Re: [sfc] Some questions about NSH

"Paul Quinn (paulq)" <paulq@cisco.com> Fri, 05 May 2017 17:55 UTC

From: "Paul Quinn (paulq)" <paulq@cisco.com>
To: "ao.ting@zte.com.cn" <ao.ting@zte.com.cn>
CC: "uri.elzur@intel.com" <uri.elzur@intel.com>, "sfc@ietf.org" <sfc@ietf.org>
Thread-Topic: Some questions about NSH
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Date: Fri, 05 May 2017 17:55:11 +0000
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Subject: Re: [sfc] Some questions about NSH
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Hi Ting,

Thank you for the review and comments!

Please see comments below.

Paul

On Apr 18, 2017, at 10:02 PM, ao.ting@zte.com.cn<mailto:ao.ting@zte.com.cn> wrote:

Hi authors，

After I reviewed the NSH draft, I have some questions and comments.

1.Section 4: In Figure 8, I think Classifier should also have function to select SFP, the Classifier need to know how to forward the traffic to the first SFF of the SFP.


In section 2.1, the classifier definition specifies that the classifier delivers the NSH packet to the first SFF.  Bear in mind that the classifier and the SFF are logical, and may be co-resident.



2.Section 7.1: There is a mapping between next hop and transport in every SFF. So the traffic forwarded from one SFF to anther SFF is on a kind of transport tunnel. I think there should be an example to illustrated the packet format from SFF on a transport. That is how to choose a specific tunnel according to the next hop and tranport in Figure 9, so that the packet can be forwarded to right next SFF. And in this part, it is assumed that the NVE( function for tunnel) and SFF are co-located. What if they are split? There is no specification about it. In my opinion, only if SFF forwarding is independent with NVE, so we can say that NSH is agonostic with transport.

We originally had example but the AD and WG agreed that the example did not belong in the main protocol draft, hence they were removed.  There was some interest in companion drafts that depict transport stacks so perhaps that's a place to start?


3.Section 8.2: There are already Metadata Augment and Metadata Update. What about the Metadata Delete? For some cases, one metadata once be used by a SF, and the metadata will not by used anymore, maybe the SF should delete that metadata if it is not useful anymore.

That's a good point and I think it's come up before on list but I'm not certain.  In general, I view delete as a form of update.



Best Regards.
Ting

[sfc] Some questions about NSH ao.ting
Re: [sfc] Some questions about NSH Paul Quinn (paulq)
Re: [sfc] Some questions about NSH ao.ting