Hi Jeffery, wondering if you got chance to updated text & if you are fine with it.
Mankamana > On Feb 13, 2019, at 7:09 PM, zhang.zh...@zte.com.cn wrote: > > Hi Greg, > > Thank you very much for your clarification! > I made a mistake that I thought the BFD session is the base solution for UMH > failover. > Now I get it. Thank you! > BTW: In section 3.1.2, "draft-ietf-rtgwg-bgp-pic-08" may be mentioned as > another example like MPLS FRR. > > Thanks, > Sandy > ------------------原始邮件------------------ > 发件人：GregMirsky <gregimir...@gmail.com> > 收件人：张征00007940; > 抄送人：zzh...@juniper.net <zzh...@juniper.net>;bess-cha...@ietf.org > <bess-cha...@ietf.org>;Thomas Morin <thomas.mo...@orange.com>;Robert Kebler > <rkeb...@juniper.net>;BESS <bess@ietf.org>; > 日 期 ：2019年02月14日 10:38 > 主 题 ：Re: [bess] WGLC,IPR and implementation poll for > draft-ietf-bess-mvpn-fast-failover > Hi Sandy, > thank you for your kind consideration of the proposed updates. I've logged my > answers under GIM3>> tag. > > Regards, > Greg > > On Mon, Feb 11, 2019 at 11:44 PM <zhang.zh...@zte.com.cn> wrote: > Hi Greg, > Thank you for your good modification and clarification! > About two sections I still have some comments, I copy the contents here > because the mail is too long: > 1, > 3. I am confused with section 3.1.1/3.1.2/3.1.3. IMO only the X-PMSI tunnel's > state influence the BFD session, there is no need for other decision. > GIM2>> The Upstream PE as MultipointHead of the p2mp BFD session may use a > combination of conditions (the combination being determined by policy) to > control the state of the BFD session, e.g., set it to AdminDown. I think that > the use of policy to control the conditions that affect the P-tunnel > reception state is the advantage of the proposed solution. What do you think? > 4. For section 3.1.5, IMO the counter method has no relationship with the BFD > function defined in this document. If the counter method will be used as a > supplement for BFD session? > GIM2>> As above, this is one of the conditions, controlled by the policy, > that may be considered to influence the state of the BFD session. > Sandy2> Since BFD packet is forwarding through by x-PMSI tunnel, egress PE > can get the tunnel states by BFD detection timer expiration. So administrator > may choose different policies to control the session state, but the bfd > packets detection should be the base. IMO section 3.1.1~4 are optional. > GIM3>> I re-read the 3.1 and I think now better understand the original idea. > All methods listed in sub-sections, including the one that describes use of > p2mp BFD, are alternatives, options to detect a failure in the tunnel. Would > the following update be helpful: > OLD TEXT: > The procedure proposed here also allows that all downstream PEs don't > apply the same rules to define what the status of a P-tunnel is > (please see Section 6), and some of them will produce a result that > may be different for different downstream PEs. > NEW TEXT: > The optional procedures proposed in this section also allow that all > downstream PEs don't > apply the same rules to define what the status of a P-tunnel is > (please see Section 6), and some of them will produce a result that > may be different for different downstream PEs. > > For section 3.1.5 counter information, how do the configurable timer work > with the bfd detection timer? What should egress PE do with the expiration of > the two timers when they are both used? > GIM3>> MPLS FRR is mentioned in the draft as an example of the "fast > restoration mechanism". Likely, FRR will be enabled by single-hop p2p BFD per > protected link. If that's the case, for the scenario described in this > sub-section, p2mp BFD is unnecessary. > > 2. > For section 3.1.7.1, the last sentence. > GIM2>> I think that Jeffrey asked why the new BFD Discriminator must be sent > and the new p2mp BFD session must be initiated. Your question, as I interpret > it, is to how operationally an implementation can minimize the disruption > when the new BFD session advertised to replace one that already exists. > Firstly, would we agree that sending the new BGP-BFD Discriminator and > starting the new p2mp BFD session when the RPF interface changes is the right > action? If we agree, then I can add a sentence or two to describe optional > procedure for the upstream PE to minimize the disruption when the egress PE > switches to the new p2mp BFD session. > Sandy2>If the "old" BFD discriminator can be reused in the new advertisement > when the switchover is happened on a same upstream PE? If the "old" > discriminator can be reused, it seems like it isn't necessary to build a new > BFD session. But if a new BFD discriminator MUST be generated, then the new > add sentence looks good to me. > GIM3>> Would the following update to the last paragraph address your concern: > OLD TEXT: > If the route to the > src/RP changes such that the RPF interface is changed to be a new PE- > CE interface, then the upstream PE will update the S-PMSI A-D route > with included BGP-BFD Attribute so that value of the BFD > Discriminator is associated with the new RPF link. > NEW TEXT: > If the route to the > src/RP changes such that the RPF interface is changed to be a new PE- > CE interface, then the upstream PE will update the S-PMSI A-D route > with included BGP-BFD Attribute so that the previously advertised value of > the BFD > Discriminator is associated with the new RPF link. > > Thanks, > Sandy > ------------------原始邮件------------------ > 发件人：GregMirsky <gregimir...@gmail.com> > 收件人：张征00007940; > 抄送人：zzh...@juniper.net <zzh...@juniper.net>;bess-cha...@ietf.org > <bess-cha...@ietf.org>;Thomas Morin <thomas.mo...@orange.com>;Robert Kebler > <rkeb...@juniper.net>;BESS <bess@ietf.org>; > 日 期 ：2019年02月07日 08:16 > 主 题 ：Re: [bess] WGLC,IPR and implementation poll for > draft-ietf-bess-mvpn-fast-failover > Hi Sandy,much appreciate your comments. Please find my answers below tagged > GIM2>>. > Attached, please find the updated working version and the diff to the last > published version. > Kind regards, > Greg > On Thu, Jan 31, 2019 at 7:40 PM <zhang.zh...@zte.com.cn> wrote: > Hi Greg, Jeffrey, co-authors, > About the questions provided by Jeffrey, I have some concerns, please see > below with Sandy>. > And I have some other questions: > 1. According to "draft-ietf-bfd-multipoint-19" and the function defined in > this draft, IMO the BFD session should be demultiplexed by the combination of > upstream peer address, the discriminator and the X-PMSI which is used for > flow forwarding. IMO these content should be written in the draft clearly. > GIM2>> Agreed and to clarify I propose the following update to the Downstream > PE Procedures: > OLD TEXT: > On receiving the BGP-BFD Attribute in the x-PMSI A-D Route, the > Downstream PE: > o MUST associate the received BFD discriminator value with the > P-tunnel originating from the Root PE; > o MUST create p2mp BFD session and set bfd.SessionType = > MultipointTail as described in [I-D.ietf-bfd-multipoint]; > o MUST use the source IP address of a BFD control packet, the value > of BFD Discriminator from the BGP-BFD Attribute to properly > demultiplex BFD sessions; > NEW TEXT: > Upon receiving the BGP-BFD Attribute in the x-PMSI A-D Route, the > Downstream PE: > o MUST associate the received BFD discriminator value with the > P-tunnel originating from the Root PE and the IP address of the > Upstream PE; > o MUST create p2mp BFD session and set bfd.SessionType = > MultipointTail as described in [I-D.ietf-bfd-multipoint]; > o MUST use the source IP address of the BFD control packet, the > value of the BFD Discriminator field, and the x-PMSI tunnel > identifier the BFD control packet was received to properly > demultiplex BFD sessions. > 2. The P2MP BFD packet should be delivered in the X-PMSI tunnel. The BFD > multicast packet MUST be encapsulated in associated tunnel. It seems like > there is no specifiction for it. > GIM2>> Agree and to clarify I propose the following text to be added to the > Upstream PE Procedures section: > NEW TEXT: > o MUST periodically transmit BFD control packets over the x-PMSI > tunnel. > 3. I am confused with section 3.1.1/3.1.2/3.1.3. IMO only the X-PMSI tunnel's > state influence the BFD session, there is no need for other decision. > GIM2>> The Upstream PE as MultipointHead of the p2mp BFD session may use a > combination of conditions (the combination being determined by policy) to > control the state of the BFD session, e.g., set it to AdminDown. I think that > the use of policy to control the conditions that affect the P-tunnel > reception state is the advantage of the proposed solution. What do you think? > 4. For section 3.1.5, IMO the counter method has no relationship with the BFD > function defined in this document. If the counter method will be used as a > supplement for BFD session? > GIM2>> As above, this is one of the conditions, controlled by the policy, > that may be considered to influence the state of the BFD session. > Thanks, > Sandy > 原始邮件 > 发件人：GregMirsky <gregimir...@gmail.com> > 收件人：zzh...@juniper.net <zzh...@juniper.net>; > 抄送人：bess-cha...@ietf.org <bess-cha...@ietf.org>;Thomas Morin > <thomas.mo...@orange.com>;Robert Kebler <rkeb...@juniper.net>;BESS > <bess@ietf.org>; > 日 期 ：2018年12月06日 02:38 > 主 题 ：Re: [bess] WGLC,IPR and implementation poll for > draft-ietf-bess-mvpn-fast-failover > _______________________________________________ > BESS mailing list > BESS@ietf.org > https://www.ietf.org/mailman/listinfo/bess > Hi Jeffrey,thank you for the review, detailed questions and helpful comments. > Please find my notes, answers in-line tagged GIM>>. > Regards, > Greg > On Fri, Nov 30, 2018 at 5:14 PM Jeffrey (Zhaohui) Zhang <zzh...@juniper.net> > wrote: > Hi, > I have the following questions/comments: > The procedure described here is an OPTIONAL procedure that consists > of having a downstream PE take into account the status of P-tunnels > rooted at each possible upstream PEs, for including or not including > each given PE in the list of candidate UMHs for a given (C-S,C-G) > state. The result is that, if a P-tunnel is "down" (see > Section 3.1), the PE that is the root of the P-tunnel will not be > considered for UMH selection, which will result in the downstream PE > to failover to the upstream PE which is next in the list of > candidates. > Is it possible that a p2mp tunnel is considered up by some leaves but down > by some other leaves, leaving to them choosing different UMH? In that case, > procedures described in Section 9.1.1 ("Discarding Packets from Wrong PE") of > RFC 6513 must be used. I see that this is actually pointed out later in > section 6 – good to have a pointer to it right here. > GIM>> Would the following new text that follows the quoted text address your > concern: > NEW TEXT: > If rules to determine the state of the P-tunnel are not > consistent across all PEs, then some may arrive at a different > conclusion regarding the state of the tunnel, In such a scenario, > procedures described in Section 9.1.1 of [RFC 6513] MUST be used. > Sandy> I think Jeffrey means that a egress PE may choose a new UMH after the > the "old" UMH fails. Then the egress PE may also receive (C-S, C-G) flows > from old UMH p-tunnel, these flows MUST be discarded according to section > 9.1.1 of RFC6513. > GIM2>> I think that the proposed text may address the comment. I'm,as always, > open to suggestions on how to modify, refine the proposed new text. > Additionally, the text in section 3 seems to be more biased on Single > Forwarder Election choosing the UMH with the highest IP address. Section 5 of > RFC6513 also describes two other options, hashing or based on “installed UMH > route” (aka unicast-based). It is not clear how the text in this document > applies to hashing based selection, and I don’t see how the text applies to > unicast-based selection. Some rewording/clarification are needed here. > GIM>> How would the use of an alternative UMH selection algorithm change > documented use of p2mp BFD? Do you think that if the Upstream PE selected > using, for example, hashing then defined use of BGP-BFD and p2mp BFD itself > no longer applicable? > Sandy> Diffrent UMH selection methods don't influent p2mp BFD documented in > this draft. IMO both of section 3 and section 5 need to be mentioned here in > order to avoid confusion. > GIM2>> Very helpful clarification, thank you. Please consider the following > update to section 4: > OLD TEXT: > The procedures > require all the PEs of that MVPN to follow the single forwarder PE > selection, as specified in [RFC6513]. > NEW TEXT: > The procedures > require all the PEs of that MVPN to follow the single forwarder PE > selection, as specified in [RFC6513], whether the PE selected based > on its IP address, hashing algorithm described in section 5.1.3 > [RFC6513], or Installed UMH Route. > For P-tunnels of type P2MP MPLS-TE, the status of the P-tunnel is > considered up if one or more of the P2MP RSVP-TE LSPs, identified by > the P-tunnel Attribute, are in Up state. > Why is “one or more of …” used in the above text? > GIM>> Would s/one or more of/at least one of/ address your concern? > Sandy> I am not sure there are the situations that two or more LSPs are used > to deliver a same (C-S, C-G). IMO only the LSP used by forwarding need to be > mointor in egress PE. > GIM>> I need to defer this to Thomas and Rob. If you agree with Sandy, should > we just remove the sentence? > There are several occurrences of ((S, G)). I assume they should be changed > to (C-S, C-G). > GIM>> Indeed, globally replaced s/((S,G))/(C-S,C-G)/ > A PE can be removed from the UMH candidate list for a given ((S, G)) > if the P-tunnel for this (S, G) (I or S , depending) is leaf > triggered (PIM, mLDP) > Perhaps either remove the (I or S , depending)or move it to before the “for”. > GIM>> Moved before the "for". > This document defines the format and ways of usingr a new BGP > attribute called the "BGP- BFD attribute". > s/usingr/using/ > GIM>> Yes, great catch. > o MUST use [Ed.note] address as destination IP address when > transmitting BFD control packets; > [Ed.note]? > GIM>> Replaced [Ed...note] to make it as follows: > o MUST use address in 127.0.0.0/8 range for IPv4 or in > 0:0:0:0:0:FFFF:7F00:0/104 range for IPv6 as destination IP address > when transmitting BFD control packets; > If tracking of the P-tunnel by using a p2mp BFD session is to be > enabled after the P-tunnel has been already signaled, the the > procedure described above MUST be followed. > What if the tracking is to be enabled before the P-tunnel has been signaled? > The text implies different behavior? > GIM>> Not really, I guess. I think that the second sentence is important: > Note that x-PMSI A-D Route MUST be re-sent with exactly the same attributes > as before and > the BGP-BFD Attribute included. > s/the the/then the/ > GIM>> Done. > … The dedicated p2mp BFD session MAY monitor the state of > the Standby Upstream PE. > What does the above text mean? Do you mean “A different p2mp BFD session …”? > GIM>> Yes, thank you for the suggested re-wording. Applied s/The dedicated/A > different/ > When such a procedure is used, in the context where fast restoration > mechanisms are used for the P-tunnels, leaf PEs should be configured > to wait before updating the UMH, to let the P-tunnel restoration > mechanism happen. A configurable timer MUST be provided for this > purpose, and it is recommended to provide a reasonable default value > for this timer. > What does “such a procedure” refers to? > GIM>> Would s/When such a procedure is used/In such a scenario/ > s/recommended/RECOMMENDED/? > GIM>> Great catch, thank you. Done. > 3.1.7. Per PE-CE link BFD Discriminator > The following approach is defined for the fast failover in response > to the detection of PE-CE link failures, in which UMH selection for a > given C-multicast route takes into account the state of the BFD > session associated with the state of the upstream PE-CE link. > 3.1.7.1. Upstream PE Procedures > For each protected PE-CE link, the upstream PE initiates a multipoint > BFD session [I-D.ietf-bfd-multipoint] as MultipointHead toward > downstream PEs. A downstream PE monitors the state of the p2mp > session as MultipointTail and MAY interpret transition of the BFD > session into Down state as the indication of the associated PE-CE > link being down. > Since the BFD packets are sent over the P2MP tunnel not the PE-CE link, my > understanding is that the BFD discriminator is still for the tunnel and not > tied to the PE-CE link; but different from the previous case, the root will > stop sending BFD messages when it detects the PE-CE link failure. As far as > the egress PEs are concerned, they don’t know if it is the tunnel failure or > PE-CE link failure. > If my understanding is correct, the wording should be changed. > GIM>> There are other than stopping transmission of BFD control packets ways > to distinguish two conditions for the egress PE. For example, the > MultipointHead MAY set the State to AdminDown and continue sending BFD > control packets. If and when PE-CE link restored to Up, the MultipointHead > can set the state to Up in the BFD control packet. > Sandy> I agree with Jeffrey. The BFD detection should be mapping to specific > flow/flows associated with X-PMSIs, not the PE-CE link. The PE-CE link should > influence the X-PMSIs and associated (C-S, C-G) flows. The AdminDown function > defined in BFD works normally. > GIM2>> The described behavior of the egress PE is optional and can be > controlled by the local policy. > … If the route to the > src/RP changes such that the RPF interface is changed to be a new PE- > CE interface, then the upstream PE will update the S-PMSI A-D route > with included BGP-BFD Attribute so that value of the BFD > Discriminator is associated with the new RPF link. > If the RPF interface changes on the upstream PE, why should it update the > route to send a new discriminator? As long as there is a new RPF interface > couldn’t the upstream PE do nothing but start tracking the new RPF interface? > GIM>> I'll defer this one to Thomas and Rob. > Sandy> I have the same question with Jeffrey. If RPF interface changes on the > upstream PE, and a new route generated with a new BFD discriminator, a new > P2MP BFD session need to be established and the network stability will be > influenced. We need a function to guarantee the existed BFD session should > not be influenced. > GIM2>> I think that Jeffrey asked why the new BFD Discriminator must be sent > and the new p2mp BFD session must be initiated. Your question, as I interpret > it, is to how operationally an implementation can minimize the disruption > when the new BFD session advertised to replace one that already exists. > Firstly, would we agree that sending the new BGP-BFD Discriminator and > starting the new p2mp BFD session when the RPF interface changes is the right > action? If we agree, then I can add a sentence or two to describe optional > procedure for the upstream PE to minimize the disruption when the egress PE > switches to the new p2mp BFD session. > Regardless which way (the currently described way and my imagined way), some > text should be added to discuss how the downstream would not switch to > another upstream PE when the primary PE is just going through a RPF change. > GIM>> Would appending the following text be acceptable to address your > concern: > NEW TEXT: > To avoid unwarranted switchover a downstream PE MUST gracefully handle the > updated S-PMSI A-D route and switch to the use of the associated BFD > Discriminator value. > 4. Standby C-multicast route > The procedures described below are limited to the case where the site > that contains C-S is connected to exactly two PEs. The procedures > require all the PEs of that MVPN to follow the single forwarder PE > selection, as specified in [RFC6513]. > Why would it not work with more than two upstream PEs? > Why is it limited to single forwarder selection? What about unicast based > selection? > GIM>> Again, asking for Thomas and Rob to help. > Sandy> I agree with Jeffrey. There is no limition for advertising same flows > through more than two PEs. Maybe the text should be modify to the UMH and the > next best UMH. > GIM2>> Thank you for the suggestion. Jeffrey and Sandy, would the following > update address your concerns: > OLD TEXT: > The procedures described below are limited to the case where the site > that contains C-S is connected to exactly two PEs. The procedures > require all the PEs of that MVPN to follow the single forwarder PE > selection, as specified in [RFC6513]. > NEW TEXT: > The procedures described below are limited to the case where the site > that contains C-S is connected to two or more PEs though, to simplify > the description, the case of dual-homing is described. The > procedures require all the PEs of that MVPN to follow the UMH > selection, as specified in [RFC6513], whether the PE selected based > on its IP address, hashing algorithm described in section 5.1.3 > [RFC6513], or Installed UMH Route. > This route, that has the semantics of being a 'standby' > C-multicast route, is further called a "Standby BGP C-multicast > route", and is constructed as follows: > o the NLRI is constructed as the original C-multicast route, except > that the RD is the same as if the C-multicast route was built > using the standby PE as the UMH (it will carry the RD associated > to the unicast VPN route advertised by the standby PE for S) > Since you mention RD, you might as well mention it carries a Route Target > derived from the standby RE’s UMH route’s VRF RT Import EC. > GIM>> Woud the following be acceptable: > NEW TEXT: > o the NLRI is constructed as the original C-multicast route, except > that the RD is the same as if the C-multicast route was built > using the standby PE as the UMH (it will carry the RD associated > to the unicast VPN route advertised by the standby PE for S and a > Route Target derived from the standby PE's UMH route's VRF RT > Import EC) > If at some later point the local PE determines that C-S is no longer > reachable through the Primary Upstream PE, the Standby Upstream PE > becomes the Upstream PE, and the local PE re-sends the C-multicast > route with RT that identifies the Standby Upstream PE, except that > now the route does not carry the Standby PE BGP Community (which > results in replacing the old route with a new route, with the only > difference between these routes being the presence/absence of the > Standby PE BGP Community). > Additionally the LOCAL_PREF should also change? > GIM>> Like normative SHOULD? > 4.3. Reachability determination > The standby PE can use the following information to determine that > C-S can or cannot be reached through the primary PE: > Shouldn’t this be 4.2.1 instead of 4.3? > GIM>> Yes, agree. Thank you. > 5. Hot leaf standby > The mechanisms defined in sections Section 4 and Section 3 can be > used together as follows. > This section is a little confusing to me. It seems that it really should be > how a leaf should behave when hot root standby is used, not that there is a > “hot leaf” mode. A leaf is just a leaf, not a cold/warm/hot/primary/standby > leaf. > GIM>> Would re-naming the section to "Use of Standby C-multicast Route" > better reflect the content of the section? > Thanks. > Jeffrey > From: BESS <bess-boun...@ietf.org> On Behalf Of stephane.litkow...@orange.com > Sent: Thursday, November 22, 2018 2:54 AM > To: bess@ietf.org > Cc: bess-cha...@ietf.org > Subject: [bess] WGLC, IPR and implementation poll for > draft-ietf-bess-mvpn-fast-failover > Hello Working Group, > This email starts a two-week Working Group Last Call on > draft-ietf-bess-mvpn-fast-failover-04 [1] > This poll runs until *the 6th of December*. > We are also polling for knowledge of any undisclosed IPR that applies to this > Document, to ensure that IPR has been disclosed in compliance with IETF IPR > rules (see RFCs 3979, 4879, 3669 and 5378 for more details). > If you are listed as an Author or a Contributor of this Document please > respond to this email and indicate whether or not you are aware of any > relevant undisclosed IPR. The Document won't progress without answers from > all the Authors and Contributors. > Currently two IPRs have been disclosed against this Document. > If you are not listed as an Author or a Contributor, then please explicitly > respond only if you are aware of any IPR that has not yet been disclosed in > conformance with IETF rules. > We are also polling for any existing implementation as per [2]. > Thank you, > Stephane & Matthew > [1] https://datatracker.ietf.org/doc/draft-ietf-bess-mvpn-fast-failover/ > [2] https://mailarchive.ietf.org/arch/msg/bess/cG3X1tTqb_vPC4rg56SEdkjqDpw > _________________________________________________________________________________________________________________________ > Ce message et ses pieces jointes peuvent contenir des informations > confidentielles ou privilegiees et ne doivent donc > pas etre diffuses, exploites ou copies sans autorisation. Si vous avez recu > ce message par erreur, veuillez le signaler > a l'expediteur et le detruire ainsi que les pieces jointes. Les messages > electroniques etant susceptibles d'alteration, > Orange decline toute responsabilite si ce message a ete altere, deforme ou > falsifie. Merci. > This message and its attachments may contain confidential or privileged > information that may be protected by law; > they should not be distributed, used or copied without authorisation. > If you have received this email in error, please notify the sender and delete > this message and its attachments. > As emails may be altered, Orange is not liable for messages that have been > modified, changed or falsified. > Thank you. _______________________________________________ BESS mailing list BESS@ietf.org https://www.ietf.org/mailman/listinfo/bess
