Re: [Detnet] L2/L3 model?

In my view the PCE will be both a L3 and L2 PCE but L3 will get services from L2 to establish a path based on the circuit constraints. They could be many L2 parameters that do not need to be exposed to L3 and and in my view this L2/L3 interface is the key but against this is my humble view and we are at the start of this discussion with wise open minds.
Trying to blend the L2/L3 in a single path computation might be very difficult. Having said that the L3 and L2 topology DB could be unified

Sent from my iPhone

> On Nov 18, 2014, at 8:28, "Pascal Thubert (pthubert)" <pthubert@cisco.com> wrote:
> 
> I do not think so Philippe.
> 
> I do not see the PCE talking only to L3 devices and let the L3 devices set up a path through a UNI interface. The PCE needs to know the capabilities and topology of all the hops, so as to guarantee an optimized path.
> Whether a hop is L2 or L3 is actually a secondary artifact from that perspective; and in practice, I expect that the L3 TSN switching will often be L2.5,  MPLS or TSCH.
> From the detnet and the 6TiSHC meetings, I gathered that:
> - the IETF is forming a TEAS WG that would define a Yang data model for topologies. We could probably extend that.
> - we could extend PCEP to configure and maintain the paths and related state info if we use the model whereby the PCE talks individually to the intermediate nodes
> - OTOH, if we decide to set up the path hop-by-hop using a source-route indication computed by the PCE, then CCAMP may become useful, to be monitorind for new work just being started.
> 
> Cheers,
> 
> Pascal
> 
> 
>> -----Original Message-----
>> From: detnet [mailto:detnet-bounces@ietf.org] On Behalf Of Philippe Klein
>> Sent: mardi 18 novembre 2014 07:15
>> To: Anca Zamfir (ancaz); Erik Nordmark
>> Cc: detnet@ietf.org
>> Subject: Re: [Detnet] L2/L3 model?
>> 
>> Ana,
>> Thank you for your question.
>> In my humble view I am not sure we must create a single heterogeneous view of
>> the network. It seems to me that we must keep both topology separated and  let
>> the L3 ask the L2 to create a path with the given QoS (delay, jitter, bw...AND
>> REDUNDACY if needed) constrains.
>> 
>> /Philippe
>> 
>> 
>> -----Original Message-----
>> From: Anca Zamfir (ancaz) [mailto:ancaz@cisco.com]
>> Sent: Monday, November 17, 2014 9:32 PM
>> To: Philippe Klein; Erik Nordmark
>> Cc: detnet@ietf.org
>> Subject: Re: [Detnet] L2/L3 model?
>> 
>> Hi Philippe,
>> My understanding is that QoS (delay, jitter, b/w, etc) must be guaranteed for the
>> end-to-end path, whether the path spans L3 only, L2 only or a mixture. One
>> solution would be for PCE to get the L2 and L3 island topologies (yes, make PCE
>> work at L2 with SPB + extensions which is new) and create a single
>> heterogeneous view of the network. Once the path is computed, PCE can
>> determine how the different segments (could be TE LSPs in L3 or multicast
>> groups for L2) should be created. I think PW-s (if
>> used) would be carried inside these segments and it would be good to only
>> expose the label at the termination point (listener or the node that eliminates
>> the duplicates). This is to avoid having to do stitching.
>> There are other possibilities to explore, with some (like where L2 and L3 islands
>> independently establish these paths) I am struggling with the end-to-end
>> guarantee.
>> 
>> thanks
>> -ana
>> 
>>> On 11/17/14 8:02 PM, "Philippe Klein" <philippe@broadcom.com> wrote:
>>> 
>>> Erik,
>>> In my humble view, the L3 must only indicate the L3 router path over of
>>> the L2 island with its path attributes  and let the L2 protocol select
>>> the constrained path.
>>> Essentially the inner L2 topology could be ignored by the L3.
>>> 
>>> /Philippe
>>> Broadcom
>>> 
>>> Sent from my iPhone
>>> 
>>>> On Nov 17, 2014, at 20:11, "Erik Nordmark" <nordmark@acm.org> wrote:
>>>> 
>>>> 
>>>> After the BoF I realized there was one thing we didn't talk about
>>>> which is what combined L2 and L3 topologies that folks have in mind.
>>>> It is true that from a packet forwarding perspective both L2 and L3
>>>> have queues and clocks, but the interaction with the control plane and
>>>> the approach might be different for different forms of combinations.
>>>> 
>>>> First of all we have 6TISCH which is an L3-only network.
>>>> 
>>>> But in combined L2/L3 networks we could have at least
>>>> - interconnecting L2 islands using L3
>>>> - arbitrary topologies with mixtures of L2 and L3 forwarding devices
>>>> 
>>>> A suggestion (at the mike during the BoF) was to consider pseudo-wires.
>>>> That might make sense when interconnecting L2 islands.
>>>> But with arbitrary topologies one could end with with a path that as
>>>> a mixture of bridges and routers e.g.
>>>> 
>>>>    Sender - B1 - B2 - R1 - B3 - B4 - B5 - R2 - R3 - Listener
>>>> 
>>>> Are there use cases that result in such topologies/paths?
>>>> 
>>>> Would one need one controller which is aware of both the L2 and L3
>>>> devices and can pick paths (with resources) that include both?
>>>> (Typically we separate the layers thus we might have a PCE which sees
>>>> the L3 topology but not the L2 devices in between the routers.)
>>>> 
>>>> I think it would be good to explore the combined L2/L3 use cases and
>>>> models in more detail.
>>>> 
>>>>  Erik
>>>> 
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