Re: [trill] [RTG-DIR] Routing Area Directorate QA review of draft-ietf-trill-transport-over-mpls-02

[Kingston Smiler <[e-mail]>]

Hi Andy and Mathew,

Thanks for your comments. Plz find our response inline between <Kingston>
tags

P.S: Sorry. Was tied up with some work and hence the delay.

Regards,
S. Kingston Smiler.

On Mon, Feb 27, 2017 at 10:12 PM, Andrew G. Malis <[e-mail]> wrote:

> I’ve got some comments on Matthew’s review, inline.
>
> On Mon, Feb 27, 2017 at 10:44 AM, Bocci, Matthew (Nokia - GB) <
> [e-mail]> wrote:
>
>> Routing Area Directorate QA review of draft-ietf-trill-transport-ove
>> r-mpls-02
>>
>>
>>
>> Hi,
>>
>>
>>
>> I have been assigned the QA reviewer for this draft. The general
>> guidelines for QA reviews
>>
>> can be found at:
>>
>> https://trac.ietf.org/trac/rtg/wiki/RtgDirDocQa
>>
>>
>>
>> These state:
>>
>>
>>
>>   "When reviewing a draft at WG Adoption, the QA Reviewer should
>>
>>   determine whether the draft is readable, understandable, makes sense
>>
>>   and is a good start for a WG draft. Any issues the QA Reviewer finds
>>
>>   are written down, sent to the mailing list and discussed for future
>>
>>   versions"
>>
>>
>>
>> Here is my review of this draft:
>>
>>
>>
>> ** Summary.
>>
>> Generally, the draft is well written - thank you. I have a few minor
>> comments below,
>>
>> mostly related to the relationship between TRILL over MPLS and
>> established VPLS mechanisms.
>>
>>
>>
>> ** Is the draft readable?
>>
>>
>>
>> Yes. There are a few minor grammatical errors and it would help if the
>> draft was proof-read
>>
>> to weed-out these. An example is:
>>
>> Abstract
>>
>> "..that are separated by MPLS provider network."
>>
>> s/by MPLS/by an MPLS
>>
>>
>>
>>
>>
>> ** Is the draft understandable?
>>
>>
>>
>> Yes, provided the reader is familiar with TRILL, MPLS and VPLS.
>>
>>
>>
>> ** Does it make sense?
>>
>> I think it is mostly clear, but I have a few comments, as follows:
>>
>>
>>
>> Section 3.4. MPLS encapsulation for VPLS model
>>
>>
>>
>> "Use of VPLS [RFC4762] to interconnect TRILL sites requires no changes to
>>
>> a VPLS implementation, in particular the use of Ethernet pseudowires
>>
>> between VPLS PEs. A VPLS PE receives normal Ethernet frames from an
>>
>> RBridge (i.e., CE) and is not aware that the CE is an RBridge device. As
>>
>> a result, an MPLS-encapsulated TRILL packet within the MPLS network will
>>
>> use the format illustrated in Appendix A of [RFC7173]."
>>
>>
>>
>> It doesn't look like the encapsulation shown in Appendix A of
>>
>> RFC7173 takes account of the case where PBB VPLS [RFC7041] is used in the
>> provider's
>>
>> MPLS network, but I would have thought this would still be a valid VPLS
>> type to transport
>>
>> TRILL. It might be worth qualifying your reference with some text to
>> state that
>>
>> this is just an example in the non-PBB case.
>>
>

> Andy: As the author of this paragraph, I agree with Matthew’s comment. We
> can change the last sentence to say:
>
> "As an example, an MPLS-encapsulated TRILL packet within the MPLS network
> will
> use the format illustrated in Appendix A of [RFC7173] for the non-PBB
> case, or
> in the PBB case, with the additional header fields illustrated in
> [RFC7041]."
>
> <Kingston>
Typically PBB-VPLS is used to avoid exposing the customer MAC in service
provider network. In case of TRILL packet over MPLS, already the customer
MAC is encapsulated inside the TRILL header. Having said that, do we really
need to consider TRILL over PBB-VPLS.
</Kingston>

>
>>
>> Section 4.1.1:
>>
>> "TIR devices are a superset of the VPLS-PE devices defined in [RFC4026]
>> with the
>>
>> additional functionality of TRILL."
>>
>> Is this really true? Later you state that TIRs use PPP PWs, not the
>> Ethernet PWs used in
>>
>> VPLS. It is also not clear if TRILL needs some of the LDP or BGP
>> signaling extensions
>>
>> used for VPLS. Wouldn't it be cleaner just to define a TIR as a new kind
>> of PE?
>>
>
> Andy: I also agree with this comment.
>
>
>>
>>
> <Kingston>
Agreed to your comment. We need to consider ethernet encapsulation. Will
update the draft
</Kingston>

Section 6. VPTS Model Versus VPLS Model
>>
>> "An issue with the above rule is that if a pseudowire between PEs fails,
>>
>> frames will not get forwarded between the PEs where pseudowire went
>>
>> down."
>>
>>
>>
>> I think this is only true for a simple full mesh VPLS where there are not
>> other protection
>>
>> mechanisms. I am not sure this is applicable to H-VPLS with PW
>> redundancy, for example,
>>
>> which I think is likely to be a widespread deployment case for the VPLS
>> model of TRILL
>>
>> over MPLS.
>>
>
> Andy: I agree. In addition, see section 4.4 of RFC 4742, which allows the
> use of spanning tree in a VPLS network to provide redundancy in the case of
> a failure in the VPLS.
>
> <Kingston>
Agreed to your comment.  Will update the same in next version of the draft
</Kingston>

>
>
>>
>>  Best regards
>>
>>  Matthew
>>
>
> Cheers,
> Andy
>
>
>