Re: FCIP: A question about framing

["Robert B. Harmon" <bharmon@entradanet.com>]

I thought URGENT would be a more appropriate mechanism, why was URG
expressly
forbidden?

Also I've heard that other protocols have wanted to keep frames
together in one IP packet.  Anyone remember which ones?

I can think of several other tunnelling protocol which use IP only
IP-IP, Ether-o-IP, PPP-o-Eth...  I can't think of any which use TCP.


"KRUEGER,MARJORIE (HP-Roseville,ex1)" wrote:
> 
> Do TCP RFCs specify the behavior of the receiver regarding when to deliver
> data to the application?  From what I've read, different implementations act
> differently - some buffer data received data and deliver it to the app when
> the buffer's full, others deliver data immediately when each packet is
> received.  In either implementation, when the PUSH flag is set, all data is
> delivered immediately to the application.  In a FCoIP device, could't the
> receipt of the packet with the PUSH flag set indicate that this is the "end
> of a frame"?  Assuming that the FC aware code can also view the TCP header.
> 
> I understand the truth of what you are saying when TCP is delivering data to
> an "application", but I'm assuming that FCoTCP implementations will have
> some level of mapping interaction between the TCP and the FC layer?
> 
> > -----Original Message-----
> > From: Randall R. Stewart [mailto:randall@stewart.chicago.il.us]
> > Sent: Thursday, November 02, 2000 11:34 AM
> > To: Murali Rajagopal
> > Cc: Douglas Otis; Merhar, Milan; ips@ece.cmu.edu
> > Subject: Re: FCIP: A question about framing
> > Murali:
> >
> > Using Push does not guarantee that you will get "datagram-like"
> > behavior. You
> > must have some mechanism to find your "message" amongst a stream of
> > bytes... this is what TCP presents you with. This usually means a
> > message/finder that can parse the incoming stream and find the
> > beginning/ending of the message boundaries... Some apps have
> > been known
> > to write every message in two pieces... write the number of bytes
> > in this message in a 4 byte int, followed by the message with the PUSH
> > flag set.  Even at that the reader side must read the 4 byte value
> > and then continue to read until it has assembled a complete message.
> >
> > The PUSH flag is just a hint to TCP it does not assure you
> > that you will
> > get a datagram behavior depending on PUSH will not help you... been
> > there ..
> > . done that.. it don't work :/
> >
> > R
> >
> 
> Marjorie Krueger
> Networked Storage Architecture
> Hewlett-Packard Storage Organization
> tel: +1 916 785 2656
> fax: +1 916 785 0391
> email: marjorie_krueger@hp.com