Re: [mpls] [spring] [SPRING] Query related to SR Architecture

"Anil Kumar S N (VRP Network BL)" <> Thu, 10 September 2015 12:47 UTC

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From: "Anil Kumar S N (VRP Network BL)" <>
To: Pushpasis Sarkar <>, Gaurav agrawal <>, Alexander Vainshtein <>
Thread-Topic: [spring] [SPRING] Query related to SR Architecture
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Date: Thu, 10 Sep 2015 12:47:38 +0000
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Subject: Re: [mpls] [spring] [SPRING] Query related to SR Architecture
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Hi Pushpasis,

                Thanks a lot for replying.

                The requirement is still under research stage once it is in a presentable format  will share the details.
we need every node on the path to perform the same service, we could even define a service globally and allocate one label to it which is understandable by all.

                Technically it must be possible right, as top label specifies to service once that service is performed then refer ILM/NHLFE table for forwarding and if service label says before sending out the packet push the label back on the stack.
                The Egress device will finally pop both service and node label.

Hope you are refering to with respect to SFC”

                As per below section a node label and service lable combination has to be pushed for each hop if the service is intended to  be performed by each node on the path to destination.
                If there is any metadata involved for service NSH has to be piggybacked in the packet. SFC don’t solve in reducing number of labels involved.

        The service classifier therefore would attach a
        segment list {SID(SN1), SID(SF1), SID(SN2), SID(SF2)} to the packet.
        This segment list is actually represented by a MPLS label stack.  In
        addition, the service classifier could optionally impose metadata on
        the packet through the Network Service Header (NSH)

Thanks & Regards
Anil S N

“Be liberal in what you accept, and conservative in what you send” - Jon Postel

From: Pushpasis Sarkar []
Sent: 10 September 2015 00:45
To: Gaurav agrawal; Alexander Vainshtein
Cc: Anil Kumar S N (VRP Network BL);;; Vinod Kumar S 70786
Subject: Re: [spring] [SPRING] Query related to SR Architecture

Hi Gaurav,

Looks like you are asking the routers to forward looking at the second innermost label and not the topmost label. This does NOT fit into the MPLS architecture. I am not sure it fits SR-IPV6 architecture or not, but I doubt.

Looks like your requirement is that each node on shortest path to the final destination (indicated by the bottom-most Node-segment) provide some service. In this regard, can you be specific about wether all the nodes will provide the same service or different service? It does not make sense to me for all the transit nodes to execute the same service on the packet. So if they are not required to provide the same service on each transit node, question is how one service label will be enough to indicate which specific service will need to be executed at each node.

Hope you have gone through SFC drafts already.


From: spring on behalf of Gaurav agrawal
Date: Wednesday, September 9, 2015 at 6:09 PM
To: Alexander Vainshtein
Cc: "Anil Kumar S N (VRP Network BL)", "<>", "<>", Vinod Kumar S 70786
Subject: Re: [spring] [SPRING] Query related to SR Architecture

Dear Alexander,

Thanks for your inputs. Let me further elaborate on the subject.

The requirement is to make every node on the path to destination to perform a specific service(Service could be anything).

Currently Service label can only follow a Node Label, because of which to let every node perform same service, SR Label stack expects to have node and service label for each transit node, this results in huge label stack.

If we can push a service label prior to node label & each intermediate node can perform below operation:
1) Pop Service Label & perform/schedule the service.
2) Decide the further forwarding based on Node Label
3) Push the service label back to stack.

With this we needn’t repeat the service label for each transit node thereby making the SR Label stack COMPACT.

We can derive many optimized implementation by having this.

So, we would like to hear from You and MPLS/SPRING community about our view point.

Thanks and Regards,
Gaurav Agrawal

Mobile: +91-7838700296
Huawei Technologies Co., Ltd.

From: Alexander Vainshtein []
Sent: Wednesday, September 09, 2015 5:01 PM
To: Gaurav agrawal
Cc: Anil Kumar S N (VRP Network BL); Vinod Kumar S 70786;<>;<>
Subject: RE: [SPRING] Query related to SR Architecture

Not sure I understand the context for your requirement.
But to the best of my understanding your requirement does not match MPLS architecture.


Office: +972-39266302
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From: spring [] On Behalf Of Gaurav agrawal
Sent: Wednesday, September 09, 2015 1:38 PM
Cc: Anil Kumar S N (VRP Network BL); Vinod Kumar S 70786
Subject: [spring] [SPRING] Query related to SR Architecture


We would like to have a label stack with only two labels such a way that service label is a top label  and the bottom label would be SR destination node label. This is to make sure each intermediate node perform the specified service based on the top label while reaching the destination.
We would appreciate if anyone could clarify whether SR architecture could allow a service label to be a top label in a label stack.

Thanks and Regards,
Gaurav Agrawal

Mobile: +91-7838700296
Huawei Technologies Co., Ltd.