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Understanding ATM Protocol Architecture for Efficient Networking

Dive into the realm of Asynchronous Transfer Mode (ATM) with this comprehensive lecture outlining ATM Protocol Architecture, Logical Connections, ATM Cells, Service Categories, and the ATM Adaptation Layer. Explore the benefits of Virtual Paths and Virtual Channels for enhanced network performance and reliability. Learn about ATM Cells' fixed size, header format, Generic Flow Control, and Header Error Control. Discover the different Service Categories and the Applications of ATM and ATM Adaptation Layer in various network scenarios. Gain insight into AAL Protocols and different AAL Types for different network applications.

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Understanding ATM Protocol Architecture for Efficient Networking

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  1. CDA 6505 Network Architecture and Client/Server Computing Lecture 5 Asynchronous Transfer Mode (ATM) by Zornitza Genova Prodanoff Lect1..ppt - 01/06/05

  2. Outline • ATM Protocol Architecture • Logical connections • ATM Cells • Service categories • ATM Adaptation Layer (AAL) ZGP002

  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 ZGP003

  4. Protocol Model has 3 planes • User • Control • management ZGP004

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  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 ZGP006

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  8. Advantages of Virtual Paths • Simplified network architecture • Increased network performance and reliability • Reduced processing and short connection setup time • Enhanced network services ZGP008

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  10. VCC Uses • Between end users • Between an end user and a network entity • Between 2 network entities ZGP0010

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  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 ZGP0012

  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 ZGP0013

  14. Control Signaling • 3 methods for VPCs • Semi-permanent • Customer controlled • Network controlled ZGP0014

  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 ZGP0015

  16. Header Format • Generic flow control • Virtual path identifier (VPI) • Virtual channel identifier (VCI) • Payload type • Cell loss priority • Header error control ZGP0016

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  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 ZGP0018

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  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 ZGP0020

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  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) ZGP0024

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  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 ZGP0026

  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) ZGP0027

  28. Applications of AAL and ATM ZGP0028

  29. 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 ZGP0029

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  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 ZGP0032

  32. AAL Type 3/4 • May be connectionless or connection oriented • May be message mode or streaming mode ZGP0033

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  36. AAL Type 5 • Streamlined transport for connection oriented protocols • Reduce protocol processing overhead • Reduce transmission overhead • Ensure adaptability to existing transport protocols ZGP0037

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