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Date:      Wed, 29 Dec 1999 21:22:40 -0300
From:      Fernando Ariel Gont <fgont@softhome.net>
To:        justin@apple.com
Cc:        freebsd-net@FreeBSD.ORG
Subject:   Re: Two many CRCs?
Message-ID:  <.19991229211419.009c8b10@pop.softhome.net>
In-Reply-To: <199912290213.SAA01337@walker3.apple.com>

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At 18:13 28/12/1999 -0800, Justin C. Walker wrote:

 >Third, there's still a chance (cosmic rays, you know) that a packet  
 >really might get munged after it is in host memory, but before the  
 >stack layers have their look at it.  This is possible, and has been  
 >observed.  It gets less likely over time.

Ok, but... Was that taken as a *reason* for adding a CRC field?
I mean, I can't understand that a CRC field was added because someone thought that the packets could get damaged in memory...  If so, what about the OS code that is in memory????



 >Forth, the protocol CRCs cover different portions of the packet.   
 >For IP, it's *just* the IP header; for TCP, it's just the TCP  
 >"packet" (plus the "pseudo header").

Ok, but.... why isn't there only one CRC field at the IP layer that covers the *whole* IP datagram?
If it were like this, I think a CRC field at TCP or UDP would not be necessary...

Best regards,

Fernando Ariel Gont

E-mail:   fgont@softhome.net
web site: http://members.xoom.com/gont/

--- "Con las computadoras crearemos una civilizacion de estupidos tecnologicos,
      y una elite se ira quedando con todo. Cuando digo elite me refiero a gente
      como yo, que puede leer." - Ray Bradbury, escritor



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