In this section, we discuss internetworking, connecting networks together to make an internetwork or an internet. In this section, we discuss internetworking, connecting networks together to make an internetwork or an internet. | Chapter 20 Network Layer: Internet Protocol Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20. 20-1 INTERNETWORKING In this section, we discuss internetworking, connecting networks together to make an internetwork or an internet. Need for Network Layer Internet as a Datagram Network Internet as a Connectionless Network Topics discussed in this section: 20. Figure Links between two hosts 20. Figure Network layer in an internetwork 20. Figure Network layer at the source, router, and destination 20. Figure Network layer at the source, router, and destination (continued) 20. Switching at the network layer in the Internet uses the datagram approach to packet switching. Note 20. Communication at the network layer in the Internet is connectionless. Note 20. 20-2 IPv4 The Internet Protocol version 4 (IPv4) is the delivery mechanism used by the TCP/IP protocols. Datagram Fragmentation Checksum . | Chapter 20 Network Layer: Internet Protocol Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20. 20-1 INTERNETWORKING In this section, we discuss internetworking, connecting networks together to make an internetwork or an internet. Need for Network Layer Internet as a Datagram Network Internet as a Connectionless Network Topics discussed in this section: 20. Figure Links between two hosts 20. Figure Network layer in an internetwork 20. Figure Network layer at the source, router, and destination 20. Figure Network layer at the source, router, and destination (continued) 20. Switching at the network layer in the Internet uses the datagram approach to packet switching. Note 20. Communication at the network layer in the Internet is connectionless. Note 20. 20-2 IPv4 The Internet Protocol version 4 (IPv4) is the delivery mechanism used by the TCP/IP protocols. Datagram Fragmentation Checksum Options Topics discussed in this section: 20. Figure Position of IPv4 in TCP/IP protocol suite 20. Figure IPv4 datagram format 20. Figure Service type or differentiated services 20. The precedence subfield was part of version 4, but never used. Note 20. Table Types of service 20. Table Default types of service 20. Table Values for codepoints 20. The total length field defines the total length of the datagram including the header. Note 20. Figure Encapsulation of a small datagram in an Ethernet frame 20. Figure Protocol field and encapsulated data 20. Table Protocol values 20. An IPv4 packet has arrived with the first 8 bits as shown: 01000010 The receiver discards the packet. Why? Solution There is an error in this packet. The 4 leftmost bits (0100) show the version, which is correct. The next 4 bits (0010) show an invalid header length (2 × 4 = 8). The minimum number of bytes in the header must .
