05-04-2012, 03:29 PM
Internet Protocol
Chap-08-ip.ppt (Size: 924 KB / Downloads: 63)
Objectives
Understand the format and fields of a datagram
Understand the need for fragmentation and the fields involved
Understand the options available in an IP datagram
Be able to perform a checksum calculation
Understand the components and interactions of an IP package
DATAGRAM
A packet in the IP layer is called a datagram, a variable-length packet consisting of two parts: header and data. The header is 20 to 60 bytes in length and contains information essential to routing and delivery.
The receiver discards the packet. Why?
There is an error in this packet. The 4 left-most bits (0100) show the version, which is correct. The next 4 bits (0010) show the header length; which means (2 × 4 = 8), which is wrong. The minimum number of bytes in the header must be 20. The packet has been corrupted in transmission.
FRAGMENTATION
The format and size of a frame depend on the protocol used by the physical network. A datagram may have to be fragmented to fit the protocol regulations.
OPTIONS
The header of the IP datagram is made of two parts: a fixed part and a variable part. The variable part comprises the options that can be a maximum of 40 bytes.
CHECKSUM
The error detection method used by most TCP/IP protocols is called the checksum. The checksum protects against the corruption that may occur during the transmission of a packet. It is redundant information added to the packet.