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ATM QoS

ATM QoS. Overview. ATM introduction ATM architecture ATM QoS IP-ATM integration IP-ATM QoS Mapping. Pre-ATM Era Service Specialization. POTS (Plain Old Telephone Service) VOICE Circuit Switching Delay Guarantee QoS Limited Speed Data No Video. Computer Network (LAN, MAN, WAN)

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ATM QoS

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  1. ATM QoS Engineering Internet QoS

  2. Overview • ATM introduction • ATM architecture • ATM QoS • IP-ATM integration • IP-ATM QoS Mapping Engineering Internet QoS

  3. Pre-ATM EraService Specialization POTS (Plain Old Telephone Service) VOICE Circuit Switching Delay Guarantee QoS Limited Speed Data No Video Computer Network (LAN, MAN, WAN) DATA Packet Switching No Delay Guarantee No QoS (best effort) Not suitable for Voice and Video TV Network (CATV, Satellite, etc.) VIDEO Circuit Switching Delay Guarantee QoS No data or voice Engineering Internet QoS

  4. Consequence of Service Specialization • Several Independent networks, each has its own • design • manufacturing • implementation • maintenance • Low utilization : Free resources in one network cannot be utilized by another network • Inflexible : cannot benefit from technological advances that change service requirements (e.g. NISDN switches cannot handle 32Kbps ADPCM voice) Engineering Internet QoS

  5. ATM Era : Multiservice NetworksDeparture from Service Specialization bulk data video Multiservice Network voice interactive data Engineering Internet QoS

  6. ATM Convergence POTS Voice N-ISDN ATM Network 10 Mbps Ethernet FastEthernet FDDI Digital TV VOD Analog TV Video Cass Data : LAN Video Frame Relay Data : WAN X.25 Engineering Internet QoS

  7. Management Plane Control Plane User Plane Higher Layer (e.g. Q.2931) Higher Layer (e.g. TCP) Adaptation Layer (e.g. AAL5) ATM Layer Physical Layer (e.g. SONET) ATM Protocol Architecture Reprinted with Permission from “Engineering Internet QoS - Jha & Hassan, Artech House Publishing, Norwood, MA, USA. www.artechhouse.com Engineering Internet QoS

  8. End-to-End ATM Architecture ATM terminal ATM terminal ATM switch Reprinted with Permission from “Engineering Internet QoS - Jha & Hassan, Artech House Publishing, Norwood, MA, USA. www.artechhouse.com Engineering Internet QoS

  9. Virtual Channels • ATM is connection oriented • AN ATM connection is called virtual channel/connection/circuit (VC) • A VC must be established between two end points before data can be transmitted • Tens of thousands of VCs per fiber • Different VC, different bandwidth, QoS • User data and signaling on different VCs Engineering Internet QoS

  10. Virtual Paths • Virtual Private Network over public ATM • many individual VCs between two sites • switches need to switch VCs individually even if they start and end at the same points • VCs starting and ending at the same points can be bundled in virtual paths or VPs • Switches may switch only VPs, not aware of individual VCs inside the VP Engineering Internet QoS

  11. Reprinted with Permission from “Engineering Internet QoS - Jha & Hassan, Artech House Publishing, Norwood, MA, USA. www.artechhouse.com Virtual Paths & Virtual Channels VC VC VP VC VC VC VC VP VC VC Physical Channel VC VC VP VC VC VC VP VC VC VC Engineering Internet QoS

  12. Virtual Path Connection (VPC) Reprinted with Permission from “Engineering Internet QoS - Jha & Hassan, Artech House Publishing, Norwood, MA, USA. www.artechhouse.com Engineering Internet QoS

  13. Virtual Channel Connection (VCC) Reprinted with Permission from “Engineering Internet QoS - Jha & Hassan, Artech House Publishing, Norwood, MA, USA. www.artechhouse.com Engineering Internet QoS

  14. Permanent Virtual Circuit • VPIs and VCIs for the end-to-end connection are preconfigured in hardware • Semi-PVC : VPIs and VCIs are preconfigured, but can be erased and reconfigured later • PVC is good for Virtual Leased Line for VPN • PVC does not scale well for an ATM LAN/WAN with many stations : too many PVCs required Engineering Internet QoS

  15. Switched Virtual Circuit • Circuit on demand • Scalable solution to ATM connectivity • Different VPIs and VCIs at successive call setups for the same source-destination. Engineering Internet QoS

  16. ATM Interfaces • User-Network Interface (UNI) • public • private • Network-Network Interface (NNI) Copy figure 9.3 from text Engineering Internet QoS

  17. ATM Cells • 53-byte long • 5-byte header • 48-byte payload • Slightly different format for User-Network and Network-Network communications Engineering Internet QoS

  18. Advantages of Short, Fixed Size Cells • Minimise delay for voice/video traffic • minimise delay variance (jitter) • Easier to process (fast switching) Engineering Internet QoS

  19. UNI Cell Structure 8 7 6 5 4 3 2 1 GFC VPI VPI VCI VCI VCI PT CLP HEC Cell Payload (48 octets) Reprinted with Permission from “Engineering Internet QoS - Jha & Hassan, Artech House Publishing, Norwood, MA, USA. www.artechhouse.com Engineering Internet QoS

  20. Reprinted with Permission from “Engineering Internet QoS - Jha & Hassan, Artech House Publishing, Norwood, MA, USA. www.artechhouse.com NNI Cell Structure 8 7 6 5 4 3 2 1 VPI VPI VCI VCI VCI PT CLP HEC Cell Payload (48 octets) Engineering Internet QoS

  21. Application TCP/UDP IP AAL5 ATM ATM Adaptation Layer 5 Reprinted with Permission from “Engineering Internet QoS - Jha & Hassan, Artech House Publishing, Norwood, MA, USA. www.artechhouse.com Engineering Internet QoS

  22. 1 2 4 1 Size in Octets 0-65,535 0-47 Payload CPI Length PAD CRC UU 8-octet Trailer AAL5 Format Reprinted with Permission from “Engineering Internet QoS - Jha & Hassan, Artech House Publishing, Norwood, MA, USA. www.artechhouse.com Engineering Internet QoS

  23. QoS Support • Traffic contract • Traffic descriptions • QoS parameters • Service classes Engineering Internet QoS

  24. Traffic Contract Traffic Descriptor Part (obeyed by the user) Traffic Parameters PCR, SCR, MBS, MCR, CDVT QoS Descriptor Part (guaranteed by the network) QoS Parameters maxCTD, CDV, CLR ATM Traffic Contract Reprinted with Permission from “Engineering Internet QoS - Jha & Hassan, Artech House Publishing, Norwood, MA, USA. www.artechhouse.com Engineering Internet QoS

  25. Traffic Descriptors • Peak cell rate • Sustainable cell rate • Minimum cell rate • Maximum burst size • Maximum frame size • Cell delay variation tolerance Engineering Internet QoS

  26. QoS Parameters • Maximum cell transfer delay • Cell delay variation • Cell loss ratio Engineering Internet QoS

  27. Service Classes • Constant bit rate • Variable bit rate • Available bit rate • Unspecified bit rate • Guaranteed frame rate Engineering Internet QoS

  28. IP-ATM Integration • ATM to the desk-top • ATM in the backbone Engineering Internet QoS

  29. TCP/IP Host equipped with ATM NIC TCP/IP Host equipped with ATM NIC ATM used to emulate Legacy LANs TCP/IP Host equipped with ATM NIC TCP/IP Host equipped with ATM NIC ATM to the Desktop Reprinted with Permission from “Engineering Internet QoS - Jha & Hassan, Artech House Publishing, Norwood, MA, USA. www.artechhouse.com Engineering Internet QoS

  30. TCP/IP Host Ethernet Ethernet TCP/IP Host ATM ATM IP ATM gateway IP ATM gateway ATM Network TCP/IP Host TCP/IP Host ATM in the Backbone Reprinted with Permission from “Engineering Internet QoS - Jha & Hassan, Artech House Publishing, Norwood, MA, USA. www.artechhouse.com Engineering Internet QoS

  31. Encapsulation IP into ATM • Encapsulating IP packets into Ethernet or Token Ring frames were trivial • IP into ATM is not that trivial as ATM is connection-oriented (VC-Based) and ATM has high protocol overhead Engineering Internet QoS

  32. LLC/SNAP Encapsulation • Traditional encapsulation technique • Multiprotocol support (same VC, many protocols) • 8-byte additional overhead IP Datagram IP, IPX, Netbeui LLC/SNAP Header VC 1 8 AAL5 Trailer 8 AAL5 packet Source Destination Reprinted with Permission from “Engineering Internet QoS - Jha & Hassan, Artech House Publishing, Norwood, MA, USA. www.artechhouse.com Engineering Internet QoS

  33. VC-Based Multiplexing Reprinted with Permission from “Engineering Internet QoS - Jha & Hassan, Artech House Publishing, Norwood, MA, USA. www.artechhouse.com • Each VC is configured and dedicated for a given protocol • LLC/SNAP header is not required IP VC 1 IP Datagram AAL5 Trailer Netbeui 8 VC 2 IPX AAL5 packet VC 3 Source Destination Engineering Internet QoS

  34. IP-ATM QoS Mapping Reprinted with Permission from “Engineering Internet QoS - Jha & Hassan, Artech House Publishing, Norwood, MA, USA. www.artechhouse.com • Intserv over ATM • Diffserv over ATM • Performance implications of QoS mapping Engineering Internet QoS

  35. Intserv over ATM Show Tables 9.2, 9.3 and 9.4 Engineering Internet QoS

  36. Diffserv over ATM Figure 9.17 Engineering Internet QoS

  37. Performance of QoS Mapping • Mapping provides approximate solution • ATM has two drop precedences, Diffserv AF has three • ATM uses cells/sec, IP uses bytes/sec • not the same due to padding • Experiments show problems with QoS mapping • Over provision may be needed to account for QoS mapping inaccuracies Engineering Internet QoS

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