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

Jeff Tantsura <jefftant.ietf@gmail.com> Sat, 09 May 2020 19:23 UTC

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From: Jeff Tantsura <jefftant.ietf@gmail.com>
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Date: Sat, 9 May 2020 12:23:33 -0700
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References: <28938a998b384038b6dd513db00072cf@nokia-sbell.com>
Cc: "Ketan Talaulikar (ketant)" <ketant@cisco.com>, "lsr@ietf.org" <lsr@ietf.org>
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To: "Wang, Weibin (NSB - CN/Shanghai)" <weibin.wang@nokia-sbell.com>
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Subject: Re: [Lsr] draft-ietf-lsr-flex-algo
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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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