RE: FCIP: A question about framing

["Murali Rajagopal" <muralir@lightsand.com>]

Doug/Milan:

Although there are 4 bytes specified, only a single byte is really used.
The reason for using 4 bytes instead of one was word boundary alignement 
previously discussed in FC-BB T11 WG.

Hope this helps.

Murali Rajagopal

-----Original Message-----
From: owner-ips@ece.cmu.edu [mailto:owner-ips@ece.cmu.edu]On Behalf Of
Merhar, Milan
Sent: Wednesday, November 01, 2000 10:11 AM
To: ips@ece.cmu.edu
Subject: FCIP: A question about framing


I was pleased to see the new draft for FC over IP
( draft-ietf-ips-fcovertcpip-00.txt ) but something 
in it left me a bit puzzled.

The encapsulation that is described envelops the 
entire FC frame, including its SOF and EOF delimiters,
and then transports it over TCP.  The draft correctly 
points out that in FC the SOF and EOF sequences 
are encoded at the 8b10b level starting with a "comma" 
character, which is a reserved 10-bit code, which does not 
correspond to any 8 bit value.  But, it then says 
that SOF and EOF are encoded in TCP as 4 byte sequences.

This is where I get confused.  Don't you then have to 
prohibit the appearance of the SOF and EOF sequences
(which are now just a set of four regular bytes) 
in the normal payload stream, using a processing-intensive
technique like escape sequence insertion, etc? 

The only other alternative that comes to mind is to use 
the presence of a valid CRC as a gate to on accepting an EOF
sequence.  And that, I believe, is patented technology.

- milan