Hi Aijun, Please check inline below.
On Sat, Jan 29, 2022 at 2:15 PM Aijun Wang <[email protected]> wrote: > Hi, Ketan: > > OK, then back to my original question: > > If one of the BFD session(between DRothers) is DOWN, will it bring DOWN > the OSPF adjacency(between the DRother and DR/BDR)? > KT> No. Those are different neighborships and the document does not bring any dependencies between them. > If not, then the traffic between these DRothers will be lost; > KT> Yes. Since there is a issue with forwarding (which is what BFD detects), the traffic would not get forwarded between those neighbors in any way. The neighborship going down (and staying down) prevents silent failures and flapping of that neighborship as explained in the draft. There is the possibility that an alternate path exists which might be used instead. > If yes, it seems strange, because the BFD session between the DRother and > DR/BDR may be still UP. > KT> That makes no difference. It isn't as if all traffic between routers on the LAN goes through the DR. Thanks, Ketan > I think here there are some mismatch between the BFD sessions and the OSPF > adjacency in Broadcast/NBMA network, then some clarification for the > procedures are needed. > > > > > > Best Regards > > > > Aijun Wang > > China Telecom > > > > *From:* [email protected] <[email protected]> *On Behalf Of *Ketan > Talaulikar > *Sent:* Saturday, January 29, 2022 4:22 PM > *To:* Aijun Wang <[email protected]> > *Cc:* [email protected]; [email protected]; Albert > Fu <[email protected]>; Acee Lindem (acee) <acee= > [email protected]> > *Subject:* Re: [Lsr] Working Group Last Call for "OSPF Strict-Mode for > BFD" - draft-ietf-lsr-ospf-bfd-strict-mode-04 > > > > Hi Aijun, > > > > The choice of the term "adjacency" was not accurate in my previous > response to you. I meant "neighborship". > > > > That said, the substance of my response still remains the same. > > > > Thanks, > > Ketan > > > > > > On Sat, Jan 29, 2022 at 1:42 PM Aijun Wang <[email protected]> > wrote: > > Hi, Ketan: > > For the Broadcast/NMBA network type, if you establish BFD sessions > before the DR/BDR selection, then there will be full mesh BFD sessions > within the routers on such media type? > > Instead of establishing the BFD sessions with DR/BDR only, the same as the > OSPF adjacency relationship? If so, if one of the BFD session that not with > the DR/BDR is DOWN, what’s the action then? > > > > KT> I think there is perhaps a misunderstanding of the purpose of BFD use > with OSPF. Perhaps a careful reading of RFC5882 would help? In short, BFD > is used to verify bidirectional connectivity between neighbors to ensure > data may be forwarded between them. OSPF adjacency is built between every > router in a LAN since they can directly forward packets between themselves. > > *[WAJ] In Broadcast/NBMA network, OSPF adjacency is built only between the > routers and DR/BDR. * > > > > Thanks, > > Ketan > > > > > > > > Best Regards > > > > Aijun Wang > > China Telecom > > > > *From:* Ketan Talaulikar <[email protected]> > *Sent:* Saturday, January 29, 2022 11:13 AM > *To:* Aijun Wang <[email protected]> > *Cc:* Acee Lindem (acee) <[email protected]>; [email protected]; > [email protected]; Albert Fu < > [email protected]> > *Subject:* Re: [Lsr] Working Group Last Call for "OSPF Strict-Mode for > BFD" - draft-ietf-lsr-ospf-bfd-strict-mode-04 > > > > Hi Aijun, > > > > Please check inline below. > > > > > > On Sat, Jan 29, 2022 at 7:38 AM Aijun Wang <[email protected]> > wrote: > > Hi, Acee: > > > > Yes. Then I think the sentence in > https://datatracker.ietf.org/doc/html/draft-ietf-lsr-ospf-bfd-strict-mode#section-2 > as the following should be relaxed: > > “A router MUST include the LLS block with the LLS Type 1 Extended > > Options and Flags TLV with the B-bit set in its Hello and DD packets > > when strict-mode for BFD is enabled on the link.” > > It seems that there is no use for such information being included in the > DD packets. > > > > KT> Since LLS is present in both Hello and DD packets, not including the B > bit in DD packets will result in a different LLS options being seen in > Hello and DD. This can trigger the change in LLS option logic > unnecessarily. Hence, to keep things simple and consistent (and this should > be for technically all LLS options), it makes sense to include them in both > Hello and DD packets. > > > > > > And, one more question to the Authors of this draft: > > What’s the procedures for the interaction of BFD session and OSPF > adjacency establishment in the Broadcast/NBMA network type interface, which > is involved the DR/BDR election procedures? The BFD session establishment > should be after the DR/BDR election? > > Should the procedures in section 4 be updated to cover such scenario? > > > > KT> The procedures in Sec 4 update the transition to INIT state in the > OSPF Neighbor FSM. This happens before DR election and is independent of > the type of network/link - applies also to Broadcast/NMBA. The main goal of > this proposal is to first verify BFD session establishment and only then > trigger OSPF adjacency procedures. Doing DR election before BFD session > does not serve the purpose. > > > > Thanks, > > Ketan > > > > > > > > > > Best Regards > > > > Aijun Wang > > China Telecom > > > > *From:* [email protected] <[email protected]> *On Behalf Of *Acee > Lindem (acee) > *Sent:* Friday, January 28, 2022 8:30 PM > *To:* Aijun Wang <[email protected]>; 'Ketan Talaulikar' < > [email protected]> > *Cc:* [email protected]; [email protected]; 'Albert > Fu' <[email protected]> > *Subject:* Re: [Lsr] Working Group Last Call for "OSPF Strict-Mode for > BFD" - draft-ietf-lsr-ospf-bfd-strict-mode-04 > > > > Hi Aijun, > > > > *From: *Aijun Wang <[email protected]> > *Date: *Friday, January 28, 2022 at 1:41 AM > *To: *'Ketan Talaulikar' <[email protected]> > *Cc: *"[email protected]" <[email protected]>, " > [email protected]" < > [email protected]>, Acee Lindem <[email protected]>, > 'Albert Fu' <[email protected]> > *Subject: *RE: [Lsr] Working Group Last Call for "OSPF Strict-Mode for > BFD" - draft-ietf-lsr-ospf-bfd-strict-mode-04 > > > > Hi, Ketan: > > > > I know. According to the description of RFC 5613, the LLS Data Block is > only attached at the OSPF hello and DD packets. > > > > If you read section 4 of the draft, you’ll see that the strict mode > behavior is based on the LLS block in OSPF Hello packets. > > > > Thanks, > Acee > > > > > > *From:* [email protected] <[email protected]> *On Behalf Of *Aijun > Wang > *Sent:* Friday, January 28, 2022 2:02 PM > *To:* 'Ketan Talaulikar' <[email protected]> > *Cc:* [email protected]; [email protected]; 'Acee > Lindem (acee)' <[email protected]>; 'Albert Fu' <[email protected]> > *Subject:* Re: [Lsr] Working Group Last Call for "OSPF Strict-Mode for > BFD" - draft-ietf-lsr-ospf-bfd-strict-mode-04 > > > > Hi, Ketan: > > What I want to know is that where to encapsulate the LLS Data Block if the > router uses OSPFv3 Extended LSAs to establish the adjacency? > > > > Best Regards > > > > Aijun Wang > > China Telecom > > > > *From:* [email protected] <[email protected]> *On Behalf Of *Ketan > Talaulikar > *Sent:* Friday, January 28, 2022 12:56 PM > *To:* Aijun Wang <[email protected]> > *Cc:* [email protected]; [email protected]; Acee > Lindem (acee) <[email protected]>; Albert Fu <[email protected]> > *Subject:* Re: [Lsr] Working Group Last Call for "OSPF Strict-Mode for > BFD" - draft-ietf-lsr-ospf-bfd-strict-mode-04 > > > > Hi Aijun, > > > > This document proposes changes to the adjacency establishment procedures > and the use of LLS for negotiations. As such, it is independent of OSPFv3 > Extended LSAs. Please let us know if you believe otherwise. > > > > Thanks, > > Ketan > > > > > > On Fri, Jan 28, 2022 at 8:29 AM Aijun Wang <[email protected]> > wrote: > > Hi, Albert: > > > > Want to how to accomplish this aim when router conforms to RFC8362? > > > > > > Best Regards > > > > Aijun Wang > > China Telecom > > > > *From:* [email protected] <[email protected]> *On Behalf Of *Albert > Fu (BLOOMBERG/ 120 PARK) > *Sent:* Friday, January 28, 2022 4:25 AM > *To:* [email protected]; [email protected] > *Cc:* [email protected] > *Subject:* Re: [Lsr] Working Group Last Call for "OSPF Strict-Mode for > BFD" - draft-ietf-lsr-ospf-bfd-strict-mode-04 > > > > > > I support this draft, as one of the authors, as well as a BFD user, and > hope it becomes a standard. > > > > This draft addresses an issue that we have encountered in our production > network, hence we have been actively working with our vendors. > > > > Most people deploy BFD with OSPF (or any routing protocols) to enable fast > failure detection. This is to ensure that routing/forwarding path is > diverted as soon as a connectivity issue is detected. > > > > OSPF BFD strict mode ensures this, in that it requires that the BFD > session to be established before OSPF adjacency will be allowed to be > established, thus ensuring that routing/forwarding will not use the path > without a working BFD adjacency. > > > > Without this standard, as per most current default OSPF BFD deployment, > OSPF adjacency is established without BFD. OSPF adjacency then triggers the > BFD session to be established. If a "break-in-middle" issue occurred (where > last mile interface status remains up) before BFD session comes up, we > would lose the fast failure detection capability. This situation will > require lengthy OSPF protocol timeout to detect such failure, resulting in > traffic being black-holed for extended period. > > > > We have a large network consisting of several thousand links throughout > the world, and have seen this issue several times that had impacted > production traffic negatively. > > > > As mentioned in a previous email, we have successfully tested this feature > on the Juniper MX (JUNOS 19.4) and also Cisco ASR9k (XR 7.3.2) platforms. > > > > Thanks > > Albert Fu > > Bloomberg > > > > From: [email protected] At: 01/27/22 12:08:36 UTC-5:00 > > To: [email protected] > Cc: [email protected] > Subject: Working Group Last Call for "OSPF Strict-Mode for BFD" - > draft-ietf-lsr-ospf-bfd-strict-mode-04 > > > > LSR WG, > > > > This begins a two week last call for the subject draft. Please indicate > your support or objection on this list prior to 12:00 AM UTC on February 11 > th, 20222. Also, review comments are certainly welcome. > > Thanks, > Acee > > > > > >
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