Re: [Lsr] Flooding Topology Computation Algorithm - draft-cc-lsr-flooding-reduction-08 Working Group Adoption Call

["Acee Lindem (acee)" <[e-mail]>]

Speaking as WG Co-chair:

Hi Gyan,

I guess you’ve joined this discussion late. It might be a good idea to review the LSR mailing list archives.

From: Gyan Mishra <[e-mail]>
Date: Thursday, May 21, 2020 at 1:51 PM
To: Huaimo Chen <[e-mail]>
Cc: Acee Lindem <[e-mail]>, "[e-mail]" <[e-mail]>
Subject: Re: [Lsr] Flooding Topology Computation Algorithm - draft-cc-lsr-flooding-reduction-08 Working Group Adoption Call



On Thu, May 21, 2020 at 11:01 AM Huaimo Chen <[e-mail]<mailto:[e-mail]>> wrote:
Hi Gyan,

    Thanks much for your questions.

 Gyan> How does this draft compare to the WG LC draft for flood reduction.  Would they be two eventual standard options in the operators toolbox  or competing features for optimized flood reduction. Would having two flood reduction features standardized versus one default IGP flood reduction feature be confusing for operators.  Just as it was confusing to me.
https://datatracker.ietf.org/doc/draft-ietf-lsr-dynamic-flooding/<https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdatatracker.ietf.org%2Fdoc%2Fdraft-ietf-lsr-dynamic-flooding%2F&data=02%7C01%7Chuaimo.chen%40futurewei.com%7C60df274544ba4b75447f08d7fd947201%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C0%7C637256686327604003&sdata=TGrkecn6m9liviazX7qqPglGqYEWu5Ekg2FRIaDpBZ8%3D&reserved=0>

    [HC]: This draft plus the draft for flooding reduction can provide two modes of flooding reductions (i.e., centralized mode and distributed mode). The latter describes the two modes, but does not include any flooding topology computation algorithm for the distributed mode. The former proposes a flooding topology computation algorithm to be used in the distributed mode.

   Gyan> It maybe a good idea for both documents to reference each other as to how they play together or  in some respects if any provide a homogeneous complete holistic solution for flooding problem being solved.

It is a good idea to have this new draft reference the dynamic-flooding but not vice-versa. The existing dynamic flooding draft provides a framework for any dynamic flooding algorithm that provides a separate flooding topology. This algorithm is just the first to be formally proposed in a draft. Note that another algorithm was presented during the LSR virtual interim which replaced IETF 107.

In my opinion it may not be a bad idea even to combine both drafts so the solution is complete and holistic.  This will also make the overall specification flow nicely.

No – we’re not going to do this.

Thanks,
Acee

I know that efforts were made by LSR to have a common IGP solution, however there are many inherent differences between ISIS and OSPF that from IGP Link state protocol perspective you can treat like apples to apples but really it’s apples and oranges.  Maybe it might we wise to have separate draft for both and have references linking together as the same algorithm concept and mathematically however the actual code implementation would vary as the LSDB link state data structures are completely different.

Later = Dynamic flooding = 2 modes Centralized leader based and distributed

https://datatracker.ietf.org/doc/draft-ietf-lsr-dynamic-flooding/

This later draft per section excerpt provides both centralized and distributed algorithm see below


6.4<https://datatracker.ietf.org/doc/html/draft-ietf-lsr-dynamic-flooding-05#section-6.4>.  Area Leader Responsibilities



   If the Area Leader operates in centralized mode, it MUST advertise

   algorithm 0 in its Area Leader Sub-TLV.  In order for Dynamic

   Flooding to be enabled it also MUST compute and advertise a flooding

   topology for the area.  The Area Leader may update the flooding

   topology at any time, however, it should not destabilize the network

   with undue or overly frequent topology changes.  If the Area Leader

   operates in centralized mode and needs to advertise a new flooding

   topology, it floods the new flooding topology on both the new and old

   flooding topologies.



   If the Area Leader operates in distributed mode, it MUST advertise a

   non-zero algorithm in its Area Leader Sub-TLV.



   When the Area Leader advertises algorithm 0 in its Area Leader Sub-

   TLV and does not advertise a flooding topology, Dynamic Flooding is

   disabled for the area.  Note this applies whether the Area Leader

   intends to operate in centralized mode or in distributed mode.



   Note that once Dynamic Flooding is enabled, disabling it risks

   destabilizing the network.



6.5<https://datatracker.ietf.org/doc/html/draft-ietf-lsr-dynamic-flooding-05#section-6.5>.  Distributed Flooding Topology Calculation



   If the Area Leader advertises a non-zero algorithm in its Area Leader

   Sub-TLV, all nodes in the area that support Dynamic Flooding and the

   value of algorithm advertised by the Area Leader MUST compute the

   flooding topology based on the Area Leader's advertised algorithm.



   Nodes that do not support the value of algorithm advertised by the

   Area Leader MUST continue to use standard flooding mechanism as

   defined by the protocol.



   Nodes that do not support the value of algorithm advertised by the

   Area Leader MUST be considered as Dynamic Flooding incapable nodes by

   the Area Leader.



   If the value of the algorithm advertised by the Area Leader is from

   the range 128-254 (private distributed algorithms), it is the responsibility of the

network operator to guarantee that all nodes in the area have a common understanding of what the given algorithm value represents.


Former = WG LC
https://datatracker.ietf.org/doc/html/draft-cc-lsr-flooding-reduction-08

Provides algorithm for distributed mode for this draft as well as the algorithm to be used for distributed mode later dynamic flooding draft

Separate question-

In light of the flooding algorithm and seeing that at the bottom of section 6.5 mentions flooding algorithm are the IANA codepoints reserved for flooding unique and non overlapping with the flex algo codepoints I believe 0-127.  I would think the flooding algorithm range of values is completely separate since a different function then flex algo values.

https://datatracker.ietf.org/doc/html/draft-ietf-lsr-flex-algo-07


Best Regards,
Huaimo
________________________________
From: Gyan Mishra <[e-mail]<mailto:[e-mail]>>
Sent: Thursday, May 21, 2020 10:36 AM

To: Huaimo Chen <[e-mail]<mailto:[e-mail]>>
Cc: Acee Lindem (acee) <acee=[e-mail]<mailto:[e-mail]>>; [e-mail]<mailto:[e-mail]> <[e-mail]<mailto:[e-mail]>>
Subject: Re: [Lsr] Flooding Topology Computation Algorithm - draft-cc-lsr-flooding-reduction-08 Working Group Adoption Call



On Wed, May 20, 2020 at 11:59 PM Huaimo Chen <[e-mail]<mailto:[e-mail]>> wrote:
Hi Gyan,

    Thanks much for your questions. My answers are inline below with [HC].

Best Regards,
Huaimo
________________________________
From: Gyan Mishra <[e-mail]<mailto:[e-mail]>>
Sent: Wednesday, May 20, 2020 11:14 AM
To: Huaimo Chen <[e-mail]<mailto:[e-mail]>>
Cc: Acee Lindem (acee) <acee=[e-mail]<mailto:[e-mail]>>; [e-mail]<mailto:[e-mail]> <[e-mail]<mailto:[e-mail]>>
Subject: Re: [Lsr] Flooding Topology Computation Algorithm - draft-cc-lsr-flooding-reduction-08 Working Group Adoption Call

Huaimo

This is a much needed feature that operators have been needing for densely meshed topologies that commonly exist in data centers to accommodate very high bandwidth E-W traffic.
[HC]: Thank you very much.

Below is link from Cisco which has introduced feature for dynamic flooding in clos high density ECMP data center topologies.

Please look at the feature description and it does seem to be exactly the same as this draft.  Please confirm.
[HC]: It seems different.

There maybe other vendors due to industry demand have to get the feature deployed before it reaches standards vendor consensus with the IETF.

https://www.cisco.com/c/en/us/products/collateral/switches/nexus-9000-series-switches/white-paper-c11-743015.html<https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.cisco.com%2Fc%2Fen%2Fus%2Fproducts%2Fcollateral%2Fswitches%2Fnexus-9000-series-switches%2Fwhite-paper-c11-743015.html&data=02%7C01%7Chuaimo.chen%40futurewei.com%7C60df274544ba4b75447f08d7fd947201%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C0%7C637256686327604003&sdata=CPEu2451qkfD9440Ihj1bKPWl%2BzH%2BiuYUwuWpfzR%2B0Q%3D&reserved=0>

We are testing this feature and planning to deploy but wanted to ensure that this is the same as the draft on the standards track.
[HC]: The feature appears implemented draft "Dynamic Flooding on Dense Graphs", which does not include any flooding topology computation algorithm..

    Gyan> How does this draft compare to the WG LC draft for flood reduction.  Would they be two eventual standard options in the operators toolbox  or competing features for optimized flood reduction. Would having two flood reduction features standardized versus one default IGP flood reduction feature be confusing for operators.  Just as it was confusing to me.


https://datatracker.ietf.org/doc/draft-ietf-lsr-dynamic-flooding/<https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdatatracker.ietf.org%2Fdoc%2Fdraft-ietf-lsr-dynamic-flooding%2F&data=02%7C01%7Chuaimo.chen%40futurewei.com%7C60df274544ba4b75447f08d7fd947201%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C0%7C637256686327604003&sdata=TGrkecn6m9liviazX7qqPglGqYEWu5Ekg2FRIaDpBZ8%3D&reserved=0>

Kind regards

Gyan


On Tue, May 19, 2020 at 11:52 PM Huaimo Chen <[e-mail]<mailto:[e-mail]>> wrote:
Hi Gyan,

    Thank you very much for your questions and support.

    This Flooding Topology Computation algorithm can be used in the Dynamic Flooding on Dense Graphs to compute the flooding topologies for the data center clos dense meshed topologies with many ECMP paths. It can be used by the area leader in the centralized mode to compute the flooding topology.

Best Regards,
Huaimo
________________________________
From: Lsr <[e-mail]<mailto:[e-mail]>> on behalf of Gyan Mishra <[e-mail]<mailto:[e-mail]>>
Sent: Tuesday, May 19, 2020 2:39 AM
To: Yanhe Fan <[e-mail]<mailto:[e-mail]>>
Cc: [e-mail]<mailto:[e-mail]> <[e-mail]<mailto:[e-mail]>>; Acee Lindem (acee) <acee=[e-mail]<mailto:[e-mail]>>
Subject: Re: [Lsr] Flooding Topology Computation Algorithm - draft-cc-lsr-flooding-reduction-08 Working Group Adoption Call


I support WG adoption and have a few questions related to the draft.

Does this flooding algorithm use the dynamic flooding algorithm used in data center clos dense meshed topologies with many ECMP paths where the flood is decoupled from the physical topology.  In the dynamic flooding algorithm mentioned in centralized mode the flooding is computed by the area leader and distributed to all nodes.  In distributed mode each mode the area leader determines the algorithm and then each node computes the flooding topology based on the algorithm.

This dynamic algorithm for optimized flood reduction would reduce the amount of redundant flooding in highly densely meshed ospf or Isis topologies.  So this optimization of flooding would improving overall link state routing protocol convergence.

Gyan

On Mon, May 18, 2020 at 3:37 PM Yanhe Fan <[e-mail]<mailto:[e-mail]>> wrote:

Support it as a co-author.



Thanks,

Yanhe



From: Lsr <[e-mail]<mailto:[e-mail]>> On Behalf Of Acee Lindem (acee)
Sent: Friday, May 15, 2020 3:40 PM
To: [e-mail]<mailto:[e-mail]>
Subject: [Lsr] Flooding Topology Computation Algorithm - draft-cc-lsr-flooding-reduction-08 Working Group Adoption Call



This begins a 3 week (due to holidays) WG adoption call for the “Flooding Topology Computation Algorithm” draft. Please issue your support or objection to this list by 11:59 PM, UTC on June 5th, 2020. Here is a URL for your convenience.



https://datatracker.ietf.org/doc/draft-cc-lsr-flooding-reduction/<https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdatatracker.ietf.org%2Fdoc%2Fdraft-cc-lsr-flooding-reduction%2F&data=02%7C01%7Chuaimo.chen%40futurewei.com%7C60df274544ba4b75447f08d7fd947201%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C0%7C637256686327614000&sdata=FkKUWXneiQIUtjkGB6RITfo0vAt2qhkwDWB%2BghP7%2FLg%3D&reserved=0>



Thanks,
Acee
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Gyan <https://www.google.com/maps/search/13101%0D%0A+Columbia+Pike+%0D%0A+Silver%0D%0A+Spring,+MD?entry=gmail&source=g> Mishra

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