Re: [bess] New short WGLC for draft-ietf-bess-evpn-unequal-lb

[Gyan Mishra <[e-mail]>]

I support publication of this important EVPN enhancement to all active
multi homed PE-CE AC  ESI backup path aliasing ECMP per flow load balancing
to now support weighed and bandwidth or link count based uneven load
balancing in case of MLAG link failures or uneven bandwidth upgrades.

Kind Regards

Gyan

On Fri, May 14, 2021 at 6:58 PM Neeraj Malhotra <[e-mail]>
wrote:

>
> Hi,
>
> fyi, have addressed all comments on this thread and some more comments
> from co-authors in the latest revision (rev14).
>
> Thanks,
> Neeraj
>
>
> On Wed, May 12, 2021 at 2:07 PM Neeraj Malhotra <[e-mail]>
> wrote:
>
>>
>> Hi Bruno, Sergey,
>>
>> Thanks for the additional comments and discussion. To summarize, I plan
>> to address the following comments by this weekend:
>>
>> *[Bruno] §4.1 & 5.2 have 3 iterations of “this attribute is to be
>> ignored”. I’m afraid one could read this as “this BGP attribute is to be
>> ignored”. Surely we mean “this(theses) EVPN Link Bandwidth extended
>> community(ies) is(are) to be ignored”.*
>>
>>
>> [NM]: ack.
>>
>>
>> *[Sergey] could we also expand text in section 5.2 “Remote PE behavior” a
>> little bit to include an example for non-aliased case where a MAC has been
>> learned only from a subset of PEs.*
>>
>>
>> [NM]: Although not ultra important, I think for completeness it will be
>> good to allow inclusion of the EC in RT-2 for non-aliasing ECMP use cases.
>> It is a simple extension similar to RT-5. Will add.
>>
>>
>> *[Bruno] in the draft §5.2 uses “remote PE” for the ingress PE while §4.1
>> uses “remote PE” for the egress PE  (“A receiving PE MUST check for
>> consistent 'Value-Units' received in the EVPN link bandwidth exteneded
>> community from each remote PE in an Ethernet Segment. » I’d assume that
>> terminology in §4.1 need to be fixed.*
>>
>>
>> [NM]: ack.
>>
>>
>> Please see inline for the following comment:
>>
>>
>> *[Bruno] Stricto census, what is needed is a single instance of this
>> sub-type and _Value-Units_. In order to accommodate one ingress PE in a
>> domain using “Weight in units of Mbps” and another ingress PE in a
>> different domain using “Generalized Weight”, one could imagine an egress PE
>> advertising 2 communities/both units. I have a slight preference for
>> allowing both, but up to you.*
>>
>>
>> [NM]: Yes, strictly speaking, this is correct. However, for simplicity, I
>> am inclined to have local/egress PEs that are part of the Ethernet Segment
>> specify a single / consistent weight unit they are going to use and have
>> the receiving/ingress PEs simply follow, rather than give ingress PEs a
>> choice of which units to choose out of multiple received units based on
>> some specified or locally provisioned precedence (implementation and
>> provisioning overhead as Sergey also commented).
>>
>>
>> Thanks,
>>
>> Neeraj
>>
>> On Tue, May 11, 2021 at 11:20 PM Rabadan, Jorge (Nokia - US/Mountain
>> View) <[e-mail]> wrote:
>>
>>> Thanks Sergey. I agree with that, for Layer 2 aliasing.
>>>
>>> For RT5 routes the extended community goes directly with the RT5 as
>>> stated in the document.
>>>
>>>
>>>
>>> The IP aliasing draft, that we will refresh soon, will reference to this
>>> draft and will allow the extended community to be advertised with A-D per
>>> EVI routes in the IP-VRF context.
>>>
>>>
>>>
>>> Thanks.
>>>
>>> Jorge
>>>
>>>
>>>
>>> *From: *Fomin, Sergey (Nokia - US/Mountain View) <[e-mail]
>>> >
>>> *Date: *Wednesday, May 12, 2021 at 2:07 AM
>>> *To: *Neeraj Malhotra <[e-mail]>, Rabadan, Jorge (Nokia -
>>> US/Mountain View) <[e-mail]>
>>> *Cc: *[e-mail] <[e-mail]>, BESS <
>>> [e-mail]>, [e-mail] <[e-mail]>
>>> *Subject: *RE: [bess] New short WGLC for draft-ietf-bess-evpn-unequal-lb
>>>
>>> Hi Neeraj, Jorge & all,
>>>
>>>
>>>
>>> Just wanted to clarify my previous message after a short chat with
>>> Jorge: when I say “non-aliasing” case, I mean a scenario where eth. a-d per
>>> EVI route is not used or generated [by PEs-1/2/3 in this example].
>>>
>>> It is indeed a relatively rare scenario which doesn’t bring much value,
>>> so I’m open to drop support for it in this draft and just require eth. a-d
>>> per EVI route to be present (=aliasing enabled) to support the procedures
>>> described in this document.
>>>
>>>
>>>
>>> Thank you,
>>>
>>> --
>>>
>>> Sergey
>>>
>>> *From:* BESS <[e-mail]> *On Behalf Of *Fomin, Sergey
>>> (Nokia - US/Mountain View)
>>> *Sent:* Tuesday, May 11, 2021 12:48 PM
>>> *To:* [e-mail]; Neeraj Malhotra <[e-mail]>
>>> *Cc:* Rabadan, Jorge (Nokia - US/Mountain View) <[e-mail]>;
>>> [e-mail]; BESS <[e-mail]>
>>> *Subject:* Re: [bess] New short WGLC for draft-ietf-bess-evpn-unequal-lb
>>>
>>>
>>>
>>> Hi Neeraj & Bruno,
>>>
>>>
>>>
>>> Bruno,
>>>
>>> *               > Stricto census, what is needed is a single instance of
>>> this sub-type and _Value-Units_. In order to accommodate one ingress PE in
>>> a domain using “Weight in units of Mbps” and another ingress PE in a
>>> different domain using “Generalized Weight”, one could imagine an egress PE
>>> advertising 2 communities/both units.*
>>>
>>> By "egress PE", I'm assuming, you mean "local PE" in terms of this RFC
>>> (with an attached ES)?
>>>
>>> I'm not opposed to the idea, thought it adds a layer of implementation
>>> complexity.
>>>
>>> If you see this as a valid use case (somewhat exotic, for sure), it
>>> might be worth relaxing the requirement; in this case, we also should add a
>>> remark along the lines that “remote PE” logic how to select between 2
>>> types/sets of LBW communities is left up to the implementer / may be
>>> configurable; and support for attaching 2 types of communities at the same
>>> time is optional.
>>>
>>>
>>>
>>> Thank you for your prompt response Neeraj,
>>>
>>> Following up on my aliasing/non-aliasing point, I see you added the
>>> following statement
>>>
>>> *   o  Procedures related to bridged unicast and BUM traffic are*
>>>
>>> *      applicable to both aliasing and non-alaising mode as defined in*
>>>
>>> *      [RFC7432].*
>>>
>>> (btw, a typo in ‘aliasing’)
>>>
>>> This is good, could we also expand text in section 5.2 “Remote PE
>>> behavior” a little bit to include an example for non-aliased case where a
>>> MAC has been learned only from a subset of PEs.
>>>
>>> E.g. in the current example there, calculation is performed for all 3
>>> PEs and gives weights 2 / 1 /1 for a mac entry X.
>>>
>>> If aliasing is not enabled, and a mac entry Y is known only via PE-1 &
>>> PE-3; path-list for this mac would be [PE-1, PE-3] with 2 / 1 LB ratio.
>>>
>>>
>>>
>>> Thank you!
>>>
>>> --
>>>
>>> Sergey
>>>
>>>
>>>
>>> *From:* [e-mail] <[e-mail]>
>>> *Sent:* Monday, May 10, 2021 11:39 PM
>>> *To:* Neeraj Malhotra <[e-mail]>; Fomin, Sergey (Nokia -
>>> US/Mountain View) <[e-mail]>
>>> *Cc:* Rabadan, Jorge (Nokia - US/Mountain View) <[e-mail]>;
>>> [e-mail]; BESS <[e-mail]>
>>> *Subject:* RE: [bess] New short WGLC for draft-ietf-bess-evpn-unequal-lb
>>>
>>>
>>>
>>> Thanks Neeraj,
>>>
>>>
>>>
>>> Thanks.
>>>
>>> Thanks for the text on error handling. Nothing urgent, but nitpicking on one word. §4.1 & 5.2 have 3 iterations of “this attribute is to be ignored”. I’m afraid one could read this as “this BGP attribute is to be ignored”. Surely we mean “this(theses) EVPN Link Bandwidth extended community(ies) is(are) to be ignored”
>>>
>>>
>>>
>>> One feedback that please feel free to use or ignore.
>>>
>>> “A receiving PE MUST ensure that each route contains only a single instance of this extended community attribute sub-type.”
>>>
>>> Stricto census, what is needed is a single instance of this sub-type and
>>> _*Value-Units*_. In order to accommodate one ingress PE in a domain
>>> using “Weight in units of Mbps” and another ingress PE in a different
>>> domain using “Generalized Weight”, one could imagine an egress PE
>>> advertising 2 communities/both units. I have a slight preference for
>>> allowing both, but up to you (In deployments I would personally advocate
>>> using only a single unit and the one whose implementation is mandatory, but
>>> when there’s an opportunity to go wrong, the opportunity is rarely missed
>>> ;-) )
>>>
>>>
>>>
>>> Thanks again,
>>>
>>> --Bruno
>>>
>>>
>>>
>>> *From:* Neeraj Malhotra [mailto:[e-mail]
>>> <[e-mail]>]
>>> *Sent:* Tuesday, May 11, 2021 3:59 AM
>>> *To:* Fomin, Sergey (Nokia - US/Mountain View) <[e-mail]>
>>> *Cc:* DECRAENE Bruno TGI/OLN <[e-mail]>; Rabadan,
>>> Jorge (Nokia - US/Mountain View) <[e-mail]>;
>>> [e-mail]; BESS <[e-mail]>
>>> *Subject:* Re: [bess] New short WGLC for draft-ietf-bess-evpn-unequal-lb
>>>
>>>
>>>
>>>
>>>
>>> Hi Sergey,
>>>
>>>
>>>
>>> Thanks for the detailed comments (missed in flight while publishing the
>>> previous revision). I have addressed all of the comments and nits below in
>>> the latest revision (rev13), except that a couple of hyperlinks for a
>>> reason that I can't immediately figure out are not showing up from XML
>>> source. Let me check and fix that in the next revision.
>>>
>>>
>>>
>>> Again, much appreciate your diligence in catching these.
>>>
>>>
>>>
>>> Thanks,
>>>
>>> Neeraj
>>>
>>>
>>>
>>> On Mon, May 10, 2021 at 5:36 PM Fomin, Sergey (Nokia - US/Mountain View)
>>> <[e-mail]> wrote:
>>>
>>> Thank you Neeraj, authors,
>>>
>>> -11 changes look good to resolve my previous concerns. (I second Bruno’s
>>> comment about 5 vs 6 octets)
>>>
>>> ·         Stylistically I don’t think we need to expand Mbps to
>>> Mbits/sec every time (one expanded definition should be enough), but up to
>>> you.
>>>
>>> ·         Additionally, I would add either that other “value-unit”
>>> encoding values are reserved and should not be used for non-standard
>>> implementations, or explicitly allow this usage.
>>>
>>>
>>>
>>> I have a few other comments, mostly minor and nits.
>>>
>>>
>>>
>>> General/minor comments:
>>>
>>> 1.      Can we add that only a single instance of LBW community per
>>> route is allowed, and how to handle erroneous situations, such as
>>>
>>> o    Receiving a route with multiple attached LBW community instances
>>>
>>> o    Received routes from different PEs having different value-units
>>> for the same ES (e.g. PE1 sends routes with 0x00, PE2 w. 0x01)
>>>
>>> Last paragraph in section 5.2 already describes similar case with
>>> presence/absence of the community, so it could be expanded. Though the same
>>> restrictions would apply to a recently-introduced type 5 usecase (and,
>>> perhaps to a lesser extent, to a BUM load-sharing scenarios as well) so
>>> it’s either worth moving these considerations to section 4 (community
>>> definition and usage) or expanding section 9 with the same considerations.
>>>
>>>
>>>
>>> 2.      Across the text there's an implicit assumption that either
>>> aliasing is enabled or mac addresses are learned from all PEs (and, of
>>> course, ES is in all-active mode), which may not be the case.
>>>
>>> I propose to add a remark/reference to 7432, stating that all "regular"
>>> qualifiers still apply (i.e. presence of both Eth A-D per ES + per EVI
>>> routes for aliasing, or per ES + type2 for non-aliased load-sharing).
>>>
>>> This may have some effect on weight computation procedures, i.e. likely
>>> that PEs which advertise neither should be excluded from the computation
>>> despite the presence of LBW community. Or we could require aliasing to be
>>> enabled.
>>>
>>>
>>>
>>> 3.      Section 10. IRB MH with non-EVPN routing: I think there's too
>>> much detail describing the usecase (which is not currently applicable to
>>> this document), and it feels like an intro to another draft. Is it possible
>>> to shorten it to 1 or 2 sentences?
>>>
>>>
>>>
>>> 4.      Section 5.1 Local PE Behavior:   A PE that is part of an
>>> Ethernet Segment's redundancy group would advertise an additional "link
>>> bandwidth" extended community attribute with Ethernet A-D per-ES route
>>> (EVPN Route Type 1), that represents total bandwidth of PE's physical links
>>> in an Ethernet Segment.
>>>
>>> o    Shall we replace "would" with MUST/SHOULD?
>>>
>>> o    Also, "represents total bandwidth of physical links" is probably
>>> not accurate anymore and should be rephrased?
>>>
>>>
>>>
>>> 5.      Can we explicitly state that the community should not be
>>> attached to A-D per EVI & type 2 mac/mac-ip routes (and ignored by remote
>>> PE if received on these route types)
>>>
>>>
>>>
>>> Nits:
>>>
>>> ·         It seems that ES & ESI terms are used somewhat
>>> interchangeably (starting from the very beginning in terminology section,
>>> also section 3 "Solution Overview", etc); could you please check and maybe
>>> stick to "ES" in cases where we don't specifically talk about identifiers?
>>> Also, there's no definition of ESI in the terminology section.
>>>
>>> ·         Could we add a definition of “path-list” to the terminology
>>> section? (it is used extensively throughout the document in different
>>> variations, such as "weighted path-list", "forwarding path-list", "MAC
>>> path-list" etc)
>>>
>>> ·         Same thing for “access bandwidth”, please add a definition
>>>
>>> ·         Section 2 “Introduction” - first bullet point was split into
>>> two separate bullets
>>>
>>> ·         Section 5.2, last line in the last sentence, typo  -
>>> "attribute t be used" should be "to be used"
>>>
>>> ·         Inconsistent hyperlinking to RFC/draft references in sections
>>> 6.1, 6.3, 13; also inconsistent hyperlinking in the table of contents
>>>
>>> ·         Section 6.2 contains a reference to a non-existing example in
>>> Section 3 ("Considering the same example as in Section 3, ...), probably
>>> should point to 5.2?
>>>
>>> ·         Inconsistent spelling of "per ES/per-ES" (as in "Ethernet A-D
>>> per ES"). Probably should be whitespaced, not dashed (it is spelled this
>>> way in 7432)
>>>
>>>
>>>
>>> --
>>>
>>> Sergey
>>>
>>>
>>>
>>> *From:* BESS <[e-mail]> *On Behalf Of *
>>> [e-mail]
>>> *Sent:* Monday, May 10, 2021 5:55 AM
>>> *To:* Neeraj Malhotra <[e-mail]>
>>> *Cc:* Rabadan, Jorge (Nokia - US/Mountain View) <[e-mail]>;
>>> Sergey Fomin <[e-mail]>; [e-mail]; BESS <
>>> [e-mail]>
>>> *Subject:* Re: [bess] New short WGLC for draft-ietf-bess-evpn-unequal-lb
>>>
>>>
>>>
>>> Hi Neeraj, co-authors,
>>>
>>>
>>>
>>> Thanks for taking into account the comments.
>>>
>>> -11 addresses my comments.
>>>
>>>
>>>
>>> Two comments on the new text:
>>>
>>> “EVPN Link Bandwidth Extended Community value field is to be treated
>>>
>>>    as a 6 octet unsigned integer representing total bandwidth of PE's
>>>
>>>    all physical links in an ethernet segment, expressed in Mbits/sec
>>>
>>>    (MegabitsPerSecond). »
>>>
>>>
>>>
>>>
>>>
>>> Actually with your latest change introducing the new field “Value-unit”,
>>> bandwidth is encoded in only 5 octets (not 6). (I’m assuming that the new
>>> field “Value-unit” is not to be used when computing the ratio of bandwidth
>>> as this would make no sense).
>>>
>>>
>>>
>>> §5.2 Does not say anything with regards to the new field “Value-unit”. A
>>> priori, the ratio of bandwidth is only to be computed on bandwidth/EC using
>>> the same unit, no?
>>>
>>>
>>>
>>> Thanks,
>>>
>>> Regards,
>>>
>>> --Bruno
>>>
>>>
>>>
>>> *From:* Neeraj Malhotra [mailto:[e-mail]
>>> <[e-mail]>]
>>> *Sent:* Saturday, May 8, 2021 1:29 AM
>>> *To:* Sergey Fomin <[e-mail]>
>>> *Cc:* DECRAENE Bruno TGI/OLN <[e-mail]>; Rabadan,
>>> Jorge (Nokia - US/Mountain View) <[e-mail]>;
>>> [e-mail]; BESS <[e-mail]>
>>> *Subject:* Re: [bess] New short WGLC for draft-ietf-bess-evpn-unequal-lb
>>>
>>>
>>>
>>>
>>>
>>> Hi Sergey, Bruno,
>>>
>>>
>>>
>>> Many thanks for the detailed review and comments. Discussed with
>>> co-authors and have enhanced the 'value' encoding to explicitly encode
>>> weight units as default or generalized as suggested below. I have
>>> published a revision that incorporates all comments discussed on this
>>> thread, as well as some additional editorial comments from Jorge. Please
>>> let me know if there are any additional comments (in particular on section
>>> 4).
>>>
>>>
>>>
>>> Thanks,
>>>
>>> Neeraj
>>>
>>>
>>>
>>> On Fri, May 7, 2021 at 12:33 PM Sergey Fomin <[e-mail]> wrote:
>>>
>>> Hi Neeraj,
>>>
>>> thank you for the feedback.
>>>
>>>
>>>
>>> I agree that allocating a new code point for every possible calculation
>>> method would be cumbersome.
>>>
>>> How about a middle ground solution, with allocation of just a few values
>>> (even 2 would suffice: 1 for BW in whatever units we decide; the other
>>> "catch-all" generalized weight)?
>>>
>>> This way operators will get at least basic visibility & cfg. error
>>> prevention mechanism in place (I have a preference towards explicit
>>> signaling from ops point of view; but would be glad to hear operators
>>> opinion on this one).
>>>
>>>
>>>
>>> My concern with the current text is, while striving for maximum
>>> flexibility, we may end up in a situation where 2 implementations won't be
>>> able to interoperate with each other (e.g. vendor X decides to implement
>>> link BW as a metric, vendor Y decides to implement link count as a metric -
>>> since support for any method of weight calculation is completely
>>> optional). I believe we, as a technical community, should give guidance on
>>> implementing sensible defaults (i.e. "an implementation SHOULD support BW
>>> weight calculation method") where it makes sense.
>>>
>>>
>>>
>>> --
>>>
>>> Sergey
>>>
>>>
>>>
>>>
>>>
>>> 07.05.2021, 09:18, "Neeraj Malhotra" <[e-mail]>:
>>>
>>>
>>>
>>> Hi Sergey,
>>>
>>>
>>>
>>> Thanks for the comments. We would like to avoid adding another code
>>> point within the value field, as every new encoding of the "weight" will
>>> require a new code point. Agree that we should specify the default units
>>> (for which the consensus on the thread appears to be Mbps), but would
>>> rather leave it to implementations to support any additional units such as
>>> number of links, configured weight, or anything else, than have a
>>> standardized code point for each unit. Please let me know if this sounds
>>> fine. I will fix the units in section 5.2, and the text in section 4.1 as
>>> suggested by you and Bruno.
>>>
>>>
>>>
>>> Thanks,
>>>
>>> Neeraj
>>>
>>>
>>>
>>> On Thu, May 6, 2021 at 9:19 PM <[e-mail]> wrote:
>>>
>>> Hi Bruno, Jorge, et al.,
>>>
>>>
>>>
>>> Jorge,
>>>
>>> *> Among the co-authors we also discussed the possibility of defining
>>> two ECs: one for BW and one for a generalized-weight, so that the remote PE
>>> can catch if the multi-homed PEs were indeed using the same meaning of the
>>> weight. However, we thought it was easier/simpler to use a generalized
>>> value in a single EC sub-type, and add the sentence below. *
>>>
>>> Have you considered reserving a byte in the value field to signal a
>>> weight type? Similar to how it is done with DF election framework (and
>>> allocate a few right away, e.g. 0 for physical link BW, 1 for link count, 2
>>> for manually configured weight, ...). This would help not only with interop
>>> cases, but to prevent & diagnose potential configuration mistakes as well.
>>>
>>>
>>>
>>> For interop reasons, I would support Bruno & argue that it makes sense
>>> to use "SHOULD" normative language at least for one way of calculation
>>> (e.g. BW).
>>>
>>>
>>>
>>> A couple of minor comments on newly-introduced text in -09 and -10:
>>>
>>> 1.      Revision -10 introduced a curious change in section 5.2 “Remote
>>> PE Behavior”, replacing “1000 Mbps” with “1000 megabytes” in an example. It
>>> is not correct in the current form, since right above it there is an
>>> explicit statement that links are Gigabit Ethernet: *"As an example,
>>> for a CE dual-homed to PE-1, PE-2, PE-3 via 2, 1, and 1 GE physical links
>>> respectively".*
>>>
>>> (keeping the Mbps units there would be appropriate, since this is a
>>> weight calculation, not a community encoding example)
>>>
>>> 1.      Section 4.1 “Usage of EVPN Link Bandwidth Extended Community”:
>>>
>>> *“An implementation may support one or more of the above ways of
>>> encoding the value."* -> I would assume this should be "MUST support at
>>> least one", since every other possible option is included in bullet#2?
>>>
>>>
>>>
>>> --
>>>
>>> Sergey
>>>
>>> *From:* BESS <[e-mail]> *On Behalf Of *
>>> [e-mail]
>>> *Sent:* Thursday, May 6, 2021 5:46 AM
>>> *To:* Rabadan, Jorge (Nokia - US/Mountain View) <[e-mail]>;
>>> Neeraj Malhotra <[e-mail]>
>>> *Cc:* [e-mail]; [e-mail]
>>> *Subject:* Re: [bess] New short WGLC for draft-ietf-bess-evpn-unequal-lb
>>>
>>>
>>>
>>> Hi Jorge,
>>>
>>>
>>>
>>> Thanks for the feedback.
>>>
>>>
>>>
>>> Regarding the first point, I can live with the current text. But I think
>>> I would prefer that the text favour one option, and leave it to the
>>> responsibility of the SP for others usages. E.g.
>>>
>>>
>>>
>>> OLD:
>>>
>>> EVPN Link Bandwidth Extended Community value field is to be treated
>>>
>>>    as a 6 octet unsigned integer that may be set to:
>>>
>>>
>>>
>>>    o  total bandwidth of PE's all physical links in an ethernet segment,
>>>
>>>       expressed in bytes/sec.
>>>
>>>
>>>
>>>    o  or a generalized weight that may be set to link count, locally
>>>
>>>       configured weight, or a value computed based on an attribute other
>>>
>>>       than link bandwidth.
>>>
>>>
>>>
>>>    An implementation may support one or more of the above ways of
>>>
>>>    encoding the value.  Operator MUST ensure consistent encoding of this
>>>
>>>    value across all PEs in an ethernet segment.  Procedures related to
>>>
>>>    signaling and handling of this extended community defined in this
>>>
>>>    document use "total bandwidth in bytes/sec" encoding as an example to
>>>
>>>    illustrate its usage.
>>>
>>>
>>>
>>> NEW:
>>>
>>>    EVPN Link Bandwidth Extended Community value field is to be treated
>>>
>>>    as a 6 octet unsigned integer representing total bandwidth of PE's
>>> all physical links in an ethernet segment,
>>>
>>>       expressed in bytes/sec.
>>>
>>>
>>>
>>> Note however that the load balancing algorithm defines in this document
>>> uses ratio of Link Bandwidths hence the operator may choose a different
>>> unit or use the community as
>>>
>>>     a generalized weight that may be set to link count, locally
>>>
>>>       configured weight, or a value computed based on an attribute other
>>>
>>>       than link bandwidth. In such case, the operator MUST ensure
>>> consistent usage of the unit
>>>
>>> across all PEs in an ethernet segment. This may involve multiple routing
>>> domains/Autonomous Systems.
>>>
>>>
>>>
>>>
>>>
>>> But I leave this to you.
>>>
>>>
>>>
>>> Thanks,
>>>
>>> --Bruno
>>>
>>>
>>>
>>> *From:* Rabadan, Jorge (Nokia - US/Mountain View) [
>>> mailto:[e-mail] <[e-mail]>]
>>> *Sent:* Thursday, May 6, 2021 10:36 AM
>>> *To:* DECRAENE Bruno TGI/OLN <[e-mail]>; Neeraj
>>> Malhotra <[e-mail]>
>>> *Cc:* [e-mail]; [e-mail]
>>> *Subject:* Re: [bess] New short WGLC for draft-ietf-bess-evpn-unequal-lb
>>>
>>>
>>>
>>> Hi Bruno,
>>>
>>>
>>>
>>> Thanks for your comments.
>>>
>>>
>>>
>>> About the first point, we do have use cases where the bandwidth is not
>>> what we want to encode in the EC but rather a generalized weight that is
>>> derived from the link count, logical weight or simply a configured value.
>>> Among the co-authors we also discussed the possibility of defining two ECs:
>>> one for BW and one for a generalized-weight, so that the remote PE can
>>> catch if the multi-homed PEs were indeed using the same meaning of the
>>> weight. However, we thought it was easier/simpler to use a generalized
>>> value in a single EC sub-type, and add the sentence below.
>>>
>>>
>>>
>>> The sentence can be modified/fixed. But the gist is that the multi-homed
>>> PEs may support multiple meanings for the weight (BW, link-count, etc), but
>>> at least one of those MUST be common across all PEs and the multi-homed
>>> routes must use it consistently. Would it be enough if we fix it?
>>>
>>>
>>>
>>> About existing implementations, a new EVPN sub-type was defined only a
>>> couple of revisions ago, where, before, the existing non-transitive link BW
>>> EC was used, so there’s been some churn in the use of the EC anyway. I
>>> think it is important to get it as soon as possible, but get it right
>>> rather than finding gaps later once the document is done. But let us know
>>> your thoughts too.
>>>
>>>
>>>
>>> Thank you.
>>>
>>> Jorge
>>>
>>>
>>>
>>>
>>>
>>> *From: *BESS <[e-mail]> on behalf of
>>> [e-mail] <[e-mail]>
>>> *Date: *Thursday, May 6, 2021 at 10:04 AM
>>> *To: *Neeraj Malhotra <[e-mail]>
>>> *Cc: *[e-mail] <[e-mail]>, [e-mail] <
>>> [e-mail]>
>>> *Subject: *Re: [bess] New short WGLC for draft-ietf-bess-evpn-unequal-lb
>>>
>>> Hi Neeraj,
>>>
>>>
>>>
>>> Thanks for considering my comments.
>>>
>>> Much better from my perspective. Thank you.
>>>
>>>
>>>
>>> I have two comments on the changes:
>>>
>>> - Regarding deployments
>>>
>>> §4.1 allows two rather incompatible encodings/usages with no way to
>>> detect which one is used: some PE could advertise the bandwidth in bytes,
>>> while some other PE could advertise a general weight. I understand that
>>> both works, but to me there is a significant risk of issues over time or
>>> between domain/SP. I’d prefer that you only chose one in order to favour
>>> consistency in deployments and usage and I would prefer the real bandwidth
>>> (at least for consistency with the name of the community, but also because
>>> this is not subjective)  (And if a SP really wants to put an arbitrary
>>> value, I think he will figure out by himself, that it can do so).
>>>
>>> If you disagree with the above, then I would have a comment on the two
>>> below sentences:
>>>
>>> An implementation may support one or more of the above ways of
>>>
>>>    encoding the value.  Operator MUST ensure consistent encoding of this
>>>
>>>    value across all PEs in an ethernet segment.
>>>
>>> Logic dictates that the second sentence (MUST) can only be fulfilled if
>>> the first sentence mandates that all implementations MUST support both
>>> options, or one specifically defined.
>>>
>>>
>>>
>>> - Regarding existing implementations:
>>>
>>> previous version of the draft did not really specify the format of the
>>> EVPN EC. I had personally assumed that the format was similar to the
>>> draft-ietf-idr-link-bandwidth link bandwidth community hence encoded in
>>> IEEE floating point format. Latest version of the draft defines it in
>>> unsigned integer. Integer looks good to me, but for an existing
>>> implementation this may be seen as an incompatible change very late in the
>>> process. Obviously, if there are no implementation, there is no issue. In
>>> which case, you could also express the bandwidth in unit of bit/s _*if
>>> you*_ wish to. (I have no preference). However given that the draft had
>>> indicated a codepoint, there seem to be a risk of existing implementations
>>> hence incompatible change. BTW the codepoint is squatted even though the
>>> registry is FCFS hence easy to request.
>>>
>>>
>>>
>>> Thanks,
>>>
>>> --Bruno
>>>
>>>
>>>
>>>
>>>
>>> *From:* Neeraj Malhotra [mailto:[e-mail]
>>> <[e-mail]>]
>>> *Sent:* Thursday, May 6, 2021 7:41 AM
>>> *To:* DECRAENE Bruno TGI/OLN <[e-mail]>
>>> *Cc:* [e-mail]; [e-mail]
>>> *Subject:* Re: [bess] New short WGLC for draft-ietf-bess-evpn-unequal-lb
>>>
>>>
>>>
>>>
>>>
>>> Hi Bruno,
>>>
>>>
>>>
>>> Many thanks for the review comments. We have revised the draft
>>> addressing your comments.
>>>
>>>
>>>
>>> More inline.
>>>
>>>
>>>
>>> Thanks,
>>>
>>> Neeraj
>>>
>>>
>>>
>>> On Mon, May 3, 2021 at 2:20 AM <[e-mail]> wrote:
>>>
>>> Hi Stéphane, authors,
>>>
>>>
>>>
>>> I have not followed the discussions on this document, but I’ll
>>> nonetheless raise one point  regarding the bandwidth community (better safe
>>> than sorry).
>>>
>>> - why has [BGP-LINK-BW] been moved to informational reference while its
>>> reading seem mandatory?
>>>
>>>
>>>
>>> [NM]: There was a leftover reference to this in one of the sections that
>>> has been fixed now to use new EVPN EC. With this, reference to
>>> [BGP-LINK-BW] is purely informational (as was intended).
>>>
>>>
>>>
>>> - A new EVPN Link Bandwidth extended community is defined, but I could
>>> not find its specification. I guess that this is the same format as
>>> [BGP-LINK-BW] but transitive. Could this be explicitly stated?
>>>
>>>
>>>
>>> [NM]: clarified in section 4.
>>>
>>>
>>>
>>> - [BGP-LINK-BW] advertises the bandwidth in unit of bytes (not bits!)
>>> per second. Could the unit of the new EVPN Link Bandwidth extended
>>> community be also clearly spelled out? Especially give the history on this
>>> (cf below). Also in order to avoid misleading the readers could the
>>> examples use the correct unit (vs bits per seconds as writen)
>>>
>>>
>>>
>>> [NM]: done.
>>>
>>>
>>>
>>> - 10 years ago or so, I had raised a similar point (distinction between
>>> bits and bytes) on [BGP-LINK-BW] in the IDR WG. And it turned out that 1
>>> major implementation had implemented and deployed “bytes per second” as per
>>> the spec, while another implementation had implemented and deployed “bits
>>> per second” which is the typical unit of link bandwidth. Given the
>>> deployments, none was willing to change its implementation as it would be a
>>> non-backward compatible change with themselves. What’s the status on this?
>>> Could we have an implementation status on this?
>>>
>>>
>>>
>>> [NM]: I don't have this information. Perhaps someone else could comment.
>>>
>>>
>>>
>>>
>>>
>>> Thanks
>>>
>>> Regards,
>>>
>>> --Bruno
>>>
>>>
>>>
>>>
>>>
>>> *From:* BESS [mailto:[e-mail]] *On Behalf Of *
>>> [e-mail]
>>> *Sent:* Monday, May 3, 2021 9:21 AM
>>> *To:* [e-mail]
>>> *Subject:* [bess] New short WGLC for draft-ietf-bess-evpn-unequal-lb
>>>
>>>
>>>
>>> Hi WG,
>>>
>>>
>>>
>>>
>>>
>>> We got final updates from authors on draft-ietf-bess-evpn-unequal-lb.
>>>
>>>
>>>
>>> I'm opening a new short Working Group Last Call (to be closed on 5/10) to
>>>
>>> get any last comments before moving to the next step.
>>>
>>> However, the document having normative references to EVPN PREF DF, and PER-MCAST-FLOW-DF, the draft will not be sent to IESG until these drafts are ready.
>>>
>>>
>>>
>>>  Feel free to send comments to the list before next Monday.
>>>
>>>
>>>
>>>
>>>
>>> Thanks,
>>>
>>>
>>>
>>>
>>>
>>> Stephane
>>>
>>>
>>>
>>> https://datatracker.ietf.org/doc/draft-ietf-bess-evpn-unequal-lb/
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
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