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Hi Igor,



On Tue, Mar 21, 2017 at 10:02 PM, Duarte Cardoso, Igor <
igor.duarte.cardoso at intel.com> wrote:

> Hi Vikash,
>
>
>
> It’s best to start with RFC 7665.
>
>
>
> NSH decouples traffic forwarding from both the internals of packets and
> service functions. A special entity called SFF will take on that job. L2/L3
> then become something that the SFF might have to deal with it.
>

​which means it can co-exist with (L2/L3 insertion mode) and not
necessarily mutually exclusive.
​


> However, networking-sfc API doesn’t expose or require details about
> individual SFC dataplane elements such as the SFF… it is up to the
> backend/driver to know those low-level details.
>

​Agree.

> ​
>

>
> NSH doesn’t classify and forward traffic itself. It’s only a header that
> identifies what and where in the chain the packet belongs to/is (plus other
> goodies such as metadata). Classifier will classify, SFF will forward.
>

​   I was referring to NSH in totality and not excluding SFF (
https://tools.ietf.org/html/draft-ietf-sfc-nsh-12). Look like I extended
the scope of NSH in term of  SFC. ​


>
>
>
>
> By the way, I left a question on the tap blueprint whiteboard, I’ll copy
> it here too:
>
> “Is there a use case for "tap chains"? I.e. not only you send traffic to
> your tap function, but then your tap function also sends traffic to a next
> hop too, so a full chain starts after traffic gets tapped at the first
> chain (the first chain also continues).”
>
> I suppose the answer is no since you mentioned “Note - TAP SFs do not
> forward packet”, but I’m happy to hear extended info about this – from
> anyone reading.
>
>
>
> Best regards,
>
> Igor.
>
>
>
> *From:* Vikash Kumar [mailto:vikash.kumar at oneconvergence.com]
> *Sent:* Tuesday, March 21, 2017 3:32 PM
> *To:* OpenStack Development Mailing List (not for usage questions) <
> openstack-dev at lists.openstack.org>
> *Subject:* Re: [openstack-dev] [networking-sfc] About insertion modes and
> SFC Encapsulation
>
>
>
> Hi,
>
>    Moving definition of SF from port-pair to port-pair-group looks good.
>
>    TAP is also an insertion mode like L2/L3 but since it simplifies to
> keep 'tap-enabled' field also in port-pair-group, so it should be fine from
> implementation point of view (Note - TAP SFs do not forward packet). TAP
> enabled and L2/L3 insertion mode should be mutually exclusive.
>
>    According to IETF draft NSH can classify & forward traffic (correct ?)
> but then the draft assumes uniformity of working of devices (which IMHO
> refers L3) which doesn't cover the entire use case. Can insertion mode
> (L2/L3) & traffic encapsulation(NSH) co-exist also ?
>
>
>
>
>
>
> On Mon, Mar 20, 2017 at 11:35 PM, Cathy Zhang <Cathy.H.Zhang at huawei.com>
> wrote:
>
> Hi Igor,
>
>
>
> Moving the correlation from port-pair to port-pair-group makes sense. In
> the future I think we should add all new attributes for a SF to
> port-pair-group-param.
>
>
>
> But I think L2/L3 is different from encap type NSH or MPLS. An L3 type SF
> can support either NSH or MPLS. I would suggest the following:
>
>
>
> port-pair-group (port-pair-group-params):
>
>                 insertion-mode:
>
>                                 - L2
>
>                                 - L3 (default)
>
>                Correlation:
>
>                                 - MPLS
>
>                                 - NSH
>
>                 tap-enabled:
>
>                                 - False (default)
>
>                                 - True
>
>
>
> Thanks,
>
> Cathy
>
>
>
> *From:* Duarte Cardoso, Igor [mailto:igor.duarte.cardoso at intel.com]
> *Sent:* Monday, March 20, 2017 8:02 AM
> *To:* OpenStack Development Mailing List (not for usage questions)
> *Subject:* [openstack-dev] [networking-sfc] About insertion modes and SFC
> Encapsulation
>
>
>
> Hi networking-sfc,
>
>
>
> At the latest IRC meeting [1] it was agreed to split TAP from the possible
> insertion modes (initial spec version [2]).
>
>
>
> I took the ARs to propose coexistence of insertion modes, correlation and
> (now) a new tap-enabled attribute, and send this email about possible
> directions.
>
>
>
> Here are my thoughts, let me know yours:
>
>
>
> 1.       My expectation for future PP and PPG if TAP+insertion modes go
> ahead and nothing else changes (only relevant details outlined):
>
>
>
> port-pair (service-function-params):
>
>                 correlation:
>
>                                 - MPLS
>
>                                 - None (default)
>
> port-pair-group (port-pair-group-params):
>
>                 insertion-mode:
>
>                                 - L2
>
>                                 - L3 (default)
>
>                 tap-enabled:
>
>                                 - False (default)
>
>                                 - True
>
>
>
> 2.       What I propose for future PP and PPG (only relevant details
> outlined):
>
>
>
> port-pair (service-function-params):
>
>                 <remove correlation – reasons outlined in [3] and below>
>
> port-pair-group (port-pair-group-params):
>
>                 mode:
>
>                                 - L2
>
>                                 - L3 (default)
>
>                                 - MPLS
>
>                                 - NSH
>
>                 tap-enabled:
>
>                                 - False (default)
>
>                                 - True
>
>
>
> With what’s proposed in 2.:
>
> - every combination will be possible with no clashes and no validation
> required.
>
> - port-pair-groups will always group “homogeneous” sets of port-pairs,
> making load-balacing and next-hop processing simpler and consistent.
>
> - the “forwarding” details of a Service Function are no longer dictated
> both by port-pair and port-pair-group, but rather only by port-pair-group.
>
>
>
> Are there any use cases for having next-hop SF candidates (individual
> port-pairs) supporting different SFC Encapsulation protocols?
>
> I understand, however, that removing correlation from port-pairs might not
> be ideal given that it’s a subtractive API change.
>
>
>
> [1] http://eavesdrop.openstack.org/meetings/service_chaining/
> 2017/service_chaining.2017-03-16-17.02.html
>
> [2] https://review.openstack.org/#/c/442195/
>
> [3] https://github.com/openstack/networking-sfc/blob/
> 17c537b35d41a3e1fd80da790ae668e52cea6b88/doc/source/system_
> design%20and_workflow.rst#usage
>
>
>
> Best regards,
>
> Igor.
>
>
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>
>
>
> --
>
> Regards,
>
> Vikash
>
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>


-- 
Regards,
Vikash
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