RE: TCP limitations (was Re: ISCSI: Urgent Flag requirementviolates TCP.)

["GUPTA,SOMESH (HP-Cupertino,ex1)" <somesh_gupta@hp.com>]

By the way, you do want to avoid IP layer fragmentation if
at all possible (fortunately pretty much everyone does
MTU path discovery now - UDP still causes fragmentation).
It really adds a lot more processing burden and complexity.

Somesh

> -----Original Message-----
> From: Randall R. Stewart [mailto:randall@stewart.chicago.il.us]
> Sent: Tuesday, November 21, 2000 12:25 PM
> To: ronald lee
> Cc: ips@ece.cmu.edu
> Subject: Re: TCP limitations (was Re: ISCSI: Urgent Flag
> requirementviolates TCP.)
> 
> 
> Ronald:
> 
> Comments below...
> 
> 
> ronald lee wrote:
> > 
> > I was wondering, is it possible to use TCP option field to
> > do the framing.  This will require a change to TCP protocol
> > to handle this option,
> > but for implementations that want to get the higher performance
> > they can make this change, else stick with what is there.
> > Just a suggestion.
> > 
> 
> I believe this is clearly OUTSIDE the scope of the WG. We CANNOT
> change TCP.. period... if you desire to do this, you must take
> this to the end2end group (as Scott suggested)...
> 
> 
> > Also, is defragging IP packets any issue with iSCSI hardware
> > implementations ?  We at MaxStrat did a hardware to accelerate
> > TCP/IP over HIPPI and I had to deal with fragmented IP packets which
> > caused
> > a change in the hardware architecture.  Buffer management is a
> > big issue when trying to accelerate TCP/IP with hardware.  What
> > happens if a fragment is missing and lets say many IP packets
> > have a missing fragment or fragments that arrives late.  We might
> > get our buffers filled with fragments.
> 
> Hmm, seems to me if you implement P-MTU discovery this problem would
> go away, but I do agree that if there is no P-MTU discovery you may
> have a problem with fragments....
> 
> 
> R
> 
> > 
> > -- ron
> 
> -- 
> Randall R. Stewart
> randall@stewart.chicago.il.us or rrs@cisco.com
> 815-342-5222 (cell) 815-477-2127 (work)
>