Re: [mpls] New Version Notification for draft-mirsky-spring-bfd-00.txt

"Carlos Pignataro (cpignata)" <> Wed, 10 May 2017 20:01 UTC

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From: "Carlos Pignataro (cpignata)" <>
To: Robert Raszuk <>
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Thread-Topic: [mpls] New Version Notification for draft-mirsky-spring-bfd-00.txt
Date: Wed, 10 May 2017 20:01:52 +0000
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Subject: Re: [mpls] New Version Notification for draft-mirsky-spring-bfd-00.txt
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You are right — sorry about that! “TFS” is not used in any of those RFCs or drafts, although it is used on email discussions about LSP Ping.

Indeed, TFS for “Target FEC Stack” from Section 3.2 of RFC 8029.


— Carlos.

On May 10, 2017, at 3:41 PM, Robert Raszuk <<>> wrote:

Never mind .. I guess you made it up from "Target FEC Stack" :)

On Wed, May 10, 2017 at 9:40 PM, Robert Raszuk <<>> wrote:
Hi Carlos,

Sorry what is "TFS" ?

RFC 7110 does not even use such abbreviation neither do draft-ietf-mpls-bfd-directed :) Google also seems to be pretty clueless about it.

Just curious as you keep using this term in each email :)


On Wed, May 10, 2017 at 9:24 PM, Carlos Pignataro (cpignata) <<>> wrote:

In the MPLS data plane, FECs are also instantiated through a label stack. But RFC 7110 does not use numeric label values, it uses TFSs. That does not create any additional state. E.g.,:


— Carlos.

On May 9, 2017, at 3:43 PM, Greg Mirsky <<>> wrote:

Hi Carlos,
I probably would characterize anything that starts with Why not as a technical comment but rather as a question.
According to draft-ietf-spring-segment-routing-mpls, "In the MPLS dataplane,the SR header is instantiated through a label stack".
At the same time, one of advantages of SR is that "per-flow state only [maintained] at the ingress node to the SR domain".
Thus, for the case of monitoring unidirectional SR tunnels, I consider that there's no need to create any additional state on the egress node.
Of course, if there were bidirectional SR tunnels, then control of the reverse direction of the BFD session would not require use of the Return Path sub-TLV.
As for LSP-Ping, I just propose that the Segment Routing MPLS Tunnel sub-TLV MAY be used Reply Path TLV defined in RFC 7110. I viewed the proposal as invitation to technical discussion.


On Tue, May 9, 2017 at 9:07 AM, Carlos Pignataro (cpignata) <<>> wrote:
Thank you Greg!

Since seems quite similar to the text removed at, then the complete set of outstanding technical comments that triggered the removal of that text from draft-ietf-mpls-bfd-directed-05.txt might peek your interest :-)

One that I recall is: why use label values when every other return-path sub-TLV for BFD and for LSP-Ping, including draft-ietf-mpls-bfd-directed, uses TFSs?


— Carlos.

On May 9, 2017, at 12:00 PM, Greg Mirsky <<>> wrote:

Dear Carlos,
I've decided to re-start the discussion and am interested to hear technical comments to the proposed solution.


On Tue, May 9, 2017 at 8:51 AM, Carlos Pignataro (cpignata) <<>> wrote:
Dear Greg,

Cursorily scanning through this, it seems that most concerns raised and comments made about the SR sections of draft-ietf-mpls-bfd-directed-0N (with N < 5) apply to your new draft.

This is one of those: — the list archive shows a few more. The copy/paste did not address the comments.


— Carlos.

On May 8, 2017, at 11:33 PM, Greg Mirsky <<>> wrote:

Dear All,
perhaps this new draft may is of interest to you.
Your comments, suggestions are most welcome and greatly appreciated.


---------- Forwarded message ----------
From: <<>>
Date: Mon, May 8, 2017 at 8:29 PM
Subject: New Version Notification for draft-mirsky-spring-bfd-00.txt
To: Gregory Mirsky <<>>

A new version of I-D, draft-mirsky-spring-bfd-00.txt
has been successfully submitted by Greg Mirsky and posted to the
IETF repository.

Name:           draft-mirsky-spring-bfd
Revision:       00
Title:          Bidirectional Forwarding Detection (BFD) in Segment Routing Networks Using MPLS Dataplane
Document date:  2017-05-08
Group:          Individual Submission
Pages:          7

   Segment Routing architecture leverages the paradigm of source
   routing.  It can be realized in the Multiprotocol Label Switching
   (MPLS) network without any change to the data plane.  A segment is
   encoded as an MPLS label and an ordered list of segments is encoded
   as a stack of labels.  Bidirectional Forwarding Detection (BFD) is
   expected to monitor any kind of paths between systems.  This document
   defines how to use Label Switched Path Ping to bootstrap and control
   path in reverse direction of a BFD session on the Segment Routing
   network over MPLS dataplane.

Please note that it may take a couple of minutes from the time of submission
until the htmlized version and diff are available at<>g/>.

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