Home

Inverse multiplexing of digital data

1. AT LEAST P Rx LINKS READY ACTIVATE ALL READY LINKS AND START SENDING ATM CELLS OVER THEM FIG 13b FIG 13a neus FIG 14 U S Patent Mar 20 2001 Sheet 11 of 14 US 6 205 142 B1 FIG 15 US 6 205 142 B1 Sheet 12 of 14 Mar 20 2001 U S Patent 9L 91513 SMNITS3HLONV N3 LIVd 153 H3JAO AHL AO LNO AYOW HO H3AO 153 AWVS 1 153 Ne3 LIvd XL 3AVS ONION3S 91313 1531 XH OLNO 1S31 XL 1531 AdOO 1591 MAN 3AISO3H 1 NH3 LLVd 1991 LINO AWIL 1531 14 15 NH3llVvd 1531 1 GNAS 91313 1531 H3AO 1531 OL YNI 3LVOIQNI 1531 ONIGNAS QNVININOO N3 LLVd 1531 ANAS XH XL8 XWH XL V GNA U S Patent Mar 20 2001 Sheet 13 of 14 US 6 205 142 B1 FIG 18 US 6 205 142 B1 Sheet 14 of 14 Mar 20 2001 U S Patent TIME SICP SICP SICP ICP SICP D D ICP 5 ICP ICP 6 ICP 7 FIG 19 US 6 205 142 B1 1 INVERSE MULTIPLEXING OF DIGITAL DATA This application claims benefit 10 0 8 provisional 60 024 023 filed Aug 26 1996 FIELD OF THE INVENTION The invention relates to new mechanism for sending ATM cells transparently over multiple slower transmission links In particular
2. 1739 SANIT 1139 30N3no3s 1139 SEZSA SEINA OL WLY U S Patent Mar 20 20010 Sheet 7 of 14 US 6 205 142 B1 E 6 7 8 9 13 14 15 16 17 20 UE MS E 50 51 UNUSED 52 53 CRC 10 FIG 10 US 6 205 142 B1 Sheet 8 of 14 Mar 20 2001 U S Patent VNI L 3NI1 AWVYS YNI LL 914 AWVYS VNI U S Patent Mar 20 20010 Sheet 9 of 14 US 6 205 142 B1 START START SENDING ICP CELLS OVER PROVISIONED LINKS INDICATE LINKS IN GROUP PROPOSE IMA ID AND FRAME LENGTH OVER ICP CELLS CHECK STATUS OF PROVISIONED INCOMING OUTGOING LINKS SEND GROUP ABORT SIGNAL OVER ICP CELLS START TIME OUT TO SUSPEND START UP STOP SENDING GROUP ABORT SIGNAL AT LEAST P DEFECTS REJECT LINKS WITH LINK DEFECTS CONTINUE PROCEDURE WITH GOOD LINKS CHECK IMA FRAME LENGTH AND ADJUST IF NECESSARY CHECK IMA ID OVER GOOD LINKS ENSURE PROPER LINK CONNECTIVITY AT LEAST P LINKS PROPERLY CONNECTED IN GROUP CHECK LDS FOR GOOD LINKS AT LEAST P Rx LINKS IN LDS FIG 13a U S Patent Mar 20 2001 Sheet 10 of 14 US 6 205 142 B1 SEND ICP CELLS WITH LDS BIT SET FOR Rx LINKS IN LDS LOOK FOR INCOMING ICP CELLS WITH LDs SET FOR ALL Tx LINKS AT LEAST P Tx LINKS IN LDS SEND READY SIGNAL ON ALL ACCEPTED LINKS
3. 17 The method of claim 16 wherein the stuff code further indicates that a stuff cell is one out of two stuff cells inserted in the respective frame 18 A method for use at a destination node of receiving inverse multiplexed digital data transmitted from a source node using a plurality of communication links comprising receiving from the source node one or more inverse multiplexing control cells including information iden 10 30 45 50 55 60 65 US 6 205 142 B1 13 tifying an order in which a series of ATM data cells that is segmented into a plurality of frames are to be transmitted over the plurality of communication links transmitting one or more inverse multiplexing control cells including information indicating that the destina tion node is ready to receive ATM data cells in the order receiving the series of ATM data cells transmitted from the source node in the order wherein each frame includes at least one inverse multiplexing control cell that contains cell stuff information 19 The method of claim 18 wherein the cell stuff information includes stuff code indicating the location of stuff cells inserted in a respective frame 20 The method of claim 19 wherein the stuff code further indicates that a stuff cell is one out of two stuff cells inserted in the respective frame 21 A method of inverse multiplexing digital data from a source node to a destination node over a connection includ ing
4. over a given period the bad link may have to be removed from the round robin A link reconfiguration also occurs when it takes too much time for one link to receive cells from the far end receiving node that 15 to say no cells within e g 32 milliseconds 10 15 20 25 30 35 40 45 50 55 60 65 8 Cell Sequence Number Range Because an ATM inverse multiplexer must absorb a differential delay between individual links of up to 32 milliseconds in one embodiment and because the system needs to deal with a maximum of 8 1 1 links it is necessary to have a sequence number whose modulo is large enough to accommodate such delay As a practical example the following parameters for E1 are considered full rates 2 048 Mbit s payload rates 30 32 2 048 Mbit s 1 92 Mbps ATM cell 53 bytes ATM cell period time 221 microseconds ATM cells 32 milliseconds 144 cells For a delay of up to 32 milliseconds on each link there is need to queue cells for at least the same length of time each link Therefore in this example this means that a delay of up to a period of 144 cells between two links is possible An ATM inverse multiplexer can handle a maximum of 8 T1 E1 links Therefore up to 1008 cells 144 7 cells must be queued at one time by one ATM inverse multiplexer This requires a sequence number modulo large enough to cover this scenario simple case in one embodiment is to use a 16 bit count that ha
5. ATM cell stream distributed in a round robin manner over multiple links such as T1 E1 links It must adjust up to 32 milliseconds of differential link delays between individual links in a case where T1 E1 links are used It must reconfigure multiple links in the event that a link has to be added deleted or is considered inadequate to provide service It must be defined for not only UNIs but also for PNNIs and BICIs It must be transparent to the devices handling the con vergence of ATM cells into the PDH signal It must be transparent to the devices dealing with ATM layer cells The present invention achieves all of the above require ments and solves the problems discussed earlier The inven tion relates to a new ATM inverse multiplexing scheme that makes use of a physical layer operation administration and maintenance OAM cell which has been properly defined This OAM cell is defined to contain valuable information to US 6 205 142 B1 5 allow proper operation of the ATM inverse multiplexing mechanism and also to provide opportunity for handling a link failure situation The newly defined OAM cell is called an AIM OAM cell or AIM Sequence Number SN cell and is mainly designed to carry a cell sequence number and a feedback link status field The sequence number in the SN cell is made available for the receiver end for recovering the initial cell stream from the incoming links The feedback link status is made available fo
6. data cells in the round robin order over the connection and 12 transmitting the series of ATM data cells to the destination node in the round robin order wherein each frame includes at least one inverse multiplexing control cell that contains cell stuff information 5 10 The method of claim 9 wherein the cell stuff infor mation includes stuff code indicating the location of stuff cells inserted in a respective frame 11 The method of claim 10 wherein the stuff code further indicates that a stuff cell is one out of two stuff cells inserted in the respective frame 12 A method of inverse multiplexing digital data to be transmitted from a source node to a destination node using a plurality of communication links comprising the steps of transmitting from the source node to the destination node one or more inverse multiplexing control cells includ ing information identifying a specific order in which a series of ATM data cells that is segmented into a plurality of frames are to be transmitted over the plurality of communication links transmitting from the destination node to the source node one or more inverse multiplexing control cells includ ing information indicating that the destination node is ready to receive ATM data cells in the specific order and transmitting from the source node to the destination node the series of ATM data cells in the specific order wherein each frame includes at least one inverse mul tiplexin
7. in the figure SICP indicate stuffing control cells The receiving node maintains synchronization for cases 1 2 and 3 The receiv ing node optionally maintain synchronization for cases 4 5 and 6 The receiving node optionally maintain synchroniza tion for case 7 if b gt 2 and when passing stuff indication over more than one of the previous ICP cells b is the number of invalid corrupted ICP cells before declaring the link OIF out of IMA frame What is claimed is 1 A method of inverse multiplexing digital data over a connection consisting of a plurality of transmission links said data containing a series of ATM data cells comprising steps of sending a series of inverse multiplexing control cells indicating a specific round robin order in which the series of ATM data cells are to be transmitted over the connection receiving from the plurality of transmission links a series of inverse multiplexing control cells whose receive ready field is set US 6 205 142 B1 11 sending each ATM data cell in said series of ATM data cells in said specific round robin order and further sending two consecutive inverse multiplexing control cells in a frame indicating cell stuffing 2 The method of claim 1 wherein the inverse multiplex ing control cells include stuff code indicating the location and sequence of stuff cells inserted in the frame 3 A method of inverse multiplexing digital data over a connection having a plural
8. low speed UNIs such as T1 and E1 September 1994 by Digital Link Corporation It proposes a bit pipe inverse multiplexing technique requiring the definition of a bonding bandwidth on demand like specification for N positive number T1 E1 inverse multi plexing It is not clear in the proposal how both ends of the links exchange information concerning the order of cells to be transferred from one end to another over multiple links The proposal mentions the existence and deployment of physical layer protocols that perform inverse multiplexing The inverse multiplexer which can be used in this proposal is presumably the one defined by Digital Link Corporation in their DL3800 051 Inverse Multiplexer Users Manual 1993 The inverse multiplexing protocol defined in the above user s manual relies on the definition of an extra bit taken from T1 E1 payload bits to configure the multiple links and adjust differential link delays This protocol introduces the need for extra processing of data between devices dealing with T1 E1 frames and cell delineation It also causes the ATM cells to no longer be byte aligned with the DS1 E1 frame This is a requirement by the ATM Forum UNI DS1 E1 Physical Layer specifications Changes like this would not be welcome by end users vendors and service providers who are already using and deploying ATM equip ment U S Pat No 5 608 733 Mar 4 1997 Vallee et al describes good ways of obviating th
9. node in an ATM communications system for inverse multiplexing digital data to be transmitted from a source node to a destination node using a plurality of communica tion links comprising a transmitting device for transmitting from the source node to the destination node one or more inverse multiplexing control cells including information iden tifying a specific order in which a series of ATM data cells that is segmented into a plurality of frames are to be transmitted over the plurality of communication links a receiving device for receiving at the source node trans mitted from the destination node one or more inverse multiplexing control cells including information indi cating that the destination node is ready to receive ATM data cells in the specific order and a data cell transmitting device for transmitting from the source node to the destination node the series of ATM data cells in the specific order wherein each frame includes at least one inverse multiplexing control cell that contains cell stuff information 46 The node of claim 45 wherein the cell stuff informa tion includes stuff code indicating the location of stuff cells inserted in a respective frame 47 The node of claim 46 wherein the stuff code further indicates that a stuff cell is one out of two stuff cells inserted in the respective frame 48 A node in an ATM communications system for receiv ing inverse multiplexed digital data transmitted from a source n
10. of two stuff cells inserted in the respective frame 42 A node in an ATM communications system for inverse multiplexing digital data to be transmitted from a source node to a destination node using a plurality of communica tion links comprising a transmitting device for transmitting from the source node to the destination node one or more inverse 5 15 20 25 45 50 55 60 65 16 multiplexing control cells including information iden tifying a specific order in which a series of ATM data cells that is segmented into a plurality of frames are to be transmitted over the plurality of communication links a transmitting device for transmitting from the destination node to the source node one or more inverse multi plexing control cells including information indicating that the destination node is ready to receive ATM data cells in the specific order and data cell transmitting device for transmitting from the source node to the destination node the series of ATM data cells in the specific order wherein each frame includes at least one inverse multiplexing control cell that contains cell stuff information 43 The node of claim 42 wherein the cell stuff informa tion includes stuff code indicating the location of stuff cells inserted in a respective frame 44 The node of claim 43 wherein the stuff code further indicates that a stuff cell is one out of two stuff cells inserted in the respective frame 45 A
11. send it over the multiple links by spreading cells over the available links and ensure that the initial cell stream can be retrieved at the far end Thus the AIMs preferably make the ATM traffic transparent to the ATM layer over multiple links which connect them As far as the ATM layer is concerned it should only see a pipe whose rate is now the sum of the multiple link rates It is assumed that each link is run in clear mode without the presence of intermediate ATM nodes processing ATM cells This means that there should be no cell discard by any intermediate transmission equipment Currently no ATM inverse multiplexing protocols have been proposed which can properly interwork existing ATM inverse multiplexers or other ATM products which are already available on the market and yet are flexible enough to fit into the current standard ATM specifications Two proposals for an ATM inverse multiplexing protocol have so far been made and are described in detail below New Transmission Convergence Protocol Using Bits This protocol was presented in Physical Layer Sub Working Group ATM Forum 94 0775 ATM Inverse Multi plexing Mechanism September 1994 by StrataCom Inc The protocol robs two of the Generic Flow Control GFC bits contained in each cell transmitted over the multiple T1 E1 links to implement a new transmission convergence TC layer FIG 3 shows the ATM cell structure which is defined in the ITU Recommendation The TC la
12. the invention is directed to a method of inverse multiplexing of a series of ATM cells transparently over N transmission links N being a positive integer of slower speed BACKGROUND OF THE INVENTION It has been recognized that the T1 E1 rate 1 544 2 048 Mbit s is a cost effective way of user access to an ATM network as well as connection between ATM network switches However as ATM technology for wide area net works is deployed more and more demands for transmission links of a rate higher than 1 1 are increasing Links of higher rates such as T3 E3 44 736 34 368 Mbit s have been designed to meet these needs However the cost of T3 E3 links is still prohibitive in many cases and the ratio of cost versus realistic utilization of the entire rate is not always attractive and fully justified for new ATM end users and service providers ATM inverse multiplexers AIMs have been proposed to satisfy the need by using multiple TI E1 links which are grouped collectively to provide the service at a higher rate FIG 1 and FIG 2 show two sample configurations in which AIMs are used FIG 1 depicts a user access to a network through user network interfaces UNIs and FIG 2 a link connection between ATM switches through broadband inter carrier interfaces BICIs or private network to net work interfaces PNNIs Referring to the figures the basic function of AIMs is to work in pairs to take an ATM cell stream coming from the ATM layer
13. 43 544 sequential order Inverse multiplexing control cells are used to communicate between the source node and destination 56 References Cited node for connectivity testing of transmission links Cell stuffing is also provided in one embodiment to accommodate U S PATENT DOCUMENTS non synchronized links among transmission links In a par 5 285 441 2 1994 Bansal et al 370 223 ticular embodiment two consecutive control cells indicate a 5 608 733 3 1997 Vallee et al 370 394 stuffing cell A start up procedure is described when not all 5 617 417 4 1997 Sathe et al 370 394 the transmission links are usable 5 875 192 2 1999 Cam et al 370 474 5 970 067 10 1999 Sathe et al 370 394 74 Claims 14 Drawing Sheets FIELD ATM CELL HEADER IMA LABEL CELL ID LINK ID IMA FRAME SEQUENCE NUMBER ICP CELL OFFSET LINK STUFF INDICATION STATUS amp CONTROL CHANGE INDICATION Tx IMA ID Rx IMA ID GROUP STATUS amp CONTROL 15 Tx TEST CONTROL 16 Tx TEST PATTERN 17 Rx TEST PATTERN 18 LINK 0 INFORMATION LINK 1 INFORMATION LINK 2 31 INFORMATION UNUSED CRC 10 US 6 205 142 B1 Sheet 1 of 14 Mar 20 2001 U S Patent 3SIN3Hd 15 4 91 AMYOMLAN WLY 4 914 JSINJ Hd YIWOLSNOD 3SIIN3d INN JYSWOLSND ASINAdd YAWOLSNO U S Patent Ma
14. ATM data cells at the destination node in the specific round robin order wherein each frame includes at least one inverse multiplexing control cell that contains cell stuff information 28 The method of claim 27 wherein the cell stuff information includes stuff code indicating the location of stuff cells inserted in a respective frame 29 The method of claim 28 wherein the stuff code further indicates that a stuff cell is one out of two stuff cells inserted in the respective frame 30 A method of inverse multiplexing digital data from a first node to a second node over a connection consisting of a plurality of transmission links the data containing a series of ATM data cells that is segmented into a plurality of frames comprising whenever the connection is to be reconfigured the first node sending to the second node one or more inverse multiplexing control cells containing information indi cating a specific round robin order in which the series of ATM data cells are to be transmitted over the connection receiving at the first node from the second node one or more inverse multiplexing control cells containing information indicating that the second node is ready to receive ATM data cells in the specific round robin order from the plurality of transmission links sending each ATM data cell in the series of ATM data cells from the first node to the second node in the specific round robin order wherein each frame includes at leas
15. M layer cells This means that the receiving node always scans for AIM SN cells in order to determine if it is always reading cells from the multiple links in the correct order How often a burst of AIM SN cells is sent depends upon the link utilization but the maximum period has been set to 50 milliseconds in one embodiment An example of cells sent over a virtual link composed of a plurality of transmission links is shown in FIG 9 Link Reconfiguration As mentioned above the protocol according to the inven tion also deals with link reconfiguration There are three possible cases in which reconfiguration can occur a new link has to be added to the round robin a link has to be intentionally removed from the round robin and a link has been declared inadequate to provide service e g link down by failure etc In the first two cases a node starts link reconfiguration by performing the same initialization process for a connection start up that is to say it chooses a round robin order among the links and starts sending AIM SN cells using the chosen round robin order The receiving node seeing the occurrence of AIM SN cells will stop transmitting traffic and starts sending AIM SN cells of its own while adjusting itself to receive traffic from the incoming links The rest of the protocol is as described earlier for start up Two possible cases for reporting failure conditions are 1 A medium problem reported through Loss
16. a United States Patent Vallee US006205142B1 US 6 205 142 B1 Mar 20 2001 10 Patent No 45 Date of Patent 54 INVERSE MULTIPLEXING OF DIGITAL FOREIGN PATENT DOCUMENTS DIS 0 584 398 3 1994 EP 75 Inventor Richard Vallee Gatineau Mia dr NS 73 Assignee Nortel Networks Limited CA OTHER PUBLICATIONS Notice Subject to any disclaimer the term of this Palmer Inverse Multiplexing of ATM Cells Over Low patent is extended or adjusted under 35 Speed UNI s Such as T1 and E1 1994 E U S C 154 b by 0 days Sathe ATM Inverse Multiplexing Mechanism 1994 cited by examiner 21 Appl No 08 209 060 Primary Examiner Alpus H Hsu 22 Filed Aug 14 1997 74 Attorney Agent or Firm Finnegan Henderson Farabow Garrett amp Dunner L L P Related U S Application Data 57 ABSTRACT 60 Provisional application No 60 024 023 filed on Aug 16 1996 In ATM networks digital data in ATM cells are sent to a 51 esses H04J 3 02 HO4L 12 56 destination node over more than one transmission link in 52 U S O cori 370 394 370 395 370 471 round robin fashion This is called inverse multiplexing At 370 536 connection start up the source node informs the destination 58 Field of Search cs 370 389 394 node of the specific round robin fashion of the transmission 370 395 400 408 465 470 471 474 links so that the ATM cells are reassembled in a proper 476 477 506 536 542 5
17. a plurality of transmission links the data containing a series of ATM data cells that is segmented into a plurality of frames comprising the source node sending to the destination node one or more inverse multiplexing control cells informing the destination node of a round robin order in which the series of ATM data cells are to be transmitted over the connection the destination node sending one or more inverse multi plexing control cells including information indicating that the destination node is ready to receive ATM data cells in the round robin order from the plurality of transmission links and the source node sending the series of ATM data cells to the destination node in the round robin order wherein each frame includes at least one inverse multiplexing control cell that contains cell stuff information 22 The method of claim 21 wherein the cell stuff information includes stuff code indicating the location of stuff cells inserted in a respective frame 23 The method of claim 22 wherein the stuff code further indicates that a stuff cell is one out of two stuff cells inserted in the respective frame 24 A method of inverse multiplexing digital data over a connection including a plurality of transmission links the data containing a series of ATM data cells that is segmented into a plurality of frames comprising sending to a destination node one or more inverse mul tiplexing control cells indicating a specific round ro
18. ad consists of a series of fields whose locations are shown in FIG 7 The following fields are identified for the AIM protocol according to one embodiment of the invention 10 15 20 25 30 35 40 45 50 55 60 65 6 inverse multiplexing remote defect indicator AIMRD I one octet is allocated and the proposed coding is all 1 ATM inverse multiplexing far end receiver ready AIMFERR one octet is allocated and the proposed coding is all 1 ATM inverse multiplexing cell sequence number is defined to contain the sequence num ber of the cells sent over the multiple links handled by the ATM inverse multiplexers It is designed so as to have a sufficiently large cycle to allow the ATM inverse multiplexer to absorb link delays of up to 32 millisec onds There are 16 bits allocated to the AIMCSN field The counting is then done modulo 65536 Cell error control CEC is used to detect errors in the cell payload It is proposed to CRC 10 as proposed in ITU Recommendation I 432 Reserve field R contains the octet pattern of 01101010 which is the same as that of the idle cell as proposed in ITU Recommendation 1 361 Referring to FIG 8 the ATM inverse multiplexing pro tocol according to one embodiment is described in detail below The figure only shows one direction for clarity It is shown that transmission links are all T1 E1 links but of course links c
19. an have a different speed from T1 E1 as long as all the links have the same speed A transmitting node 20 collects digital data consisting of a series of ATM data cells from the ATM layer An ATM inverse multiplexer AIM at the transmitting node spreads over multiple links 24 for transmission to a receiving node 26 An AIM at the receiving node reassembles ATM data cells received from the links in proper order and sends them to the ATM layer Link Start up Upon connection start up AIMs at both nodes start insert ing AIM OAM cells AIM SN cells carrying cell sequence number over the available links in round robin fashion The sequencing of cells is based on the order in which cells have to be transmitted on the virtual link composed of N physical links However the sequence number is only carried over the SN cells This sequence number assignment allows the receiving AIM to retrieve the original cell sequence The receiving node queues the received AIM SN cells until it determines the sequence in which to read the ATM data cells from the incoming links as well as the differential delay among individual links Then it starts sending AIM SN cells of its own with the AIMFERR field set to one for each link which is now considered ready to receive traffic From that moment the receiving node knows the sequence of cells coming from the links A link is being considered available if cells are currently delineated and AIM RDI is no
20. at contains cell stuff infor mation 70 The system of claim 69 wherein the cell stuff infor mation includes stuff code indicating the location of stuff cells inserted in a respective frame 71 The system of claim 70 wherein the stuff code further indicates that a stuff cell is one out of two stuff cells inserted in the respective frame 72 method of inverse multiplexing digital data from a source node to a destination node over a connection con sisting of a plurality of transmission links said data con taining a series of ATM data cells that are segmented into a plurality of frames comprising steps of sending at a connection start up from the source node to the destination node inverse multiplexing control cells informing the latter of a specific round robin order in which the series of ATM data cells are to be transmitted over the connection the destination node sending inverse multiplexing control cells whose receive ready field is set to indicate that the destination node is ready to receive ATM data cells in said specific round robin order from the plurality of transmission links and the source node sending each ATM data cell in said series of ATM data cells that are arranged into a plurality of frames to the destination node in said specific round robin order wherein each frame includes at least one inverse multiplexing control cell that contains cell stuff information 73 The method of claim 72 wherein the c
21. ative link delay As mentioned above the SN cell also carries an extra field used by each T1 E1 link to indicate that both AIMs belong to the same link round robin This information can then be used locally to determine if at the corresponding local node a link should be added removed or maintained in the round robin When a change of link configuration occurs by a link being added removed or declared as being down each node sends a series of SN cells to allow the far end node to reestablish the sequence of cells to read from the incoming links The protocol of the invention calls for a physical layer OAM cell that is defined to be exclusively processed by the ATM inverse multiplexers The new cell structure has to be consistent with the cell structure defined in ITU Recom mendation 1 361 FIG 3 shows that structure of UNI NNI AIM cells that is defined in 1361 ITU Recommendations 1 361 and 1 432 state that ATM cells consisting of a header whose VPI and VCI fields are set to zero are reserved for use by the physical layer So far three preassigned values of the cell header are reserved for use by the physical layer They are shown in FIG 5 The physical layer OAM cell according to one embodi ment of the invention is then defined by using a non assigned value by setting the PT field to 111 or some such code This is shown in FIG 6 The AIM OAM cell payload is then available for exchanging information between AIMs The cell paylo
22. bin order in which the series of ATM data cells are to be transmitted over the connection receiving from the destination node one or more inverse multiplexing control cells including information indi cating that the destination node is ready to receive ATM data cells sending the series of ATM data cells to the destination node in the specific round robin order wherein each frame includes at least one inverse multiplexing control cell that contain cell stuff information 25 The method of claim 24 wherein the cell stuff information includes stuff code indicating the location of stuff cells inserted in a respective frame 26 The method of claim 25 wherein the stuff code further indicates that a stuff cell is one out of two staff cells inserted in the respective frame 27 A method of inverse multiplexing digital data over a connection including a plurality of transmission links the 14 data containing a series of ATM data cells that is segmented into a plurality of frames comprising receiving at a destination node from a source node one or more inverse multiplexing control cells indicating a 5 specific round robin order in which the series of ATM data cells are to be transmitted over the connection transmitting from the destination node to the source node one or more inverse multiplexing control cells includ ing information indicating that the destination node is ready to receive ATM data cells receiving the series of
23. ceive ATM data cells in the specific round robin order from the plurality of transmission links and receiving device for receiving at the other node each AIM data cell in the series of ATM data cells in the specific round robin order wherein each frame includes at least one inverse multiplexing control cell that con tains cell stuff information 64 The node of claim 63 wherein the cell stuff informa tion includes stuff code indicating the location of stuff cells inserted in a respective frame US 6 205 142 B1 19 65 The node of claim 64 wherein the stuff code further indicates that a stuff cell is one out of two stuff cells inserted in the respective frame 66 A node in an ATM communications system for inverse multiplexing digital data to be transmitted from a source node to a destination node using a plurality of communica tion links comprising means for transmitting from the source node to the destination node one or more inverse multiplexing control cells including information identifying a spe cific order in which a series of ATM data cells that is segmented into a plurality of frames are to be trans mitted over the plurality of communication links means for transmitting from the destination node to the source node one or more inverse multiplexing control cells that include information indicating that the desti nation node is ready to receive ATM data cells in the specific order means for transmitting from
24. d over the connection receiving at the source node one or more inverse multi plexing control cells containing information indicating that the destination node is ready to receive ATM data cells in the round robin order over the connection and sending the series of ATM data cells in the round robin order to the destination node wherein each frame includes at least one inverse multiplexing control cell that contains cell stuff information 7 The method of claim 6 wherein the cell stuff informa tion includes stuff code indicating the location of stuff cells inserted in a respective frame 8 The method of claim 7 wherein the stuff code further indicates that a stuff cell is one out of two stuff cells inserted in the respective frame 9 A method of inverse multiplexing digital data from a source node to a destination node over a connection includ ing a plurality of transmission links the data including a series of ATM data cells that is segmented into a plurality of frames comprising initiating the connection between the source node and the destination node by transmitting from the source node one or more inverse multiplexing control cells contain ing information defining a round robin order in which the series of ATM data cells are to be transmitted over the connection receiving at the source node one or more inverse multi plexing control cells containing information indicating that the destination node is ready to receive ATM
25. de inverse multiplexing control cells containing informa tion indicating that the other node is ready to receive ATM data cells in the specific round robin order from the plurality of transmission links and a data cell transmitting device for sending each ATM data cell in the series of ATM data cells to the other node in the specific round robin order wherein each frame includes at least one inverse multiplexing control cell that contains cell stuff information 61 The node of claim 60 wherein the cell stuff informa tion includes stuff code indicating the location of stuff cells inserted in a respective frame 62 The node of claim 61 wherein the stuff code further indicates that a stuff cell is one out of two stuff cells inserted in the respective frame 63 A node in an ATM communication system for inverse multiplexing digital data to another node over a connection consisting of a plurality of transmission links the data containing a series of ATM data cells that 15 segmented into a plurality of frames comprising a receiving device for receiving at the other node when ever the connection is to be reconfigured one or more cells containing information indicating a specific round robin order in which the series of ATM data cells are to be transmitted over the connection transmitting device for sending from the other node inverse multiplexing control cells containing informa tion indicating that the other node is ready to re
26. e ICPs The receive end node receives the ICPs and copies Tx Test Pattern onto Rx Test Pattern It keeps sending same test pattern copied on Rx Test Pattern field over its all outgoing links FIG 17 illus 10 15 20 25 30 35 40 45 50 55 60 65 10 trates looping of a test pattern at node B The transmit node receives and verifies Rx Test Pattern returned over the other links It now knows that all the links which belong to the same IMA group FIG 18 depicts diagrammatically a scenario where the test pattern procedure can be used to detect a link that is not connected to the expected IMA Links identified as Link ID 1 are being added to existing groups using links with Link ID 0 Link 30 carries the IMA B Test Pattern to looped back by IMA A and links 32 and 34 carry the IMA D Test Pattern to be looped back to IMA B In this case the wrong test pattern will be received by IMA B If IMA B was not commanding a Test Pattern loopback IMA B would simply not receive the right test pattern The Test Pattern procedure also allows to deal with some pathological cases One of them is when two IMA connected to the same far end IMA node are trying to start up at the same time The far end receive end node will have to determine which set of links corresponding to one end it wants to be connected to This will require the received end to select the link s to be part of the group as mentioned above the receive end s
27. e above noted problems The patent uses ATM sequence number cells indicating a specific round robin order of a plurality of transmission links over which ATM data cells are transmitted The ATM sequence number cells also indicate whether or not a des tination is ready to receive ATM data cells in that specific round robin order The present invention extends further variety of function alities which are useful in inverse multiplexing OBJECTS OF THE INVENTION It is therefore an object of the invention to provide a method of sending ATM traffic over a connection consisting of a plurality of transmission links It is another object of the invention to provide a method of sending a series of ATM cells spread over a plurality of transmission links in a specific round robin order US 6 205 142 B1 3 It is yet another object of the invention to provide a method of sending ATM cells containing sequence numbers therein over a plurality of transmission links in a specific round robin order It is a further object of the invention to provide a method of sending a series of ATM cells between ATM inverse multiplexers over a connection consisting of a plurality of transmission links transparent to the ATM layer It is yet another object of the invention to provide a method of sending ATM traffic over a connection which consists of a plurality of transmission links and has been reconfigured after the connection start up It is still another ob
28. ell stuff information includes stuff code indicating the location of stuff cells inserted in a respective frame 74 The method of claim 73 wherein the stuff code further indicates that a stuff cell is one out of two stuff cells inserted in the respective frame UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO 6 205 142 Page of 1 DATED March 20 2001 INVENTOR S Richard Vallee It is certified that error appears in the above identified patent and that said Letters Patent is hereby corrected as shown below Claims Column 13 Line 59 change contain to contains Line 64 change staff cells to stuff cells Column 16 Line 67 change nodes the serie of ATM data cells to node the series of data cells Signed and Sealed this Twenty eighth Day of August 2001 P Lodi Attest NICHOLAS P GODICI Attesting Officer Acting Director of the United States Patent and Trademark Office
29. emultiplexing of AIM OAM cells according to one embodiment of the invention and FIG 9 is a schematic illustration of periodic multiplexing and demultiplexing of AIM OAM cells during transmission of ATM data cells according to one embodiment of the invention FIG 10 is an ICP cell format used for implementing embodiments of the invention FIG 11 shows a circumstance where node A may be using a group of three links to send data to node B and another group of two links to send data to node C FIG 12 shows a typical sequence of cells on a three link group FIGS 13a and 136 show an algorithmic flow chart for the start up procedure according to one embodiment FIG 14 indicates how FIGS 13a and 13b should be connected FIG 15 shows a configuration when links with Link ID 1 are added to groups with active Link ID 0 links FIG 16 shows the timing diagram of the test procedure of the invention FIG 17 illustrates looping of a test pattern at node B FIG 18 depicts diagrammatically a scenario where the test pattern procedure can be used to detect a link that is not connected to the expected IMA FIG 19 shows cases 1 7 when the ICP cell preceding the stuff event and the stuff ICP cells are cor rupted DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS There are requirements that have to be considered when defining a new ATM inverse multiplexing protocol These requirements are It must multiplex and demultiplex an
30. erted in a respective frame 38 The node of claim 37 wherein the stuff code further indicates that a stuff cell is one out of two stuff cells inserted in the respective frame 39 A node in an ATM communications system for inverse multiplexing digital data from a source node to a destination node over a connection including a plurality of transmission links the data including a series of ATM data cells that is segmented into a plurality of frames comprising a transmitting device that transmits from the source node one or more inverse multiplexing control cells contain ing information defining a round robin order in which the series of ATM data cells are to be transmitted over the connection a receiving device for receiving at the source node one or more inverse multiplexing control cells containing information indicating that the destination node is ready to receive ATM data cells in the round robin order from the plurality of transmission links and data cell transmitting device for transmitting the series of ATM data cells to the destination node in the round robin order wherein each frame includes at least one inverse multiplexing control cell that contains cell stuff information 40 The node of claim 39 wherein the cell stuff informa tion includes stuff code indicating the location of stuff cells inserted in a respective frame 41 The node of claim 40 wherein the stuff code further indicates that a stuff cell is one out
31. g control cell that con tains cell stuff information 34 The method of claim 33 wherein the cell stuff information includes stuff code indicating the location of stuff cells inserted in a respective frame 35 The method of claim 34 wherein the stuff code further indicates that a stuff cell is one out of two stuff cells inserted in the respective frame 36 A node in an ATM communications system for inverse multiplexing digital data from a source node to a destination node over a connection including a plurality of transmission links comprising transmitting device for transmitting from the source node one or more inverse multiplexing control cells containing information defining a round robin order in which a series of ATM data cells that is segmented into plurality of frames are to be transmitted over the connection a receiving device for receiving at the source node inverse multiplexing control cells containing informa tion indicating that the destination node is ready to receive ATM data cells in the round robin order from the plurality of transmission links and a data cell transmitting device for transmitting to the receiving node the series of ATM data cells in the round robin order wherein each frame includes at least one inverse multiplexing control cell that contains cell stuff information 37 The node of claim 36 wherein the cell stuff informa tion includes stuff code indicating the location of stuff cells ins
32. g control cell that contains cell stuff informa tion 13 The method of claim 12 wherein the cell stuff information includes stuff code indicating the location of stuff cells inserted in a respective frame 14 The method of claim 13 wherein the stuff code further indicates that a stuff cell is one out of two stuff cells inserted in the respective frame 15 A method at a source node of inverse multiplexing digital data to be transmitted from the source node to a destination node using a plurality of communication links comprising transmitting from the source node to the destination node one or more inverse multiplexing control cells includ ing information identifying an order in which a series of ATM data cells that is segmented into a plurality of frames are to be transmitted over the plurality of communication links receiving at the source node transmitted from the desti nation node one or more inverse multiplexing control cells including information indicating that the destina tion node is ready to receive ATM data cells in the specified order and transmitting from the source node to the destination node the series of ATM data cells in the specified order wherein each frame includes at least one inverse mul tiplexing control cell that contains cell stuff informa tion 16 The method of claim 15 wherein the cell stuff information includes stuff code indicating the location of stuff cells inserted in a respective frame
33. hall only respond to one Test Pattern command at a time that has been validated over one or more links that are or likely to be recognized as part of the group In accordance with a further embodiment a stuff cell is inserted to control cell rate decoupling between the links in order to accommodate the use of links non synchronized to each other within the link groups The transmitting node may be locked to one clock source or may be plesiochro nous When plesiochronous one of the buffers at the trans mitting node may be depleted To prevent underrun the cell stuffing procedure is invoked When there is one clock source the buffer will never deplete The transmitting node send ICP cells which indicate a cell is stuffed at a certain location within the IMA frame Any cell can be used for stuffing as long as the location is indicated so that the receiving node can remove it In actual embodiment the transmitting node repeats the ICP cell containing the stuff code indicating that this cell is 1 out of 2 stuff cells The receiving node uses the stuff indications over the ICP cells to determine when to remove stuff cells from the incoming cell stream The receiving node relies on at least one ICP cell with a correct CRC 10 Amore robust approach is to look for a majority of valid codes FIG 19 shows cases 1 7 when the ICP cell preceding the stuff event and the stuff ICP cells are cor rupted Corrupted cells are indicated by crosses
34. ing control cells indicating a first specific round robin order of the transmission links The method further includes steps of receiving a series of inverse multiplexing control cells whose receive ready field is set to indicate a second specific round robin order in a group formed by P number out of N transmission links P being a positive integer smaller than N and finally sending each ATM data cell in said series of ATM data cells in said second specific round robin order BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding of the invention and for further objects and advantages thereof reference may now be made to the following description taken in conjunc tion with the accompanying drawings in which FIG 1 shows a sample configuration involving AIM UNIs FIG 2 shows a sample configuration involving AIM BICIs or PNNIs FIG 3 depicts the ATM cell structure defined in the ITU Recommendation FIG 4 is a schematic illustration of multiplexing and demultiplexing of ATM cells over AIMs and links 10 15 20 25 30 35 40 45 50 55 60 65 4 FIG 5 shows preassigned cell header values for use by the physical layer FIG 6 shows a header pattern of an AIM OAM cell according to one embodiment of the invention FIG 7 indicates allocation of OAM functions in the information field according to one embodiment of the inven tion FIG 8 is a schematic illustration of multiplexing and d
35. ity of transmission links the data containing a series of ATM data cells that is segmented into a plurality of frames the method comprising transmitting from a first node a series of inverse multi plexing control cells indicating a round robin order in which the ATM data cells are to be transmitted over the connection receiving at the first node a series of inverse multiplexing control cells whose receive ready field is set transmitting from the first node the series of ATM data cells in the round robin order the first node inserting at least one inverse multiplexing control cell that contains cell stuff information into each frame 4 The method of claim 3 wherein the cell stuff informa tion includes stuff code indicating the location of stuff cells inserted in a respective frame 5 The method of claim 4 wherein the stuff code further indicates that a stuff cell is one out of two stuff cells inserted in the respective frame 6 A method of establishing a communication link for inverse multiplexing digital data from a source node to a destination node over a connection including a plurality of transmission links the data containing a series of ATM data cells that is segmented into a plurality of frames compris ing initiating the connection by transmitting from the source node one or more inverse multiplexing control cells containing information defining a round robin order in which the series of ATM data cells are to be transmitte
36. ject of the invention to provide an ATM inverse multiplexing method which is applicable to UNIs BICIs and PNNs It is a further object of the invention to provide a method of preserving link integrity by periodically sending sequence number cells It is a further object of the invention to provide a method of handling link failure and link reconfiguration It is still a further object of the invention to provide a method of stuffing cells to accommodate non synchronized links SUMMARY OF THE INVENTION Briefly stated the invention reside in the inverse multi plexing digital data over a connection consisting of a plu rality of transmission links said data containing a series of ATM data cells According to one aspect the invention is directed to a method of cell stuffing to prevent underrun in a plesiochronous AIM network In accordance with a yet another aspect the method further includes a step of sending two consecutive inverse multiplexing control cells in a frame indicating cell stuffing According to a further aspect the invention is directed to a method of inverse multiplexing digital data over a con nection consisting of a plurality of transmission links said data containing a series of ATM data cells In particular the method comprises steps of identifying N number of trans mission links over which the series of ATM data cells are to be transmitted N being a positive integer and sending a series of inverse multiplex
37. ll be sent over all the links A group status and control field is used to indicate status of the group of links at a connection start up link addition and abort procedures In particular the start up procedure would become complicated if one of the links does not meet all the criteria to be part of the group e g link cleared of defects corresponding incoming outgoing links in loss of delay synchronization This requires intervention of the operator to remove the bad link s from the link group FIGS 13a and 136 as combined in the way shown in FIG 14 show an algorithmic flow chart for the start up procedure according to one embodiment Instead of requiring all N number of links in the group being good before starting up the procedure of the invention proceeds as long as there is at least P out of N good link available for service A good link is defined as a link that is not exhibiting link and loss of frame defects recognized as being part of the group and having an acceptable link differential delay The value of P could be any number less than N The figure also shows cases where the group start up is aborted and later resumed The ICP format also includes a field for link s connec tivity testing at the time of start up link addition or link re activation In particular a protocol must always ensure proper connectivity of the links which belong to a group For example FIG 15 shows when links with Link ID 1 are added to groups wi
38. nd robin order in which the series of ATM data cells are to be transmitted over the connection a transmitting device for transmitting from the destination node one or more inverse multiplexing control cells including information indicating that the destination node is ready to receive ATM data cells and data cell receiving device for receiving the series of ATM data cells at the destination node in the specific round robin order wherein each frame includes at least one inverse multiplexing control cell that contains cell stuff information 58 The node of claim 57 wherein the cell stuff informa tion includes stuff code indicating the location of stuff cells inserted in a respective frame 59 The node of claim 58 wherein the stuff code further indicates that a stuff cell is one out of two stuff cells inserted in the respective frame 60 A node in an ATM communication system for inverse multiplexing digital data to another node over a connection consisting of a plurality of transmission links the data containing a series of ATM data cells that is segmented into a plurality of frames comprising a transmitting device for sending to the other node whenever the connection is to be reconfigured one or more inverse multiplexing control cells containing information indicating a specific round robin order in which the series of ATM data cells are to be transmitted over the connection a receiving device for receiving from the other no
39. ode to the destination node using a plurality of communication links comprising receiving device that receives at the destination node one or more inverse multiplexing control cells trans mitted from the source node wherein the inverse multiplexing control cells include information identi fying a specific order in which a series of ATM data cells that is segmented into a plurality of frames are to be transmitted over the plurality of communication links a transmitting device transmitting from the destination node to the source node one or more inverse multi plexing cells including information indicating that the destination node is ready to receive ATM data cells in the specific order and a data cell receiving device that receives at the destination nodes the serie of ATM data cells transmitted from the US 6 205 142 B1 17 source node in the specific order wherein each frame includes at least one inverse multiplexing control cell that contains cell stuff information 49 The node of claim 48 wherein the cell stuff informa tion includes stuff code indicating the location of stuff cells inserted in a respective frame 50 The node of claim 49 wherein the stuff code further indicates that a stuff cell is one out of two stuff cells inserted in the respective frame 51 A node in an ATM communications system for inverse multiplexing digital data from a source node to a destination node over a connection including a pluralit
40. of Delinea tion LCD failure condition In this case the corresponding link should not be used for service When detecting LCD SN cells with AIMRDI set to 1 should be sent over the corresponding outgoing link SN cells containing AIM RDI do not carry a valid sequence number At the far end the detection of AIM RDI signals will indicate that the link 15 not to be used Therefore if LCD or AIM RDI is detected the link is no longer considered available and won t be allowed to be part of the round robin on both sides When this has happens SN cells are re sent over the remaining links to reestablish the connection between the two ends 2 Cells are lost without an LCD or AIM RDI being reported For instance this would occur when a few cells are discarded by the physical layer device due to bit errors in cell headers This would cause the cell sequencing to be affected One symptom would be the detection of SN cells whose number is no longer the same as that expected since one or more of the previous cells are missing In this case the problem might be partially corrected by re adjusting the receiver buffering system assuming the difference between the SN cell number and the expected number is small The other symptom would be the absence of a SN cell on one link when getting a burst of SN cells on all the other links In that case the local end would have to force the links to be re configured If the symptoms described above reoccur
41. r 20 2001 Sheet 2 of 14 US 6 205 142 B1 Lu O O CELL PAYLOAD 48 OCTETS 53 GFC GENERAL FLOW CONTROL VPI VIRTUAL PATH IDENTIFIER VCI VIRTUAL CHANNEL IDENTIFIER PT PAYLOAD TYPE CLP CELL LOSS PRIORITY HEC HEADER ERROR CHECK FIG 3 PRIOR ART U S Patent Mar 20 2001 Sheet 3 of 14 US 6 205 142 B1 FIG 4 US 6 205 142 B1 Sheet 4 of 14 Mar 20 2001 U S Patent 9 914 LLLLOOOO 00000000 00000000 00000000 v 131290 131290 13190 13100 LLOLOOLL 13120 214 00010110 10010000 00000000 00000000 00000000 7130 00111010 1000000 00000000 00000000 00000000 1130 WYO L3 01001010 10000000 00000000 00000000 00000000 NOILVOISILNAG 31d 1139 U S Patent Mar 20 2001 Sheet 5 of 14 US 6 205 142 B1 ALLOCATION AIM RDI 1 2 W O MSB MOST SIGNIFICANT BYTE LSB LEAST SIGNIFICANT BYTE FIG 7 US 6 205 142 B1 Sheet 6 of 14 Mar 20 2001 U S Patent 6 914 001 101 201 3ON3noO3S 1139 001 104 20 1139 51130 VVC WLW 96 S1139 VLVG WLY 96 1139 NO 7739 L Z 3DN3nO3S 1139 STI3O 1 0 C STI3O VLVG LOL AJAV Iv 57789 V1VQ 00L CL LZE
42. r the receiver to inform the transmitter by sending its own SN cells that it is receiving cells and it is also an integral part of the same round robin mechanism that is to say the feedback link status value SN cells in either direction must agree with each other although the sequence numbers at both ends may be different When the receiver sends its own SN cells in response to the transmitter that it is receiving cells it is in fact acknowledging that the receiver is ready to receive subsequent ATM data cells FIG 4 shows how the ATM cells are multiplexed and then demultiplexed over AIMs in one direction At the transmit ting node an AIM 10 takes a series of ATM cells from an ATM layer device It spreads ATM cells and transmits each cell over each of N transmission links N being a positive integer The order of transmission is in round robin fashion This process is called an inverse multiplexing At the receiv ing node cells from N links are inverse demultiplexed assembled and sent to an ATM layer device by an AIM 14 The same order must be employed at this node to recover a proper sequence of cells Both nodes must be aware of the round robin order which is to be employed Upon initialization therefore both AIMs send a series of SN cells in round robin fashion over the links e g T1 E1 links This allows the receiver AIM at both nodes to establish the sequence in which to read cells from the incoming links as well as to adjust rel
43. re identified by IMA ID Tx and Rx IMA ID ATM cells on each link are grouped in a certain number e g M of cells to form IMA frames which belong to substantially same time scale An IMA frame sequence number field counts cells in each group FIG 12 shows a typical sequence of cells on a three link group One ICP cell is sent at a set location in each group for each link M can be any number for example 32 64 128 and 256 In the figure on link 0 the ICP cells have their cell offset set to zero 1 they are the first cell in the IMA frame On link 1 the ICP cells have the ICP cell offset set to 3 and on link 2 the ICP cells have their ICP cell offset set to 1 In practice these ICP cells should be distributed US 6 205 142 B1 9 even more over the IMA frame but are shown closer for ease of illustration The ICP cell also includes fields concerning with stuffing action and test control action both of which will be described in detail below A status and control change indication field is used to indicate an update of the link status field value The value is incremented to indicate a change on at least one of the link status fields The field is also used as a tag to differentiate link status changes over time The field will always remain set to the same value as long as there will be no change on any link status fields If one or more link status fields need to be modified ICP cells with new link status values incremented wi
44. s comprising a transmitting device for sending to a destination node one or more inverse multiplexing control cells indicating a specific round robin order in which the series of ATM data cells are to be transmitted over the connection a receiving device for receiving from the destination node one or more inverse multiplexing control cells includ ing information indicating that the destination node is ready to receive ATM data cells and data cell transmitting device for sending the series of ATM data cells to the destination node in the specific round robin order wherein each frame includes at least one inverse multiplexing control cell that contains cell stuff information 55 The node of claim 54 wherein the cell stuff informa tion includes stuff code indicating the location of stuff cells inserted in a respective frame 56 The node of claim 55 wherein the stuff code further indicates that a stuff cell is one out of two stuff cells inserted in the respective frame 57 A node in an ATM communication system for inverse multiplexing digital data over a connection including a plurality of transmission links the data containing a series of ATM data cells that is segmented into a plurality of frames comprising a receiving device for receiving at a destination node from source node one or more inverse multiplexing control 10 15 20 25 30 35 40 45 50 55 60 18 cells indicating a specific rou
45. s modulo 65536 ATM inverse multiplexing protocol according to the invention realizes the following characteristics it is applicable to UNIs BICIs and PNNIs any applicable points in an ATM network it does not affect the ATM cell header of currently defined cells it does not require a change to current ATM physical layer devices dealing with the convergence of ATM cells into 1 1 it operates transparently to the layer it does not require a change to current devices dealing with the processing of the ATM layer cell it is self configuring among available links upon start up and self reconfiguring among the multiple links in the case when a new link has to be added deleted or considered inadequate to provide service and it includes a sequence number whose modulo is large enough to meet the requirement of a large differential delay among the links An embodiment of the present invention involves special Inverse mux Controller Processor ICP cells which are more detailed versions of the SN cells The ICP cell format is shown in FIG 10 In this embodiment ATM cells are transmitted over an N number of links N being a positive integer Cell ID is set for ICP cell and Link ID identifies links being used As seen in FIG 11 a node A may be using a group of three links to send data to node B and another group of two links to send data to node C Nodes A and B form one IMA group and nodes A and C form another IMA groups a
46. t one inverse multiplexing control cell that contains cell stuff information 31 The method of claim 30 wherein the cell stuff information includes stuff code indicating the location of stuff cells inserted in a respective frame 32 The method of claim 31 wherein the stuff code further indicates that a stuff cell is one out of two stuff cells inserted in the respective frame 33 A method of inverse multiplexing digital data from a first node to a second node over a connection consisting of a plurality of transmission links the data containing a series of ATM data cells that is segmented into a plurality of frames comprising whenever the connection is to be reconfigured the second node receiving from the first node one or more inverse multiplexing control cells containing information indi cating a specific round robin order in which the series of ATM data cells are to be transmitted over the connection sending from the second node to the first node one or more inverse multiplexing control cells containing information indicating that the second node is ready to receive ATM data cells in the specific round robin order from the plurality of transmission links receiving at the second node each ATM data cell in the series of ATM data cells from the first node in the specific round robin order wherein each frame includes 10 30 35 40 45 50 55 60 65 US 6 205 142 B1 15 at least one inverse multiplexin
47. t received on the incoming link When the transmitting node starts sending the AIM SN cells it starts a time out of 100 milliseconds within which the receiving node determines the sequence of AIM SN cells which it is receiving from the links The time out expires unless the transmitting node receives the ready signal from all the links which were considered available at the initialization If there 15 no link when the time out expires the local node reevaluates the availability of the links using cell delineation starts sending AIM SN cells over the available links and re starts the time out This procedure is repeated until at least one available link is declared ready When the time out has been cancelled due to the reception of the ready signal from all the available links or when there is at least one link ready when the time out expires the local end starts sending ATM layer cells over the ready US 6 205 142 B1 7 link or links using the same round robin order used at the time of initialization Each ATM layer cell gets a sequence number assigned to it but only the AIM SN cells carry that number across the links After both nodes have started sending ATM layer cells they periodically send a series of AIM SN cells over links to allow the receiving node to readjust the differential delays among the links The value of is equal to the number of ready links used to carry AI
48. th active Link ID 0 links Two new links Link ID 1 links are inversely connected with respect to the expected configuration The difficulty is then that both Link ID and IMA ID are the same for two independent IMAs This can cause an invalid configuration which will not be detected This kind of problem can occur at a start up link addition or even at a link re activation For example it is possible to reactivate a link which has exhibited a link failure since it has been accidentally inverted with another link with or without the same Link ID and IMA ID IMA ID is also used to detect loopback situations This problem occurs when both end nodes of the IMA virtual link wants to use the same IMA ID The invention addresses this problem also According to a further embodiment the above problems are solved by sending a test pattern contained in ICP cells over a link to be validated The test pattern will be looped back over all the other links in the group at the far end node This ensures that the tested link is connected to the same end node as the other links When one IMA node wants to determine if one or more links are connected to the same far end IMA node it selects one link for testing FIG 16 shows the timing diagram of the test procedure of the invention The transmit node sets the Tx Test control field for link test in an ICP cell It identifies Link ID Tx IMAID Rx IMAID and inserts Test Pattern in the cell It continues to send sam
49. the source node to the destination node the series of ATM data cells in the specific order wherein each frame includes at least one inverse multiplexing control cell that contains cell stuff information 67 The node of claim 66 wherein the cell stuff informa tion includes stuff code indicating the location of stuff cells inserted in a respective frame 68 The node of claim 67 wherein the stuff code further indicates that a stuff cell is one out of two stuff cells inserted in the respective frame 69 A system for inverse multiplexing digital data from one node to another node over a connection the data containing a series of ATM data cells that is segmented into a plurality of frames the system comprising a plurality of transmission links in communication with the one node a transmitting device for transmitting from the one node one or more cells containing information defining a round robin order in which a series of ATM data cells are to be transmitted over the connection a receiving device for receiving at the one node cells containing information indicating that the another node 10 15 20 25 30 35 40 20 is ready to receive ATM data cells in the round robin order from the plurality of transmission links and data cell transmitting device for transmitting from the one node to the another node the series of ATM data cells wherein each frame includes at least one inverse multiplexing control cell th
50. y of transmission links the data containing a series of ATM data cells that is segmented into a plurality of frames comprising a transmitting device for sending from the source node to the destination node at a connection start up one or more inverse multiplexing control cells informing the destination node of a specific round robin order in which the series of ATM data cells are to be transmitted over the connection a transmitting device for sending one or more inverse multiplexing control cells including information indi cating that the destination node is ready to receive ATM data cells in the specific round robin order from the plurality of transmission links and a data cell transmitting device for sending the series of ATM data cells to the destination node in the specific round robin order wherein each frame includes at least one inverse multiplexing control cell that contains cell stuff information 52 The node of claim 51 wherein the cell stuff informa tion includes stuff code indicating the location of stuff cells inserted in a respective frame 53 The node of claim 52 wherein the stuff code further indicates that a stuff cell is one out of two stuff cells inserted in the respective frame 54 A node in an ATM communications system for inverse multiplexing digital data over a connection including a plurality of transmission links the data containing a series of ATM data cells that is segmented into a plurality of frame
51. yer is defined by one GFC bit for framing and the other one for link 10 15 30 35 40 45 50 55 60 65 2 control The framing bit is used to determine relative link delays while the link control bit is used for communication control and administration between two TC points at two ends of the inverse multiplexer In order to establish the sequence of cells over the links in a round robin manner one end is defined as being master and the other as slave The master decides and informs the slave about the multiple link configuration using the control channel implemented through the link control bits This protocol is only applicable however for UNI appli cation points because GFC bits that are robbed to implement the TC layer are only present in a cell defined for UNI For NNI cells the corresponding bits are no longer available since they are captured under the VPI field Service provid ers are interested in ATM inverse multiplexers for carrying ATM traffic at rates higher than T1 E1 and lower than T3 E3 but this protocol will not satisfy their need It should also be noted that the protocol calls for a need to identify a master and a slave TC point and that requires an additional setting to be performed by the network operator Bit Pipe Inverse Multiplexing This protocol was presented in Physical Layer Sub Working Group ATM Forum 94 0956 Inverse Multiplexing of ATM cells over

Inverse multiplexing of digital data

Contents

Download Pdf Manuals

Related Search

Related Contents