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Chapter 21 - Network layer: Address mapping, error reporting, and multicasting. This chapter is devoted to some auxiliary protocols defined at the network layer, that help the IP protocol do its job. These protocols perform address mapping (logical to physical or vice versa), error reporting, and facilitate multicast delivery. | Chapter 21 Network Layer: Address Mapping, Error Reporting, and Multicasting Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 21. 21-1 ADDRESS MAPPING The delivery of a packet to a host or a router requires two levels of addressing: logical and physical. We need to be able to map a logical address to its corresponding physical address and vice versa. This can be done by using either static or dynamic mapping. Mapping Logical to Physical Address Mapping Physical to Logical Address Topics discussed in this section: 21. Figure 21.1 ARP operation 21. Figure 21.2 ARP packet 21. Figure 21.3 Encapsulation of ARP packet 21. Figure 21.4 Four cases using ARP 21. An ARP request is broadcast; an ARP reply is unicast. Note 21. A host with IP address 130.23.43.20 and physical address B2:34:55:10:22:10 has a packet to send to another host with IP address 130.23.43.25 and physical address A4:6E:F4:59:83:AB. The two hosts are on the same Ethernet network. Show the ARP request and reply packets encapsulated in Ethernet frames. Solution Figure 21.5 shows the ARP request and reply packets. Note that the ARP data field in this case is 28 bytes, and that the individual addresses do not fit in the 4-byte boundary. That is why we do not show the regular 4-byte boundaries for these addresses. Example 21.1 21. Figure 21.5 Example 21.1, an ARP request and reply 21. Figure 21.6 Proxy ARP 21. Figure 21.7 BOOTP client and server on the same and different networks 21. DHCP provides static and dynamic address allocation that can be manual or automatic. Note 21. 21-2 ICMP The IP protocol has no error-reporting or error-correcting mechanism. The IP protocol also lacks a mechanism for host and management queries. The Internet Control Message Protocol (ICMP) has been designed to compensate for the above two deficiencies. It is a companion to the IP protocol. Types of Messages Message Format Error Reporting . | Chapter 21 Network Layer: Address Mapping, Error Reporting, and Multicasting Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 21. 21-1 ADDRESS MAPPING The delivery of a packet to a host or a router requires two levels of addressing: logical and physical. We need to be able to map a logical address to its corresponding physical address and vice versa. This can be done by using either static or dynamic mapping. Mapping Logical to Physical Address Mapping Physical to Logical Address Topics discussed in this section: 21. Figure 21.1 ARP operation 21. Figure 21.2 ARP packet 21. Figure 21.3 Encapsulation of ARP packet 21. Figure 21.4 Four cases using ARP 21. An ARP request is broadcast; an ARP reply is unicast. Note 21. A host with IP address 130.23.43.20 and physical address B2:34:55:10:22:10 has a packet to send to another host with IP address 130.23.43.25 and physical address A4:6E:F4:59:83:AB. The two hosts are on
