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

["Susan Hares" <[e-mail]>]

Andrew and Matthew: 

 

Thank you for the review. 

 

Sue 

 

From: rtg-dir [mailto:[e-mail]] On Behalf Of Andrew G. Malis
Sent: Monday, February 27, 2017 11:43 AM
To: Bocci, Matthew (Nokia - GB)
Cc: [e-mail]; [e-mail]; [e-mail]
Subject: Re: [RTG-DIR] Routing Area Directorate QA review of draft-ietf-trill-transport-over-mpls-02

 

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-over-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]."

 

 

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.

 

 

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.

 

 

 

 Best regards

 Matthew

 

Cheers,

Andy