Internet Protocol: Connectionless Datagram Delivery Chapter 7

Introduction An internet is an abstraction of physical networks because it provides the same functionality: Accepting packets and delivering them Conceptual layers of internet services Applications Reliable Transport Service Connectionless Packet Delivery Service

Connectionless Delivery System Service is defined as unreliable, best-effort, connectionless packet delivery system Unreliable because delivery is not guaranteed the packet may be lost, duplicated, delayed, or delivered out of order the service will not detect such conditions, nor will it inform the sender or receiver - how will they know? Connectionless because each packet is treated independently from all others Best-effort because bad things are not done intentionally

Purpose of the Internet Protocol IP provides the basic unit of data transfer used in a TCP/IP internet, and the format of all data IP software which performs the routing, the path over which data is sent a set of rules for unreliable packet delivery: how packets are processed, how and when error messages are generated, when packets can be discarded

What is a Datagram? The basic unit of information passed across a TCP/IP internet IP datagram : internet = frame : physical network A datagram is separated into header and data areas (like a frame) as shown in Figure 7.2 The datagram header contains IP addresses The frame header contains hardware addresses See Figure 7.3

Summary IP formally specifies the format of internet packets, called datagrams The IP datagram header contains source and destination IP addresses fragmentation information, precedence, and a checksum for the header may contain options: record routing, timestamps

For Next Time Read Chapter 8 What else?