Re: [mpls] Review and Consensus call on text from the MPLS Open DT on in-stack indicators

Rakesh Gandhi <> Fri, 06 August 2021 14:01 UTC

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From: Rakesh Gandhi <>
Date: Fri, 06 Aug 2021 10:00:40 -0400
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To: Loa Andersson <>
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Subject: Re: [mpls] Review and Consensus call on text from the MPLS Open DT on in-stack indicators
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Hi WG,

One comment on the following text with <RG>:

   - We have a standardized associated channel, the GAL/GACH. We are not
   going to change the associated channel in anyway that breaks existing
   implementations. The ACH is found immediately after the label carrying the
   Bottom of Stack (BoS) bit. Currently, there is no defined method to carry
   multiple ACHs in the same MPLS packet. *GAL/GACH will only be an OAM or
   instrumentation tool and will not be used to carry meta-data with
   user-traffic. *

<RG> The last sentence needs some clarification. The packet with GAL is
punted out of the fast path in forwarding, so user-traffic does not carry
it, so it makes sense. However, packets could carry GACH without GAL. The
user-traffic could also carry a GACH without GAL if use-case makes sense. I
am not sure we are ready to add this restriction just yet.


On Thu, Aug 5, 2021 at 10:52 AM Loa Andersson <> wrote:

> Working Group, MPLS Open DT,
> The week before IETF 111 the Open DT met and agreed upon a text on
> "indicators". The terminology we use is that somewhere in the label
> stack there is an indicator tell the processing node that a specific
> packet needs a certain set of Forwarding Actions, for example some iOAM
> action might be required. To support the forwarding action there is
> often ancillary data with the packet.
> The text the DT produced is about the indicators, a companion text on
> ancillary data will follow.
> The text was discussed in the Joint meeting and reported to the MPLS
> working group at IETF 111. The Open DT itself can only propose, the text
> is therefore now sent out to the working group for review and consensus
> call.
> The proposed text is found at:
> Please review the proposed text and comment on the MPLS wg mailing list
> (
> We plan to keep the consensus call open until 2021-08-20.
> /Loa
> Open DT Co-ordinator / MPLS wg co-chair
> --
> Loa Andersson                        email:
> Senior MPLS Expert                
> Bronze Dragon Consulting             phone: +46 739 81 21 64
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> mpls mailing list