Subject: [Gen-art] Gen-ART LC review of draft-ietf-mpls-p2mp-lsp-ping-16

From: Alexey Melnikov <[email-masked]>
Date: Tue, 31 May 2011 13:59:24 +0100

I am the assigned Gen-ART reviewer for this draft. For background on 
Gen-ART, please see the FAQ at 
<http://wiki.tools.ietf.org/area/gen/trac/wiki/GenArtfaq>. Please 
resolve these comments along with any other Last Call comments you may 
receive.

Document: draft-ietf-mpls-p2mp-lsp-ping-16

Reviewer: Alexey Melnikov

Review Date:2011-05-31

IETF LC End Date: 2011-05-30

IESG Telechat date:

Summary: This draft is almost ready for publication as a standard track 
RFC. There are some minor clarity issues (or reviewer confusions) that 
are worth clarifying.

Major issues: none

Minor issues:

 1.1. Design Considerations

   As is described in [RFC4379], to avoid potential Denial of Service
   attacks, it is RECOMMENDED to regulate the LSP Ping traffic passed to
   the control plane.  A rate limiter should be applied to the
   well-known UDP port defined for use by LSP Ping traffic.

What is this port? Is mentioning of the port significant?

3.1.2.1. Multicast LDP FEC Stack Sub-TLVs

   Address Family

      Two octet quantity containing a value from ADDRESS FAMILY NUMBERS
      in [IANA-PORT] that encodes the address family for the Root LSR
      Address.

   [IANA-PORT] IANA Assigned Port Numbers, http://www.iana.org

Which IANA registry do you have in mind? Seeing a link would be helpful.

3.2. Limiting the Scope of Responses

   The P2MP Responder Identifier TLV only has meaning on an echo request
   message.  If present on an echo response message, it SHOULD be
   ignored.

Are there known reasons for violating the SHOULD? I.e. what are the reasons
for having multiple sub-TLVs in the first place?

3.2.2. Node Address P2MP Responder Identifier Sub-TLVs

   The address in this Sub-TLV SHOULD be of any transit, branch, bud or
   egress node for that P2MP LSP.

Is the use of SHOULD correct here (instead of a MUST)? Are there any choices
left if the SHOULD is violated?

3.5. Downstream Detailed Mapping TLV

  Downstream Detailed Mapping TLV is described in [DDMT].  A transit,
  branch or bud node can use the Downstream Detailed Mapping TLV to
  return multiple Return Codes for different downstream paths. This
  functionality can not be achieved via the Downstream Mapping TLV.

Are "Downstream Detailed Mapping TLV" and "Downstream Mapping TLV" two 
different things?

  As
  per Section 4.3 of [DDMT], the Downstream Mapping TLV as described in
  [RFC4379] is being deprecated.

4.1.2. Jittered Responses to Echo Requests

   Echo response jittering SHOULD be used for P2MP LSPs.  If the Echo
   Jitter TLV is present in an echo request for any other type of LSPs,
   the responding egress MAY apply the jitter behavior as described
   here.

Can you provide a bit more information about how this work?

4.2.1.1. Responses from Transit and Branch Nodes

   The presence of a Downstream Detailed Mapping TLV will influence the
   choice of Return Code.  As per [DDMT], the Return Code in the echo
   response header MAY be set to value TBD ('See DDM TLV for Return Code

Am I correct that the value TBD is specified in [DDMT]?
If not, it is missing in the IANA Considerations section.

   and Return SubCode') as defined in [DDMT].  The Return Code for each
   Downstream Detailed Mapping TLV will depend on the downstream path as
   described in [DDMT].

6. OAM and Management Considerations

      - A MIB module is required for the control and management of LSP
        Ping operations, and to enable the reported information to be
        inspected.

I think it would be better to be explicit that this document doesn't 
define such a MIB.

7.2. New TLVs

     P2MP Responder Identifier TLV (see Section 3.2) is a mandatory

What does "mandatory" means in this section? Mandatory for IANA?

     TLV.  Suggested value 11.
     Four sub-TLVs are defined.
       - Type 1: IPv4 Egress Address P2MP Responder Identifier
       - Type 2: IPv6 Egress Address P2MP Responder Identifier
       - Type 3: IPv4 Node Address P2MP Responder Identifier
       - Type 4: IPv6 Node Address P2MP Responder Identifier

     Echo Jitter TLV (see Section 3.3) is a mandatory TLV.  Suggested

As above.

     value 12.

Nits/editorial comments:

4.3.1. End of Processing for Traceroutes

   For P2MP TE LSP, the initiating LSR has a priori knowledge about
   number of egress nodes and their addresses.  Hence it possible to

Missing "is" after "it".

   continue processing till a valid response has been received from each
   end-point, provided the responses can be matched correctly to the
   egress nodes.