[mpls] Re: Fwd: New Version Notification for draft-li-mpls-mna-entropy-03.txt

[Stewart Bryant <[e-mail]>]

@Loa:

As part of determining the number of entropy bits we need, we need to consider the number of paths that a packet may take through the network. 

What normally happens is that the entropy is reduced to a much smaller number of bits at each path split point to pick - from n possible next hops for the packet.

So prior question: for any given communicating pair, how many end to end paths do we need to design for?

Best regards 

Stewart 

> On 2 Sep 2024, at 9:56 AM, Loa Andersson <[e-mail]> wrote:
> 
> Adrian,
> 
> inlline.
> 
>> Den 02/09/2024 kl. 16:20, skrev Adrian Farrel:
>> How do you measure?
>> Size : 2^20 bits available in EL and LSE-C
>> Place in stack : No restriction on either
>> Repetition in stack : No restriction on either
>> 
>> A
> 
> OK, I was struggling  before, this does not make it better :(.
> 
> If all our methods are "equal", why do we struggle to develop
> new methods?
> 
> One question I really can't keep from asking. Hope someone can
> lay it to rest.
> 
> In hashing the stack a stack with 6 non-SPL labels gives me entropy
> based on 6 x 2^20 bits, to give me entropy based on the same number of bit with EL/ELI I need 12 LSEs, right?
> 
> AS for an MNA based method you can use 20 bits in the LSE Format C and
> another 30 in an LSE Format D, right
> 
> /Loa
>> -----Original Message-----
>> From: Loa Andersson <[e-mail]>
>> Sent: 02 September 2024 09:11
>> To: Stewart Bryant <[e-mail]>; Tony Li <[e-mail]>
>> Cc: mpls <[e-mail]>
>> Subject: [mpls] Re: Fwd: New Version Notification for draft-li-mpls-mna-entropy-03.txt
>> 
>> Stewart and Tony,
>> 
>> This might be classified as naive questions :).
>> 
>>> Den 02/09/2024 kl. 15:15, skrev Stewart Bryant:
>>> Hi Tony
>>> 
>>> I am struggling to see whether this has a sufficient advantage over
>>> the existing EL/ELI mechanism to justify us recommending it existence.
>>> 
>>> It is obvious that this can be done, and it saves an LSE, but is that
>>> sufficient justification for the complexity introduced by having two
>>> mechanisms that of necessity need to co-exist?
>>> 
>>> We also need to understand what happens in a legacy routers that are
>>> looking for EL/ELI and older routers that just hash the stack. I think
>>> they just provide less (no?) entropy.
>> Is there a scientific way of calculating "how much" entropy the
>> different  generate?
>> 
>> Is more entropy always better?
>> 
>> What are the factors that determine how much entropy you need?
>> 
>> /Loa
>> 
>> 
>>> I imagine this ends with routers needing to parse for both types of
>>> entropy which is not a great position to be in.
>>> 
>>> Best regards
>>> 
>>> Stewart
>>> 
>>>> On 30 Aug 2024, at 5:26 PM, Tony Li <[e-mail]> wrote:
>>>> 
>>>>  [WG chair hat: off]
>>>> 
>>>> Hi,
>>>> 
>>>> This update addresses comments from Adrian Farrel as part of the WG
>>>> adoption process.
>>>> 
>>>> Comments and corrections are most welcome.
>>>> 
>>>> Thanks,
>>>> Tony
>>>> 
>>>> 
>>>>> Begin forwarded message:
>>>>> 
>>>>> *From: *"internet-drafts at ietf.org" <[e-mail]>
>>>>> *Subject: **New Version Notification for
>>>>> draft-li-mpls-mna-entropy-03.txt*
>>>>> *Date: *August 30, 2024 at 9:24:05 AM PDT
>>>>> *To: *"John Drake" <[e-mail]>, "Tony Li" <[e-mail]>
>>>>> *Reply-To: *[e-mail]
>>>>> 
>>>>> A new version of Internet-Draft draft-li-mpls-mna-entropy-03.txt has
>>>>> been
>>>>> successfully submitted by Tony Li and posted to the
>>>>> IETF repository.
>>>>> 
>>>>> Name:     draft-li-mpls-mna-entropy
>>>>> Revision: 03
>>>>> Title:    MPLS Network Action for Entropy
>>>>> Date:     2024-08-28
>>>>> Group:    Individual Submission
>>>>> Pages:    5
>>>>> URL:
>>>>>      https://www.ietf.org/archive/id/draft-li-mpls-mna-entropy-03.txt
>>>>> Status:   https://datatracker.ietf.org/doc/draft-li-mpls-mna-entropy/
>>>>> HTMLized:
>>>>> https://datatracker.ietf.org/doc/html/draft-li-mpls-mna-entropy
>>>>> Diff:
>>>>>     https://author-tools.ietf.org/iddiff?url2=draft-li-mpls-mna-entropy-03
>>>>> 
>>>>> Abstract:
>>>>> 
>>>>>   Load balancing is a powerful tool for engineering traffic across a
>>>>>   network and has been successfully used in MPLS as described in RFC
>>>>>   6790, "The Use of Entropy Labels in MPLS Forwarding".  With the
>>>>>   emergence of MPLS Network Actions (MNA), there is signficant benefit
>>>>>   in being able to invoke the same load balancing capabilities within
>>>>>   the more general MNA infrastructure.
>>>>> 
>>>>>   This document describes a network action for entropy to be used in
>>>>>   conjunction with "MPLS Network Action (MNA) Sub-Stack Solution".
>>>>> 
>>>>> 
>>>>> 
>>>>> The IETF Secretariat
>>>>> 
>>>>> 
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> 
> --
> Loa Andersson
> Senior MPLS Expert
> Bronze Dragon Consulting
> [e-mail]
> [e-mail]
>