Re: [bess] Shepherd's review of draft-ietf-bess-mvpn-fast-failover
Greg Mirsky <gregimirsky@gmail.com> Sat, 01 February 2020 21:19 UTC
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From: Greg Mirsky <gregimirsky@gmail.com>
Date: Sat, 01 Feb 2020 13:19:09 -0800
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To: "Jeffrey (Zhaohui) Zhang" <zzhang@juniper.net>
Cc: "slitkows.ietf@gmail.com" <slitkows.ietf@gmail.com>, "bess-chairs@ietf.org" <bess-chairs@ietf.org>, BESS <bess@ietf.org>
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Subject: Re: [bess] Shepherd's review of draft-ietf-bess-mvpn-fast-failover
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Hi Jeffrey, tons of thanks for your help and patience. Regards, Greg On Sat, Feb 1, 2020 at 12:04 PM Jeffrey (Zhaohui) Zhang <zzhang@juniper.net> wrote: > Right š > > > > > > *From:* Greg Mirsky <gregimirsky@gmail.com> > *Sent:* Friday, January 31, 2020 4:41 PM > *To:* Jeffrey (Zhaohui) Zhang <zzhang@juniper.net> > *Cc:* slitkows.ietf@gmail.com; bess-chairs@ietf.org; BESS <bess@ietf.org> > *Subject:* Re: [bess] Shepherd's review of > draft-ietf-bess-mvpn-fast-failover > > > > Hi Jeffrey, > > my apologies, I misunderstood your proposed change. Should it be the > following change: > > OLD TEXT > > The downstream PE can immediately update its UMH > when the reachability condition changes. > > NEW TEXT > > As a result, the downstream PE can immediately update its UMH > when the reachability condition changes. > > > > Thank you for your help. > > > > Regards, > > Greg > > > > On Fri, Jan 31, 2020 at 1:16 PM Jeffrey (Zhaohui) Zhang < > zzhang@juniper.net> wrote: > > In 3.1.4 you missed āas a resultā. > > > > *From:* BESS <bess-bounces@ietf.org> *On Behalf Of *Greg Mirsky > *Sent:* Friday, January 31, 2020 3:55 PM > *To:* slitkows.ietf@gmail.com > *Cc:* Jeffrey (Zhaohui) Zhang <zzhang@juniper.net>; bess-chairs@ietf.org; > BESS <bess@ietf.org> > *Subject:* Re: [bess] Shepherd's review of > draft-ietf-bess-mvpn-fast-failover > > > > Hi Jeffrey, > > many thanks for your suggestions. I've updated the document accordingly. I > much appreciate you checking that changes are in the right places. I'll > upload the new version ones you approve the changes. > > > > Regards, > > Greg > > > > On Fri, Jan 31, 2020 at 11:49 AM <slitkows.ietf@gmail.com> wrote: > > Iām fine with the proposal > > > > > > *From:* Jeffrey (Zhaohui) Zhang <zzhang@juniper.net> > *Sent:* vendredi 31 janvier 2020 20:44 > *To:* Greg Mirsky <gregimirsky@gmail.com>; slitkows.ietf@gmail.com > *Cc:* BESS <bess@ietf.org>; bess-chairs@ietf.org > *Subject:* RE: Shepherd's review of draft-ietf-bess-mvpn-fast-failover > > > > Hi Greg, Stephane, > > > > The first MAY should actually be a SHOULD; for the second MAY, it actually > can go back to ācanā. > > > > Then this will match the previous RSVP-TE section. The āin this caseā > sentence is more about the result, not the action to take. Perhaps also > change āin this caseā to āas a resultā in both sections? > > > > Jeffrey > > > > *From:* Greg Mirsky <gregimirsky@gmail.com> > *Sent:* Wednesday, January 22, 2020 3:41 PM > *To:* slitkows.ietf@gmail.com; Jeffrey (Zhaohui) Zhang <zzhang@juniper.net > > > *Cc:* BESS <bess@ietf.org>; bess-chairs@ietf.org > *Subject:* Re: Shepherd's review of draft-ietf-bess-mvpn-fast-failover > > > > Hi Jeffrey, > > happy New Years (the Spring Festival is just upon us) and best wishes. > > Stephane suggested to ask you another, hopefully quick, review of the part > of this draft. Please see our discussion copied below: > > Section 3.1.4: > > As the document is standard track, could you introduce normative language > in the expected behavior description ? > GIM>> Updating to the normative language as follows: > > OLD TEXT: > > A PE can be removed from the UMH candidate list for a given (C-S, > C-G) if the P-tunnel (I or S, depending) for this (S, G) is leaf > triggered (PIM, mLDP), but for some reason internal to the protocol > the upstream one-hop branch of the tunnel from P to PE cannot be > built. In this case, the downstream PE can immediately update its > UMH when the reachability condition changes. > > NEW TEXT: > > A PE MAY be removed from the UMH candidate list for a given (C-S, > C-G) if the P-tunnel (I-PMSI or S-PMSI) for this (S, G) is leaf- > triggered (PIM, mLDP), but for some reason internal to the protocol > the upstream one-hop branch of the tunnel from P to PE cannot be > built. In this case, the downstream PE MAY immediately update its > UMH when the reachability condition changes. > > > [SLI] I understand the first āMAYā as optional feature, however the second > āMAYā is more a āSHOULDā IMO. Thoughts? > > GIM2>> Thank you for the clarification. The UMH list will certainly be > updated once the reachability of the downstream PE changes. In some > scenarios, such an update may be immediate, i.e., ASAP, but in some, it > might be better to delay it. Would you suggest adding a note about the > option to delay the update? > > > > [SLI] Could you check with Jeffrey Zhang on this point ? Iām not enough > expert here to tell what may be the best option. On my side, I just want > the text to be clear š > > > > What do you think of the use of the normative language in the newly > updated text? > > > > Best regards, > > Greg > > > > On Tue, Jan 7, 2020 at 5:59 AM <slitkows.ietf@gmail.com> wrote: > > Hi Greg, > > > > More inline, > > > > > > *From:* Greg Mirsky <gregimirsky@gmail.com> > *Sent:* mercredi 4 dĆ©cembre 2019 23:22 > *To:* slitkows.ietf@gmail.com; BESS <bess@ietf.org>; bess-chairs@ietf.org > *Subject:* RE: Shepherd's review of draft-ietf-bess-mvpn-fast-failover > > > > Hi Stephane, > > thank you for the review and your thoughtful comments. Please find my > answers and notes in-lined under GIM>> tag. > > Attached, please find the diff and copy of the working version. > > > > Regards, > > Greg > > > > Hi, > > > > Please find below my review of the document. > > > > Nits: > > > > > Section 3.1.1: > > As the document is standard track, could you introduce normative language > in the expected behavior description ? > > > > GIM2>> My apologies, I've pasted the same text twice. I propose to remove > "may be omitted" altogether. Hence the updated text: > > If BGP next-hop tracking is done for VPN routes and the root address > of a given tunnel happens to be the same as the next-hop address in > the BGP auto-discovery route advertising the tunnel, then the use of > this > > mechanism for the tunnel will not bring any specific benefit. > > Do you see this version without any normative language as acceptable? > > > > [SLI] Looks good thanks > > > > > > > Section 3.1.2: > > As the document is standard track, could you introduce normative language > in the expected behavior description ? > > > > āThis method should not be usedā. Wouldnāt this be a normative statement ? > > GIM>> Would the following modification of the text be acceptable: > > OLD TEXT: > > This method should not be used when there is a fast restoration > mechanism (such as MPLS FRR [RFC4090]) in place for the link. > > NEW TEXT: > Using this method when a fast restoration mechanism (such as MPLS FRR > [RFC4090]) is in place for the link requires careful consideration > and coordination of defect detection intervals for the link and the > tunnel. In many cases, it is not practical to use both methods at > the same time. > > > > [SLI] Are we strongly disencouraging the practice ? if yes, āit is not > practicalā is a bit too soft. Iām wondering if āis NOT RECOMMENDEDā could > be a good wording. But it is up to you. > > GIM2>> The use of OAM in multi-layer fashion is a question I'd be > interested to discuss. But I feel that it deserves a separate document and > would prefer to leave the text as a note of caution for now. > > > > [SLI] Ok > > > > > > Section 3.1.4: > > As the document is standard track, could you introduce normative language > in the expected behavior description ? > GIM>> Updating to the normative language as follows: > > OLD TEXT: > > A PE can be removed from the UMH candidate list for a given (C-S, > C-G) if the P-tunnel (I or S, depending) for this (S, G) is leaf > triggered (PIM, mLDP), but for some reason internal to the protocol > the upstream one-hop branch of the tunnel from P to PE cannot be > built. In this case, the downstream PE can immediately update its > UMH when the reachability condition changes. > > NEW TEXT: > > A PE MAY be removed from the UMH candidate list for a given (C-S, > C-G) if the P-tunnel (I-PMSI or S-PMSI) for this (S, G) is leaf- > triggered (PIM, mLDP), but for some reason internal to the protocol > the upstream one-hop branch of the tunnel from P to PE cannot be > built. In this case, the downstream PE MAY immediately update its > UMH when the reachability condition changes. > > > [SLI] I understand the first āMAYā as optional feature, however the second > āMAYā is more a āSHOULDā IMO. Thoughts? > > GIM2>> Thank you for the clarification. The UMH list will certainly be > updated once the reachability of the downstream PE changes. In some > scenarios, such an update may be immediate, i.e., ASAP, but in some, it > might be better to delay it. Would you suggest adding a note about the > option to delay the update? > > > > [SLI] Could you check with Jeffrey Zhang on this point ? Iām not enough > expert here to tell what may be the best option. On my side, I just want > the text to be clear š > > > > > > > > > > > > Section 3.1.6: > > As the document is standard track, could you introduce normative language > in the expected behavior description ? > > GIM>> Sub-sections of 3.1..6 define the use of RFC 8562 and the new > attribute. In the introduction to these sub-sections, I propose s/can/MAY/ > > > >From a wider perspective, do you foresee other use case of signaling BFD > information in BGP ? Iām just wondering if we may need something > extensible for future use or not. > > GIM>> Great question. BGP, and I'm speculating here, may be used to for > other BFD-related scenarios. I think that we may use the Flags field. > [SLI] Is it enough or should you add some optional TLVs behind the > discriminator ? (with nothing defined yet). > > GIM2>> Great idea, thank you! Please see the updated figure and the text: > > 0 1 2 3 > 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > | BFD Mode | Reserved | > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > | BFD Discriminator | > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > | Reserved TLV | > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > > > > Format of the BFD Discriminator Attribute > > Where: > > BFD Mode is the one octet long field. This specification defines > the P2MP value (TBA3) Section 7.1. > > Reserved field is three octets long and the value MUST be zeroed > on transmission and ignored on receipt. > > BFD Discriminator is four octets long field. > > Reserved TLV field is four octets long. It MAY be used for future > extensions of the BFD Discriminator Attribute using Type-Length- > Value format. This specification defines that the value in > Reserved TLV field MUST be zeroed on transmission and ignored on > > receipt. > > > > [SLI] If your field is 4-bytes long, it is not extensible, I was thinking > of options encoded as TLVs. > > If there is no TLV, the attribute ends on BFD discriminator, the attribute > length should tell if there are TLVs or not. > > > > 0 1 2 3 > 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > | BFD Mode | Reserved | > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > | BFD Discriminator | > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > | optional TLVs | > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > > Another point I have missed, you should define error handling procedures > for your attribute as per RFC7606. > > > > > > > > > > > > > > > > >
- Re: [bess] Shepherd's review of draft-ietf-bess-mā¦ Greg Mirsky
- Re: [bess] Shepherd's review of draft-ietf-bess-mā¦ slitkows.ietf
- Re: [bess] Shepherd's review of draft-ietf-bess-mā¦ Greg Mirsky
- [bess] Shepherd's review of draft-ietf-bess-mvpn-ā¦ slitkows.ietf
- Re: [bess] Shepherd's review of draft-ietf-bess-mā¦ Greg Mirsky
- Re: [bess] Shepherd's review of draft-ietf-bess-mā¦ slitkows.ietf
- Re: [bess] Shepherd's review of draft-ietf-bess-mā¦ Greg Mirsky
- Re: [bess] Shepherd's review of draft-ietf-bess-mā¦ Greg Mirsky
- Re: [bess] Shepherd's review of draft-ietf-bess-mā¦ slitkows.ietf
- Re: [bess] Shepherd's review of draft-ietf-bess-mā¦ Greg Mirsky
- Re: [bess] Shepherd's review of draft-ietf-bess-mā¦ Jeffrey (Zhaohui) Zhang
- Re: [bess] Shepherd's review of draft-ietf-bess-mā¦ slitkows.ietf
- Re: [bess] Shepherd's review of draft-ietf-bess-mā¦ Greg Mirsky
- Re: [bess] Shepherd's review of draft-ietf-bess-mā¦ Jeffrey (Zhaohui) Zhang
- Re: [bess] Shepherd's review of draft-ietf-bess-mā¦ Greg Mirsky
- Re: [bess] Shepherd's review of draft-ietf-bess-mā¦ Jeffrey (Zhaohui) Zhang
- Re: [bess] Shepherd's review of draft-ietf-bess-mā¦ Greg Mirsky
- Re: [bess] Shepherd's review of draft-ietf-bess-mā¦ Greg Mirsky
- Re: [bess] Shepherd's review of draft-ietf-bess-mā¦ slitkows.ietf
- Re: [bess] Shepherd's review of draft-ietf-bess-mā¦ Greg Mirsky