[rbridge] Final outcome of outer VLANtagsonRBridge-RBridgepackets?

[Anoop Ghanwani]

Silvano,

I am not opposed to using per-VLAN connectivity
detection (which we're saying should be done by
hellos) if it is shown to be absolutely essential.
As long as there is a way around it, I prefer to
avoid having to send them.

We should probably delay the decision until
we understand what scenarios make it an absolute
requirement before we make it such.

Anoop

> -----Original Message-----
> From: rbridge-bounces at postel.org 
> [mailto:rbridge-bounces at postel.org] On Behalf Of Silvano Gai
> Sent: Wednesday, October 24, 2007 10:13 AM
> To: Eastlake III Donald-LDE008
> Cc: Developing a hybrid router/bridge.
> Subject: Re: [rbridge] Final outcome of outer 
> VLANtagsonRBridge-RBridgepackets?
> 
> 
> 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