Re: Packet length 1284 instead of 1280

[Lars Eggert]

Audsin wrote:

Sir / Madam

I am doing my research on fragmentation avoidance technique for mip6. I am using FreeBSD4.4 with kame snap and ethereal to capture packets

I have a query regarding the packet length

If i am correct ,
packet length = IPHdr +extHdr+TCPHdr+TCPOpt+Data

=IPHdr+Routing Header + Frag Header + TCP Header+ Tcpopt+ Data

40+24+8+20+12+1176=1280 (Which is the MTU of the gif0 interface)

But my ethereal capture says the packet length to be 1284 btyes. Can anyone please let me know what that 4 bytes is accounted for?

Can't help you with your question, but if you're using 4.4-RELEASE, the KAME -SNAP you're using must be ancient. There have been many fixes, especially to the MIP6 code, so upgrading to a recent -SNAP may simply make the problem go away.

Lars
--
Lars Eggert <[EMAIL PROTECTED]> USC Information Sciences Institute

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