Re: [Lsr] IETF-116 LSR - IGP extensions for AdvertisingOffsetforFlex-Algorithm

[Liyan Gong <[e-mail]>]

Hi All，

Thanks for your discussion, here are some informations to help understanding better.

1. About the application scenario, please refer to the following draft.

https://datatracker.ietf.org/doc/draft-gong-teas-hierarchical-slice-solution/

Flex-Algo can be associated with the level-1 network slice which provides dynamic programming topology.

The number of Flex-Algos is the same as the number of the level-1 network slices. Maybe it can reach dozens.



2. About the performance impact, Maybe we can think of it as advertising massive routes through multi-pair neighbors in IGP domain.

Since the advertising and flooding process occupy a lot of router resources, Network changes can not be converged in time.

This will result in wrong traffic forwarding. That is why there is limitation on the number of routes in IGP domain.

According to the anaysis by Changwang in the following email, SIDs take up a big part.

We think it is better if Flex-Algo can be scaled up by optimizing the SIDs format without changing the IGP basic mechanism.



Best Regards,

Liyan














----邮件原文----发件人：Louis Chan  <louisc=[e-mail]>收件人：Ketan Talaulikar  <[e-mail]>抄　送: Krzysztof Szarkowicz  <[e-mail]>,Robert Raszuk <[e-mail]>,linchangwang  <[e-mail]>,Acee Lindem <[e-mail]>,Peter Psenak  <[e-mail]>,"程伟强" <[e-mail]>,"Les Ginsberg(ginsbe" <[e-mail]>,lsr  <[e-mail]>发送时间：2023-04-13 12:31:12主题：Re: [Lsr] IETF-116 LSR - IGP extensions for Advertising OffsetforFlex-Algorithm     

Hi Ketan,


 


Just a short response.


 


If you remember ATM days, there are VP shaping/policing and VC shaping/policing. It can solve quite complicated QOS problem.


Here we are not doing the costly ATM again.


 


With kind of hierarchical QOS readily available in ASIC today, it potentially solves some complex multipoint to multipoint QOS problem.


But first, it requires labeling the packet, like VCI and VPI.


 


I am going to stop here because it would be too much to discuss.


 


Rgds


Louis


 



From: Ketan Talaulikar <[e-mail]> Sent: Thursday, April 13, 2023 12:02 PM To: Louis Chan <[e-mail]> Cc: Krzysztof Szarkowicz <[e-mail]> Robert Raszuk <[e-mail]> linchangwang <[e-mail]> Acee Lindem <[e-mail]> Peter Psenak <[e-mail]> 程伟强 <[e-mail]> Les Ginsberg (ginsbe <[e-mail]> lsr <[e-mail]> Subject: Re: [Lsr] IETF-116 LSR - IGP extensions for Advertising Offset forFlex-Algorithm




 


[External Email. Be cautious of content]


 


Hi Louis,


 



First we need to ascertain if it is necessary before we get things flooded into IGPs. Then we can get to the evaluation of whether or how "evil" it is.



 



The VLAN analogy seems incorrect to me and a debate on that may be orthogonal to this topic. I39ll wait for the "necessity" to be first described before taking a bite at this PIZZA -)



 



Once again, thanks for your work on this document.



 



Thanks,



Ketan




 


On Thu, Apr 13, 2023 at 9:15AM Louis Chan <[e-mail]> wrote:



Hi Ketan,


 


First, I like “PIZZA” more than “VFA”, and at least it is closer to “real” and tasty instead of “virtual” and boring. :)


 


For VFA, it is just a further identification method. History has VLAN first introduced in ethernet. People might think it was already enough in that period. But later, market asked  for stacked vlan, and find its application.


 


Having VFA/PIZZA might give more possibilities for future usage. It is only ~30B advertisement per VFA per node, and it would not be a big harm. And there is no further header overhead  (or cell tax) in forwarding plane, and make it easy of vendor interop. This is more important.


 


I have no intention to swamp IGP with control plane kind of info, like QOS profile.  My view is to leave IGP as slim as possible for quick reaction to network changes.


 


If it is a necessary evil, it should be minimum. My take would be getting minimum but useful enough info into FAD. In this case, the advertisement size is small, with ease of management.   That is what I refer to “good to have” info in previous email.


 


Rgds


Louis


 



From: Ketan Talaulikar <[e-mail]> Sent: Thursday, April 13, 2023 12:06 AM To: Krzysztof Szarkowicz <[e-mail]> Cc: Robert Raszuk <[e-mail]> linchangwang <[e-mail]> Acee Lindem <[e-mail]>  Peter Psenak <[e-mail]> 程伟强 <[e-mail]> Louis Chan <[e-mail]>  Les Ginsberg (ginsbe <[e-mail]> lsr <[e-mail]> Subject: Re: [Lsr] IETF-116 LSR - IGP extensions for Advertising Offset forFlex-Algorithm




 


[External Email. Be cautious of content]


 


Hi Krzysztof,


 



I got the impression that the use-case/need for these VFA SIDs in the first place was to carry some indication in the packet for local treatment at each hop (e.g,, bandwidth profile  or QoS treatment?) in the data path since the forwarding is based on FlexAlgo. 



 



If not, then I am not sure that I follow the use-case or motivation for VFA (or pizza -) as Louis calls it) in the first place.



 



Thanks,



Ketan



 




 


On Wed, Apr 12, 2023 at 9:28PM Krzysztof Szarkowicz <[e-mail]> wrote:



Hi Ketan,


 



I agree with you. The draft doesn’t propose to carry ’service bandwidth profile’ parameters in the IGP.



 



The draft is dealing only with label/SID assignment/generation and distribution.



 



Thanks,



Krzysztof



 


 


On 2023 -Apr-12, at 17:49, Ketan Talaulikar <[e-mail]> wrote:



 


 



[External Email. Be cautious of content]


 


 



Hi Krzysztof,


 



A further question is if it is necessary to carry this "service bandwidth profile" information in the IGPs in the first place. Why not indicate this just in the packet? Wouldn39t  that be a better way to help scale IGPs by not introducing this into IGPs in the first place? -)



 



One such simple solution is proposed by https://datatracker.ietf.org/doc/draft-decraene-mpls-slid-encoded-entropy-label-id/



 



Thanks,



Ketan



 




 


On Wed, Apr 12, 2023 at 9:13PM Krzysztof Szarkowicz <kszarkowicz=[e-mail]> wrote:



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 <[e-mail]> 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 4:52PM linchangwang <[e-mail]> wrote:



Hi Acee


 


An operator39s 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:[e-mail]] 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 <[e-mail]> wrote:



 


Changwang, please see inline (##PP2): On 12/04/2023 15:13, linchangwang wrote:


Hi Peter  Please see inline [changwang lin].


We39ve 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, it39s 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 don39t 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:[e-mail]] 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. We39ve 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 Louis39draft 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 don39t 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://datatracker.ietf.org/doc/draft-cheng-lsr-isis-srv6-sid-block/> Thanks, Weiqiang Cheng     ----邮件原文----     *发件人：*Louis Chan  <louisc=[e-mail]>     *收件     人：*"Les Ginsberg (ginsberg)" <[e-mail]>,Acee  Lindem <[e-mail]>     *抄　送:     *lsr  <[e-mail]>,Krzysztof Szarkowicz  <[e-mail]>,Weiqiang Cheng  <[e-mail]>     *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) <[e-mail]>     *Sent:* Tuesday, April 11, 2023 11:03 PM     *To:* Louis Chan <[e-mail]> Acee Lindem <[e-mail]>     *Cc:* lsr <[e-mail]> Krzysztof Szarkowicz     <[e-mail]> Weiqiang Cheng     <[e-mail]>     *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 <[e-mail] <mailto:[e-mail]>>      > Sent: Monday, April 10, 2023 11:01 PM      > To: Les Ginsberg (ginsberg) <[e-mail]     <mailto:[e-mail]>> Acee Lindem      > <[e-mail] <mailto:[e-mail]>>      > Cc: lsr <[e-mail] <mailto:[e-mail]>> Krzysztof     Szarkowicz <[e-mail] <mailto:[e-mail]>>      > Weiqiang Cheng <[e-mail]     <mailto:[e-mail]>>      > 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) <[e-mail]     <mailto:[e-mail]>>      > Sent: Saturday, April 8, 2023 7:34 AM      > To: Acee Lindem <[e-mail]     <mailto:[e-mail]>> Louis Chan <[e-mail]     <mailto:[e-mail]>>      > Cc: lsr <[e-mail] <mailto:[e-mail]>>      > 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:] Let39s 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-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://datatracker.ietf.org/doc/draft-ietf-lsr-isis-fast-flooding/>   (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.     Let39s 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, 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 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 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 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 <[e-mail] <mailto:[e-mail]>>     On Behalf Of Acee Lindem      > > Sent: Friday, April 7, 2023 11:43 AM      > > To: Louis Chan <[e-mail] <mailto:[e-mail]>>      > > Cc: lsr <[e-mail] <mailto:[e-mail]>>      > > 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      > > [e-mail] <mailto:[e-mail]>      > >     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 [e-mail] https://www.ietf.org/mailman/listinfo/lsr ------------------------------------------------------------------------------------------------------------------------------------- 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. Any use of the information contained herein in any way (including, but not limited to, total or partial disclosure, reproduction, or dissemination) by persons other than the intended recipient(s) is prohibited. If you receive this e-mail in error, please notify the sender by phone or email immediately and delete it!




 





_______________________________________________ Lsr mailing list [e-mail] https://www.ietf.org/mailman/listinfo/lsr








 




_______________________________________________ Lsr mailing list [e-mail] https://www.ietf.org/mailman/listinfo/lsr







 







 


Juniper Business Use Only







 
Juniper Business Use Only