Protocols

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Submitted By gichuhi
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4.7 NETWORK LAYER PROTOCOLS
• IP (Internet Protocol)
• ICMP (Internet Control Message Protocol)
• ARP (Address Resolution Protocol)
• RARP (Reverse Address Resolution Protocol)

4.7.1 The IP PROTOCOL
• IP represents the heart of the Internet Protocol suite
• Provides the main service of the layer: data transmission in connectionless mode – datagram

IP Header Format IP Header Format
(Including user data, this makes an IP packet)
IP Header fields:

• Version - Indicates the version of IP currently used (now 4);
• IP Header Length - Indicates the datagram header length in 32-bit words (value = 5);
• Type-of-service - Specifies how a particular upper-layer protocol would like the current datagram to be handled. Datagrams can be assigned various levels of importance through this field;
• Total length - Specifies the length of the entire IP packet, including data and header, in bytes.
• Identification - Contains an integer that identifies the current datagram (sequence number). This field is used for re-assembling the datagram fragments;
• Flags - A 3-bit field for fragmentation control:
 000 - last fragment;
 001 - not last fragment;
 010 - the fragmentation not allowed.
• Fragment offset - measured in double-words (offset from main datagram);
• Time-to-live - Maintains a counter that gradually decrements down to zero, at which point the datagram is discarded. This keeps packets from looping endlessly;
• Protocol - Indicates which upper-layer protocol receives incoming packets after IP processing is complete ( 6 - TCP, 17 - UDP);.
• Header checksum - Ensures IP header integrity to make sure all fields are correct;
• Source address - Specifies the sending node;
• Destination address - Specifies the receiving node;
• Options - Allows IP to support various options, such as security;
• Padding - Completes the length of…...

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