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why does router only incude datapart for fragmentation.why doesn't it include ip header also as datapart during fragmentation like it includes header of tcp/udp?

fragmentation has done by routers because of capacity of data link layer is less than the network layer .for ex. standard Ethernet can only send data of 1500 bytes  .where network layer can send data of( 65535-20) bytes.  

the whole fragmentation is done by the router on network layer .so,is that the reason of excluding header of ip Packet  ?

please clear it . its hazy for me . Thank you
asked in Computer Networks by Active (3.2k points)
edited by | 77 views
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i think header is required at destination only. So, after fragmention ,when the data reached the destination, then entire packets are joined and we have header there.
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No during fragmentation  also header is added on fragments .  I am asking something  else  . Please read my question  once again (I have edited  it )

Thanks
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the header contains a lot of information like version, header length, total length, fragmentation offset, source IP address and many more important things....

If we fragment the header itself then complete information that is present in the header, will be scattered here and there because of this how can we apply reassembly algorithm(this algorithm is used to collect all packets in proper order at destination)  on destination,
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@akash.dinkar12

 I got ur answer Akash.  But  now I am asking that when a message  comes from application layer  then transport layer adds  some header  and network  layer also adds some header,   but we consider transport layer's header as datapart  during fragmentation  and we don't consider  the network layer's  header as datapart.  

That is because of the fragmentation  is done by routers and router has network layer so it remove or dissolve the network layer header .

That is what I had to confirm  .

Please  notify  me if I am wrong  anywhere.
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@bharti

Consider this:

Say if router includes IP header also in fragmentation. So it will fragment the header too. Now let us say 4 fragments are created. Now to send them, router needs to provide a full IP header so that the next router can understand about about the packet and router is appropriately. So router would add the IP header with appropriate information. Now, the packets would contain full IP header (added just now) and also the partial headers present due to fragmentation. This is clearly a waste of bandwidth.

So, IP headers are not considered for fragmentation
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@Arunav khare

thank you for explaining arunav . :)

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