Re: [spring] Different MSDs for different traffic types on the same headend.
Nat Kao <lekao@pyxisworks.org> Thu, 09 January 2020 02:33 UTC
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From: Nat Kao <lekao@pyxisworks.org>
Date: Thu, 09 Jan 2020 10:33:32 +0800
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To: Jeff Tantsura <jefftant.ietf@gmail.com>, "Ketan Talaulikar (ketant)" <ketant@cisco.com>
Cc: Robert Raszuk <robert@raszuk.net>, SPRING WG <spring@ietf.org>
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Subject: Re: [spring] Different MSDs for different traffic types on the same headend.
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Hi, Jeff & Ketan. Should I provide more details about the use cases? I'm not sure whether this is enough. Thanks! On Wed, Dec 18, 2019 at 2:20 PM Nat Kao <lekao@pyxisworks.org> wrote: > Hi, Jeff & Ketan. > > For better discussion, let's assume these first: > > "TP-MSD" denotes the maximum transport label depth for traffic without > service labels. > "SRV-TP-MSD" denotes the maximum transport label depth for traffic with 1+ > service label(s). > > Here's one of the use cases: > > A customized best-effort TE process: > > 1. Decide which route R (incl. VPN routes) to diverge from its > shortest-path. > > 2. Compute SID-list S for R that satisfies the (TE or whatever) > constraints. > > 3a. If R is a plain IPv4/IPv6 route, we consult TP-MSD. > If length(S) <= headend's TP-MSD: > Inject an SR-TE policy candidate path P with color X by BGP. > Inject a new route R' with color X and larger localpref value. > else: > This path is not feasible, consider another route. > > 3b. If R is a service route, we consult SRV-TP-MSD. > If length(S) <= headend's SRV-TP-MSD: > Inject an SR-TE policy candidate path P with color X by BGP. > Inject a new route R' with color X and larger localpref value. > else: > This path is not feasible, consider another route. > > 4. Repeat 1 to 3 until the main objectives are met.(best-effort approach, > some might fail) > > Notes: > > a) Clearly, BMI-MSD >= TP-MSD >= SRV-TP-MSD > b) TP-MSD & SRV-TP-MSD can be signaled by the same methods as BMI-MSD. > c) If a change on headend that modifies transport label depths(ex: > recirculation), TP-MSD & SRV-TP-MSD shall reflect that change accordingly. > d) If a change on headend that modifies transport label depths of certain > LCs, TP-MSD & SRV-TP-MSD of those links shall reflect that change, too. > > Hope this helps. > > Regards, > Nat > > > > > On Wed, Dec 18, 2019 at 8:44 AM Jeff Tantsura <jefftant.ietf@gmail.com> > wrote: > >> Hi Nat, >> >> Please bring your use case to the wg, MSD has specifically been designed >> to address new types with a very little effort. >> >> Cheers, >> Jeff >> On Dec 17, 2019, 4:21 AM -0800, Ketan Talaulikar (ketant) < >> ketant@cisco.com>, wrote: >> >> Hi Nat, >> >> >> >> The MSD framework enables us to define more/new MSD types. If there is a >> real use-case and requirement (as you express) and the necessary MSD >> type(s) can be formally defined then perhaps the WG can evaluate it. >> >> >> >> Thanks, >> >> Ketan >> >> >> >> *From:* spring <spring-bounces@ietf.org> *On Behalf Of* Nat Kao >> *Sent:* 17 December 2019 17:16 >> *To:* Robert Raszuk <robert@raszuk.net> >> *Cc:* SPRING WG <spring@ietf.org>; Nat Kao <lekao@pyxisworks.org> >> *Subject:* Re: [spring] Different MSDs for different traffic types on >> the same headend. >> >> >> >> Hello, Robert. >> >> Surely the current BMI-MSD definition is sufficient for platforms without >> artificial boundaries. >> >> In this ideal case, maximum labels available for SR-TE policy can be >> inferred from BMI-MSD and VPN routes. >> >> >> However we have 3 different artificial boundaries across 3 different >> platforms now. >> >> Hardcoding these boundaries might not scale well. (Especially different >> OS versions may behave differently.) >> >> A standard mechanism to discover this boundary would greatly help >> constructing SR-TE policy candidate paths. >> >> >> >> Regards, >> >> Nat. >> >> >> >> >> >> On Tue, Dec 17, 2019 at 5:58 PM Robert Raszuk <robert@raszuk.net> wrote: >> >> Hi Nat, >> >> >> >> I am having a bit of difficulty understanding reasoning and the way you >> are separating transport from service labels. >> >> >> >> The processing label limit usually comes from data plane capabilities of >> the platform namely LFIB or hardware below. >> >> >> >> Such layer is function agnostic and it does not matter what role the >> label serves. >> >> >> >> Label lookup results in pointer to a adj. rewrite on the outbound side. >> It really does not matter if the adjacent peer is your P router, segment >> endpoint or CE. >> >> >> >> Of course there are number of processing exceptions - for example concept >> of aggregate VPN label, additional header modifications etc ... >> >> >> >> Likely some platforms put such artificial boundary between transport and >> service hence your request. But if so IMHO this is more of an issue with >> specific platform or its marketing message then IETF :). >> >> >> >> Many thx, >> R. >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> On Tue, Dec 17, 2019 at 6:06 AM Nat Kao <lekao@pyxisworks.org> wrote: >> >> Hi, Jeff. >> >> Consider a headend that can perform 1 of the following 2 modes(but not >> both): >> >> 1) Plain IPv4: 6 transport labels + 0 service label => traffic can be >> steered into a 6-label SR-TE policy. >> >> 2) Any type of VPN: 3 transport labels + 1~3 service labels => traffic >> cannot be steered into a 6-label SR-TE policy. >> >> a) As defined in RFC8491, the BMI-MSD is 6 for this headend. Do we have a >> standardized way to signal the transport label depth in mode 2? >> >> Maybe in a different MSD type? >> >> b) Since plain IPv4 and VPN routes can be steered into the same SR-TE >> policy, do we have a standardized headend behavior in this situation? >> >> (Should I open a new thread to discuss this? It seems not quite >> MSD-relative.) >> >> >> >> Thanks... >> >> Nat >> >> >> >> On Tue, Dec 17, 2019 at 7:19 AM Jeff Tantsura <jefftant.ietf@gmail.com> >> wrote: >> >> Gyan, >> >> >> >> MSD is only relevant for a device that either imposes the label stack >> (head-end) or manipulates it (BSID anchor). There are some other constrains >> when it comes to entropy labels and ERLD, please read the respective drafts. >> >> In general, SID stack would grow when TE is in use (any time you need to >> use additional SID to deviate from SPT), another case is when additional >> SID’s are used for services on the nodes, other than the tail-end. >> >> That’s why we've designed MSD to be very flexible to accommodate all the >> different use cases, it is upto computational logic to decide how to deal >> with different constrains (MSD types) >> >> >> >> Cheers, >> >> Jeff >> >> >> >> P.S. you might want to see the NANOG MSD presentation I did some time ago. >> >> >> https://pc.nanog.org/static/published/meetings/NANOG71/1424/20171004_Tantsura_The_Critical_Role_v1.pdf >> >> On Dec 14, 2019, 11:59 PM -0800, Gyan Mishra <hayabusagsm@gmail.com>, >> wrote: >> >> Jeff >> >> >> >> With SR-MPLS with SR-TR let’s say if you use cSPF snd don’t have an ERO >> strict explicit path defined or is a loose path, then the for the cSPF >> would the transport labels be 1. For loose would also be 1 also. If the >> path were explicit defined to egress PE and was 7 hops from ingress to >> egress then transport would be 6. And if L3 vpn service sid was signaled >> that would be 1 vpn label. >> >> >> >> Let me know if I have that right. >> >> >> >> In Nats scenario for IPv6 he has 3 vpnv6 labels. >> >> >> >> Why is that? >> >> >> >> With both SR-MPLS and SRv6 the L3 vpn AFI/SAFI MBGP services overlay >> single label sits on top off SR as if does today with MPLS so why 3 vpn >> labels. >> >> >> >> So with this draft with BGP-LS and BMI-MSD you can flood into the IGP the >> SID depth so all the nodes along the SR-TE path don’t go over the maximum >> which would result in an error. >> >> >> >> If you set your MTU high enough in the core like 9216, does that overcome >> the SID depth issues with SR-TE? >> >> >> >> Warm regards, >> >> >> >> Gyan >> >> >> >> On Sat, Dec 14, 2019 at 2:43 AM Nat Kao <lekao@pyxisworks.org> wrote: >> >> Hi, Jeff. >> >> >> >> Thanks for the BMI-MSD reference. If I understand correctly: >> >> >> >> BMI-MSD = Transport Label Depth + Service Label Depth >> >> Only former can be utilized by SR-TE policies. >> >> >> >> Currently do we have any method to determine the composition of BMI? >> >> We need to know the transport label depth when doing service route >> per-destination steering. >> >> >> >> This problem arises when trying to steer a plain IPv4 route and a VPN >> service route into the same SR-TE policy that exceeds the transport label >> depth of the service route. I'm trying to figure out the standard behavior >> in this case since the headend we use currently produces some interesting >> results. >> >> >> >> Regards, >> >> Nat. >> >> >> >> On Sat, Dec 14, 2019 at 2:42 AM Jeff Tantsura <jefftant.ietf@gmail.com >> <jefftant..ietf@gmail.com>> wrote: >> >> Hi Nat, >> >> >> >> Please read https://tools.ietf.org/html/rfc8491#section-5 >> >> Currently defined MSD types are: >> >> 1: BMI >> >> 2: ERLD >> >> >> >> Specifically to BMI: >> >> Base MPLS Imposition MSD (BMI-MSD) signals the total number of >> MPLS labels that can be imposed, including all >> service/transport/special labels. >> >> The answer to your question is 6 >> >> >> >> Cheers, >> >> Jeff >> >> On Dec 13, 2019, 3:42 AM -0800, Nat Kao <lekao@pyxisworks.org>, wrote: >> >> Hello, SPRING WG. >> >> How do we deal with an SR-TE policy headend with different MSDs for >> different types of traffic? >> >> For example, a headend H can impose: >> 6 transport labels for plain IPv4 packets; >> 5 transport labels + 1 IPv6 ExpNull label for plain IPv6 packets; >> >> 3 transport labels + 3 VPN labels for VPN packets. >> >> >> >> a) For a plain IPv4 route R4 and a VPN route Rv both steered into the >> SR-TE policy P1 with SID list <S1, S2, S3, S4, S5>, what will H perform in >> this situation? >> b) What is the MSD of H? 6, 5 or 3? >> >> >> >> Thanks, >> >> Nat. >> >> _______________________________________________ >> spring mailing list >> spring@ietf.org >> https://www.ietf.org/mailman/listinfo/spring >> >> _______________________________________________ >> spring mailing list >> spring@ietf.org >> https://www.ietf.org/mailman/listinfo/spring >> >> -- >> >> Gyan S. Mishra >> >> IT Network Engineering & Technology >> >> Verizon Communications Inc. (VZ) >> >> 13101 Columbia Pike FDC1 3rd Floor >> >> Silver Spring, MD 20904 >> >> United States >> >> Phone: 301 502-1347 >> >> Email: gyan.s.mishra@verizon.com >> >> www.linkedin.com/in/networking-technologies-consultant >> >> >> >> _______________________________________________ >> spring mailing list >> spring@ietf.org >> https://www.ietf.org/mailman/listinfo/spring >> >> _______________________________________________ >> spring mailing list >> spring@ietf.org >> https://www.ietf.org/mailman/listinfo/spring >> >>
- [spring] Different MSDs for different traffic typ… Nat Kao
- Re: [spring] Different MSDs for different traffic… Jeff Tantsura
- Re: [spring] Different MSDs for different traffic… Nat Kao
- Re: [spring] Different MSDs for different traffic… Gyan Mishra
- Re: [spring] Different MSDs for different traffic… Gyan Mishra
- Re: [spring] Different MSDs for different traffic… Jeff Tantsura
- Re: [spring] Different MSDs for different traffic… Gyan Mishra
- Re: [spring] Different MSDs for different traffic… Nat Kao
- Re: [spring] Different MSDs for different traffic… Robert Raszuk
- Re: [spring] Different MSDs for different traffic… Nat Kao
- Re: [spring] Different MSDs for different traffic… Ketan Talaulikar (ketant)
- Re: [spring] Different MSDs for different traffic… Gyan Mishra
- Re: [spring] Different MSDs for different traffic… Jeff Tantsura
- Re: [spring] Different MSDs for different traffic… Jeff Tantsura
- Re: [spring] Different MSDs for different traffic… Jeff Tantsura
- Re: [spring] Different MSDs for different traffic… Nat Kao
- Re: [spring] Different MSDs for different traffic… Gyan Mishra
- Re: [spring] Different MSDs for different traffic… Jeff Tantsura
- Re: [spring] Different MSDs for different traffic… Gyan Mishra
- Re: [spring] Different MSDs for different traffic… Nat Kao