1. updated 12/20011 Asynchronous Transfer Mode Networks Nirmala Shenoy Information Technology Department Rochester Institute of Technology

2. updated 12/20012 Asynchronous Transfer Mode Scope –Purpose –Cells vs packets –Topology –Virtual connections –VP and VPC switching –ATM layers

3. updated 12/20013 Asynchronous Transfer Mode Scope –Delays in ATM networks –Service & QoS –Traffic control –UNI –B-ICI –Switch fabric –ATM addressing

4. updated 12/20014 Asynchronous Transfer Mode Purpose –Cells over frames –Optimal use of transmission and equipment technology –Interface with various packet switching networks –WAN connectivity

5. updated 12/20015 Asynchronous Transfer Mode Purpose –Easy and inexpensive implementation –Support exiting telecommunication hierarchies Local loops, local providers, long distance carriers –Connection oriented – reliable and predictable delivery especially for real-time application –protocol functions from sw to hw –High-speed low delay packet switching for all types of traffic

6. updated 12/20016 Asynchronous Transfer Mode Cell vs Frames Frames - Packets Current packet sizes- 200bytes to 64kbytes Elaborate software at intermediate nodes to accommodate variable size packets Variable header evaluations Packets to be checked for integrity Non-uniformity of service for different types of packet networks

7. updated 12/20017 Asynchronous Transfer Mode Packets Consistent data rate delivery not possible In-time delivery for some packets –Real-time packets may be smaller compared to data packets Cells Predictable processing Uniformity guaranteed

8. updated 12/20018 Asynchronous Transfer Mode Cells Deterministic delays = n*cell transmission High speed + small cell size = continuous stream effect Cells handled as cells not as bit stream – faster Fixed cells – more hardware implementable

9. updated 12/20019 Asynchronous Transfer Mode Asynchronous TDM

10. updated 12/200110 Asynchronous Transfer Mode Topology

11. updated 12/200111 Asynchronous Transfer Mode Topology –Similar to ISDN has all reference points and functional groupings (b tag) – Public and private UNI may use different different interfaces & schemes –ATM can be used as a LAN, WAN, hub –interconnecting networks, backbone

12. updated 12/200112 Asynchronous Transfer Mode Virtual connections Transmission Path –Physical connection between two points –Switches and end points or between switches Virtual Path –Transmission path is divided into several virtual paths

13. updated 12/200113 Asynchronous Transfer Mode Virtual connections –The set of all virtual path = transmission path Virtual circuit –A single message flow circuit –A number of virtual circuits make a virtual path

14. updated 12/200114 Asynchronous Transfer Mode Virtual connections – relationship

15. updated 12/200115 Asynchronous Transfer Mode Virtual connections – relationship

16. updated 12/200116 Asynchronous Transfer Mode Virtual connections – relationship VPI & VCI

17. updated 12/200117 Asynchronous Transfer Mode Virtual connections set-up PVC – permanent virtual circuit –Negotiated with the network on long term basis SVC – switched virtual circuit –On per call basis

18. updated 12/200118 Asynchronous Transfer Mode Virtual connections set-up

19. updated 12/200119 Asynchronous Transfer Mode VP switching

20. updated 12/200120 Asynchronous Transfer Mode VPC switching – VP & VC switching

21. updated 12/200121 Asynchronous Transfer Mode ATM layers –ATM Adaptation Layer – AAL Convergence Sub layer Segmentation and Reassembly sub layer –ATM Layer –Physical layer SONET/SDH

22. updated 12/200122 Asynchronous Transfer Mode ATM layers & the OSI layers –ATM layer performs layers 2 & 3 functions of the OSI layers –AAL combines, 2,4 and 5 of the OSI layers –Not adhering to the OSI layers OSI layers getting obsolete?

23. updated 12/200123 Asynchronous Transfer Mode ATM Planes SSCF – service specific coordination function SSCOP – service specific connection- oriented protcol

24. updated 12/200124 Asynchronous Transfer Mode ATM Adaptation Layer – at the end points ATM & Physical layer through the network

25. updated 12/200125 Asynchronous Transfer Mode ATM Adaptation Layer – application specific Classification of traffic –Class A – constant bit rate –Class B - variable bit rate, connection oriented, timing requirements –Class C- Variable Bit Rate, connection oriented, timing not required –Class D – Variable Bit Rate, connectionless, timing not required

26. updated 12/200126 Asynchronous Transfer Mode ATM Adaptation Layer –AAL1 – to support Class A –AAL2 – Class B – later for voice –AAL3/4 – connection oriented data & connectionless data, Class C & D – AAL5 – signaling – data Simple and most popular

27. updated 12/200127 Asynchronous Transfer Mode ATM Adaptation Layer- AAL1 –Convergence Sub layer –Segments PDU from upper layer to 47 byte segments –Passes to SAR

28. updated 12/200128 Asynchronous Transfer Mode ATM Adaptation Layer- AAL1 –Segmentation And Reassembly layer –SAR –adds a 1 byte header 1bit CSI – convergence sublayer id 3 bits – sequence count 3 bits – CRC on the above 1 bit parity

29. updated 12/200129 Asynchronous Transfer Mode Delays and real-time service support Transmission efficiency = Li/(Li+Lo) –Li – information field length –Lo – length of control header Variable SDU – Li can be large –Processing delays at switch Fixed SDU – predictable delays

30. updated 12/200130 Asynchronous Transfer Mode Transmission delay –To provide for time transparency Circuit emulation for some applications –Responsibility of the AAL Buffering schemes –Delay at sender end Convergence and reassembly – C/S 1 At the receiver end C/S 2 –Propagation Delay – PD 4-5  sec per Km

31. updated 12/200131 Asynchronous Transfer Mode Transmission delay –Cell loss Loss of one cell – 4-16 msec –Switching Delay – SD – fixed 2-100  sec –Delays to overcome jitter –Queuing Delay – traffic peaks

32. updated 12/200132 Asynchronous Transfer Mode Transmission delay –C/S = 12000  sec (6000  sec at each end) –PD = 2000  sec –SD= 72  sec (24  sec for each switch –3) –QD =225  sec (total for 3 switch) Predominant PD and C/S C/S can be higher if some other layers include more mapping & convergence

33. updated 12/200133 Asynchronous Transfer Mode ATM Adaptation Layer- AAL3/4 –Convergence sub layer

34. updated 12/200134 Asynchronous Transfer Mode ATM Adaptation Layer- AAL3/4 –Convergence Sub layer bits T – type BT – Begin Tag BA – Buffer Allocation PAD- padding to proper multiple size AL – align trailer to 4 bytes ET – End Tag L – length of data unit

35. updated 12/200135 Asynchronous Transfer Mode ATM Adaptation Layer- AAL3/4 –Segmentation and Reassembly sub layer

36. updated 12/200136 Asynchronous Transfer Mode ATM Adaptation Layer- AAL3/4 –SAR sub layer bits ST – segment type CSI – convergence sublayer identifier SC - Sequence count MID – Multiplexing identifier LI – length indicator CRC -

37. updated 12/200137 Asynchronous Transfer Mode ATM Adaptation Layer- AAL5 –SEAL – Simple and Efficient Adaptation Layer –Assumes most sequencing and error control if required are provided by end system ULP –

38. updated 12/200138 Asynchronous Transfer Mode ATM Adaptation Layer- AAL5 –UU – user-to user id –T – type –L- length –CRC - checksum

39. updated 12/200139 Asynchronous Transfer Mode ATM layer –

40. updated 12/200140 Asynchronous Transfer Mode ATM layer – PT – payload type (3 bits) – 1 st bit User Data – 0 Management data – 1 –User data 2 nd bit 0- no congestion, 1 congestion 3 rd bit – 0 no signaling, 1 signaling bit

41. updated 12/200141 Asynchronous Transfer Mode ATM layer –Management data – 1 st bit = 1 00 – link associated 01 – end-to-end management 10 – resource management 11 – reserved –CLP – cell loss priority bit –HEC- header error correction/detection

42. updated 12/200142 Asynchronous Transfer Mode Services supported over ATM –CBR –VBR rt, nrt –ABR –UBR

43. updated 12/200143 Asynchronous Transfer Mode Utilization of bandwidth by Services

44. updated 12/200144 Asynchronous Transfer Mode Quality of Service QoS –User oriented –SCR – Sustained Cell Rate –PCR – Peak Cell Rate –MCR – Minimum Cell Rate –CVDT – cell variation delay tolerance

45. updated 12/200145 Asynchronous Transfer Mode Quality of Service QoS –Network oriented –CLR – cell loss ratio –CTD – cell transfer delay –CDV – cell delay variation –CER – Cell Error Ratio Traffic Descriptors

46. updated 12/200146 Asynchronous Transfer Mode Network parameters –Error Free Cells arriving before a specified time T are successfully delivered cells –Lost cells if it arrives after time T or discarded, header error –Mis-inserted cells due to wrong header –Severely damaged cells

47. updated 12/200147 Asynchronous Transfer Mode Allocation of resources

48. updated 12/200148 Asynchronous Transfer Mode Traffic control CBR – Peak cell rate – pcr VBR – pcr, scr and maximum burst size Burst tolerance - BT –BT = (MBS – 1)/(1/SCR – 1/PCR) Generic cell rate algorithm –Virtual scheduling –Continuous leaky bucket

49. updated 12/200149 Asynchronous Transfer Mode Virtual scheduling algorithm –Theoretical Arrival Time TAT is the expected arrival time –Cell arriving before TAT + L is confirming –Cell arrival time is ta, then TAT is set to ta if it was a confirming cell

50. updated 12/200150 Asynchronous Transfer Mode ATM at the UNI –Supports symmetric and asymmetric connections – bandwidth allocation independent in the 2 directions –Negotiation of QoS –

51. updated 12/200151 Asynchronous Transfer Mode ATM at the UNI –Identification of end-to-end capabilities –Client registration Address, administrative information exchange across the UNI Facilitate network administrator –A number of messages defined to facilitate the above

52. updated 12/200152 Asynchronous Transfer Mode ATM B-ICI – Inter carrier interface –Internetworking specification –ITU-T -> NNI based on SDH –ATM Forum – B-ICI based on SONET, DS3 –To accommodate Frame Relay Cell relay service as ATM cells Circuit emulation service DS1, DS3 SMDS

53. updated 12/200153 Asynchronous Transfer Mode Switch fabric – crossbar switch

54. updated 12/200154 Asynchronous Transfer Mode Switch fabric – Knockout switch

55. updated 12/200155 Asynchronous Transfer Mode Switch fabric – Knockout switch –To avoid collisions at switch Two input cells to one output –Uses distributors and queues –n 2 crossover points still required n – number of inputs/outputs

56. updated 12/200156 Asynchronous Transfer Mode Switch fabric – Banyan switch

57. updated 12/200157 Asynchronous Transfer Mode Switch fabric – Batcher Banyan switch

58. updated 12/200158 Asynchronous Transfer Mode ATM Addressing –OSI model –Initial Domain Part – IDP Authority Format Identifier –DCC ATM format –ICD ATM format –E.164 format

59. updated 12/200159 Asynchronous Transfer Mode ATM Addressing Initial Domain Identifier Domain Specific Part –DFI –AA – administrative authority –RD – routing domain id –Area –ESI – end system id –SEL – ULP entities – not used in ATM network