Chapter 2 Protocols and the TCP/IP Suite 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