Re: [mpls] working group last call on draft-ietf-mpls-spring-entropy-label

<> Mon, 09 May 2016 15:29 UTC

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To: "Carlos Pignataro (cpignata)" <>, Stewart Bryant <>
Thread-Topic: [mpls] working group last call on draft-ietf-mpls-spring-entropy-label
Date: Mon, 09 May 2016 15:29:03 +0000
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Subject: Re: [mpls] working group last call on draft-ietf-mpls-spring-entropy-label
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Hi Carlos,

In your example (N1-A1-A2-A3-N2-Payload), if you consider RLD=4 network wide, with a bottom_to_top EL insertion you may have (considering no limit in push) : N1-ELI-EL-A1-A2-ELI-EL-A3-N2-ELI - EL - Payload. 
With a top_to_bottom insertion, you may have : N1-N2-ELI-EL-A1-A2-ELI-EL-N2-ELI-EL-Payload

Keeping EL for Adj-SID is still good as Adj-SID can represent a bundle of links (L2 or L3). In theory, there is a bigger advantage for Node-SID, but only if we are sure that all nodes along the path can process the ELI/EL. Now from a practical point of view, we have no insurance.

Best Regards,

-----Original Message-----
From: mpls [] On Behalf Of Carlos Pignataro (cpignata)
Sent: Sunday, May 08, 2016 03:19
To: Stewart Bryant
Subject: Re: [mpls] working group last call on draft-ietf-mpls-spring-entropy-label

Stewart, see inline. 

> On May 7, 2016, at 16:52, Stewart Bryant <> wrote:
>> On 07/05/2016 18:20, Carlos Pignataro (cpignata) wrote:
>> The paraphrasing is accurate, but I feel it does matter. Say you have a series of Adj-labels. For example (N=node, A=Adj): N1-A1-A2-A3-N2-Payload. N1 is top, N2 is bottom of stack. There's an RLD of 4. Placing a EL/ELI after A2 or A3 is effectively of null value practically. (E.g., A2 and A3 are specific links, but N1 and N2 are long loose paths). The places where LB could happen while the packet is switched with N1 and N2 will not have an EL/ELI readable, and A2 A3 won't use EL/ELI.
> Why would you put an ELI in the middle of a set of adj labels? Surely you want the packet to unconditionally go through those labels?

Well, that was exactly my point...

What I tried to exemplify is that the algorithm does not differentiate between Node labels and Adj labels, and I am asking if it should...

Thumb typed by Carlos Pignataro.
Excuze typofraphicak errows

> - Stewart
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