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

Protocols and the TCP/IP Suite Introduction ATM Protocol Architecture Logical connections ATM Cells Service categories ATM Adaptation Layer (AAL) Chapter 5 Asynchronous Transfer Mode Chapter 2

ATM Protocol Architecture Protocols and the TCP/IP Suite 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 5 Asynchronous Transfer Mode Chapter 2

Protocol Model has 3 planes Protocols and the TCP/IP Suite Protocol Model has 3 planes User Control Management Chapter 5 Asynchronous Transfer Mode Chapter 2

Protocols and the TCP/IP Suite Figure 5.1 Chapter 5 Asynchronous Transfer Mode Chapter 2

Protocols and the TCP/IP Suite 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 5 Asynchronous Transfer Mode Chapter 2

Protocols and the TCP/IP Suite Figure 5.2 Chapter 5 Asynchronous Transfer Mode Chapter 2

Advantages of Virtual Paths Protocols and the TCP/IP Suite Advantages of Virtual Paths Simplified network architecture Increased network performance and reliability Reduced processing and short connection setup time Enhanced network services Chapter 5 Asynchronous Transfer Mode Chapter 2

VPC/VCC Characteristics Protocols and the TCP/IP Suite 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 5 Asynchronous Transfer Mode Chapter 2

Protocols and the TCP/IP Suite Control Signaling A mechanism to establish and release VPCs and VCCs Methods to request for a VC: Semi-permanent VCCs Request as needed Chapter 5 Asynchronous Transfer Mode Chapter 2

Protocols and the TCP/IP Suite 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 5 Asynchronous Transfer Mode Chapter 2

Protocols and the TCP/IP Suite Header Format Generic flow control Virtual path identifier (VPI) Virtual channel identifier (VCI) Payload type Cell loss priority Header error control Chapter 5 Asynchronous Transfer Mode Chapter 2

Protocols and the TCP/IP Suite Figure 5.4 CLP = Cell Loss Priority bit Chapter 5 Asynchronous Transfer Mode Chapter 2

Protocols and the TCP/IP Suite 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 5 Asynchronous Transfer Mode Chapter 2

Protocols and the TCP/IP Suite Header Error Control 8-bit field calculated based on remaining 32 bits of header For error detection In some cases, error correction of single-bit errors in header Chapter 5 Asynchronous Transfer Mode Chapter 2

Protocols and the TCP/IP Suite 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) Slides with details for these? Chapter 5 Asynchronous Transfer Mode Chapter 2

Protocols and the TCP/IP Suite Figure 5.8 Chapter 5 Asynchronous Transfer Mode Chapter 2

ATM Adaptation Layer (AAL) Protocols and the TCP/IP Suite ATM Adaptation Layer (AAL) Support non-ATM protocols Maps to ATM cells AAL Services Handle transmission errors Segmentation/reassembly (SAR) Handle lost and misinserted cell conditions Flow control and timing control Chapter 5 Asynchronous Transfer Mode Chapter 2

Applications of AAL and ATM Protocols and the TCP/IP Suite Applications of AAL and ATM Circuit emulation (e.g., E-1/T-1 synchronous TDM circuits) VBR voice and video General data services IP over ATM Multiprotocol encapsulation over ATM (MPOA) LAN emulation (LANE) Chapter 5 Asynchronous Transfer Mode Chapter 2

Protocols and the TCP/IP Suite 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 5 Asynchronous Transfer Mode Chapter 2

Protocols and the TCP/IP Suite Figure 5.9 Chapter 5 Asynchronous Transfer Mode Chapter 2

Protocols and the TCP/IP Suite Figure 5.10 (CBR source) CBR Service (connectionless or connection-oriented) VBR Service (higher-layer connection-oriented services) Connection-oriented Service Chapter 5 Asynchronous Transfer Mode Chapter 2

Protocols and the TCP/IP Suite AAL Type 1 Constant-bit-rate source SAR simply packs bits into cells and unpacks them at destination Sequence Number (SN) used in reassembling SAR PDUs Sequence Number Protection (SNP) provides error detection/correction No CS PDU since CS sublayer primarily for clocking and synchronization Chapter 5 Asynchronous Transfer Mode Chapter 2

Protocols and the TCP/IP Suite AAL Type 3/4 May be connectionless or connection oriented May be message mode or streaming mode Chapter 5 Asynchronous Transfer Mode Chapter 2

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

Protocols and the TCP/IP Suite Figure 5.13 Chapter 5 Asynchronous Transfer Mode Chapter 2