Re: [Lsr] draft-ietf-lsr-flex-algo

Gyan Mishra <hayabusagsm@gmail.com> Tue, 19 May 2020 01:52 UTC

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From: Gyan Mishra <hayabusagsm@gmail.com>
Date: Mon, 18 May 2020 21:52:02 -0400
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To: "Wang, Weibin (NSB - CN/Shanghai)" <weibin.wang@nokia-sbell.com>
Cc: Jeff Tantsura <jefftant.ietf@gmail.com>, "Ketan Talaulikar (ketant)" <ketant@cisco.com>, "lsr@ietf.org" <lsr@ietf.org>
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Subject: Re: [Lsr] draft-ietf-lsr-flex-algo
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Flex algo is usually mentioned in the context of SR-TE to help reduced SRH
size to circumvent MSD issues for both SRV6 and SR-MPLS, however can the
0-127 flex algo extensions since it’s an IGP extension used in any pure IP
network independent of SR flavors SR-MPLS or SRv6.

Also can flex algo be used in conjunction with RSVP-TE or PPR(preferred
path routing).

Kind regards

Gyan

On Sat, May 9, 2020 at 9:25 PM Wang, Weibin (NSB - CN/Shanghai) <
weibin.wang@nokia-sbell.com> wrote:

> Jeff, I see what you said, thank you for sharing information;
>
>
>
>
>
>
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> Cheers!
>
>
>
> Wang Weibin
>
>
>
> *From:* Jeff Tantsura <jefftant.ietf@gmail.com>
> *Sent:* 2020年5月10日 3:24
> *To:* Wang, Weibin (NSB - CN/Shanghai) <weibin.wang@nokia-sbell.com>
> *Cc:* Ketan Talaulikar (ketant) <ketant@cisco.com>om>; lsr@ietf.org
> *Subject:* Re: [Lsr] draft-ietf-lsr-flex-algo
>
>
>
> Weibin,
>
>
>
> One could have an algo with MSD/ERLD as optimizations constrains, would be
> quite similar to colored links. Note - ERLD has implemented node
> capabilities only, so all links on a node will have to be pruned.
>
> The tradeoffs are - having centralized controller with global view
> computing a path that meets the constraints(classical BGP-LS + PCEP
> scenario) vs building a dynamic topology of connected nodes that meet a set
> of constrains, in first case, change in topology/capabilities would cause
> path recalculation/reoptimization on the PCE while in the second - IGP
> would recompute the topology locally.
>
>
>
> Regards,
>
> Jeff
>
>
>
> On May 9, 2020, at 01:27, Wang, Weibin (NSB - CN/Shanghai) <
> weibin.wang@nokia-sbell.com> wrote:
>
> 
>
> Ketan, thank you for clarification.
>
>
>
>
>
>
>
> Cheers!
>
>
>
> Wang Weibin
>
>
>
> *From:* Ketan Talaulikar (ketant) <ketant@cisco.com>
> *Sent:* 2020年5月9日 14:52
> *To:* Wang, Weibin (NSB - CN/Shanghai) <weibin.wang@nokia-sbell.com>om>;
> lsr@ietf.org
> *Subject:* RE: draft-ietf-lsr-flex-algo
>
>
>
> Hi Wang,
>
>
>
> You are correct. Though I wouldn’t call it a goal but rather a
> benefit/advantage – same applies to SR-MPLS where the label stack can be
> reduced.
>
>
>
> Thanks,
>
> Ketan
>
>
>
> *From:* Lsr <lsr-bounces@ietf.org> *On Behalf Of *Wang, Weibin (NSB -
> CN/Shanghai)
> *Sent:* 08 May 2020 19:07
> *To:* lsr@ietf.org
> *Subject:* [Lsr] draft-ietf-lsr-flex-algo
>
>
>
> Hi authors:
>
>
>
> After reading through this draft lsr-flex-algo, I want to know whether
> there is a potential goal of this draft to reduce the SRH size with
> enabling flex-algo with admin group in SRv6 deployment, because without
> flex-algo we have to have a big SRH size when the SRH include more SRv6
> SIDs, if we enable flex-algo under special topology and link constraint
> condition, in theory we can even construct  a end to end SR path/tunnel
> without SRH, but it still meet TE requirement. So my question is whether
> the flex-algo can be used as tool to reduce SRH size?
>
>
>
>
>
>
>
> *Cheers !*
>
>
>
> *WANG Weibin*
>
> _______________________________________________
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>
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>
-- 

Gyan  Mishra

Network Engineering & Technology

Verizon

Silver Spring, MD 20904

Phone: 301 502-1347

Email: gyan.s.mishra@verizon.com