Re: multiple TCP connections

[csapuntz@cisco.com]

Hi Steve,

First off, I'm not sure what you mean by IP mulithoming.

To an extent, the draft supports IP multihoming, in that:
	- a multihomed host has multiple IP addresses
	- each TCP connection binds to only one IP address
	- howver, iSCSI supports using multiple TCP connections
	  for a single iSCSI sessions.
	- thus, iSCSI supports multihoming.

One advantage of using multiple TCP connections is that you can have 
multiple independent TCP and DMA engines operating in parallel,
each at a slower speed (8 TCP engines at 1 gigabit instead of one
TCP enginea t 8 gigabits).

-Costa


"Steve Byan" <steve_byan@hotmail.com> writes:

> I don't understand the motivation for creating the concept of a session
> consisting of multiple TCP connections in the iSCSI draft.
> 
> If the motiviation is a desire to share the load over multiple physical
> paths, IIRC IP already provides this in the form of multihoming. I
> suspect there is some current activity in this area, although I'm not
> network-literate enough to point to any such work.
> 
> If the motiviation is to work around performance flaws in the
> implementation of multihoming in some TCP/IP stacks, then I suggest that
> it would be better to fix the implementations.
> 
> If the motiviation is to work around a fundamental performance flaw in
> IP multihoming, then I suggest that IP should be fixed, or that some
> other generic solution be engineered.
> 
> If the motiviation is to make it easier to implement TCP/IP hardware
> acceleration by pushing the aggregation of multiple paths up into the
> application protocol, then I suggest that a general solution should be
> engineered (one that can be applied to multiple protocols), rather than
> creating a special hack for iSCSI.
> 
> Is there a rationale for multiple TCP connections that I have missed?
> 
> If not, which is the claimed rationale?
> 
> Thanks.
> 
> Regards,
> -Steve
> 
> Steve Byan <stephen.byan@quantum.com>
> Design Engineer
> Quantum Corp.
> MS 1-3/E23
> 333 South Street
> Shrewsbury MA 01545
> (508) 770-3414
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