Re: [mpls] Consensus poll on Design directive for the MPLS Open DT Tue, 24 August 2021 19:51 UTC

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Subject: Re: [mpls] Consensus poll on Design directive for the MPLS Open DT
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Dear Loa, WGs Chairs, et al.,

I've got a couple of questions and much appreciate it if you can help me with clarifications:

Would it be correct to assume that ancillary data apply to MPLS PW?

If the ancillary data apply to MPLS PW, how does it coexists when PW VCCV is used? The case I am considering - using PW ACH (RFC 4385), i.e., PW Control Channel Type 1. The PW ACH includes the Channel Type field that, like G-ACh, defines the format of data that immediately follows it. Possible issues between PW ACH and the ancillary data are similar to questions discussed concerning GAL and the ancillary data in the same packet.

Thank you in advance for sharing your opinions.


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


Original Mail

Sender: LoaAndersson
CC:;;DetNet Chairs;
Date: 2021/08/24 01:36
Subject: [mpls] Consensus poll on Design directive for the MPLS Open DT

Working Group, Design Tean,
The Open DT has discussed the relationship between GAL/G-ACh and the new  
methods for indicating and transporting ancillary data in and after the  
label stack.
We have decided to give the MPLS Open DT the following design directive:
---------------------------- start ---------------------------------
Following the discussion in the MPLS Open DT 2021-08-19 we have have  
decided to give the MPLS Indicator and Open Design team this design  
RFC 5586 "MPLS Generic Associated Channel" (including the updates by RFC  
7274, RFC 6423, RFC 7214, and RFC 7026) will not be changed by the MPLS  
Open Design Team. The associated channel (GAL/G-ACh) will continue to  
operate as specified. No changes should be made to the associated  
channel, without careful coordination with what will be specified by the  
MPLS Pen design team.
The Open design team will continue define methods bases on indicators  
(e.g. FAI-style SPL) and ancillary data.
A packet can not carry both the associated channel and the new methods  
for transporting ancillary data indicated by the FAI-style SPL, i.e. the  
GAL and the FAI-style SPL can not both be present in a label stack. The  
reason is that the way the ACH is specified there is a high risk of  
collision of "data after the BoS" specified by other methods.
---------------------end --------------------------------------------
The design team will start working according to this design directive,  
but for a period of two weeks we will comments on the directive.
Please send comments to the MPLS wg mailing list (
for the co-chairs
Loa Andersson                        email:
Senior MPLS Expert                
Bronze Dragon Consulting             phone: +46 739 81 21 64
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