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Re: [Roll] using the flow label instead of hop by hop

Michael Richardson <mcr+ietf@sandelman.ca> Thu, 25 October 2012 12:39 UTC

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From: Michael Richardson <mcr+ietf@sandelman.ca>
To: roll@ietf.org
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Comments: In-reply-to "Adrian Farrel" <adrian@olddog.co.uk> message dated "Wed, 24 Oct 2012 18:45:54 +0100."
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Date: Thu, 25 Oct 2012 08:16:56 -0400
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Subject: Re: [Roll] using the flow label instead of hop by hop
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Adrian Farrel <adrian@olddog.co.uk> wrote:
    AF> I guess I need to look at this in more detail (it always helps to read the
    AF> draft) this still sounds exactly like label switching.

It sure looks like it at first.

However, labelled switching uses the label to get across a series of
routers.. The label mostly denotes a specific path which the source has
chosen.  Labelled switching is therefore a form of source route (except
that the source route is abstracted).

The presence of this label in RPL does not pick a route, rather it picks
one routing table among many.  It is therefore more akin to the DSCP
than the MPLS label, but even that's not correct.

RPL is doing storing mode (LPM at each hop), or non-storing mode (source
routing) at each hop regardless of the label.  The label picks a DODAG.
It's probably more relevant to storing mode where there is an evaluation
(longest-prefix-match) at each hop, and when there are multiple DODAG,
there are multiple fib.

-- 
Michael Richardson
-on the road-

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