1. Internet Protocol: Connectionless Datagram Delivery
Chapter 7

2. 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

3. 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

4. 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

5. 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

6. 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

7. For Next Time
Read Chapter 8
What else?