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Clarification Regarding the Definition of Total Length Field in the IP Header
by Mahmoud EL-HADIDI - Thursday, 1 December 2011, 12:33 PM
 

Dear Students

I checked about the definition of the "Total Length" field in the IP Header, by referring to the original standard "RFC 791". It says the following:

Total Length:  16 bits

    Total Length is the length of the datagram, measured in octets,
    including internet header and data.  This field allows the length of
    a datagram to be up to 65,535 octets.  Such long datagrams are
    impractical for most hosts and networks.  All hosts must be prepared
    to accept datagrams of up to 576 octets (whether they arrive whole
    or in fragments).  It is recommended that hosts only send datagrams
    larger than 576 octets if they have assurance that the destination
    is prepared to accept the larger datagrams.

    The number 576 is selected to allow a reasonable sized data block to
    be transmitted in addition to the required header information.  For
    example, this size allows a data block of 512 octets plus 64 header
    octets to fit in a datagram.  The maximal internet header is 60
    octets, and a typical internet header is 20 octets, allowing a
    margin for headers of higher level protocols.

 

So, make sure to apply the proper definition when solving problems of sheet 3.

 
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