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Overview of Asynchronous Transfer Mode (ATM) and TCP/IP Protocols

This chapter delves into the Asynchronous Transfer Mode (ATM) protocol architecture, detailing its functionalities, such as logical connections (VCC and VPC), ATM cells, and service categories. It discusses the roles of the ATM Adaptation Layer (AAL) in mapping non-ATM protocols, error handling, and traffic flow management. With a focus on the advantages of virtual paths and connections, the chapter emphasizes the significance of quality of service (QoS) and provides insights into various service categories, application examples, and header formats relevant to ATM systems.

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Overview of Asynchronous Transfer Mode (ATM) and TCP/IP Protocols

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  1. Chapter 5 Asynchronous Transfer Mode (ATM) Chapter 2 Protocols and the TCP/IP Suite

  2. Introduction • ATM Protocol Architecture • Logical connections • ATM Cells • Service categories • ATM Adaptation Layer (AAL) Chapter 2 Protocols and the TCP/IP Suite

  3. ATM Protocol Architecture • Fixed-size packets called cells • Streamlined: minimal error and flow control • 2 protocol layers relate to ATM functions: • Common layer providing packet transfers • Service dependent ATM adaptation layer (AAL) • AAL maps other protocols to ATM Chapter 2 Protocols and the TCP/IP Suite

  4. Protocol Model has 3 planes • User • Control • management Chapter 2 Protocols and the TCP/IP Suite

  5. Figure 5.1 Chapter 2 Protocols and the TCP/IP Suite

  6. Logical Connections • VCC (Virtual Channel Connection): a logical connection analogous to virtual circuit in X.25 • VPC (Virtual Path Connection): a bundle of VCCs with same endpoints Chapter 2 Protocols and the TCP/IP Suite

  7. Figure 5.2 Chapter 2 Protocols and the TCP/IP Suite

  8. Advantages of Virtual Paths • Simplified network architecture • Increased network performance and reliability • Reduced processing and short connection setup time • Enhanced network services Chapter 2 Protocols and the TCP/IP Suite

  9. Table 5.1 Chapter 2 Protocols and the TCP/IP Suite

  10. VCC Uses • Between end users • Between an end user and a network entity • Between 2 network entities Chapter 2 Protocols and the TCP/IP Suite

  11. Figure 5.3 Chapter 2 Protocols and the TCP/IP Suite

  12. VPC/VCC Characteristics • Quality of Service (QoS) • Switched and semi-permanent virtual channel connections • Cell sequence integrity • Traffic parameter negotiation and usage monitoring • (VPC only) virtual channel identifier restriction within a VPC Chapter 2 Protocols and the TCP/IP Suite

  13. Control Signaling • A mechanism to establish and release VPCs and VCCs • 4 methods for VCCs: • Semi-permanent VCCs • Meta-signaling channel • User-to-network signaling virtual channel • User-to-user signaling virtual channel Chapter 2 Protocols and the TCP/IP Suite

  14. Control Signaling • 3 methods for VPCs • Semi-permanent • Customer controlled • Network controlled Chapter 2 Protocols and the TCP/IP Suite

  15. ATM Cells • Fixed size • 5-octet header • 48-octet information field • Small cells reduce delay for high-priority cells • Fixed size facilitate switching in hardware Chapter 2 Protocols and the TCP/IP Suite

  16. Header Format • Generic flow control • Virtual path identifier (VPI) • Virtual channel identifier (VCI) • Payload type • Cell loss priority • Header error control Chapter 2 Protocols and the TCP/IP Suite

  17. Figure 5.4 Chapter 2 Protocols and the TCP/IP Suite

  18. Generic Flow Control • Control traffic flow at user-network interface (UNI) to alleviate short-term overload conditions • When GFC enabled at UNI, 2 procedures used: • Uncontrolled transmission • Controlled transmission Chapter 2 Protocols and the TCP/IP Suite

  19. Table 5.3 Chapter 2 Protocols and the TCP/IP Suite

  20. Header Error Control • 8-bit field calculated based on remaining 32 bits of header • error detection • in some cases, error correction of single-bit errors in header • 2 modes: • error detection • Error correction Chapter 2 Protocols and the TCP/IP Suite

  21. Figure 5.5 Chapter 2 Protocols and the TCP/IP Suite

  22. Figure 5.6 Chapter 2 Protocols and the TCP/IP Suite

  23. Figure 5.7 Chapter 2 Protocols and the TCP/IP Suite

  24. Service Categories • Real-time service • Constant bit rate (CBR) • Real-time variable bit rate (rt-VBR) • Non-real-time service • Non-real-time variable bit rate (nrt-VBR) • Available bit rate (ABR) • Unspecified bit rate (UBR) • Guaranteed frame rate (GFR) Chapter 2 Protocols and the TCP/IP Suite

  25. Figure 5.8 Chapter 2 Protocols and the TCP/IP Suite

  26. ATM Adaptation Layer (ATM) • Support non-ATM protocols • e.g., PCM voice, LAPF • AAL Services • Handle transmission errors • Segmentation/reassembly (SAR) • Handle lost and misinserted cell conditions • Flow control and timing control Chapter 2 Protocols and the TCP/IP Suite

  27. Applications of AAL and ATM • Circuit emulation (e.g., T-1 synchronous TDM circuits) • VBR voice and video • General data services • IP over ATM • Multiprotocol encapsulation over ATM (MPOA) • LAN emulation (LANE) Chapter 2 Protocols and the TCP/IP Suite

  28. AAL Protocols • AAL layer has 2 sublayers: • Convergence Sublayer (CS) • Supports specific applications using AAL • Segmentation and Reassembly Layer (SAR) • Packages data from CS into cells and unpacks at other end Chapter 2 Protocols and the TCP/IP Suite

  29. Figure 5.9 Chapter 2 Protocols and the TCP/IP Suite

  30. Figure 5.10 Chapter 2 Protocols and the TCP/IP Suite

  31. AAL Type 1 • Constant-bit-rate source • SAR simply packs bits into cells and unpacks them at destination • One-octet header contains 3-bit SC field to provide an 8-cell frame structure • No CS PDU since CS sublayer primarily for clocking and synchronization Chapter 2 Protocols and the TCP/IP Suite

  32. AAL Type 3/4 • May be connectionless or connection oriented • May be message mode or streaming mode Chapter 2 Protocols and the TCP/IP Suite

  33. Figure 5.11 Chapter 2 Protocols and the TCP/IP Suite

  34. Figure 5.12 Chapter 2 Protocols and the TCP/IP Suite

  35. AAL Type 5 • Streamlined transport for connection oriented protocols • Reduce protocol processing overhead • Reduce transmission overhead • Ensure adaptability to existing transport protocols Chapter 2 Protocols and the TCP/IP Suite

  36. Figure 5.13 Chapter 2 Protocols and the TCP/IP Suite

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