There work group adoption process started several months ago.  We asked Loa to 
initiate the process and he asked four members of the MPLS review team to 
review the draft, which they subsequently did, with all four indicating that 
they thought the draft should be adopted.  Then and only then did Loa initiate 
a poll for WG adoption on the MPLS mailing list.

I thought it might be useful for the author of the subject draft to share their 
perspective on the various drafts that have been mentioned on this thread.

From a technical perspective, the idea of using SR for service function 
chaining has been there since SR's advent, so any draft that talks about SFC 
using SR is not originating anything new. 
draft-xuclad-spring-sr-service-chaining clearly explains how SR can be used to 
steer packets between SFFs and cause them to be delivered to SFs. It may not be 
describing anything new or radical, but at the same time it may be a useful 
informational document for the SPRING working group.

The SFC working group may have an opinion on the use of the NSH as a metadata 
container in the MPLS-SR case, and may want to consider whether the draft is 
consistent with the SFC architecture.  E.g., it is not clear to me how SR can 
support branching, looping, and jumping which are a key element of the SFC 

On the other hand, draft-farrel-mpls-sfc is about using the MPLS forwarding 
plane to achieve the forwarding behaviour defined in the SFC architecture. The 
principal use case for this draft is label swapping (which, as is noted in 
draft-xuclad-spring-sr-service-chaining, requires network state and so is not 
consistent with the SR architecture). However, since the MPLS data plane 
strives to be consistent across use cases, this draft also describes how one 
encoding can be applied to swapping or stacking, and we do see a use case where 
an arbitrary mix of label swapping and label stacking may be useful to allowing 
the ingress classifier to select specific SFFs along an SFP.

The IANA considerations sections give a good indication of where the drafts 
belong. draft-xuclad-spring-sr-service-chaining asks for allocations from the 
"Segment-routing with IPv6 dataplane (SRv6) Parameters"  registry: that 
registry has not been created yet, but is probably intended to be the registry 
discussed in draft-filsfils-spring-srv6-network-programming so the discussion 
would belong in SPRING. draft-farrel-mpls-sfc asks for allocations the 
"Special-Purpose Multiprotocol Label Switching (MPLS) Label Values" registry 
and that means it should be discussed in the MPLS WG.

In summary, when draft-xuclad-spring-sr-service-chaining references 
draft-farrel-mpls-sfc it says "This label stacking  (i.e., the SR approach 
described in draft-xuclad) is completely different from other proposals such as 
[RFC8300] and the MPLS label swapping mechanism described in 

I agree with that statement and think each draft should progress at its own 
speed and in its own appropriate WG.

Yours Irrespectively,


From: Bernier, Daniel [mailto:daniel.bern...@bell.ca]
Sent: Friday, March 9, 2018 12:15 AM
To: Kamran Raza (skraza) <skr...@cisco.com>; Zafar Ali (zali) <z...@cisco.com>; 
Francois Clad (fclad) <fc...@cisco.com>; 徐小虎(义先) <xiaohu....@alibaba-inc.com>
Cc: mpls <m...@ietf.org>; SPRING WG List <spring@ietf.org>; s...@ietf.org; 
draft-farrel-mpls-sfc <draft-farrel-mpls-...@ietf.org>; mpls-chairs 
<mpls-cha...@ietf.org>; mpls <mpls-boun...@ietf.org>
Subject: Re: [mpls] [spring] The MPLS WG has placed draft-farrel-mpls-sfc in 
state "Call For Adoption By WG Issued"


As co-author of both initial draft-xu-mpls-service-chaining, 
draft-clad-spring-segment-routing-service-chaining and the merged 
draft-xuclad-spring-sr-service-chaining, I also have concerns about the current 
WG adoption process and haste.  I do hope we will be in a position to discuss 
in London, which is merely days away.


Daniel Bernier | Bell Canada​

From: mpls <mpls-boun...@ietf.org<mailto:mpls-boun...@ietf.org>> on behalf of 
Kamran Raza (skraza) <skr...@cisco.com<mailto:skr...@cisco.com>>
Sent: Thursday, March 8, 2018 11:43 PM
To: Zafar Ali (zali); Francois Clad (fclad); 徐小虎(义先)
Cc: mpls; SPRING WG List; s...@ietf.org<mailto:s...@ietf.org>; 
draft-farrel-mpls-sfc; mpls-chairs; mpls
Subject: Re: [mpls] [spring] The MPLS WG has placed draft-farrel-mpls-sfc in 
state "Call For Adoption By WG Issued"

I second the concerns raised by Xiaohu, Francois, and Zafar.

From: mpls <mpls-boun...@ietf.org<mailto:mpls-boun...@ietf.org>> on behalf of 
"Zafar Ali (zali)" <z...@cisco.com<mailto:z...@cisco.com>>
Date: Thursday, March 8, 2018 at 7:02 PM
To: "Francois Clad (fclad)" <fc...@cisco.com<mailto:fc...@cisco.com>>, 
"徐小虎(义先)" <xiaohu....@alibaba-inc.com<mailto:xiaohu....@alibaba-inc.com>>
Cc: mpls <m...@ietf.org<mailto:m...@ietf.org>>, SPRING WG List 
"s...@ietf.org<mailto:s...@ietf.org>" <s...@ietf.org<mailto:s...@ietf.org>>, 
mpls-chairs <mpls-cha...@ietf.org<mailto:mpls-cha...@ietf.org>>, mpls 
Subject: Re: [mpls] [spring] The MPLS WG has placed draft-farrel-mpls-sfc in 
state "Call For Adoption By WG Issued"

Dear MPLS WG Chairs and the authors of draft-farrel-mpls-sfc,

I would like to draw your attention to the serious issue raised by Xiaohu and 


Please note that this working group adaption against the IETF process and its 
spirit. Please recall the adaption call.


Just to reiterate the issue raised by Xiaohu and Francois. At last IETF we 
discussed 3 drafts (draft-xu-mpls-service-chaining-03, draft-farrel-mpls-sfc 
and draft-clad-spring-segment-routing-service-chaining) in SFC, Spring and MPLS 
WG. There was the specific conversation on which WG the work belongs, and the 
assumed follow-up was for the chairs and ADs to have the discussion on home for 
these drafts.

From IETF process viewpoint, this call for adaption is like putting the "cart 
ahead of the horse." MPLS WG comes last in the process after there is an 
agreement from Spring and SFC groups on the need for MPLS data plane changes 
proposed by the draft. I raised this point at the mic at SFC WG meeting at 
IETF100 and Adrian agreed to it. I.e., MPLS WG comes at the last stage in the 
process; expert to review this work does not sit in the MPLS WG.

The drafts also did not stay dormant after IETF100. There were email 
conversations among the authors of the concerned drafts 

Authors of draft-xu- and draft-clad- followed the proper IETF process, 
discussed and merged the contents. They published 
draft-xuclad-spring-sr-service-chaining-01 and asked WG for a "presentation 
slot" at IETF100. Only to find that draft-farrel-mpls-sfc used a backdoor to 
force this "WG adaption call"!

One also has to question the timing of this adaption call when the WGs are 
meeting face-to-face in a couple of weeks. Is it no longer IETF spirit to make 
use of the face-to-face to do the right thing, especially when we are meeting 
in two weeks?

In the light of the above, my request to the authors of draft-farrel and MPLS 
WG chairs to please do the right thing and recall this WG adaptation call.


Regards ... Zafar

From: mpls <mpls-boun...@ietf.org<mailto:mpls-boun...@ietf.org>> on behalf of 
"Francois Clad (fclad)" <fc...@cisco.com<mailto:fc...@cisco.com>>
Date: Thursday, March 8, 2018 at 5:21 AM
To: "徐小虎(义先)" <xiaohu....@alibaba-inc.com<mailto:xiaohu....@alibaba-inc.com>>
Cc: draft-farrel-mpls-sfc 
"m...@ietf.org<mailto:m...@ietf.org>" <m...@ietf.org<mailto:m...@ietf.org>>, 
SPRING WG List <spring@ietf.org<mailto:spring@ietf.org>>, mpls-chairs 
<mpls-cha...@ietf.org<mailto:mpls-cha...@ietf.org>>, mpls 
Subject: Re: [mpls] [spring] The MPLS WG has placed draft-farrel-mpls-sfc in 
state "Call For Adoption By WG Issued"

Hi Xiaohu, all,

I agree with the point raised by Xiaohu. The draft-farrel-mpls-sfc is copying 
ideas described in draft-xu-mpls-service-chaining. Please note that the work in 
draft-xu-mpls-service-chaining started one year before draft-farrel-mpls-sfc.

At IETF100, three drafts in this area were discussed / presented:
- draft-xu-mpls-service-chaining
- draft-farrel-mpls-sfc
- draft-clad-spring-segment-routing-service-chaining

There was discussion over the mic on the right home for these drafts among SFC, 
SPRING and MPLS, but no consensus was reached.

As Xiaohu mentioned, draft-xu-mpls-service-chaining and 
draft-clad-spring-segment-routing-service-chaining have later merged as 
draft-xuclad-spring-sr-service-chaining. We have also requested a slot for 
presenting this draft during the upcoming IETF meeting.
In this context, we believe that asking for WG adoption for one of these drafts 
is premature.

On 7 Mar 2018, at 01:13, 徐小虎(义先) 
<xiaohu....@alibaba-inc.com<mailto:xiaohu....@alibaba-inc.com>> wrote:

Hi all,

As I had pointed out at the last IETF meeting, section 6 of this draft has an 
serious overlap with 
 that has now been updated by 
 with a merge with draft-clad-spring-segment-routing-service-chaining.

Hence, I'm very interesting to know the intention of such rewritting of a given 
mechanism that has been described in another draft. Is there any special 

Best regards,
发件人:IETF Secretariat 
发送时间:2018年3月6日(星期二) 22:09
<draft-farrel-mpls-...@ietf.org<mailto:draft-farrel-mpls-...@ietf.org>>; mpls 
<m...@ietf.org<mailto:m...@ietf.org>>; mpls-chairs 
主 题:[mpls] The MPLS WG has placed draft-farrel-mpls-sfc in state "Call For 
Adoption By WG Issued"

The MPLS WG has placed draft-farrel-mpls-sfc in state
Call For Adoption By WG Issued (entered by Loa Andersson)

The document is available at

mpls mailing list
spring mailing list

spring mailing list

Reply via email to