Re: [mpls] draft-fang-mpls-label-forwarding-no-swap - how much does it really save?

Alexander Vainshtein <> Tue, 21 July 2015 08:26 UTC

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From: Alexander Vainshtein <>
To: "Andrew G. Malis" <>, "S. Davari" <>
Thread-Topic: [mpls] draft-fang-mpls-label-forwarding-no-swap - how much does it really save?
Date: Tue, 21 Jul 2015 08:26:13 +0000
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Subject: Re: [mpls] draft-fang-mpls-label-forwarding-no-swap - how much does it really save?
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Andy, Shahram and all,

I may have missed something, but I do not understand why this draft is needed even as an Informational since, as Eric has noticed, it describes a local optimization trick.


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From: mpls [] On Behalf Of Andrew G. Malis
Sent: Tuesday, July 21, 2015 11:03 AM
To: S. Davari
Subject: Re: [mpls] draft-fang-mpls-label-forwarding-no-swap - how much does it really save?

As there are no architectural or protocol changes or IANA considerations, this draft should be informational if it goes forward (it currently says "standards track").


On Mon, Jul 20, 2015 at 8:52 PM, S. Davari <<>> wrote:

I agree no standard change is required since this is a local optimization issue.


> On Jul 20, 2015, at 11:43 AM, Eric C Rosen <<>> wrote:
>> On 7/20/2015 2:07 PM, Shahram Davari wrote:
>> The new swapped labels (The outgoing  label that replaces the
>> incoming label) need to be stored in a table. Using this draft
>> reduces the number of swapped labels that needs to be stored,
>> regardless of  implementation. Don't you agree?
> No.  If you notice that the incoming label needs to be 'replaced' by an outgoing label of the same value, you could just make the rewrite string shorter, so it won't overwrite the top label on the stack.  This seems to be what the draft suggests, but it could be done as an optimization for the particular case where the incoming and outgoing labels have the same value.  You could do this today, as a local implementation optimization. There doesn't seem to be any interop issue or any change to the data plane semantics.
>> It also reduces the configuration and management of the new swapped labels.
> We're not discussing whether there are any advantages to the use of domain-wide labels.  We're discussing whether the use of domain-wide labels requires a change in the forwarding plane architecture.  I just don't see that it does.
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