Hi Rishabh,

The first question is solved. Thank you for taking the comment into 
consideration.
For the second one regarding the SID after the replication SID, I still have 
some further question when considering it a “VPN SID”:

In MPLS data plane, Is the SID an Upstream-assigned Label ? Or an SRGB label 
(though may be a more strictly unique number than SRGB that is a relatively 
unique index/offset ) ?
In SRv6 data plane, is the SID an “Upstream-assigned SRv6 SID”, which is 
allocated on Ingress PE and put in the SID list after the replication SID ?

Thanks
Jingrong


From: Rishabh Parekh [mailto:risha...@gmail.com]
Sent: Wednesday, December 7, 2022 6:32 AM
To: Xiejingrong (Jingrong) <xiejingr...@huawei.com>
Cc: James Guichard <james.n.guich...@futurewei.com>; SPRING WG 
<spring@ietf.org>; spring-cha...@ietf.org
Subject: Re: [spring] WGLC for draft-ietf-spring-sr-replication-segment

Jingrong,

In section 2.1 and 2.2, it says “An Anycast SID or BGP PeerSID MUST NOT appear 
in segment list preceding a Replication SID.”
I don’t know BGP PeerSID very well, but for anycast SID, I think it may be 
useful and suitable to appear in seg list preceding a Replication SID.
Can you please explain the two things and why MUST NOT ?

SIDs in the segment list guide a packet to a Downstream Node, typically along a 
specific path. For example, the SR-MPLS Node SID of the downstream node in 
segment list can be used for this. An Anycast SID by definition belongs to two 
or more nodes and a packet is forwarded to only one of the nodes in an Anycast 
set. Therefore, Anycast SID of the downstream nodes cannot be used in the 
segment list. I realize now this restriction is really for SIDs identifying the 
downstream node, not for intermediate nodes in path from Replication node to 
the downstream node. I will see if we can make this clear in the next revision 
of the document.

For BGP, we should have specified "BGP PeerSet SID" (RFC 8402 Section 4.2) to 
be exact. The reason is the same as the Anycast SID restriction.

I feel hard to understand how the SIDs after the Replication SID are used. Does 
it mean a “VPN SID” or something like that ?

The SIDs after the Replication SID provide additional context for processing 
the packet at the downstream node. "VPN SID" is one example of a context.

Thanks,
Rishabh.

On Mon, Dec 5, 2022 at 6:54 PM Xiejingrong (Jingrong) 
<xiejingrong=40huawei....@dmarc.ietf.org<mailto:40huawei....@dmarc.ietf.org>> 
wrote:
Hi WG and authors,

I have read this document and have some questions.

In section 2.1 and 2.2, it says “An Anycast SID or BGP PeerSID MUST NOT appear 
in segment list preceding a Replication SID.”
I don’t know BGP PeerSID very well, but for anycast SID, I think it may be 
useful and suitable to appear in seg list preceding a Replication SID.
Can you please explain the two things and why MUST NOT ?

In Section 2.1, it says below:
                              There MAY be SIDs after the
                              Replication SID in the segment list of a packet. 
These SIDs are used
                              to provide additional context for processing a 
packet locally at the
                              node where the Replication SID is the Active 
Segment.  The processing
                              of SIDs following the Replication SID MUST NOT 
forward the SR-MPLS
                              packet to another node.
In Section 2.2, it says below:
                              There MAY be SIDs after the Replication
                              SID in the SRH of a packet.  These SIDs are used 
to provide
                              additional context for processing a packet 
locally at the node where
                              the Replication SID is the Active Segment.  The 
processing of SIDs
                              following the Replication SID MUST NOT forward 
the SRv6 packet to
                              some other node.  The restrictions described in 
this paragraph apply
                              to both un-compressed and compressed SRv6 
encapsulation.
I feel hard to understand how the SIDs after the Replication SID are used. Does 
it mean a “VPN SID” or something like that ?

Thanks
Jingrong

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From: spring [mailto:spring-boun...@ietf.org<mailto:spring-boun...@ietf.org>] 
On Behalf Of James Guichard
Sent: Monday, November 28, 2022 11:10 PM
To: SPRING WG <spring@ietf.org<mailto:spring@ietf.org>>
Cc: spring-cha...@ietf.org<mailto:spring-cha...@ietf.org>
Subject: [spring] WGLC for draft-ietf-spring-sr-replication-segment

Dear WG:

This email starts a 2-week Working Group Last Call for 
https://datatracker.ietf.org/doc/draft-ietf-spring-sr-replication-segment/

Please read the updated document if you haven’t already and send your comments 
to the SPRING WG list no later than December 12th 2022.

If you are raising a point which you expect will be specifically debated on the 
mailing list, consider using a specific email/thread for this point.

Lastly, if you are an author or contributor please respond to indicate whether 
you know of any undisclosed IPR related to this document.

Thanks!

Jim, Joel & Bruno


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