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

[Gyan Mishra <[e-mail]>]

On Thu, May 21, 2020 at 11:01 AM Huaimo Chen <[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.

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.

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]>
> *Sent:* Thursday, May 21, 2020 10:36 AM
>
> *To:* Huaimo Chen <[e-mail]>
> *Cc:* Acee Lindem (acee) <acee=[e-mail]>; [e-mail] <
> [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]>
> wrote:
>
> Hi Gyan,
>
>     Thanks much for your questions. My answers are inline below with [HC].
>
> Best Regards,
> Huaimo
> ------------------------------
> *From:* Gyan Mishra <[e-mail]>
> *Sent:* Wednesday, May 20, 2020 11:14 AM
> *To:* Huaimo Chen <[e-mail]>
> *Cc:* Acee Lindem (acee) <acee=[e-mail]>; [e-mail] <
> [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]>
> 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]> on behalf of Gyan Mishra <
> [e-mail]>
> *Sent:* Tuesday, May 19, 2020 2:39 AM
> *To:* Yanhe Fan <[e-mail]>
> *Cc:* [e-mail] <[e-mail]>; Acee Lindem (acee) <acee=
> [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]> wrote:
>
> Support it as a co-author.
>
>
>
> Thanks,
>
> Yanhe
>
>
>
> *From:* Lsr <[e-mail]> *On Behalf Of *Acee Lindem (acee)
> *Sent:* Friday, May 15, 2020 3:40 PM
> *To:* [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>
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>
>
> Thanks,
> Acee
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> Mishra*
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> *Gyan Mishra*
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> *Network Solutions A**rchitect *
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