Re: [spring] SRV6 - SR-TE support & Flex Alg support ? and comparison and contrast of those two steering strategies

[Gyan Mishra <[e-mail]>]

Thank you both for your feedback.  That really helps a lot and clarifies.

So flex-algo can be used with SR-TE as part of the policy specifying a
delay metric and also be used as part of the IGP flex algo cSPF.

Their might be some slight nuances but overall as far as features for both
SR-MPLS & SRv6 the SR-TE policy would require binding SID and have
similarities with lose or strict with prefix-sid or ad-sid specified
correct and all same features and functionality.  Correct?

Also for inter-as or inter-domain SR -  for both SR-MPLS or SRv6  the SR-TE
w/ binding sid could be used as well in place of traditional BGP-LU for
inter-as or csc.  Correct?

So operators have the option to stay with inter-as BGP-LU or go with SR-TE
which is more attractive and powerful with simplicity.

Kind regards

Gyan

On Tue, Mar 31, 2020 at 5:15 AM Ketan Talaulikar (ketant) <[e-mail]>
wrote:

> Hi Gyan,
>
> To add to what Peter has clarified, SR Policy architecture also supports
> SRv6 (as you've pointed out in the references) - loose and strict paths as
> well as steering for colored BGP routes.
>
> Thanks,
> Ketan
>
> -----Original Message-----
> From: spring <[e-mail]> On Behalf Of Peter Psenak
> Sent: 31 March 2020 13:42
> To: Gyan Mishra <[e-mail]>; SPRING WG <[e-mail]>
> Subject: Re: [spring] SRV6 - SR-TE support & Flex Alg support ? and
> comparison and contrast of those two steering strategies
>
> Hi Gyan,
>
> let me comment on the flex-algo aspect. Please see inline:
>
> On 30/03/2020 23:50, Gyan Mishra wrote:
> >
> > Does SRv6 support SR-TE and flex Alg?
>
> yes, it does support both.
>
> >
> >
> > Since SRv6 supports native traffic steering with SRH with end prefix
> > sid and end.x adjacency sid you can achieve the basic steering and
> > ECMP capability with prefix sid lose or strict hop by hop with every
> > node specified in SRH SL.
> >
> > I want to confirm that SRv6 fully supports all of the  SR-TE
> > capabilities available with SR-MPLS with static lose or strict paths
> > and coloring of vpn flows.
> >
> >  From the SR policy draft I did see that section 4 lists segment types
> > and does appear to support SRv6 sid.
> >
> > https://tools.ietf.org/html/draft-ietf-spring-segment-routing-policy-0
> > 6
> >
> >
> >     4
> >     <
> https://tools.ietf.org/html/draft-ietf-spring-segment-routing-policy-06#section-4
> >.
> >     Segment Types
> >
> >
> >
> >     A Segment-List is an ordered set of segments represented as <S1, S2,
> >     ... Sn> where S1 is the first segment.
> >
> >     Based on the desired dataplane, either the MPLS label stack or the
> >     SRv6 SRH is built from the Segment-List.  However, the Segment-List
> >     itself can be specified using different segment-descriptor types and
> >     the following are currently defined:
> >
> >
> > Flex Alg - SRv6 support?
>
> yes.
>
> >
> > Flex Alg is orthogonal to SR TE as it provides IGP extensions for
> > constrained SPF versus traditional RSVP or SR-TE providing the
> > extensions for cSPF - basically another method of steering which as
> > well is very powerful tool for operators.
> >
> > It does appear SRv6 supports flex Alg draft below.
>
> yes.
>
> >
> > https://tools.ietf.org/html/draft-ietf-lsr-flex-algo-06
> >
> > Abstract
> >
> > IGP protocols traditionally compute best paths over the network based
> >     on the IGP metric assigned to the links.  Many network deployments
> >     use RSVP-TE based or Segment Routing based Traffic Engineering to
> >     enforce traffic over a path that is computed using different metrics
> >     or constraints than the shortest IGP path.  This document proposes a
> >     solution that allows IGPs themselves to compute constraint based
> >     paths over the network.  This document also specifies a way of using
> >     Segment Routing (SR) Prefix-SIDs and SRv6 locators to steer packets
> >     along the constraint-based paths.
> >
> >
> >
> > What are the benefits of using SR-TE over flex Alg and vice versa?
>
> you can think of them as different tools in your SR-TE tool set. You pick
> them as you need them. They can be used independently in parallel or can
> even be combined together to give you even more flexibility.
>
> The principal difference is that SR-TE provisions point-to-point path(s)
> between two end-points, while flex-algo provides any to any paths between
> set of participating nodes.
>
> >
> > Also can SR-TE use flex Alg steered paths as the dynamic cSPF paths?
>
> yes
>
> >
> > Can SR-TE use and specify flex Alg to be used for traffic steering?
>
> yes
>
> thanks,
> Peter
>
> >
> >
> > Kind regards
> >
> >
> > Gyan
> > Verizon
> > Cell 301 502-1347
> > --
> >
> > Gyan  Mishra
> >
> > Network Engineering & Technology
> >
> > Verizon
> >
> > Silver Spring, MD 20904
> >
> > Phone: [phone]
> >
> > Email: [e-mail] <mailto:[e-mail]>
> >
> >
> >
>
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-- 

Gyan  Mishra

Network Engineering & Technology

Verizon

Silver Spring, MD 20904

Phone: [phone]

Email: [e-mail]