Re: [Detnet] L2/L3 model?

Hi Norm,
Interesting viewpoint. Please see my comments inline:

B.R.
Frank

> -----Original Message-----
> From: detnet [mailto:detnet-bounces@ietf.org] On Behalf Of Norman Finn
> (nfinn)
> Sent: Wednesday, November 19, 2014 8:16 AM
> To: Erik Nordmark; detnet@ietf.org
> Subject: Re: [Detnet] L2/L3 model?
> 
> Catching up on my email.
> 
> I agree most definitely that we want to explore arbitrary combinations of
> L2/L3, with paths including any combination of routers and bridges.
> 
> Without going too deep into MPLS/Pseudo-wire topics, let me point out that
> what the bridges need is a pair {VLAN, multicast destination MAC address}
> that uniquely identifies the flow to which the Ethernet frame belongs (at
> least among the packets seen by that bridge).  The bridges don’t care
> whether MPLS is present in the frame or not.  So, if the routers can apply a
> {VLAN, MAC address} to the packet that will be handled by a bridge, then the
> routers can switch on the MPLS labels and the bridges on the Ethernet stuff.	
[Frank] : I agree above analysis from aspect of data plane handling. But IMO the key points of hybrid L2/L3 network for DetNet is about resource allocation and path computation in control plane. And I think we already achieve a rough sync in the thread. 

> 
> Note that MPLS labels can go end-to-end, or as close to the ends as you want
> them to go, as is normal for MPLS; you don’t need to get rid of MPLS when
> going through the bridges.
[Frank] : I have no idea about the reason of using of MPLS label. Can you clarify me?

> 
> How close this gets to the Talker and Listener is another matter, and we can
> talk about that in another message.
> 
> — Norm
> 
> -----Original Message-----
> From: Erik Nordmark <nordmark@acm.org>
> Date: Monday, November 17, 2014 at 10:11 AM
> To: "detnet@ietf.org" <detnet@ietf.org>
> Subject: [Detnet] L2/L3 model?
> 
> >
> >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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> >detnet@ietf.org
> >https://www.ietf.org/mailman/listinfo/detnet
> 
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