[rbridge] Final outcome of outer VLAN tagsonRBridge-RBridgepackets?

[Silvano Gai]

Donald,

My concern is misconfiguration.

If we don't send at least a simple Hello per VLAN misconfigurations go
undetected and can cause frame duplication.

See also my latest reply to Anoop: we don't need to send an LSP.

Whatever scheme that sends frames only on one VLAN cannot detect VLAN
misconfiguration by definition.

We have a simple and tested solution: "Let's send Hellos on all VLANs
for discovery and LSP only on one VLAN."

This solves the issue of Anoop, of not sending multiple LSPs.

Let's use it

-- Silvano

P.S. I'll not be able to make the December TRILL meeting, since it is at
the same time as T11/FCoE. Dinesh can present a slide set with the most
important issues related to misconfiguration.



> -----Original Message-----
> From: Eastlake III Donald-LDE008 [mailto:Donald.Eastlake at motorola.com]
> Sent: Tuesday, October 23, 2007 1:46 PM
> To: Silvano Gai
> Cc: Developing a hybrid router/bridge.
> Subject: RE: [rbridge] Final outcome of outer VLAN tagsonRBridge-
> RBridgepackets?
> 
> Hi Silvano,
> 
> I have two questions:
> 
> (1) What exactly is the problem you see with doing adjacency on one
> VLAN? It could be that you think that Hellos on one VLAN would be OK
but
> it is too much of a configuration burden to expect network
> administrators to figure out which VLAN and to then configure their
> Rbridges. Or it could be that you think that even if each port on each
> Rbridge was configured to the "best" single VLAN, the adjacencies
found
> would be too sparse compared to those potentially possible. Or you
could
> think that both of these and/or other things are the main problem...
> 
> (2) If multiple Hellos on different VLANs, or some other technique,
are
> used to learn the full VLAN connectivity, what are Rbriges supposed to
> do when no single VLAN will get to all the desired destinations? For
> example, assume that Rbridge-A is connected as follows:
> 
> 	On VLAN 2 to B and C
> 	On VLAN 3 to C, D, and E
> 	On VLAN 4 to F, G, and H
> 	On VLAN 5 to D, E, F, and G
> 
> If Rbrdige-A wants to send a multi-destination frame to all of B
through
> H, it would seem that it has to send it at least three times to get to
> all the one-Rbridge-hop destinations and to avoid duplication. For
> example, multicast on VLANs 3 and 4 and unicast to B. Or,
alternatively,
> multicast on VLANs 2 and 5 and unicast to H. Or, if the complexity
> exceeds some threshold, Rbridge-A could just forget about optimality
and
> unicast the frame separately to B through H.
> 
> How would you suggest handling such situations?
> 
> Thanks,
> Donald
> 
> -----Original Message-----
> From: rbridge-bounces at postel.org [mailto:rbridge-bounces at postel.org]
On
> Behalf Of Silvano Gai
> Sent: Tuesday, October 23, 2007 6:21 AM
> To: Anoop Ghanwani; Radia Perlman; Developing a hybrid router/bridge.
> Subject: Re: [rbridge] Final outcome of outer VLAN
> tagsonRBridge-RBridgepackets?
> 
> I want to restate that IMHO a design that sends messages on a single
> VLAN is so week to be completely useless.
> 
> I met Anoop on a plane back from a T11 meeting and we discussed the
> issue of sending messages on all the configured VLANs. Anoop pointed
out
> that, if these messages are ISIS messages, this can overload the
RBrige
> supervisor.
> 
> We identified a possible solution based on two different message
types:
> - ISIS used on a single VLAN to compute adjacency
> - simple per-VLAN checking on all the VLANs to verify reachability.
> 
> The second kind of messages is much simpler and therefore they load
less
> the RBrige supervisor. In the future, per-VLAN checking can be
> implemented by the port ASIC. This seems a viable solution that
requires
> design effort, but it is promising.
> 
> Without the per-VLAN checking, running ISIS on a single VLAN holds
water
> like a pasta-strainer.
> 
> -- Silvano
> 
> 
> > -----Original Message-----
> > From: rbridge-bounces at postel.org [mailto:rbridge-bounces at postel.org]
> On
> > Behalf Of Anoop Ghanwani
> > Sent: Monday, October 22, 2007 11:01 AM
> > To: Radia Perlman; Developing a hybrid router/bridge.
> > Subject: Re: [rbridge] Final outcome of outer VLAN tags onRBridge-
> > RBridgepackets?
> >
> >
> > If we want to make implementations work with
> > only a single Hello for all VLANs than the
> > option is (a).  I think that is what it should be.
> > Basically, as a part of RBridge configuration
> > there should be a "RBridge Control VLAN" configuration
> > that applies to the whole device.  It should default
> > to VLAN 1, but an operator can choose to change it.
> > A RBridge only emits Hellos on that VLAN.  If it
> > receives Hellos on any other VLAN that should
> > be detected as an error condition and reported.
> >
> > There have been some problem corner cases that
> > have been pointed out previously on the list
> > that may result in temporary duplication of
> > traffic when there is misconfiguration.  Those
> > should be documented.
> >
> > Anoop
> >
> > > -----Original Message-----
> > > From: rbridge-bounces at postel.org
> > > [mailto:rbridge-bounces at postel.org] On Behalf Of Radia Perlman
> > > Sent: Saturday, October 20, 2007 9:47 PM
> > > To: Developing a hybrid router/bridge.
> > > Subject: [rbridge] Final outcome of outer VLAN tags on
> > > RBridge-RBridgepackets?
> > >
> > > I'm not sure I understood the final consensus on what we
> > > should do for outer VLAN tags on inter-RBridge packets.
> > >
> > > The possibilities I think the consensus might have been are:
> > >
> > > a) only use VLAN 1, explicit tag, no configuration possible.
> > > b) default is VLAN 1, explicit tag, configuration is possible
> > > to change sending with VLAN tag(s) something other than 1. If
> > > this is what was decided, I don't believe we've worked out
> > > the design details. I'd assume this would mean RBridges
> > > should be willing to receive packets from other RBridges
> > > regardless of outer VLAN tag. Would we then mark in the
> > > Hellos what VLAN tag(s) you've heard from what other RBridges
> > > with? What do we do with multicast if there isn't a single
> > > VLAN tag that seems to work to send to everyone? Would we
> > > allow configuration to send on a set of VLAN tags, or just on
> > > one at a time (and we allow configuration to say which one it is)?
> > >
> > > Certainly a) is simpler. If the consensus was b), we'd better
> > > work out the details.
> > >
> > > Radia
> > > _______________________________________________
> > > rbridge mailing list
> > > rbridge at postel.org
> > > http://mailman.postel.org/mailman/listinfo/rbridge
> > >
> >
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> > rbridge at postel.org
> > http://mailman.postel.org/mailman/listinfo/rbridge
> 
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