Security Basics mailing list archives
Re: TCP/IP CRC question
From: Ansgar -59cobalt- Wiechers <bugtraq () planetcobalt net>
Date: Thu, 7 Oct 2004 11:43:42 +0200
On 2004-10-06 Jorge Mendez Bonini wrote:
I've been reading about the TCP/IP protocol stack (TCP/Ilustrated Vol1 by Richard Stevens) lately and since Ethernet is quite common nowadays almost all link layer examples refer to it (I also checked Douglas Comer Internetworking with TCP/IP vol1). I tried searching RFC but found it very time consuming without good results (maybe I'm not used to it...yet) The Ethernet Frame contains a field known as FCS which contains a CRC. Now, my question is: If the CRC is generated from DATA field among others, What's the point of using checksums on the upper protocolos (IP checksums etc..)?
Not sure if I understand your question correctly. The FCS is a checksum on the entire Ethernet frame. Its purpose is to detect transmission failures on the link-layer (and discard erroneous frames so they don't have to be processed by upper layers). Regards Ansgar Wiechers -- "Those who would give up liberty for a little temporary safety deserve neither liberty nor safety, and will lose both." --Benjamin Franklin
Current thread:
- TCP/IP CRC question Jorge Mendez Bonini (Oct 06)
- RE: TCP/IP CRC question David Gillett (Oct 07)
- Re: TCP/IP CRC question Jonathan Loh (Oct 07)
- RE: TCP/IP CRC question Shaineel Singh (Oct 07)
- Re: TCP/IP CRC question Alex V . Lukyanenko (Oct 07)
- Re: TCP/IP CRC question Fernando Gont (Oct 07)
- RE: TCP/IP CRC question Shaineel Singh (Oct 07)
- Re: TCP/IP CRC question Ansgar -59cobalt- Wiechers (Oct 07)
- Re: TCP/IP CRC question Fernando Gont (Oct 07)
- Re: TCP/IP CRC question Miles Stevenson (Oct 07)
- Re: TCP/IP CRC question Miles Stevenson (Oct 08)
- RE: TCP/IP CRC question Clement Dupuis (Oct 12)
- Re: TCP/IP CRC question Miles Stevenson (Oct 08)
- <Possible follow-ups>
- Re: TCP/IP CRC question Don Parker (Oct 07)
- RE: TCP/IP CRC question Ted A (Oct 07)
- RE: TCP/IP CRC question Simon Zuckerbraun (Oct 13)