RE: Common Encapsulation: CRC at beginning of frame?

[Robert Snively <rsnively@Brocade.COM>]

Your "easier" and "more resilient" statements are implementation
dependent.  Our work indicates that both of those are incorrect
statements for at least one very efficient implementation.

Bob

>  -----Original Message-----
>  From: Douglas Otis [mailto:dotis@sanlight.net]
>  Sent: Thursday, June 14, 2001 4:12 PM
>  To: Robert Snively; Harmon, Robert; Ips (E-mail)
>  Subject: RE: Common Encapsulation: CRC at beginning of frame?
>  
>  
>  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
>  
>  > 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:rharmon@entradanet.com]
>  > 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.
>  >
>  
>