Re: iSCSI: Towards Urgent Pointer Consensus

[Glen Turner <glen.turner@aarnet.edu.au>]

David Robinson wrote:
> 
> While I am not convinced in the value of using URG, the lack of an API
> specification MUST NOT stop discussion of the architectural merits.

A protocol definition does specify what OSI called "services".
The TCP RFC specifies these before specifying the on-the-wire
formats and the state machine.

A change to the services is a change to the protocol, so Douglas
is correct in as far as a proposal to use URG for inter-PDU
marking should specify the altered TCP services that this provides
in an update to the TCP RFC.

As others have pointed out, such a change obviously requires
the agreement of people outside of this WG and a discussion
of the architectural merits must include them and, in the end,
it is those people that will pass/veto the URG proposal.

The practical implications seem to be:

 - we need a better handle on the non-URG behaviour of
   iSCSI over TCP.  People with sample implementations
   need to step up to the plate.

 - iSCSI should be specified with TCP as the preferred
   transport, but iSCSI should allow other transports to
   be used (which the enterprise users may choose, since they
   have no firewall concerns, etc).  This probably implies
   splitting the current draft into two: one to define
   the iSCSI PDUs, another to define their encapsulation
   in TCP.  Other WGs have done this (eg: SNMP).

 - negotiation of URG must be easily removed in a future
   draft after some implementation experience has occurred
   and also easily expanded to allow negotiation of some
   other PDU-marking mechanism.

-- 
 Glen Turner                                 Network Engineer
 (08) 8303 3936      Australian Academic and Research Network
 glen.turner@aarnet.edu.au          http://www.aarnet.edu.au/
--
 The revolution will not be televised, it will be digitised