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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: FCIP: A question about framingMurali, I fully understand a need for alignment. TCP however will not provide any alignment! With respect to the FC frame bytes, an encapsulation process could easily move both SOF and EOF into a prefix to aid in processing these bytes. This prefix could include a timestamp as well. Do you know the algorithm for creating these byte codes? For alignment, you should review RFC 2960. You can see an example at: http://search.ietf.org/internet-drafts/draft-otis-fc-sctp-ip-01.txt Doug > 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 >
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