Comments on: TCP/IP MTU and MSS

By: buchankas

buchankas — Sat, 19 Mar 2011 20:44:20 +0000

” It may be that you are seeing the packets before they hit the wire and are fragmented when reaching the destination. Try capturing on both sides and see if the results are similar. ”

That was it! The capture was at the sending device, which I thought Wireshark would show them already divided into pieces, but it only shows the segments divided in the receiving device! Thanks a lot!!

Also, if the MSS should be at 536, is it possible that a single IP packet could contain two TCP segments or each IP packet must contatain exactly one TCP segment?

Thanks again

By: buchankas

buchankas — Wed, 09 Mar 2011 20:20:20 +0000

Hey, sorry about the delay, I have been very busy at work. And sorry, I meant WIRESHARK!! Don’t know where I got this fire from…

It would take sometime to mount the setup again to print an output. Do you really think that would be necessary?

Basically, the question is why host A is sending host B (and vice-versa) a TCP segement with over 4000 bytes within my LAN, since the LAN IP MTU size is 1500 bytes and TCP MSS is 1460. Shouldn’t this segment be broken into 1460 or 1500 pieces? In Wireshark it shows just a single message with 4000-byte long received.

Also, the jumbo packet feature in my ethernet adapter is set to 1514 bytes.

Thanks!

By: sixball

sixball — Mon, 28 Feb 2011 14:48:01 +0000

Just a quick question, did you intentionally mention FIRESHARK, or were you elluding to WIRESHARK – as they do completely different functions..

Also, please post some of the output of your analyzer so we can better assist you