Fragmentation

Posted By on October 26, 2014


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Built in HTTP request methods
Hierarchical Routing

Each network has maximum transmission unit(MTU), the size of the largest packet that a network can transmit. The packet larger than MTU is divided into smaller packets.

Fragmentation is also called as segmentation.

 

There are two types of fragmentation::

  1. Transparent fragmentation: Fragmentation in which packet is divided into smaller packets and reconstructed after transmitted. The packet is then further more divided into fragments if needed.
  2. Non-transparent fragmentation: Fragmentation in which packet is divided into smaller packets and remains divided until it reaches to the destination.

 

Types of network and size of fragments::

Network Size of fragments
Ethernet 1500
Token ring 4096

 

Packet header::

Every IP packet holds an IP header that stores information about the packet.

There are three fields involved in packet fragmentation::

  •  Flags
  • Fragment offset
  • Identification bits

 

When a packet is fragmented, it must be given a number to be reconstructed in original way. One way of doing so is to use a tree.

 

 

Example::
If a 2,366 byte packet enters an Ethernet network with a default MTU size, it must be fragmented into two packets.

The first packet will:
• Be 1,500 bytes in length. 20 bytes will be the IP header, 24 bytes will be the TCP header, and 1,456 bytes will be data.
• Have a DF bit equal to 0 to mean “May Fragment” and an MF bit equal to 1 to mean “More Fragments.”
• Have a Fragmentation Offset of 0.

The second packet will:
• Be 910 bytes in length. 20 bytes will be the IP header, 24 bytes will be the TCP header, and 866 bytes will be data.
• Have the DF bit equal to 0 to mean “May Fragment” and the MF bit equal to 0 to mean “Last Fragment.”
• Have a Fragmentation Offset of 182 (Note: 182 is 1456 divided by 8).

Built in HTTP request methods
Hierarchical Routing

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Posted by Akash Kurup

Founder and C.E.O, World4Engineers Educationist and Entrepreneur by passion. Orator and blogger by hobby

Website: http://world4engineers.com