Jie, Your Enhanced VPN documents are very well written - thx for sharing the pointer to them. However I don't think I would put NRP as a new Extension Header for IPv6 data plane or Post Stack Data for MPLS data plane to indicate PHB in the packets.
I think there are better alternatives which do not require hardware extensions or modification. Thx, Robert. On Thu, Apr 13, 2023 at 1:24 PM Dongjie (Jimmy) <jie.dong= 40huawei....@dmarc.ietf.org> wrote: > Hi Krzysztof, > > > > If my understanding is correct, you and Louis are considering about two > separate optimizations: > > > > 1. Allowing multiple “Virtual Flex-Algos” to share the SPF > calculation of one “legacy” Flex-Algo. > > > > This can be addressed by the mechanisms described in section 2 of > https://datatracker.ietf.org/doc/html/draft-dong-lsr-sr-enhanced-vpn-08. > > > > More specifically, that document allows multiple NRPs to associate with > the same Flex-Algo, so that the Flex-Algo computation could be reused. NRP > is used to represent different set of network resources, and Flex-Algo is > still used to specify the topology and computation constraints for the NRP. > In that way, no change to Flex-Algo is needed. > > > > 2. Reducing the amount of SR SIDs which are used to indicate > different set of bandwidth reservation. > > > > The approach of using SR SIDs to represent different set of network > resources is suitable for networks in which the number of NRPs are > relatively small. As the number of NRPs increases, there will be > scalability challenge not only in the control plane but also in the data > plane. In that case, a more scalable and IGP friendly approach is to > introduce a network-wide NRP ID into the packet. This is also described in > section 5.3 of draft-dong-lsr-sr-enhanced-vpn-08. > > > > Hope this helps. > > > > Best regards, > > Jie > > > > *From:* Lsr <lsr-boun...@ietf.org> *On Behalf Of *Krzysztof Szarkowicz > *Sent:* Wednesday, April 12, 2023 11:42 PM > *To:* Robert Raszuk <rob...@raszuk.net> > *Cc:* linchangwang <linchangwang.04...@h3c.com>; Acee Lindem < > acee.i...@gmail.com>; Peter Psenak <ppse...@cisco.com>; 程伟强 < > chengweiqi...@chinamobile.com>; Louis Chan <lou...@juniper.net>; Les > Ginsberg (ginsbe <ginsb...@cisco.com>; lsr <lsr@ietf.org> > *Subject:* Re: [Lsr] IETF-116 LSR - IGP extensions for Advertising Offset > forFlex-Algorithm > > > > Hi, > > > > It is the question, if we could for example have more than 20 (e.g. 200), > for 200 different service bandwidth guarantees (but having only one - or > handful - SPF calculation domains, where one SPF calculation domain is one > ‘legacy’ flex-algo ). The challenge is with SPP calculations, once the > number of flex-algos goes high. > > > > Thanks, > > Krzysztof > > > > > > On 2023 -Apr-12, at 17:13, Robert Raszuk <rob...@raszuk.net> wrote: > > > > > > *[External Email. Be cautious of content]* > > > > > > > > Ok you can use 20 flex algos today with no extension. Is going to another > level of nesting really necessary ? > > > > On Wed, Apr 12, 2023 at 4:52 PM linchangwang <linchangwang.04...@h3c.com> > wrote: > > Hi Acee > > > > An operator's backbone network is divided into different flex algorithms > planes according to different SLA requirements of users. > > A flex algo represents a service requirement, such as bandwidth > requirements. > > 20 flex algorithms represent 20 different service bandwidth guarantees, > corresponding to different resource requirements. > > > > Thanks, > > Changwang lin > > > > *From:* Acee Lindem [mailto:acee.i...@gmail.com] > *Sent:* Wednesday, April 12, 2023 10:12 PM > *To:* Peter Psenak > *Cc:* linchangwang (RD); 程伟强; Louis Chan; Les Ginsberg (ginsbe; lsr; > Krzysztof Szarkowicz > *Subject:* Re: [Lsr] IETF-116 LSR - IGP extensions for Advertising Offset > forFlex-Algorithm > > > > Hi Weiqiang, > > > > I’m also curious as to how you are using 20 different flex algorithms. Is > this just a hypothetical scenario > > to illustrate the mathematics or do you have an actual use case? > > > > On Apr 12, 2023, at 09:31, Peter Psenak <ppse...@cisco.com> wrote: > > > > Changwang, > > please see inline (##PP2): > > > On 12/04/2023 15:13, linchangwang wrote: > > Hi Peter > Please see inline [changwang lin]. > > We've met the same problem when applying Flex Algo in SRv6 network. > > what problem exactly, can you please describe it? > [changwang lin] > Advertisement size of per Flex-Algo Adj-SID in the network > Related to F(# of node, # of FA, # of links) > For a node with 1,000 links and 20 Flex-Algo > n x 20 x 1000 > MPLS-SR：If n = 10 bytes, it is 200K bytes > SRv6： If n = 24 bytes, it is 400K+ bytes > If 500 nodes: > MPLS-SR：it is 200K*500 = 100000k bytes > SRv6： it is 400K+ * 500 = 200000k bytes > If interface mtu=1500, lsp length = 1497 > LSPs num: > MPLS-SR：10000k bytes/1497 = 66800 lsps > SRv6： 20000k bytes/1497 = 160320 lsps > The number of LSPs is too large, and IS-IS needs to periodically refresh > LSPs, > resulting in a decrease in ISIS performance and unstable network operation. > > > ##PP2 > above is hardly a realistic estimation. > > In a network with 1k nodes, not every node will have 1k links. > > Advertising large number of LSPs is not caused by Adj-SIDs. > With TE enabled the amount of data flooded per link is larger than > advertisement of the 20 Adj-SID. The problem you are highlighting is not > specific to Adj-SIDs, it's generic. > > LSP refresh time can be set to 18 hours and any reasonable implementation > does not refresh all LSPs at the same time. > > So we need to optimize on the control surface to save LSP space. > > > ##PP2 > with all the respect, I don't agree. The problem as you described it does > not exist. > > Through the optimization notification mechanism mentioned in these two > documents, > we have greatly saved LSP space for IS-IS and improved the performance of > IS-IS flex algo in large-scale networking. > At the same time, through the VFA mechanism, in other non flex algo > application scenarios, > such as network slicing scenarios, the LSP space of IS-IS can also be > saved > > > ##PP2 > it seems to me you are trying to fix the implementation problem with the > protocol changes, which is never a good idea. > > thanks, > Peter > > thanks, > Changwang lin > -----Original Message----- > From: Lsr [mailto:lsr-boun...@ietf.org] On Behalf Of Peter Psenak > Sent: Wednesday, April 12, 2023 7:10 PM > To: 程伟强; Louis Chan; Les Ginsberg (ginsbe; Acee Lindem > Cc: lsr; Krzysztof Szarkowicz > Subject: Re: [Lsr] IETF-116 LSR - IGP extensions for Advertising Offset > forFlex-Algorithm > Weiqiang, > please see inline (##PP): > On 12/04/2023 12:05, 程伟强 wrote: > > Hi Louis and Les, > > > My two cents from operator perspective. > > > We've met the same problem when applying Flex Algo in SRv6 network. > > what problem exactly, can you please describe it? > [changwang lin] > Advertisement size of per Flex-Algo Adj-SID in the network > Related to F(# of node, # of FA, # of links) > For a node with 1,000 links and 20 Flex-Algo > n x 20 x 1000 > MPLS-SR：If n = 10 bytes, it is 200K bytes > SRv6： If n = 24 bytes, it is 400K+ bytes > If 500 nodes: > MPLS-SR：it is 200K*500 = 100000k bytes > SRv6： it is 400K+ * 500 = 200000k bytes > If interface mtu=1500, lsp length = 1497 > LSP num: > MPLS-SR：10000k bytes/1497 = 66800 lsps > SRv6： 20000k bytes/1497 = 160320 lsps > The number of LSPs is too large, and IS-IS needs to periodically refresh > LSPs, > resulting in a decrease in ISIS performance and unstable network operation. > So we need to optimize on the control surface to save LSP space. > Through the optimization notification mechanism mentioned in these two > documents, > we have greatly saved LSP space for IS-IS and improved the performance of > IS-IS flex algo in large-scale networking. > At the same time, through the VFA mechanism, in other non flex algo > application scenarios, > such as network slicing scenarios, the LSP space of IS-IS can also be > saved > > > > As the number of slices and the scale of the network increases, the > convergence issue which is caused by SIDs advertising and flooding > becomes more and more serious. > > > Due to the problem, it is impossible to apply Flex-Algo in the large > network, such as the network with more than 1000 routers. > > flex-algo has been successfully deployed in a networks that have more > that 1k nodes. > Maybe you want deploy the flex-algo for something that it was not > designed for. > > > > I believe Louis'draft provides a good idea to resolve this problem. > Similar solution for SRv6 SIDs is described in another draft. > > Again, what problem exactly? > From what I see the drafts tries to pack algo SIDs to save space in > LSP. I don't see how it helps to to deploy flex-algo in a large scale > network. > thanks, > Peter > > > > About the SIDs assignment, I think it is better to have a scheduled > assignment than a random assignment as Les mentioned. > > > [1] > https://datatracker.ietf.org/doc/draft-cheng-lsr-isis-srv6-sid-block/ > <https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/draft-cheng-lsr-isis-srv6-sid-block/__;!!NEt6yMaO-gk!GCoxXhuL7ryqRodFUI2f-GPQa1_Vjs9WLIB_XJtQUiKVcm6Yrxqx5p-_PmGOQFNseVacNf7mx4QUND7v7my7$> > <https://datatracker.ietf.org/doc/draft-cheng-lsr-isis-srv6-sid-block/ > <https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/draft-cheng-lsr-isis-srv6-sid-block/__;!!NEt6yMaO-gk!GCoxXhuL7ryqRodFUI2f-GPQa1_Vjs9WLIB_XJtQUiKVcm6Yrxqx5p-_PmGOQFNseVacNf7mx4QUND7v7my7$> > > > > > > Thanks, > > Weiqiang Cheng > > > > ----邮件原文---- > *发件人：*Louis Chan <louisc=40juniper....@dmarc.ietf.org> > *收件 > 人：*"Les Ginsberg (ginsberg)" <ginsb...@cisco.com>,Acee Lindem < > acee.i...@gmail.com> > *抄 送: > *lsr <lsr@ietf.org>,Krzysztof Szarkowicz > <kszarkow...@juniper.net>,Weiqiang > Cheng <chengweiqi...@chinamobile.com> > *发送时间：*2023-04-12 10:45:56 > *主题：*Re: [Lsr] IETF- > 116 LSR - IGP extensions for Advertising Offset forFlex-Algorithm > > Hi Les, > > Thanks for the prompt reply. Please see inline for clarification [lc2]. > > /Louis > > *From:* Les Ginsberg (ginsberg) <ginsb...@cisco.com> > *Sent:* Tuesday, April 11, 2023 11:03 PM > *To:* Louis Chan <lou...@juniper.net>; Acee Lindem < > acee.i...@gmail.com> > *Cc:* lsr <lsr@ietf.org>; Krzysztof Szarkowicz > <kszarkow...@juniper.net>; Weiqiang Cheng > <chengweiqi...@chinamobile.com> > *Subject:* RE: [Lsr] IETF-116 LSR - IGP extensions for Advertising > Offset for Flex-Algorithm > > *[External Email. Be cautious of content]* > > Louis - > > Please see inline. > > > -----Original Message----- > > > From: Louis Chan <lou...@juniper.net <mailto:lou...@juniper.net>> > > > Sent: Monday, April 10, 2023 11:01 PM > > > To: Les Ginsberg (ginsberg) <ginsb...@cisco.com > <mailto:ginsb...@cisco.com>>; Acee Lindem > > > <acee.i...@gmail.com <mailto:acee.i...@gmail.com>> > > > Cc: lsr <lsr@ietf.org <mailto:lsr@ietf.org>>; Krzysztof > Szarkowicz <kszarkow...@juniper.net <mailto:kszarkow...@juniper.net>>; > > > Weiqiang Cheng <chengweiqi...@chinamobile.com > <mailto:chengweiqi...@chinamobile.com>> > > > Subject: RE: [Lsr] IETF-116 LSR - IGP extensions for Advertising > Offset for > > > Flex-Algorithm > > > > > > Hi Les, > > > > > > Thanks for your questions. Please see inline [lc] below. > > > > > > /Louis > > > > > > -----Original Message----- > > > From: Les Ginsberg (ginsberg) <ginsb...@cisco.com > <mailto:ginsb...@cisco.com>> > > > Sent: Saturday, April 8, 2023 7:34 AM > > > To: Acee Lindem <acee.i...@gmail.com > <mailto:acee.i...@gmail.com>>; Louis Chan <lou...@juniper.net > <mailto:lou...@juniper.net>> > > > Cc: lsr <lsr@ietf.org <mailto:lsr@ietf.org>> > > > Subject: RE: [Lsr] IETF-116 LSR - IGP extensions for Advertising > Offset for > > > Flex-Algorithm > > > > > > [External Email. Be cautious of content] > > > > > > > > > OK - since Acee opened the door - here are some comments from me - > > > starting with the most important. > > > > > > (BTW - I still have limited enthusiasm for this draft.) > > > > > > 1)The proposal places some restrictions on how operators > provision their > > > network in terms of assigning SIDs and reserving space for future > > > assignments. > > > If operators do not use compatible assignment schemes, then this > will never > > > get deployed. It is therefore not enough to come with a nice idea > - you must > > > have some enthusiasm from the operator community. > > > > > > > > > [lc] If the operator only wants to deploy flex-algo, there is no > change in their > > > Node-sid numbering scheme. For the Adj-sid, these are local > labels with local > > > significant only, and there is no need for any special planning > for Adj-sid, > > > unless you are suggesting they want to make fixed assignment of > Adj-sid > > > label for each link. Even with fixed, the proposed draft has > benefit on that. I > > > will explain later. > > > > > [LES:] Let's discuss this in the context of prefix-sids - the same > applies to adj-sids. > > Today (i.e., in the absence of your proposal) an operator is free to > assign any label within the SRGB for a given prefix/algo pair so > long as it is not assigned to some other prefix/algo context. > > Your proposal places some new restrictions. Now, for a given > flex-algo, whenever an operator assigns a given label for a prefix > in Algo 0 (call it Label-A0), they must guarantee that > "Label-A0+offset" for an advertised flex-algo specific offset is > available to be assigned for the prefix/flex-algo pair - and this > must be true for all prefixes advertised in algo 0. > > This is certainly possible to do, but is not guaranteed to be the > case in current deployments. > > For example - and this is only an example...today an operator might > utilize a provisioning tool to assign prefix-sids for all supported > algorithms on all nodes in the network. > > To do this, the tool might maintain a database of assigned labels. > When provisioning a new node/prefix/algorithm, the logic in the tool > might simply take the next available label in the database. > > The result of this would not be consistent with the requirements of > your draft. > > Which is why I say in order to deploy the extension you propose, > such an operator would have to modify its provisioning tool. > > [lc2] There might be some misunderstanding of our proposal. Let me > give some examples. > > Case 1: Flex-Algo only > > Prefix offset advertisement: “no” > > Adj-sid offset advertisement: yes > > In slide 8’s example, FA129 is using label “402001”, and the > advertisement of this label is using existing methods. > > e.g. SRGB = 400000-460000 > > FA129: index 2001 (preferred value), or one can choose 111, 222 > > FA130 (new): index 3001 (preferred value), or 333, 4444 > > This does not change how the operator to assign label for prefix-sid > with their current method. Any index/label could be used for FA > prefix within SRGB. > > The only change is the Adj-sid label allocation, but this “mostly” > is only “local” to one node. There is no effect on global label > allocation. > > This draft will be compatible to what operators are doing today. > > Case 2: VFA only > > Prefix offset advertisement: yes > > Adj-sid offset advertisement: yes > > I agree, with VFA, there would be impact to global allocation to > node-sid/prefix-sid. But VFA is a totally new concept. No one has > deployed that yet. > > There is no impact to operators which stick to deploy only Flex-algo. > > Other case: Flex-Algo w/o Adj-sid offset > > Continue the example of Case#1 above > > Another FA131 is added, but no Adj-sid offset is > advertised > > The question would be > > * > > Either allow this configuration, and FA131 will fallback using > Algo 0’s adj-sid > > * > > Or, disallow this configuration > > I tend to “allow” such configuration with mix of FA129, FA130 (with > adj-sid offset) and FA131 (w/o adj-sid offset) > > [/lc2] > > Could this be done? Sure. > > Do operators want to do this? I do not know. > > But since this would be necessary in order to use your proposed > extension, it is necessary to gauge operator enthusiasm for making > such changes in order to know whether there is any point in > proceeding with your proposal. > > > In slide 8 of the below presentation > > > > > https://datatracker.ietf.org/meeting/116/materials/slides-116-lsr-03-ietf116- > <https://urldefense.com/v3/__https:/datatracker.ietf.org/meeting/116/materials/slides-116-lsr-03-ietf116-__;!!NEt6yMaO-gk!GCoxXhuL7ryqRodFUI2f-GPQa1_Vjs9WLIB_XJtQUiKVcm6Yrxqx5p-_PmGOQFNseVacNf7mx4QUNBlx2nlh$> > < > https://urldefense.com/v3/__https:/datatracker.ietf.org/meeting/116/materials/slides-116-lsr-03-ietf116-igp-adv-offset-01__;!!NEt6yMaO-gk!Bl7Swe9ql9VT0qGkD6FoZZzTWT2fmIx55eSncdmMgoCJetJ5-80micuqnqk79yewGB-BleOfrYpSjfI$ > > > > > igp-adv-offset-01 > < > https://urldefense.com/v3/__https:/datatracker.ietf.org/meeting/116/materials/slides-116-lsr-03-ietf116-igp-adv-offset-01__;!!NEt6yMaO-gk!Bl7Swe9ql9VT0qGkD6FoZZzTWT2fmIx55eSncdmMgoCJetJ5-80micuqnqk79yewGB-BleOfrYpSjfI$ > > > > > > > > FA129 is a prefix-sid (400201) allocated by operator, and it can > be any label. > > > There is no connection to how Adj-sid is derived. > > > Per Flex-Algo adj-sid assignment is not affecting network wide label > > > assignment from operation perspective. Each node could have > different local > > > block for such adj-sid assignment. One might need to estimate > total possible > > > number of link in one chassis for such allocation, or it could be > estimated by > > > OS software itself. I also mentioned in the session, if there is > 100 x FA with > > > 1000 links (high end), it is only 100k labels. Is it difficult to > allocate such. > > [LES:] Your proposal does not reduce the number of labels which need > to be "allocated" and installed in forwarding, it only reduces the > number of bytes used to advertise this information in LSPs/LSAs. > > [lc2] You are correct. > > I think, at the same time, it helps reducing time for global > convergence since the advertisement size is smaller, especially in > network with long diameter with multi-hops. > > Also, in > https://datatracker.ietf.org/doc/draft-ietf-lsr-isis-fast-flooding/ > <https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/draft-ietf-lsr-isis-fast-flooding/__;!!NEt6yMaO-gk!GCoxXhuL7ryqRodFUI2f-GPQa1_Vjs9WLIB_XJtQUiKVcm6Yrxqx5p-_PmGOQFNseVacNf7mx4QUNHGf6W4I$> > <https://datatracker.ietf.org/doc/draft-ietf-lsr-isis-fast-flooding/ > <https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/draft-ietf-lsr-isis-fast-flooding/__;!!NEt6yMaO-gk!GCoxXhuL7ryqRodFUI2f-GPQa1_Vjs9WLIB_XJtQUiKVcm6Yrxqx5p-_PmGOQFNseVacNf7mx4QUNHGf6W4I$>> > (which you participated in) > > >>> > > As IS-IS is deployed in greater scale both in the number of nodes in > > an area and in the number of neighbors per node, the impact of the > > historic flooding rates becomes more significant. Consider the > > bringup or failure of a node with 1000 neighbors. This will result > > in a minimum of 1000 LSP updates. At typical LSP flooding rates > used > > today (33 LSPs/second), it would take 30+ seconds simply to send > the > > updated LSPs to a given neighbor. Depending on the diameter of the > > network, achieving a consistent LSDB on all nodes in the network > > could easily take a minute or more. > > <<< > > This proposed draft will certainly help. > > [/lc2] > > > > > > So, this is why I do not understand your question in full. > > > > > > If the operator plans to use VFA, that would be a different > discussion. VFA, > > > today, does not exist in deployment. > > > > > [LES:] My comments here have nothing to do with VFA. > > > [/lc] > > > > > > Have you discussed this idea with any operators? > > > > > > [lc] I include Wei-qiang from China mobile in this thread. He has > shown his > > > need on this kind of solution. Maybe, he could give his > perspective here. [/lc] > > > > > > If so, what has been their response? > > > If they are open to the idea, how might they migrate from their > existing > > > assignment schemes to an assignment scheme compatible with the > > > proposal? > > > > > > These are questions that need to be answered before considering > this idea. > > > > > > [lc] In slide 8, if you see these label numbers > > > > > > Prefix-sid: 400001, 402001, 406001, 407001 > > > Adj-sid: 32, 2032, 6032, 7032 > > > > > > From operator perspective or troubleshooting perspective, value > xxx001 > > > represent the same node, and value x032 represent the same link. > This > > > makes things more organized and easier to understand. > > > > > > If all are random labels, I do not see any benefit at all. > > > [/lc] > > [LES:] I am not commenting on whether the label assignment scheme > you propose is better or worse than any other. > > I am only pointing out that you are imposing new restrictions on how > labels are allocated. > > As you are not in charge of how operators provision their networks > (nor am I), it is presumptuous of you to think that simply because > you think this is a better way to do things that operators will be > happy to modify their existing networks to conform to your proposed > restrictions. > > This isn’t academia - you need to vet this with the operator community. > > [lc2] Please refer to the examples at the top. The picture should be > clear by now. There is no restriction to what is deployed today. [/lc2] > > > > > > 2)Section 5 Compatibilty > > > > > > There is no "compatibility" with legacy nodes - because all nodes > in the > > > network have to have a consistent understanding of what SID is > assigned to a > > > given context (for prefixes and adjacencies) since they might > need to install > > > forwarding entries for that context. > > > I do not see any point in deploying this until all nodes support > it. If you did do > > > so, you would need to advertise old and new forms - which does the > > > opposite of what you are trying to achieve. Instead of reducing > LSP space > > > used you would increase it. > > > > > > [lc] If the operator just plans to use only Flex-Algo, and no > VFA, it should be > > > compatible with legacy implementation. If legacy nodes do not > understand > > > adj-sid offset notation, these nodes could just ignore it. The > forwarding > > > plane should work with co-existence of old and new nodes. Per > flex-algo adj- > > > sid is only local significant to one node. New nodes should > detect whether > > > legacy nodes exist in the network via such new extension > advertisement. > > > And new nodes should use only algo 0 adj-sid from legacy nodes > for any TI- > > > LFA. > > [LES:] Consider a network of 100 nodes. > > Let's say the "left-hand-side" of the network consist of legacy > nodes who do not understand your new advertisements. > > The "right-hand-side" of the network consists of upgraded nodes who > support the new advertisements. > > Consider nodes PE-LEFT and PE-RIGHT. > > PE-RIGHT advertises a prefix-SID of 1000 for 2.2.2.2/32 > <https://urldefense.com/v3/__http:/2.2.2.2/32__;!!NEt6yMaO-gk!GCoxXhuL7ryqRodFUI2f-GPQa1_Vjs9WLIB_XJtQUiKVcm6Yrxqx5p-_PmGOQFNseVacNf7mx4QUNEj8LL78$>, > and an > offset of 1000 for flex-algo 128. > > PE-LEFT supports flex-algo 128 and wants to install a forwarding > entry for 2.2.2.2 for flex-algo 128. > > It looks in the LSPs originated by PE-RIGHT. It does not see any > assigned SID for 2.2.2.2/32 > <https://urldefense.com/v3/__http:/2.2.2.2/32__;!!NEt6yMaO-gk!GCoxXhuL7ryqRodFUI2f-GPQa1_Vjs9WLIB_XJtQUiKVcm6Yrxqx5p-_PmGOQFNseVacNf7mx4QUNEj8LL78$> > flex-algo 128. > > It cannot create a forwarding entry. And neither can any other node > in the left hand side of the network. > > When PE-RIGHT stops advertising the explicit prefix SID for > 2.2.2.2/32 > <https://urldefense.com/v3/__http:/2.2.2.2/32__;!!NEt6yMaO-gk!GCoxXhuL7ryqRodFUI2f-GPQa1_Vjs9WLIB_XJtQUiKVcm6Yrxqx5p-_PmGOQFNseVacNf7mx4QUNEj8LL78$> > Algo 128, all legacy nodes are unable to create > forwarding entries for the prefix/algo tuple. > > This isn’t backwards compatible. > > In general, you cannot advertise information legacy nodes require in > a new container that legacy nodes do not understand and claim that > you are backwards compatible. > > [lc2] Please refers to the examples for clarification. > > 1. > > For existing Flex-Algo deployment, it would be compatible. There > is no change in the container format on how prefix-sid > 2.2.2.2/32 > <https://urldefense.com/v3/__http:/2.2.2.2/32__;!!NEt6yMaO-gk!GCoxXhuL7ryqRodFUI2f-GPQa1_Vjs9WLIB_XJtQUiKVcm6Yrxqx5p-_PmGOQFNseVacNf7mx4QUNEj8LL78$> > in FA128 is advertised. > > 1. > > For new VFA, it would not be compatible. But….it does not mean > that we could not have VFA running in the same network. > > There could be procedures to enhance such. With your example, one > workaround could be: > > For VFA 600, PE-RIGHT detects that PE-LEFT does not participate in > VFA600 (due to no offset advertisement seen), > > * > > Either, it spawns new CSPF for VFA600 instead of sharing FA129’s > result. Bypass PE-LEFT as a result. > > * > > Or, it uses legacy node FA129 prefix-sid and adj-sid as > replacement (note: this method needs more comment) > > In either ways, VFA600 could work without issue even with legacy > nodes co-existence. > > After PE-LEFT upgraded, VFA600 would be using FA129 CSPF result > instead, and save CPU resources in each node. > > Another question: do we need FAD for VFA600? Currently, no. Not > mandatory. > > But it could be considered if “good to have” parameters are passed > along with FAD. > > [/lc2] > > > > > > I do not see a major problem. Please give me an example to > illustrate your > > > concern if possible. > > > > > > Of course, we need to do double check on the claim and possibly lab > > > verification to see if the backward compatibility could be > achieved. It could > > > be vendor specific. > > > > > > [/lc] > > > > > > > > > What does deserve discussion is a "hitless migration strategy". > When full > > > support is available, if you were to switch to the new scheme, > you would > > > want to do so without changing any existing SIDs as this would avoid > > > forwarding disruption. Which means operators would have to modify > their > > > SID assignment scheme in advance of deploying the new scheme. > > > > > > [lc] For VFA, there would be issue for legacy nodes. I agree. In > this case, > > > solution could be > > > - either have a fallback plan for newer nodes if > detection of legacy nodes > > > exist in the network. E.g. spawn new CSPF > > > - or, totally not to deploy VFA unless all nodes are > upgraded. > > > > > > Section 5 is not updated with VFA inclusion. > > [LES:] My comments have nothing to do with VFA. > > Please reconsider them after you have understood the backwards > compatibility issues. > > > > > > [/lc] > > > > > > 3)Virtual Flex Algorithm > > > > > > You have introduced a new concept with very little explanation of > what it is > > > nor how it can be supported. > > > For example, how would we determine which nodes support a given VFA? > > > Since the algorithm value must be greater than 255, it cannot be > advertised in > > > the existing SR Algorithm sub-TLV. > > > > > > If you are serious about this idea, please provide a more complete > > > discussion. > > > > > > [lc] We could illustrate application examples in next > presentation. For > > > ethernet, we have port, and then we have VLAN and stacked vlan. > History > > > has some hints on this. > > > > > [LES:] You are writing a normative specification. Hoping that all > readers/implementors have the same "intuition" isn’t sufficient. > > Les > > > [/lc] > > > > > > 4)Section 4.3 > > > > > > "R" and "N" flags are now defined in prefix attributes sub-TLV > (RFC7794) > > > They were originally defined in the SR sub-TLV because RFC 7794 > did not exist > > > at the time. > > > The only reason they continue to exist in RFC 8667 is for backwards > > > compatibility with early implementation of SR-MPLS based on early > drafts of > > > what became RFC 8667. > > > Please do not introduce them in new sub-TLVs - there is no need. > > > > > > [lc] noted with thanks [/lc] > > > > > > 5)ADJ-SIDs are NOT allocated from the SRGB as they are local in > scope. > > > They MAY be allocated from the SRLB - or outside either GB range. > > > Please correct the document in this regard. > > > > > > [lc] noted [/lc] > > > > > > Les > > > > > > > -----Original Message----- > > > > From: Lsr <lsr-boun...@ietf.org <mailto:lsr-boun...@ietf.org>> > On Behalf Of Acee Lindem > > > > Sent: Friday, April 7, 2023 11:43 AM > > > > To: Louis Chan <lou...@juniper.net <mailto:lou...@juniper.net>> > > > > Cc: lsr <lsr@ietf.org <mailto:lsr@ietf.org>> > > > > Subject: Re: [Lsr] IETF-116 LSR - IGP extensions for Advertising > > > > Offset for Flex-Algorithm > > > > > > > > Hi Louis, > > > > > > > > In the interest of initiating discussion, I would like to > propose the > > > > term "Flex Algorithm Traffic Class (FATC)" for the sub-division of > > > > flex-algorithm traffic referred to in the draft as “Virtual > Flex Algorithm”. > > > > > > > > Also, in your terminology, you refer referred to TLVs and > fields with > > > > simply “Algorithm” when RFC 9350 uses “Flex Algorithm”. > > > > > > > > Thanks, > > > > Acee > > > > > > > > > > > > > > > > _______________________________________________ > > > > Lsr mailing list > > > > Lsr@ietf.org <mailto:Lsr@ietf.org> > > > > > https://urldefense.com/v3/__https://www.ietf.org/mailman/listinfo/lsr_ > <https://urldefense.com/v3/__https:/www.ietf.org/mailman/listinfo/lsr_> < > https://urldefense.com/v3/__https:/www.ietf.org/mailman/listinfo/lsr_> > > > > _;!!NEt6yMaO-gk!B9ufrV6k- > > > c7mtP9JUiXbrF3NCkZ15_UMLBjV_fnJovfz18M5VkkI2F > > > > EoixpkxsfMnbqwbR0bpHgoS9E$ > > > > > > Juniper Business Use Only > > Juniper Business Use Only > > > Juniper Business Use Only > > _______________________________________________ > Lsr mailing list > Lsr@ietf.org > https://www.ietf.org/mailman/listinfo/lsr > <https://urldefense.com/v3/__https:/www.ietf.org/mailman/listinfo/lsr__;!!NEt6yMaO-gk!GCoxXhuL7ryqRodFUI2f-GPQa1_Vjs9WLIB_XJtQUiKVcm6Yrxqx5p-_PmGOQFNseVacNf7mx4QUNLUwWHuZ$> > > ------------------------------------------------------------------------------------------------------------------------------------- > 本邮件及其附件含有新华三集团的保密信息，仅限于发送给上面地址中列出 > 的个人或群组。禁止任何其他人以任何形式使用（包括但不限于全部或部分地泄露、复制、 > 或散发）本邮件中的信息。如果您错收了本邮件，请您立即电话或邮件通知发件人并删除本 > 邮件！ > This e-mail and its attachments contain confidential information from New > H3C, which is > intended only for the person or entity whose address is listed above. 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