Re: Fragment : 2nd Ques

Well the answer is simple routers do not reassemble fragment along the path
as it is not efficient and not needed, if each router along the path would
look on the traffic and try to reassemble and fragment the routers would
soon crash.
in programming there is a formula that check how many bugs can happen in
single line code a good code is considered if it is efficient and that
usually mean the short's way to perform what you require to do.

So the question is Why should you try to reassemble the packet if you are
not the destination?!

routers check only if the interface MTU they need to send the packet out
is sufficient to send that packet.

On Tue, Sep 21, 2010 at 7:33 AM, Happy Singh <happynetworkingsingh_at_gmail.com
> wrote:

> Hi
>
> Again ; trying to understand Fragmentation .
> Lets have following scenario :
>
> R1 --------R2 ------------R3 ----R4
>
> R1-R2 MTU = 3300 bytes
> R2-R3 MTU = 1300 bytes
> R3-R4 MTU = 3300 bytes
>
>
> Let pkt of 12000 byte came in R1 . It fragments and send on R1-R2 link
>
> R2 must fragment each of these into smaller fragments to send them over
> the
> 1,300-byte MTU link. Note that the R3 does *not* reassemble the
> 1,300-byte fragments, even though next link has an MTU of 3,300
> bytes.WHYYYYYY ????
>
> My question is that why is re-assembly done by end router ? Reasons ?
>
> Thnx
> Happy
>
>
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