Subject: RE: Common Encapsulation: CRC at beginning of frame?

From: Robert Snively <[email-masked]>
Date: Thu, 14 Jun 2001 07:14:44 -0700

I assume you are speaking of the FCIP/iFCP common encapsulation.  The
data CRC is actually at the end of the encapsulation frame.  
The header CRC (proposed for use by iFCP only) is at the end of the 
header.  The FCIP usage of the header exploits the combination of 
TCP/IP protection, data frame verification, and data redundancy 
to achieve error detection at a comparable level and does not use 
the header CRC, simplifying the hardware and/or software 
implementations significantly.

Hope that is some help.

Bob

-----Original Message-----
From: Harmon, Robert [mailto:[email-masked]]
Sent: Wednesday, June 13, 2001 2:20 PM
To: Ips (E-mail)
Subject: Common Encapsulation: CRC at beginning of frame?

Has there been any discussion of putting the 
common encapsulation CRC at the end of the frame 
rather than -near- the beginning? 
Its possible to do CRC in H/W but to put it at the 
beginning of the frame is 5 times harder than putting 
it at the end.

---

From: "Douglas Otis" <[email-masked]>
Date: Thu, 14 Jun 2001 16:11:42 -0700

Robert,

In understanding the difference between these two approaches, iFCP could use
the header CRC as framing confirmation together with the timestamp in a more
resilient manner than FCIP.  iFCP also includes the Fibre-Channel frame
designators within the header for easier processing.

Doug