Re: WGLC for BFD Multipoint documents (last round)

"Carlos Pignataro (cpignata)" <cpignata@cisco.com> Wed, 14 February 2018 02:23 UTC

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From: "Carlos Pignataro (cpignata)" <cpignata@cisco.com>
To: Greg Mirsky <gregimirsky@gmail.com>
CC: "gregory.mirsky@ztetx.com" <gregory.mirsky@ztetx.com>, "Reshad Rahman (rrahman)" <rrahman@cisco.com>, "rtg-bfd@ietf.org" <rtg-bfd@ietf.org>
Subject: Re: WGLC for BFD Multipoint documents (last round)
Thread-Topic: WGLC for BFD Multipoint documents (last round)
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Date: Wed, 14 Feb 2018 02:23:02 +0000
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Hi, Greg,

Thanks for the very expeditious response, and iterations addressing may comments!

On Feb 13, 2018, at 9:10 PM, Greg Mirsky <gregimirsky@gmail.com<mailto:gregimirsky@gmail.com>> wrote:

Hi Carlos,
thank you for your prompt response to the proposed updates. Indeed, I've missed your comment. Please find my follow-up updates under GIM2>> tag. I've attached diff to highlight the changes.

Regards,
Greg

On Tue, Feb 13, 2018 at 3:37 PM, Carlos Pignataro (cpignata) <cpignata@cisco.com<mailto:cpignata@cisco.com>> wrote:
Hi, Greg,

On Feb 11, 2018, at 9:03 PM, Greg Mirsky <gregimirsky@gmail.com<mailto:gregimirsky@gmail.com>> wrote:

Hi Carlos,
thank you for your thorough review and detailed comments.

Anytime — but just to be clear, this is not a thorough review. I spent a quick scan through some sections only, which triggered these coarse set of comments.
GIM2>> Still, many thanks. And it would be of great help if you can find time to do more detailed review and share your comments to both documents.

Thanks! I’ll do my best to find time for a detailed review.

Please find my responses in-lined tagged GIM>>.


More inline.

Regards,
Greg

On Thu, Feb 8, 2018 at 7:19 PM, Carlos Pignataro (cpignata) <cpignata@cisco.com<mailto:cpignata@cisco.com>> wrote:
Hi, Greg,

When looking for this specific sentence, I got a chance to scan through the document a bit.

It seems to me there are still a number of editorials and potentially non-editorials to be fixed.

Looking at S4.8 only:

   BFD packets received on tails for an IP multicast group MUST be
   consumed by tails and MUST NOT be forwarded to receivers.  Session of
   type MultipointTail MUST identify the packet as BFD with the help of
   destination UDP port number "3784" on IP multipoint path.

CMP: There are a number of “the” or “a[n]” articles missing.

CMP: What is “with the help of”? What is "port number "3784" on IP multipoint path”?
GIM>> Agree, will remove the quotation marks around 3784. Proposed update:
OLD TEXT:
 Session of
   type MultipointTail MUST identify the packet as BFD with the help of
   destination UDP port number "3784" on IP multipoint path.
NEW TEXT:
Session of type MultipointTail MUST identify packet received on an IP multipoint path
as BFD control packet if the destination UDP port value equals 3784.

Who identifies the packets? The "session"? Or should this be the tail/receiver/tailend?

GIM2>> Would the following clarify it:

OLD TEXT:
 Session of
   type MultipointTail MUST identify the packet as BFD with the help of
   destination UDP port number "3784" on IP multipoint path.
NEW TEXT:
Node with
   the BFD session of type MultipointTail MUST identify packet received
   on an IP multipoint path as BFD control packet if the destination UDP
   port value equals 3784.

Thanks! It is clearer now.



   For multipoint LSPs, when IP/UDP encapsulation of BFD control packets
   is used, MultipointTail MUST use destination UDP port "3784" and
   "127.0.0.0/8<http://127.0.0.0/8>" range for IPv4 or "0:0:0:0:0:FFFF:7F00:0/104" range for
   IPv6 ([RFC8029]).  Packets identified as BFD packets MUST be consumed
   by MultipointTail and demultiplex as described in Section 4.13.2
.
CMP: The first sentence is very confusing (besides the “MUST use” that you already called out and that I agree).
CMP: For example, is this the source or destination endpoint? Which address is this (i.e., Destination)?
GIM>> Since the sentence refers to MultipointTail, I conclude this refers to the destination endpoint. As Reshad agreed to s/use/expect/
here's proposed update to the sentence:
OLD TEXT:
   For multipoint LSPs, when IP/UDP encapsulation of BFD control packets
   is used, MultipointTail MUST use destination UDP port "3784" and
   "127.0.0.0/8<http://127.0.0.0/8>" range for IPv4 or "0:0:0:0:0:FFFF:7F00:0/104" range for
   IPv6 ([RFC8029]).
NEW TEXT:
   For multipoint LSPs, when IP/UDP encapsulation of BFD control packets
   is used, MultipointTail MUST expect destination UDP port 3784 and
   destination IP address in 127.0.0.0/8<http://127.0.0.0/8> range for IPv4 or 0:0:0:0:0:FFFF:7F00:0/104 range for
   IPv6 ([RFC8029]).
GIM2>> I hope I've got it now:

OLD TEXT:
   For multipoint LSPs, when IP/UDP encapsulation of BFD control packets
   is used, MultipointTail MUST use destination UDP port "3784" and
   "127.0.0.0/8<http://127.0.0.0/8>" range for IPv4 or "0:0:0:0:0:FFFF:7F00:0/104" range for
   IPv6 ([RFC8029]).
NEW TEXT:
   For multipoint LSPs, when IP/UDP encapsulation of BFD control packets
   is used, MultipointTail MUST expect destination UDP port 3784.
   Destination IP address of BFD control packet MUST be in 127.0.0.0/8<http://127.0.0.0/8>
   range for IPv4 or in 0:0:0:0:0:FFFF:7F00:0/104 range for IPv6  ([RFC8029]).


My point was different — sorry if I was not clear.
It was that RFC 8029 does not talk about any ranges in the context of BFD.
The sentence reads:
   Destination IP address of BFD control packet MUST be in 127.0.0.0/8
   range for IPv4 or in 0:0:0:0:0:FFFF:7F00:0/104 range for IPv6  ([RFC8029]).
But why that citation? RFC 8029 does not specify the destination IP address for BFD control packets. I’d stop the sentence and add a new one like “The use of these destination addresses is consistent with the explanations and usage in [RFC8029].”
Or similar.




In addition to pointing to RFC 8029, for things like Section 2.1, etc., this is a new requirement. RFC 8029 does not specify the use of those IP addresses with UDP Port 3784. Hence the citation should go on a separate sentence.


   Use of other types of encapsulation for multipoint LSP is outside the
   scope of this document.

CMP: For BFD Control?
GIM>> Will add 'of the BFD control message over' and remove 'for' to result:
Use of other types of encapsulation of the BFD control message over multipoint LSP  is outside the scope of this document.


Thanks.


Also, checking the following section:

4.13.1.  Reception of BFD Control Packets

   The following procedure replaces section 6.8.6 of [RFC5880].
…
      If bfd.SessionType is PointToPoint, update the Detection Time as
      described in [RFC5880] section 6.8.4.  Otherwise, update the
      Detection Time as described in Section 4.11 above.

CMP: The actual set of citations is not clear. If this is a replacement to section 6.8.6 of [RFC5880], then why a citation like “[RFC5880] section 6.8.4"? Isn’t it implied that it is RFC 5880? Or conversely, if it is a replacement updating RFC 5880, how does “in Section 4.11 above” work when inserted in RFC 5880? Its ask relative :-)


Seems you missed this comment.
GIM2>> Right. The text requires update:
OLD TEXT:
       If bfd.SessionType is PointToPoint, update the Detection Time as
      described in [RFC5880] section 6.8.4.  Otherwise, update the
      Detection Time as described in Section 4.11 above.
NEW TEXT:
      If bfd.SessionType is PointToPoint, update the Detection Time as
      described in section 6.8.4 of [RFC5880].  If bfd.SessionType is
      MultipointTail, then update the Detection Time as described in
      Section 4.11.

GIM2>> RE: references to RFC 5880 in this section. I think that they are useful as long as this is separate document. Once someone will decide to do 5880bis and in fact replace section 6.8.6, the references should be removed.


The problem is that the section starts with:
   The following procedure replaces section 6.8.6 of [RFC5880]

But the procedure is not self-contained so as to be a replacement for a section of RFC 5880, because it ends with:
   update the Detection Time as described in Section 4.11

Hope that clarifies,

Thanks!

Carlos.


Thanks!

Carlos.



Thanks!

—
Carlos Pignataro, carlos@cisco.com<mailto:carlos@cisco.com>

“Sometimes I use big words that I do not fully understand, to make myself sound more photosynthesis."

On Feb 8, 2018, at 12:14 AM, gregory.mirsky@ztetx.com<mailto:gregory.mirsky@ztetx.com> wrote:


Hi Reshad,

thank you for your consideration. I've came across what looks as simple editorial change. Appreciate your comment.

In the second paragraph of section 4.8 Packet consumption on tails the following

  For multipoint LSPs, when IP/UDP encapsulation of BFD control packets

  is used, MultipointTail MUST use destination UDP port "3784" ...

reads akwardly because, I think, of 'MUST use'. I propose simple s/use/look for/ or s/use/expect/. What do you think? Is the text god as-is or minor editing may help?


Regards,

Greg Mirsky


Sr. Standardization Expert
预研标准部/有线研究院/有线产品经营部 Standard Preresearch Dept./Wireline Product R&D Institute/Wireline Product Operation Division


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E: gregory.mirsky@ztetx.com<mailto:gregory.mirsky@ztetx.com>
www.zte.com.cn<http://www.zte.com.cn/>
Original Mail
Sender: ReshadRahman(rrahman) <rrahman@cisco.com<mailto:rrahman@cisco.com>>
To: gregory mirsky10211915;rtg-bfd@ietf.org<mailto:rtg-bfd@ietf.org> <rtg-bfd@ietf.org<mailto:rtg-bfd@ietf.org>>
Date: 2018/02/08 11:03
Subject: Re: WGLC for BFD Multipoint documents (last round)
<Sorry for the delay>
Hi Greg,

I would go with normative SHOULD. What you proposed below is fine.

Regards,
Reshad.


From: "gregory.mirsky@ztetx.com<mailto:gregory.mirsky@ztetx.com>" <gregory.mirsky@ztetx.com<mailto:gregory.mirsky@ztetx.com>>
Date: Sunday, February 4, 2018 at 8:33 PM
To: "Reshad Rahman (rrahman)" <rrahman@cisco.com<mailto:rrahman@cisco.com>>, "rtg-bfd@ietf.org<mailto:rtg-bfd@ietf.org>" <rtg-bfd@ietf.org<mailto:rtg-bfd@ietf.org>>
Subject: Re: WGLC for BFD Multipoint documents (last round)


Hi Reshad,

you've said:

Hi Greg,



While OOB mechanism would improve security, my personal opinion is that we should try to improve security without requiring an OOB mechanism. I think we can add text to the security considerations to address the concerns below, e.g. A tail SHOULD prevent the number of MultipointTail sessions from exceeding the number of expected streams.  The concern expressed in b) cannot be fixed by what I proposed because of multiple streams.  So just preventing the number of MultipointTail sessions from exceeding the number of expected streams should be good enough.



Regards,

Reshad.



If we make it normative SHOULD, i.e. s/should/SHOULD/ in the third recommendation to the implementers:

     The implementation SHOULD have a reasonable upper bound on the

      number of MultipointTail sessions that can be created, with the

      upper bound potentially being computed based on the number of

      multicast streams that the system is expecting.



Or keep the lower case as it is consistent with the rest of the section, e.g. 'a MultipointTail session should not be created'?



Kind regards,

Greg Mirsky



Sr. Standardization Expert
预研标准部/有线研究院/有线产品经营部 Standard Preresearch Dept./Wireline Product R&D Institute/Wireline Product Operation Division


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