RE: iSCSI: IP fragmentation

["KRUEGER,MARJORIE (HP-Roseville,ex1)" <marjorie_krueger@hp.com>]

Mandating special behavior between the IP stack and the TCP stack is outside
the scope of the IPS charter.  However, a TCP stack that implements PMTU
discovery already sets the DF bit in IP packets.  It seems reasonable to
state recommendations regarding the RFCs implemented by the TCP stack that
iSCSI is running on top of, like "the TCP stack SHOULD support RFC 1191,
<etc>"  Implementors should also be aware of RFC 1435 and RFC 2923.

Marjorie Krueger
Networked Storage Architecture
Networked Storage Solutions Org.
Hewlett-Packard
tel: +1 916 785 2656
fax: +1 916 785 0391
email: marjorie_krueger@hp.com 

> -----Original Message-----
> From: Joshua Tseng [mailto:jtseng@NishanSystems.com]
> Sent: Thursday, June 07, 2001 6:10 PM
> To: ips@ece.cmu.edu
> Subject: iSCSI: IP fragmentation
> 
> 
> 		Folks,
> 
> 		IP fragmentation is an issue which will affect the
> performance, logic and
> 		HBA/NIC memory requirements of iSCSI 
> implementations. Note
> that
> 		fragmentation by intermediary switches and 
> routers is not
> permitted
> 		in IPv6 (hence, the DO NOT FRAGMENT bit does 
> not exist in
> IPv6).
> 		With this in mind, and in the interest of 
> optimizing iSCSI
> performance,
> 		I was wondering if it would make sense to 
> require that the
> 		DO NOT FRAGMENT bit to be set on IPv4 packets 
> carrying iSCSI
> and
> 		that iSCSI implementations not perform IP 
> fragmentation for
> IPv6.
> 		This will allow for performance optimization if
> implementations do not
> 		have to check for fragmentation and handle reassembly.
> 
> 		Any thoughts?
> 
> 		Josh
>