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Internet Protocol: Connectionless Datagram Delivery

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.

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Internet Protocol: Connectionless Datagram Delivery

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  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?

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