Subject: [Pals] Shepherd review of draft-ietf-l2vpn-vpls-pe-etree

From: Stewart Bryant <[email-masked]>
Date: Mon, 23 Feb 2015 15:47:19 +0000

I have picked up the task of shepherding this draft, and
have a number of comments which I think that you should
address before we send this text to the IESG.

As the text contains both LDP and BGP control information
I am copying the BESS WG and their chairs.

- Stewart

========

SB> The document fails I-D nits with

      Summary: 2 errors (**), 0 flaws (~~), 9 warnings (==), 1 comment (--).

Please fix this.

======

SB> Number of authors. The guideline is five but it is not
a hard limit provided that all authors made significant contribution.
If asked by the IESG can all authors point to specific
text that they wrote?

     Ethernet-Tree (E-Tree) Support in Virtual Private LAN Service (VPLS)
                    draft-ietf-l2vpn-vpls-pe-etree-04.tx

=====

  Abstract

    A generic Virtual Private LAN Service (VPLS) solution is proposed for
    Ethernet-Tree (E-Tree) services which uses VLANs to indicate root or
    leaf traffic. A VPLS Provider Edge (PE) model is illustrated as an
    example for the solution. In the solution, E-Tree VPLS PEs are
    interconnected by PWs which carry the VLAN indicating the E-Tree
    attribute, the MAC address based Ethernet forwarding engine and the
    PW work in the same way as before. A signaling mechanism for E-Tree
    capability and VLAN mapping negotiation is further described.

======

  2. Terminology

    E-Tree: Ethernet Tree, a Rooted-Multipoint EVC service as defined in
    MEF 6.1

    EVC: Ethernet Virtual Connection, as defined in MEF 4.0

    FIB: Forwarding Information Base, or forwarding table

    T-VSI: Tree VSI, a VSI with E-Tree support

    Root AC, an AC attached with a root

    Leaf AC, an AC attached with a leaf

    C-VLAN, Customer VLAN

    S-VLAN, Service VLAN

    B-VLAN, Backbone VLAN

    Root VLAN, a VLAN ID used to indicate all the frames that are
    originated at a root AC

    Leaf VLAN, a VLAN ID used to indicate all the frames that are
    originated at a leaf AC

    I-SID, Backbone Service Instance Identifier, as defined in IEEE
    802.1ah

=======

3. Introduction

    Further, an E-Tree service may
    include multiple roots and multiple leaves. Although VPMS or P2MP

SB> VPMS, P2MP and in a few line VPLS, VSI and PE need expansion (and ideally a reference)

========

    IEEE 802.1 has incorporated the generic E-Tree solution in the latest
    version of 802.1Q [802.1Q-2011], which is just an improvement on the
    traditional asymmetric VLAN mechanism (the use of different VLANs to
    indicate E-Tree root/leaf attributes and prohibiting leaf-to-leaf
    traffic with the help of VLANs was first standardized in IEEE 802.1Q-
    2003). In the solution, VLANs are used to indicate root/leaf

SB> In THE solution - which solution is THE solution?

=======

    This document introduces how the Ethernet VLAN solution can be used

SB> s/introduces/specifies/ and later s/proposed/specified/

    to support generic E-Tree services in VPLS. The solution proposed

=======

  here is fully compatible with the IEEE bridge architecture and the

SB> s/the/with/

  IETF PWE3 technology, thus it will not change the FIB (such as

SB> please expand FIB

=======

4. PE Model with E-Tree Support

    Problem scenario of E-Tree as shown in Fig. 1 of [Etree-req] is a
SB> The problem

=======

4.1. Existing PE Models

SB> In the text that follows it is clear how Fig 1 fits into the picture
but not Fig 2 (which as far as I can see you do not even reference).
I think you are saying that Fig 2 is the existing VPLS model, then
Fig 3 is the obvious mapping to E-tree, but there are problems, but this
needs to be much clearer.

========

4.2. A New PE Model with E-Tree Support

    In order to support the E-Tree in a more scalable way, a new VPLS PE
    model with a single Tree VSI (T-VSI, a VSI with E-Tree support) is
    proposed.

SB> s/proposed/specified/

=======

    For an S-VLAN tagged port, the S-VLAN tag in the Ethernet frames
    received from the root ACs SHOULD be translated to the root S-VLAN in
    the VPLS network domain. Alternatively, the PBB VPLS PE model (where

SB> PBB needs expansion

=======

    In all cases, the outermost VLAN in the resulted Ethernet header is
    used to indicate the E-Tree attribute of an Ethernet frame; this
    document will use VLAN to refer to this outermost VLAN for simplicity

SB> S/will use/uses/

5. PW for E-Tree Support

5.1. PW Encapsulation

    To support an E-Tree service, T-VSIs in a VPLS must be interconnected
    with a bidirectional Ethernet PW. The Ethernet PW may work in the
    tagged mode (PW type 0x0004) as described in [RFC4448], and a VLAN
    tag must be carried in each frame in the PW to indicate the frame

SB>s/and a VLAN tag must be carried in each frame/
in which case a VLAN tag MUST be carried in each frame/

    originated from either root or leaf (the VLAN tag indicating the
    frame originated from either root or leaf can be translated by a
    bridge module in the PE or added by an outside Ethernet edge device,
    even by a customer device). In the tagged PW mode, two service
    delimiting VLANs must be allocated in the VPLS domain for an E-Tree.

s/must/MUST/

=======

    Raw PW (PW type 0x0005 in [RFC4448]) may be used to carry E-Tree
    service for a PW in Compatible mode as shown in Section 5.3.2.

SB> I think this needs to be :
Raw PW (PW type 0x0005 in [RFC4448]) MAY also be used

========

6. Signaling for E-Tree Support

6.1. LDP Extensions for E-Tree Support

    In addition to the signaling procedures as specified in [RFC4447],
    this document proposes a new interface parameter sub-TLV to provision
    an E-Tree service and negotiate the VLAN mapping function, as follows:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  E-Tree       |   Length=8    |           Reserved        |P|V|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |          Root VLAN ID         |          Leaf VLAN ID         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                           Figure 8  E-Tree Sub-TLV

    Where:

    o E-Tree is the sub-TLV identifier to be assigned by IANA.

SB> You have an assigned value. I think it would be clearer to all
to say that and include the value in this text

========

    A PE that receives a PW label mapping message with an E-Tree Sub-TLV
    from its peer PE, after saving the VLAN information for the PW, must

SB> must or MUST? The latter I think.

=========

SB> Does what follows need to be proceeded by Else or Otherwise?
   
  PW processing as described in [RFC4448] proceeds as usual for all
    cases.

6.2. BGP Extensions for E-Tree Support

    A PE which does not recognize this attribute shall ignore it silently.

SB> I think that should be SHALL or MUST.

======

7. OAM Considerations

    Ethernet OAM for E-Tree including both service OAM and segment OAM
    frames shall undergo the same VLAN mapping as the data traffic; and
    root VLAN SHOULD be applied to segment OAM frames so that they are
    not filtered.

SB> I think s/shall/SHALL/

=======

  8. Applicability

    The solution is applicable to both LDP VPLS [RFC4762] and BGP VPLS
SB> s/The/This/ or s/The solution specified in this document/

======
  10.  IANA Considerations

    IANA is requested to allocate a value for E-Tree in the registry of
    Pseudowire Interface Parameters Sub-TLV type.

    Parameter ID   Length       Description
    =======================================
    TBD            8            E-Tree

SB> Update to show you have the assignment

=======

    IANA is requested to allocate two new LDP status codes from the
    registry of name "STATUS CODE NAME SPACE". The following values are
    suggested:

    Range/Value     E     Description
    ------------- -----   ----------------------
    TBD             1     E-Tree VLAN mapping not supported
    TBD             0     Leaf to Leaf PW released

SB> Update to show you have the assignment

======
  IANA is requested to allocate a value for E-Tree in the registry of
    BGP Extended Community.

    Type Value          Name
    =======================================
    TBD                 E-Tree Info
SB> Update to show you have the assignment

=======

Appendix A. Other PE Models for E-Tree

A.1. A PE Model With a VSI and No bridge

    This PE model may be used by an MTU-s in an H-VPLS network, or an N-
    PE in an H-VPLS network with non-bridging edge devices, wherein a
    spoke PW can be treated as an AC in this model.

SB> Please check that all of the above abbreviations have been
previously expanded.

=======

---

From: Jiangyuanlong <[email-masked]>
Date: Thu, 26 Feb 2015 12:55:43 +0000

Hi Stewart,

Thank a lot  for your exhaustive review, please see my comments in line.
I also uploaded a new version to reflect all those changes:
http://tools.ietf.org/html/draft-ietf-l2vpn-vpls-pe-etree-05

Best regards,
Yuanlong

From: Pals [mailto:[email-masked]] On Behalf Of Stewart Bryant
Sent: Monday, February 23, 2015 11:47 PM
To: [email-masked]; [email-masked]
Cc: [email-masked]; [email-masked]; [email-masked]; [email-masked]
Subject: [Pals] Shepherd review of draft-ietf-l2vpn-vpls-pe-etree

- Stewart

========

Please fix this.

======

text that they wrote?

=====

 Abstract

======

 2. Terminology

   MEF 6.1

   C-VLAN, Customer VLAN

   S-VLAN, Service VLAN

   B-VLAN, Backbone VLAN

   originated at a root AC

   originated at a leaf AC

   802.1ah

=======

3. Introduction

[Yuanlong] done.

========

[Yuanlong] The new IEEE 802.1Q solution.

=======

[Yuanlong] done.

=======

SB> s/the/with/

 [Yuanlong] done.

SB> please expand FIB
[Yuanlong] done.

=======

SB> The problem
[Yuanlong] done.

=======

4.1. Existing PE Models

needs to be much clearer.
[Yuanlong] both Figs are called out in the new texts now.

========

   proposed.

[Yuanlong] done.

=======

SB> PBB needs expansion
[Yuanlong] done.

=======

SB> S/will use/uses/
[Yuanlong] done.

5. PW for E-Tree Support

5.1. PW Encapsulation

 [Yuanlong] done.

s/must/MUST/
[Yuanlong] done.

=======

[Yuanlong] done.

========

     0                   1                   2                   3

                          Figure 8  E-Tree Sub-TLV

   Where:

[Yuanlong] done.

========

[Yuanlong] done.

=========

SB> Does what follows need to be proceeded by Else or Otherwise?
[Yuanlong] Yes, the following should be processed in all cases.

   cases.

[Yuanlong] Done.

======

7. OAM Considerations

   not filtered.

[Yuanlong] Done.

=======

 8. Applicability

[Yuanlong] Done.

======

 10.  IANA Considerations

   TBD            8            E-Tree

[Yuanlong] done.

=======

   suggested:

[Yuanlong] done.

======

   BGP Extended Community.

   Type Value          Name

   TBD                 E-Tree Info

[Yuanlong] done.

=======

previously expanded.
[Yuanlong] done.

=======