Subject: [sfc] forwarding clarification on draft-ietf-sfc-offloads

From: "Kent Leung (kleung)" <[email-masked]>
Date: Mon, 17 Jul 2017 13:29:12 +0000

Hi. The draft-ietf-sfc-offloads describes bypassing SF for flow offload. Skipping a hop requires service index (SI) to be decremented by SFF.  But this is not covered in the draft. Currently, SFC architecture is based on SFF forwarding based on service path ID and SI (which is only decremented by SF or SFC Proxy).

draft-ietf-sfc-nsh:

Service Index (SI): provides location within the SFP.  The initial
   classifier for a given SFP SHOULD set the SI to 255, however the
   control plane MAY configure the initial value of SI as appropriate
   (i.e., taking into account the length of the service function path).
   Service Index MUST be decremented by a value of 1 by Service
   Functions or by SFC Proxy nodes after performing required services
   and the new decremented SI value MUST be used in the egress NSH
   packet.

Should the draft be updated with description on how the flow is forwarded through the service path? Should SFF decrement the SI? Or some other method to support offload?

Kent

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From: Kyle Larose <[email-masked]>
Date: Mon, 17 Jul 2017 13:41:01 +0000

What if the SFF had a hidden "virtual" SF located inside it? Or is that stretching things too much...

From: sfc [mailto:[email-masked]] On Behalf Of Kent Leung (kleung)
Sent: Monday, July 17, 2017 6:59 PM
To: [email-masked]
Subject: [sfc] forwarding clarification on draft-ietf-sfc-offloads

draft-ietf-sfc-nsh:

Kent

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From: "Kent Leung (kleung)" <[email-masked]>
Date: Mon, 17 Jul 2017 13:48:28 +0000

Hi Kyle. I personally think that's not stretching too much. Actually, there are various use cases that would require a "virtual SF" like function in SFF. Please see draft-wang-sfc-receive-only as one of the use cases. In that draft, the "Extended SFC Proxy" is performing the SI decrement and packet copy. This function is typically collocated in SFF. So I like your thought process ... :)

Kent

From: Kyle Larose [mailto:[email-masked]]
Sent: Monday, July 17, 2017 3:41 PM
To: Kent Leung (kleung) <[email-masked]>; [email-masked]
Subject: RE: forwarding clarification on draft-ietf-sfc-offloads

From: sfc [mailto:[email-masked]] On Behalf Of Kent Leung (kleung)
Sent: Monday, July 17, 2017 6:59 PM
To: [email-masked]<mailto:[email-masked]>
Subject: [sfc] forwarding clarification on draft-ietf-sfc-offloads

draft-ietf-sfc-nsh:

Kent