MPA CRC check issue from San Diego

>From the San Diego Workgroup minutes:

	iSER is a protocol that uses MPA (RDDP mapping to TCP) for
iSCSI.

	The iSER draft authors have found MPA's current CRC requirements
	text to be insufficient for iSER usage of MPA, and hence 
	currently impose stronger requirements. iSER requires that RDDP 
	provide at least CRC32-class integrity, but the current MPA
draft 
	text allows CRC32C to be disabled in situations where that would

	not be the result.

	The RDDP WG's rough consensus has been that ULPs can assume at 
	least CRC-class integrity from RDDP. Hence the sense of the room

	is that the MPA draft text needs to be tightened to do this and 
	remove the need for iSER to add requirements to MPA.

	ACTION: MPA draft authors to propose specific new text on 
	reflector.

Current text (section 1.1):
	"MPA includes a CRC check to increase the ULPDU data integrity
to 
	the level provided by other modern protocols, such as SCTP 
	[RFC2960].  This check may be disabled with agreement by 
	providers and administrators at both ends of a connection.  This

	disabling of CRCs should only be done when it is clear that the 
	connection through the network has data integrity at least as 
	good as a CRC (for example when IPSEC is implemented end to
end).  
	DDP's ULP expects this level of data integrity and therefore the

	ULP SHOULD NOT have to provide its own duplicate data integrity 
	and error recovery for lost data."

Also section 5.2:
	"An MPA implementation MUST implement CRC support and MUST 
	either:
	(1) always use CRCs
	or
	(2) only negotiate the non-use of CRC on the explicit request of

	the system administrator, via an interface not defined in this 
	spec.  The default configuration for a connection MUST be to use

	CRCs.
	(3) The MPA provider at either peer MAY ignore its 
	administrator's request that CRCs not be used.

	The decision for one host to request CRC suppression MAY be made

	on an administrative basis for any path that provides equivalent

	protection from undetected errors as an end-to-end CRC32c."

Section 5.2 appears to be sufficiently strong to deal with the iSER 
issue.  The proposal is to modify the section 1.1 text as follows:

	"MPA includes a CRC check to increase the ULPDU data integrity
to 
	the level provided by other modern protocols, such as SCTP 
	[RFC2960].  It is possible to disable this CRC check, however
 	CRCs MUST be enabled unless it is clear that the end to end
	connection through the network has data integrity at least as 
	good as a MPA with CRC enabled (for example when IPSEC is 
	implemented end to end).  DDP's ULP expects this level of data 
	integrity and therefore the ULP does not have to provide its 
	own duplicate data integrity and error recovery for lost data."

Paul R. Culley
HP Fellow
281-514-5543