Subject: RE: Reordering and MPLS?

From: "J. Noel Chiappa" <[email-masked]>
Date: Sat, 8 Jan 2000 23:15:42 -0500

> From: Bora Akyol <[email-masked]>

    > I would reword it to say that packet ordering should be preserved under
    > normal operating conditions.

That sounds fine, but be careful of IETF standards terminology - if a
document says 'SHOULD' that may still allow someone to try and build a switch
that reorders every third packet. ("SHOULD: This word .. mean[s] that there
may exist valid reasons in particular circumstances to ignore a particular
item, but the full implications must be understood and carefully weighed
before choosing a different course.)

It needs to say something like "MUST only reorder packets rarely", or
something (and no, I don't think it's appropriate to be any more specific
than "rarely").

    > I would like to say that striping packets through a switch without any
    > respect to packet order is NOT acceptable

Sure, that sounds reasonable. Switches should not make a practise of
reordering packets (except as explicitly called for by resource allocation
mechanisms, and in those cases it will be between flows).

	Noel

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From: Christian Kuhtz <[email-masked]>
Date: Sat, 8 Jan 2000 23:35:35 -0500

> mechanisms, and in those cases it will be between flows).

And a flow is what exactly?  Which very large scale flow based traffic 
engineering technique has been proven to scale with very large #s of flows?  
"between flows" to me implies some amount of automagic detection of flows.

It sounds like you guys are suggesting that traffic engineering by means of
WFQ, Priority Queue w/ WFQ, CBWFQ, etc are the exception and not the norm, or
at the very least very rare..  Note: classification and scheduling are disjoint
events.

While it is perhaps _in theory_ desirable to not have reordering, reality is
that you should never assume that it doesn't happen. In fact, certain TE 
mechanism will cause reordering beyond an applications control.

Cheers,
Chris

-- 
Christian Kuhtz                                     Architecture, BellSouth.net
<[email-masked]> -wk, <[email-masked]> -hm                       Atlanta, GA
                                                    "Speaking for myself only."

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From: Frank Kastenholz <[email-masked]>
Date: Sun, 09 Jan 2000 13:45:50 -0500

>something (and no, I don't think it's appropriate to be any more specific

If it's not quantifiable, it's not a standard/specification, it's an
implementation guideline.