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Chap-23 IP over ATM - Chapter 23 IP Over ATM Objectives...

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Unformatted text preview: Chapter 23 IP Over ATM Objectives Upon completion you will be able to: • Review the features of an ATM WAN • Understand how an a datagram can pass through an ATM WAN • Understand how an IP packet is encapsulated in cells • Understand how cells are routed in an ATM network • Understand the function of ATMARP TCP/IP Protocol Suite 1 23.1 ATM WANS We review some features of the ATM WAN needed to understand IP We over ATM. The only AAL used by the Internet is AAL5, sometimes called the simple and efficient adaptation layer (SEAL). The topics discussed in this section include: The Layers Layers TCP/IP Protocol Suite 2 Figure 23.1 An ATM WAN in the Internet TCP/IP Protocol Suite 3 Figure 23.2 ATM layers in routers and switches TCP/IP Protocol Suite 4 Note: End devices such as routers use all three layers, while switches use only the bottom two layers. TCP/IP Protocol Suite 5 Figure 23.3 AAL5 TCP/IP Protocol Suite 6 Note: The AAL layer used by the IP protocol is AAL5. TCP/IP Protocol Suite 7 Figure 23.4 ATM layer TCP/IP Protocol Suite 8 Figure 23.5 ATM headers TCP/IP Protocol Suite 9 23.2 CARRYING A DATAGRAM IN CELLS We show how an example of a datagram encapsulated in four cells and We transmitted through an ATM network. transmitted The topics discussed in this section include: Why Use AAL5? Why TCP/IP Protocol Suite 10 Figure 23.6 Fragmentation TCP/IP Protocol Suite 11 Note: Only the last cell carries the 8-byte trailer added to the IP datagram. Padding can be added only to the last cell or the last two cells. TCP/IP Protocol Suite 12 Note: The value of the PT field is 000 in all cells carrying an IP datagram fragment except for the last cell; the value is 001 in the last cell. TCP/IP Protocol Suite 13 Figure 23.7 ATM cells TCP/IP Protocol Suite 14 23.3 ROUTING THE CELLS The ATM network creates a route between two routers. We call these The routers entering-point and exiting-point routers. routers The topics discussed in this section include: Addresses Addresses Address Binding TCP/IP Protocol Suite 15 Figure 23.8 Entering-point and exiting-point routers TCP/IP Protocol Suite 16 23.4 ATMARP ATMARP ATMARP given the involved. involved. finds (maps) the physical address of the exiting-point router IP address of the exiting-point router. No broadcasting is The topics discussed in this section include: Packet Format Packet ATMARP Operation TCP/IP Protocol Suite 17 Figure 23.9 ATMARP packet TCP/IP Protocol Suite 18 Table 23.1 OPER field Table OPER TCP/IP Protocol Suite 19 Note: The inverse request and inverse reply messages can bind the physical address to an IP address in a PVC situation. TCP/IP Protocol Suite 20 Figure 23.10 Binding with PVC TCP/IP Protocol Suite 21 Figure 23.11 Binding with ATMARP TCP/IP Protocol Suite 22 Note: The request and reply message can be used to bind a physical address to an IP address in an SVC situation. TCP/IP Protocol Suite 23 Note: The inverse request and inverse reply can also be used to build the server’s mapping table. TCP/IP Protocol Suite 24 Figure 23.12 Building a table TCP/IP Protocol Suite 25 23.5 LOGICAL IP SUBNET (LIS) An ATM network can be divided into logical (not physical) subnetworks. An This facilitates the operation of ATMARP and other protocols (such as IGMP) that need to simulate broadcasting on an ATM network. IGMP) TCP/IP Protocol Suite 26 Figure 23.13 LIS TCP/IP Protocol Suite 27 Note: LIS allows an ATM network to be divided into several logical subnets. To use ATMARP, we need a separate server for each subnet. TCP/IP Protocol Suite 28 ...
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