLOG PL_TRACE MyRouter is dropping packet because of ttl n drop p DROP RTR TTL return check to see if its a udp packet or a broadcast packet if daddr nsaddr_t IP_BROADCAST amp amp ih gt dport 1 amp amp ch gt num_forwards 0 it s broadcast PLOG PL_TRACE f Sending broadcast packet n Scheduler instance clock Scheduler instance schedule target_ p 0 return else it has single destination find and send on way if ch gt num_forwards_ 0 ih gt saddr agentjref_ gt addr PLOG PL_TRACE f MyRouter getting nexthop for d n Scheduler instance clock ih gt daddr nsaddr_t nextHop getNextHop ih gt daddr if mextHop INVALID amp amp make sure we don t send it back up nextHop ch gt prev_hop_ ch gt num_forwards_ 0 PLOG PL_TRACE f MyRouter trying to
5. 7075 26 U Herberg Create the specified number of nodes opt nn and attach them the channel ns_ node config adhocRouting Sopt rp 11Type Sopt 11 macType Sopt mac ifqType opt ifq ifqLen opt ifqlen antType opt ant propInstance prop phyType opt netif channel chan topoInstance topo wiredRouting OFF agentTrace ON routerTrace ON macTrace ON movementTrace opt 1m now create nodes for set i 0 i lt opt mn incr i set node_ i ns_ node node_ i set ragent_ attach agentj my personal MyRoutingAgent node_ i set ragent_ agentj setRouterAgent Agent AgentJRouter ns_ at 0 0 node_ i set ragent_ agentj startRouting ns_ at 0 0 node_ i log movement node_ i random motion 0 ns_ initial_node_pos node_ i 20 ns_ at Sopt stop 00000001 puts NS EXITING ns_ halt Node Initial Positions node_ 0 set X_ 242 955469762 node_ 0 set Y_ 987 493442159 node_ 0 set Z_ 0 000000000 node_ 1 set 225 147406876 Snode 1 set 274 091839102 Snode 1 set 0 000000000 node_ 2 set 170 330849182 node_ 2 set 525 001140426 node_ 2 set 0 000000000 Snode 3 set 573 262627815 node_ 3 set Y_ 626 589897443 node_ 3 set Z_ 0 000000000 Ka pai NI ER PG ER pa INRIA Integrating Java Support for Routing Protocols in NS2 27 Snode 4 set X_ 969 778307544 node_ 4 set Y_ 310 299546663 node_ 4 set Z_ 0 0
6. Agentj and AgentJRouter Class In the C part of AgentJ a new class called Agent JRouter has been added and a reference is kept from the Agentj class The reason for extracting the routing handling into a new class rather than just adding the functionality to the Agentj class is to separate routing tasks from agents that are only used as INRIA Integrating Java Support for Routing Protocols in NS2 19 application agents In addition it allows the user to subclass the Agent JRouter in order to modify its behavior 6 2 1 Modifications of the Agentj C Class The Agentj C class is the main class of the AgentJ package which serves as the NS2 agent that can be attached to a node In order to add the routing functionalities that class has been changed as described in this section and so to allow AgentJ to be used as both application agent protocol and routing protocol agent Every C object in NS2 that can be accessed by Tcl provides a method called command This method presents a general command interface which allows to send any user defined commands from NS2 to the routing agent It receives a string array of commands and executes them The following Tcl commands have been added in the command function of the Agentj C class e setNativeAgentRouter This Tcl command creates a new instance of the given C class name which must be AgentJRouter or a subclass thereof The command then adds a reference to the Agent JRouter object
7. Architecture of AgentJ 15 5 Overview of Routing in NS2 15 6 Architectural Modifications of AgentJ for Support of Routing 17 DU Dele me ROR Pa a oe BE ER Bes 17 6 7 C Agent and AgentJRouter Class 18 6 2 1 Modifications of the Agent C Class 19 6 2 2 AgentJRouter Class 20 6 3 Changes in the Java AgentJRouter and AgentJAgent 20 6 3 1 AgentJRouter Interface 20 6 3 2 New Tcl Command in AgentJAgent 20 6 4 Modifications of NS21 21 7 Summary 22 A Sample Tcl File 24 B MyRouter Samples 28 B 1 MykRouter hl 28 B 2 MyRouter cppl ss 4 4 ca 6 sare De ne PPS neasa 28 INRIA A Centre de recherche INRIA Paris Rocquencourt Domaine de Voluceau Rocquencourt BP 105 78153 Le Chesnay Cedex France Centre de recherche INRIA Bordeaux Sud Ouest Domaine Universitaire 351 cours de la Lib ration 33405 Talence Cedex Centre de recherche INRIA Grenoble Rh ne Alpes 655 avenue de l Europe 38334 Montbonnot Saint Ismier Centre de recherche INRIA Lille Nord Europe Parc Scientifique de la Haute Borne 40 avenue Halley 59650 Villeneuve d Ascq Centre de recherche INRIA Nancy Grand Est LORIA Technop le de Nancy Brabois Campus scientifique 615 rue du Jardin Botanique BP 101 54602 Villers l s Nancy Cedex Centre de recherche INRIA Rennes Breta
8. first letter s from RTR layer N1 RTR at time 0 004 seconds after simulations start t 0 004 The packet originates from the node with the ID 39 Hs 39 is destined to port 50000 using the broadcast address Id 1 50000 and is of type AGENTJ It AGENTJ For a detailed description of the trace file format refer to the NS2 manual 2 Sometimes it is desirable to display information from the payload of such a packet This section describes how to add more detailed packet traces Note that this advanced modification requires a recompilation of NS2 Step 1 If desired the displayed name of a control packet in the trace file can be changed from the default value AGENTJ to any other name The file NS2 34 common packet h has to be changed as described in the following name_ PT_DSR DSR name_ PT_AODV AODV change AGENTJ to the desired name name_ PT_AGENTJ AGENTJ Step 2 2Refer to the NS2 manual for more details about tracing RR n 7075 12 U Herberg For adding a detailed trace of the control traffic packet the file NS2 34 trace cmu trace cc has to be modified void CMUTrace format Packet p const char why hdr_cmn ch HDR_CMN p int offset 0 switch ch gt ptype case PT_AODV format_aodv p offset break case PT_TORA format_tora p offset break Specifically a call to a format method has to be added case PT_AGENTJ format_myrouting p offset bre
9. forward it to d n Scheduler instance clock nextHop forward p nextHop return if nextHop INVALID PLOG PL_TRACE f MyRouter dropping packet because nextHop is INVALID n Scheduler instance clock else if nextHop ch gt prev_hop_ PLOG PL_TRACE MyRouter dropping packet because nextHop last hop which is d n ih gt daddr 0 else PLOG PL_TRACE MyRouter dropping packet because ch gt num_forwards 0 n drop p DROP_RTR_NO_ROUTE end else of isbroadcast is INRIA Integrating Java Support for Routing Protocols in NS2 RR n 7075 31 32 U Herberg Contents 3 LI Availability o RAGES EEE data aie 3 1 95 Notation e a amp Sok a We LL DAA ee a ee RENE 3 1 35 O thnel og evel a ued he a a a ke BA a A HH E a arte 3 I Running a Java Routing Protocol in NS2 using Agent J 5 2 AgentJ Overview 5 7 Addition of a Helper Class as Single Point of Entry for N52 7 3 2 Installation of the Java Classes 2 2 ao 9 3 3 Scenario Tel Script co cc ee ke age ee RER AR DEA aE ES 9 3 4 Change Addressing Scheme 10 3 5 Running the NS2 Simulation 10 4 Advanced Features 11 4 1 Tracing of Routing Control Packets 11 4 2 Changing the Behavior of the Router when Data Packets arrive 12 4 3 Limitations of AgentJ with Routing Functionalities 14 IT Routing
10. int argc const char const argv F endif _MYROUTER e MyRouter cpp include MyRouter h static class MyRouterInstantiator public TclClass public MyRouterInstantiator TclClass Agent AgentJRouter MyRouter 3 TclObject create int argc const char const argv return new MyRouter my router RR n 7075 14 U Herberg void MyRouter receivePacket Packet p Handler handle treat an incoming packet Step 2 The new class has to be added to the Makefile in of NS2 The rule can be added to the OBJ_AGENTJ_CPP makefile variable OBJ AGENTJ CPP AGENTJ_UTILS LinkedList o are JAVM TimerWrapper o JAVM JAVMTimer o S AGENTJ C SRC MyRouter o NS2 has to be recompiled after these modifications i e configure and make Step 3 In the scenario Tcl file AgentJ has to be told to use the subclass instead of the default AgentJRouter At the point in the Tcl file where the nodes are created and the Java agent will be attached the following line must be changed from node_ i set ragent_ agentj setRouterAgent Agent Agent JRouter to node_ i set ragent_ agentj setRouterAgent Agent Agent JRouter MyRouter 4 3 Limitations of AgentJ with Routing Functionalities At the time this document is written AgentJ only supports routing protocols which send control traffic over UDP TCP protocols such as BGP are not currently supported In addition it is currently not p
11. is a unicast packet the getNextHop method on the Java routing protocol is invoked to determine the next hop address for the destination of the packet If no next hop RR n 7075 18 U Herberg if found the packet is dropped by NS2 This is reflected in the NS2 tracefile as usual DROP Otherwise the destination is set to the returned next hop and the packet is handed to the LL layer Receive pkt Forward to at Agentj AgentJRouter Set next hop to IP_BROADCAST Call getNextHop on Java Routing Protocol Forward to Link Layer Set next hop to return value a Outgoing packet Receive pkt Forward to at Agentj AgentJRouter Forward to de No IS multiplexer on node Yes control Forward to socket in Java routing protocol traffic b Incoming packet Drop packet Figure 5 Decisions to take on the RTR layer Incoming packets are received by the Agentj object and then handed off to the Agent JRouter object as illustrated in figure 5 b If the packet is a control packet it will be handed to a socket on the Java routing protocol Otherwise the packet will be treated by the demultiplexer as described in section 5 Note that this represents the default behavior of AgentJRouter for incom ing and outgoing packets and may be overridden by the user as described in section 4 2 In the following subsections the detailed description of the different new objects from figure 4 is presented 6 2 C
12. packet is handed to the MAC layer then to the LL layer which hands it to the Packet Entry The demultiplexer has to decide whether this node is the destination of the packet If yes then the packet has to be handed to the application agent s Otherwise the packet is to be forwarded along the path to the destination and therefore is to be handed down to the RTR layer From there the packet will proceed as depicted in figurePB a and described previously RR n 7075 16 U Herberg Packet entry targ o l po x downtarget_ downtarget_ y MAC downtarget_ Netlf El channel_ Vo a Outgoing packet address port tad Packet demux entry RTR IfQ uptarget_ uptarget_ Netlf g A uptarget_ 4 b Incoming packet Figure 3 Layer architecture of a mobile node in NS2 for outgoing and incoming packets INRIA Integrating Java Support for Routing Protocols in NS2 17 6 Architectural Modifications of AgentJ for Sup port of Routing Protocols This section details what architectural changes have been made to in order to support running a Java routing protocol within NS2 6 1 Overview Figure 4 depicts the general architecture of the modified version of AgentJ On the lefthand side the NS2 and AgentJ internal objects Agent j and Agent JRouter are depicted These are implemented in C and use some OTcl code Sec tion 6 2 details the changes t
13. properly installed as described in the AgentJ manual 4 Note that for C implementations each new protocol implementation re quires NS2 modifications and a subsequent recompilation of NS2 However once AgentJ has been installed no recompilation of NS2 is necessary any more even when a new routing protocol implementation in Java is created and added In the following step by step instruction a demonstrative example routing pro tocol called MyRoutingProtocol is used to show the interaction between the protocol implementation AgentJ and NS2 3 1 Addition of a Helper Class as Single Point of Entry for NS2 As the single point of entry for NS2 to the routing protocol implementation a new helper class in Java needs to be created This helper class as depicted on the right side of figure p serves the same purpose as the main method of Java applications to allow NS2 AgentJ to execute the routing protocol implementation In addition the helper class provides an interface with two methods called by NS2 for the purpose of routing All other calls such as for sending and receiving control packets or setting timers are directly hooked into NS2 by virtue of bytecode rewriting and do not need any changes in the Java routing protocol implementation or in the helper class etNextHop Helper Class Agent g object entry point getRoutingPort extends Java routing AgentJAgent i protocol implementatio
14. 00000000 Node Movements ns_ at 0 0 Snode 0 setdest 243 402233718 887 494440154 3 371378059 ns_ at 29 6 node_ 0 setdest 202 222490121 796 366899217 3 442128171 ns_ at 0 0 node_ 1 setdest 261 037139025 180 754134361 4 413709080 ns_ at 23 4 node_ 1 setdest 248 041392110 279 906091286 4 413709080 ns_ at 0 0 node_ 2 setdest 251 526166181 466 628882483 7 977160606 ns_ at 13 7 node_ 2 setdest 151 528816489 467 356930946 7 977160606 ns_ at 0 0 node_ 3 setdest 525 639788716 538 657734976 7 366205977 ns_ at 13 5 node_ 3 setdest 427 546365593 558 091734566 4 646736198 ns_ at 0 0 node_ 4 setdest 999 999900000 311 899405137 2 131682882 ns_ at 14 1 node_ 4 setdest 930 361317453 315 585892139 2 131682882 puts Starting Simulation flush stdout ns_ run RR n 7075 28 U Herberg B MyRouter Samples B 1 MyRouter h ifndef _MYROUTER define _MYROUTER MyRouter h AgentJ Created by Ulrich Herberg on 27 11 2008 Copyright c 2008 All rights reserved include AgentJRouter h class MyRouter public AgentJRouter public MyRouter MyRouter virtual void receivePacket Packet p Handler handle virtual bool ProcessCommands int argc const char const argv void notifyRoutingProtocol bool success nsaddr_t address end class endif _MYROUTER B 2 MyRouter cpp MyRouter cpp AgentJ Created by Ulrich on 27 10 2008
15. The parameter my personal MyRoutingAgent must be changed to the complete name of the Java class name of the helper class that has been added as described in section 3 1 RR n 7075 10 U Herberg 3 4 Change Addressing Scheme The AGENTJ conf agentj properties file has to be modified as follows If you want to change to IPv4 or IPv6 addressing you have to add a line java net preferIPv4Stack true or java net preferIPv6Stack true If the Java routing protocol uses only multicast addressing and no unicast addresses nothing needs to be changed In particular in order to run the Agent examples in AGENTJ examples udp the file should not be modified However in order to use unicast addresses in the routing protocol the line that corresponds to the preferred address family IPv4 or IPv6 needs to be uncommented Note that these modifications are to the config files read at execution time and so do not require recompilation of AgentJ nor NS2 nor the routing protocol implementation 3 5 Running the NS2 Simulation The NS2 simulation can be started by launching the Tcl file ns my sample script tcl The most common error at this point is that a java lang ClassNotFoundException is thrown In that case make sure that the location of the Java classes of the routing protocol have been correctly included in the AGENTJ_CLASSPATH envi ronmental variable as described in section 3 2 INRIA Integrating Java Support for Routing Pr
16. VAINRIA INSTITUT NATIONAL DE RECHERCHE EN INFORMATIQUE ET EN AUTOMATIQUE Integrating Java Support for Routing Protocols in NS2 Ulrich Herberg N 7075 October 2009 apport de recherche ISRN INRIA RR 7075 FR ENG ISSN 0249 6399 INSTITUT NATIONAL ET EN AUTOMATIQUE DE RECHERCHE centre de recherche EN INFORMATIQUE VAINRIA PARIS ROCQUENCOURT Integrating Java Support for Routing Protocols in NS2 Ulrich Herberg Theme COM Syst mes communicants Equipe Projet Hipercom Rapport de recherche n 7075 October 2009 32 pages Abstract This document presents a modification of the existing tool AgentJ which allows for running a Java routing protocol within the network simulator NS2 Key words Java routing protocol AgentJ NS2 simulation tool Centre de recherche INRIA Paris Rocquencourt Domaine de Voluceau Rocquencourt BP 105 78153 Le Chesnay Cedex T l phone 33 1 39 63 55 11 T l copie 33 1 39 63 53 30 Integrating Java Support for Routing Protocols in NS2 R sum Ce document pr sente une modification de l outil AgentJ qui per met d ex cuter des protocols de routage en Java dans le simulateur des r seaux NS2 Mots cl s Java protocol de routage AgentJ NS2 simulation tool Integrating Java Support for Routing Protocols in NS2 3 1 Introduction When designing a new routing protocol an important step in its development is often to implement and experime
17. ackets will be forwarded to the listening socket in the Java routing protocol This socket is the INRIA Integrating Java Support for Routing Protocols in NS2 13 one that is bound to the port number given by the method getRoutingPort in the helper class Data packets are delivered to the application layer of the NS2 node Outgoing packets will be separated into unicast and broadcast traffic For unicast packets AgentJ calls getNextHop of the Java routing protocol to get a valid next hop for the given destination Section 5 and give more details on this This particular behavior is implemented in the method receivePacket of the C file SAGENTJ core src main c agentj AgentJRouter cpp This class can be subclassed to change the above mentioned default behavior for incoming and outgoing packets The necessary steps to subclass the Agent JRouter class are presented in the following In this example the subclass will be called MyRouter Step 1 The new files MyRouter h and MyRouter cpp have to be created in the directory AGENTJ core src main c agentj These files should at least contain the following fields and methods a complete example of these files can be found in appendix B e MyRouter h ifndef _MYROUTER define _MYROUTER include Agent JRouter h class MyRouter public AgentJRouter public MyRouter AgentJRouter MyRouter void receivePacket Packet p Handler handle bool ProcessCommands
18. ak Next a method format_myrouting Packet int has to be included in cmu trace cc that formats the output string in the trace file for the control packet This method will be similar to the other format methods such as format_aodv or format_tora For more information about writing a CMU trace format method refer to the NS2 manual 2 In principle it would also be possible to write a callback handler to the Java routing protocol implementation which returns a string that will be output to the trace file This is not part of the current version of AgentJ but could be added at a later point of time NS2 has to be recompiled after these modifications i e configure and make The following NS2 trace file line represent a typical exemplary output after the before mentioned modifications s t 0 004000000 Hs 39 Hd 2 Ni 39 Nx 1216 36 Ny 594 63 Nz 0 00 Ne 1 0 N1 RTR Nw Ma O Md O Ms O Mt O Is 39 9999 Id 1 50000 It AGENTJ Il 25 If O Ii O Iv 254 P olsrv2 Pn 1 Ps 7996 Pt HELLO Po 1 Ph 1 Pms 41054 All parameters in that line that have a prefix P are created by the for mating function that has been defined by the user 4 2 Changing the Behavior of the Router when Data Pack ets arrive AgentJ provides a certain default behavior whenever a packet arrives at the routing layer If it is an incoming packet from the MAC layer AgentJ will check whether it is a control packet or a data packet Control p
19. ent is running on between 0 and 65535 AgentJRouter will decide whether a packet is a data or control packet based on the port returned by this method 6 3 2 New Tcl Command in AgentJAgent There is one new Tcl command that the AgentJAgent supports e setRouterAgent This command needs one argument which is the name of the C class that will be the Agent JRouter e g Agent Agent JRouter INRIA Integrating Java Support for Routing Protocols in NS2 21 6 4 Modifications of NS2 A new routing protocol called AgentJ has been added to the list of routing protocols in NS2 34 tcl lib ns lib tcl in NS2 The following code added to ns lib tcl will be called whenever a new node is created Simulator instproc create agentj agent node set ragent new Agent Agentj self attach agent node ragent self at 0 0 ragent startup node set ragent_ ragent return ragent A new Agentj object is instantiated and attached to the node This agent is told to initialize itself and then attached as a routing agent of the node RR n 7075 22 U Herberg 7 Summary This document describes how to run Java routing protocols within the network simulator NS2 The preexisting tool AgentJ allows for using Java agents on an NS2 node but was not capable of instantiating routing agents A modification of AgentJ is presented in this document that enables the usage of Java routing protocols in NS2 without modification of the implemented Java
20. entJ uses the Java Native Interface JNI 3 in order to connect the Java code to the C code of NS2 That allows NS2 to access of all Java classes objects and methods A callback system between the C and OTcl side of NS2 and Java is set up by AgentJ for interaction between NS2 and the Java implementation Ns2 Agentj node object Helper Class entry point Java program Timer calls Control packets OTel C Java Figure 1 Architecture of an AgentJ agent attached to an NS2 node RR n 7075 6 U Herberg Figure 1 depicts the basic architecture of a Java application running on a single NS2 node over AgentJ The parts on the left side are implemented in C and OTcl This includes the NS2 node and the AgentJ C agent that is attached to that node For launching the Java application and sending commands to it from NS2 it needs a single entry point similar to a main method Thus a helper class has to be provided by the user which serves as this entry point refer to sections 3 and 6 for more details and which is the only additional component that the user needs to implement to glue the Java implementation to NS2 INRIA Integrating Java Support for Routing Protocols in NS2 7 3 Basic Integration This section describes the integration of a routing protocol written in Java into NS2 using the AgentJ library as extended as described in this document It assumes that AgentJ is
21. form a mapping between these two address types An exemplary mapping limited to node IDs smaller than 256 would be InetAddress getByName 0 0 0 destination In a future version of AgentJ the mapping could be done within the AgentJ code e public boolean command String command String args The method command evaluates the given command and its argu ments The minimal prerequisite of this function is that it allows to start the routing protocol i e serves as the single point of entry In the before mentioned example calling the command startRouting would start the Java routing protocol Optionally any other command can be added in the command method such as for outputting the routing table as in the following example public boolean command String command String args if command equals startRouting a method needs to be added here to start the routing protocol return true else if command equals print_rtable code needs to be added here to output routing table return true return false lIn NS2 every node has a unique identifier the NS2 node ID Per default this ID is an unsigned integer including 0 INRIA Integrating Java Support for Routing Protocols in NS2 9 3 2 Installation of the Java Classes In order to run the Java routing protocol AgentJ has to find the corresponding class files The location of the Java classes of the routing protocol must be added to an e
22. gne Atlantique IRISA Campus universitaire de Beaulieu 35042 Rennes Cedex Centre de recherche INRIA Saclay le de France Parc Orsay Universit ZAC des Vignes 4 rue Jacques Monod 91893 Orsay Cedex Centre de recherche INRIA Sophia Antipolis M diterran e 2004 route des Lucioles BP 93 06902 Sophia Antipolis Cedex Editeur INRIA Domaine de Voluceau Rocquencourt BP 105 78153 Le Chesnay Cedex France http www inria fr ISSN 0249 6399
23. hreshold_ 2000 Mac 802_11 set SlotTime_ 0 000020 20us Mac 802 11 set SIFS_ 0 000010 10us Mac 802_11 set PreambleLength_ 144 144 bit Mac 802 11 set PLCPHeaderLength_ 48 48 bits Mac 802_11 set PLCPDataRate_ 1 0e6 1Mbps Mac 802 11 set dataRate_ 11 0e6 11Mbps Mac 802_11 set basicRate_ 1 0e6 1Mbps Phy WirelessPhy set CPThresh_ 10 0 Phy WirelessPhy set CSThresh_ 1 559e 11 Phy WirelessPhy set RXThresh_ 3 652e 10 250 m Phy WirelessPhy set Rb_ 2 1e6 INRIA Integrating Java Support for Routing Protocols in NS2 25 Phy WirelessPhy set Pt_ 0 2818 Phy WirelessPhy set freq 2 4e 9 Phy WirelessPhy set L_ 1 0 proc getopt argc argv global opt lappend optlist cp nn seed stop tr x y for set i 0 i lt argc incr i set arg lindex argv i if string range arg 0 0 continue set name string range arg 1 end set opt name lindex argv expr i 1 proc create god nodes global ns_ god_ tracefd set god_ new God god_ num_nodes nodes getopt Sargc argv Initialize Global Variables set ns_ new Simulator set chan new opt chan set prop new Sopt prop set topo new Topography set nf open MyNamFile opt nn nam w set f open MyTraceFile opt nn tr w ns_ namtrace all wireless nf opt x opt y ns_ trace all f ns_ use newtrace topo load flatgrid opt x opt y prop topography topo Create God create god opt nn RR n
24. n implements AgentJRouter AgentJRouter object Timer calls Control packets OTel C Java Figure 2 The helper class on the right side serves as single point of entry from NS2 to the Java routing protocol implementation The Java helper class in the following example called MyRoutingAgent needs to extend from agentj AgentJAgent and also has to implement the agentj AgentJRouter interface An example class definition looks as the fol lowing RR n 7075 8 U Herberg public class MyRoutingAgent extends AgentJAgent implements AgentJRouter By implementing the Agent JRouter interface the three methods getRoutingPort O getNextHop int and command String String must also be provided by MyRoutingAgent e public int getRoutingPort This method should return the UDP port number that the Java routing agent is running on This can be any arbitrary number between 0 and 65535 NS2 will send control traffic packets to that port and the Java routing protocol should receive control traffic from that port e public int getNextHop int destination This method will be called from NS2 whenever a unicast data packet arrives at the node The Java method should return the next hop for the given destination as NS2 node ID or 1 if no such destination has been found in the routing table If the Java routing protocol implementation uses real IP Addresses i e java net InetAddress and not only NS2 node ID this method must per
25. n section 6 1 Specifically it will acquire the next hop for data packets by calling the appropriate function on the Java routing protocol The class has the following main methods e receivePacket Packet p Handler handle Whenever the Agentj class receives an incoming packet at recv it will call receivePacket on the AgentJRouter This method will treat packets as explained in section 6 1 e nsaddr_t getNextHop nsaddr_t destination This is called from receivePacket for getting the address of the next hop from the Java routing agent This method will simply invoke the getNextHop int method on the Java side and return the result e virtual void forward Packet p nsaddr_t nexthop After having received the nexthop for a data packet the packet must be forwarded to that node 6 3 Changes in the Java AgentJRouter and AgentJ Agent A new Java interface called Agent JRouter has been added and the Agent JAgent Java class has been modified to accept some more Tcl commands 6 3 1 AgentJRouter Interface This interface is to be implemented by the Java routing protocol and mandates that two methods be provided e int getNextHop int destination Called from the native side whenever a unicast data packet arrives at the AgentJRouter class the Java routing protocol should return a valid nexthop for the given destination or 1 if no valid route is found e int getRoutingPort Returns the UDP port number the routing ag
26. nt with it in a network simulator such as NS2 I While network simulators have their limits especially in terms of the fidelity of the lower layers and for wireless network interfaces in the fidelity of the propagation model used for representing the behavior of physical radio waves their use is often allowing to understand high level and algorithmic properties of a given routing protocol In particular in the area of Mobile Ad Hoc Networks MANETs simulations are easier to perform than building a large test network of nodes simulate mobility and guarantee reproducibility of predefined scenarios Using NS2 as network simulator requires the routing protocol to be implemented in C However there is a tool called AgentJ which allows for running Java applications within NS2 In particular AgentJ enables to run unmodified and preexisting Java appli cations that work on top of an operating system such as Linux or Mac OS also on NS2 AgentJ rewrites all calls related to socket operations I O and thread handling such that the Java application as is interoperates with NS2 AgentJ was originally developed only for application layer agents and not for routing agents In this document the necessary changes to the AgentJ architecture are described that enable to use Java routing protocols within NS2 as well as detailed instructions on how to instantiate and run in NS2 a new routing protocol implemented in Java 1 1 Availability The m
27. nvironmental variable called AGENTJ_CLASSPATH In Linux this is done by running export AGENTJ_CLASSPATH path to classfiles where path to classfiles needs to be replaced by the location of the Java classes This line should be added to the HOME bashrc file if using the bourne shell in order to execute it every time the user logs on 3 3 Scenario Tcl Script The scenario Tcl file that is called by NS2 must tell AgentJ which Java routing protocol to use A complete example Tcl script can be found in appendix A Note in particular the following lines specific to using a routing protocol with AgentJ that represent a minimum set of parameters that have to be defined in the Tcl script 1 Define the routing agent set opt rp Agent J Routing Protocol ns_ node config adhocRouting opt rp The routing agent is set to AgentJ whatever Java routing protocol is used This avoids adding a new routing protocol in NS2 34 tcl lib ns lib tcl for every new Java routing protocol implementation 2 Attach the Java agent to a node set node ns_ node create a new node The following line must be changed to reflect the name of the Java class node set ragent_ attach agentj my personal MyRoutingAgent The following lines needs only be changed for advanced settings refer to section 4 node set ragent_ agentj setRouterAgent Agent Agent JRouter ns_ at 0 0 node set ragent_ agentj startRouting
28. o is also interested in the background and the architecture of routing functionalities in AgentJ should continue and also read part INRIA Integrating Java Support for Routing Protocols in NS2 5 Part I Running a Java Routing Protocol in NS2 using AgentJ This part of the document describes how to use a Java routing protocol im plementation with NS2 by using AgentJ It details all necessary steps for inte grating the implementation plus some optional more advanced features The background and the architecture of routing functionalities in AgentJ are detailed in part 2 AgentJ Overview AgentJ 5 is a tool primarily developed by Ian Taylor for the Naval Research Laboratory NRL The AgentJ tool serves the purpose of running Java applica tions as application agents on the discrete event simulator NS2 I NS2 with out AgentJ otherwise only supports C implementations AgentJ marshals the Java commands to C and rewrites Java application system calls e g for network packets I O and time events to use the equivalent system calls of NS2 Thread handling is rewritten completely as NS2 is a single threaded event driven simulator while Java applications often are multithreaded For a detailed description of the rewriting mechanism of AgentJ refer to 4 All this means that an existing Java application does not need to be changed at all for running on N82 adhering to the Java slogan Write once run anywhere Ag
29. o the C objects On the righthand side the Java helper class that connects the Java routing protocol with AgentJ is displayed This helper class is a subclass of Agent JAgent and implements the Java interface Agent JRouter Section 5 3 details the changes to the Java objects In the original AgentJ code the Agentj C agent was attached as an application agent to the NS2 node In contrast in the modified version of AgentJ with routing functionalities the Agentj C agent can now also be attached to an NS2 node as a routing agent i e it represents the RTR layer The Agent JRouter C class treats packets that arrive at the RTR layer according to the procedure illustrated in figure 5 Refer to section 6 2 Refer to section 6 3 N N 7 getNextHop Helper Class Ng Agent entry point node object getRoutingPort extends sneer AgentJAgent P implementation implements AgentJRouter AgentJRouter object ja Timer calls Control packets OTel C Java Figure 4 Modified architecture with an AgentJRouter interface Whenever an outgoing data or control packet arrives at the RTR layer i e the Agentj object it is forwarded to the Agent JRouter object as illustrated in figure Ba Then it has to be determined whether the packet is unicast or broadcast If the packet is a broadcast packet the destination is set to the IP BROADCAST address and handed to the LL layer If the packet
30. odifications to AgentJ that are described in this document have been integrated into the core distribution of AgentJ It is therefore available at http downloads pf itd nrl navy mil agentj nightly_snapshots agent j svnsnap tgz Remark At the time this document has been written only the nightly snap shot reflects a recent distribution of AgentJ The release version is four years old 1 2 Notation Throughout the document there are two different notations of AgentJ AgentJ and Agentj in Courier font The first notation with capital J is used to describe the whole tool The latter is used for some of the C files that are contained in the AgentJ project 1 3 Outline This document is composed of two parts Part details how to instantiate a Java routing protocol in AgentJ It begins with an overview of AgentJ in section 2 Section 3 contains a step by step in struction for integrating a Java routing protocol in NS2 using AgentJ Section 4 presents some advanced use cases Part IT details the modified architecture of AgentJ that allows for running routing protocols in NS2 Section 5 overviews routing in NS2 In section 6 RR n 7075 4 U Herberg the changes of the AgentJ codebase and architecture are detailed Section concludes the document Note e A reader who only wants to know how to run an existing Java routing protocol implementation in NS2 should read part e A reader wh
31. ossible to run a simulation with nodes using IPv4 and IPv6 addresses at the same time All nodes have to use the same address family INRIA Integrating Java Support for Routing Protocols in NS2 15 Part II Routing Architecture of Agent J This part presents the background and architecture of routing functionalities in AgentJ This part does not describe how to use a Java routing protocol implementation with NS2 by using AgentJ This was described in part 5 Overview of Routing in NS2 This section presents a brief overview of the routing functionality in NS2 Fig ure B depicts the architecture of routing on an NS2 node and the flow of outgoing and incoming packets In NS2 each mobile node has attached several layers such as the routing layer RTR the link layer LL the interface queue IfQ the MAC layer MAC and a network interface NetIf When a packet is ready to be sent as illustrated in figure 3 a p it arrives at what is called Packet Entry in the figure From there it is handed to the RTR layer which in turn has to consider whether it can forward the packet If the RTR layer finds a valid nexthop for the packet it hands it down to the LL layer from where the packet will progress further down the stack towards the channel Otherwise it drops the packet For a more detailed insight into what happens at these layers refer to the NS2 manual 2 Figure B b depicts the process for an incoming packet from the channel The
32. otocols in NS2 11 4 Advanced Features Section 3 described the basic and necessary steps to interface a Java routing protocol in AgentJ This section presents some more advanced features of using Java routing protocols in AgentJ Section explains the steps to include more detailed tracing of control packets Using this modification allows to output details about the payload of a control packet in NS2 trace files Section 4 2 details how to change the specific behavior of the routing pro tocol when a data packet arrives at an NS2 node The default behavior of looking up unicast addresses for the destination of a data packet can be modi fied For example for a reactive routing protocol a route discovery phase could be initiated 4 1 Tracing of Routing Control Packets Every control packet that is sent from the Java routing agent will appear in the NS2 trace fild just as any control packet sent by a native C implementation of a routing protocol Per default all control traffic packets sent by the Java agent are marked as AGENTJ packets The following NS2 trace file line represent a typical exemplary output note that the line breaks in the following trace entry do not occur in the NS2 trace file s t 0 004000000 Hs 39 Hd 2 Ni 39 Nx 1216 36 Ny 594 63 Nz 0 00 Ne 1 0 N1 RTR Nw Ma O Md O Ms O Mt O Is 39 9999 Id 1 50000 It AGENTJ Il 25 If O Ii O Iv 254 Essentially the line means that a packet has been sent
33. routing pro tocol adhering to the Java slogan write once run everywhere In addition once AgentJ has been installed NS2 does not need to be recompiled when a new Java routing protocol implementation is added All parameters that need to be changed can be set in configuration files or in environmental variables read at execution time AgentJ with the proposed routing extension keeps full compatibility with NS2 meaning that it allows for output of all events in the usual NS2 trace files Consequently all evaluation tools used for parsing NS2 trace files can be used without modification The routing functionalities have been included in the current distribution of AgentJ that is available for download at http downloads pf itd nrl navy mil agentj nightly_snapshots agent j svnsnap tgz Acknowledgments Ian Taylor was very helpful when developing the routing extension to Agent J He spent a lot of time and effort on AgentJ a tool which the author uses intensively for his current research INRIA Integrating Java Support for Routing Protocols in NS2 23 References 1 K Fall and K Varadhan The network simulator NS 2 http www isi edu nsnam ns 2 K Fall and K Varadhan The ns manual formerly ns notes and documen tation 3 S Liang Java Native Interface Programmer s Guide and Specification Prentice Hall PTR 1999 4 I Taylor AgentJ Java network simulations ins NS 2 An installation and user manual
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