Subject: Re: [Pce] Comments on draft-wu-pce-traffic-steering-sfc

From: Qin Wu <[email-masked]>
Date: Tue, 17 Mar 2015 06:30:31 +0000

FYI.

发件人: Qin Wu
发送时间: 2015年3月17日 12:01
收件人: 'Ron Parker'
抄送: Dhruv Dhody
主题: RE: Comments on draft-wu-pce-traffic-steering-sfc

Hi, Ron:
Thanks for your valuable comments. See my reply inline.

-Qin
发件人: Ron Parker [mailto:[email-masked]]
发送时间: 2015年3月17日 5:32
收件人: Qin Wu
主题: Comments on draft-wu-pce-traffic-steering-sfc

In section 5.2.1, the format incudes the SFP ID and the Service Index.   But this is a message from PCE to PCC (presumably the classifier).

[Qin]:Correct.

What does the index mean in that context?

[Qin]: The index is used to count the number of service provided by service function chain, When it is carried in the SFC encapsulation, it can further be used by SFF to provide location within the service path. We will add some text to clarify this in the next update.

Also, could you define or give more background on “PLSP-ID” in the SPI definition?

[Qin]:Okay, how about add the following text under the LSP Object format in the draft:
“
The PLSP-ID is a PCEP-specific identifier for the LSP. It is set to a
   value that is constant for the lifetime of the PCEP session. A PCC
   creates a unique PLSP-ID for each LSP and will advertise the same PLSP-ID
   on all PCEP sessions it maintains at a given times. The
   values of 0 and 0xFFFFF are reserved.
”
Is the PCC expected to “know” a priori the full sequence of SFF’s and SFI’s associated to a Service Path ID?    Or should that be conveyed in the message between PCE and PCC dynamically?

[Qin]: In case SFC forwarding is fully distributed, PCE only needs to compute the full sequence of SFF corresponding to SFP ID based on the source address and destination address specified in the END- POINTS object of PCE message. The full sequence of SFF can be carried using Explicit Route Object.

The classifier only needs to know how to map traffic to the specific SFP.
full sequence of SFI’s associated to a Service Path ID seems not needed for the case when SFC forwarding is fully distributed.

If PCC is expected to “know” a priori the full sequence of SFI’s associated to a Service Path ID, PCC can use segment routing approach proposed in draft-dw-pce-service-segment-routing<http://tools.ietf.org/id/draft-dw-pce-service-segment-routing-01.txt> and  draft-ietf-pce-segment-routing<http://tools.ietf.org/wg/pce/draft-ietf-pce-segment-routing/> to determine a explicit path traversing by SF for the traffic. Yes, full sequence of SFI can be conveyed in the message between PCE and PCC.
Alternatively, PCC as classifier can interact with SFC controller to get full sequence of SFI’s.

Is the PCC expected to concretely select the RSP ID (i.e., which SFI’s exactly) and if so, how does that factor into the approach?

[Qin]: If PCC is expected to concretely select the Rendered Service function Path, I think we can rely on service segment approach proposed in draft-dw-pce-service-segment-routing<http://tools.ietf.org/id/draft-dw-pce-service-segment-routing-01.txt> combining with the mechanism proposed in draft-wu-pce-traffic-steering-sfc and segment routing approach defined in draft-ietf-pce-segment-routing<http://tools.ietf.org/wg/pce/draft-ietf-pce-segment-routing/>.

Thanks.

    Ron