Subject: SLAAC for 1:1 VLAN model

From: Erik Nordmark <[email-masked]>
Date: Tue, 14 Sep 2010 18:23:50 -0700

I've finally caught up on the discussion about rs-mark and the N:1 VLAN 
model. One of the key technical issues is how a SLAAC host recovers 
should its three RS messages be lost.

Can someone explain to me how this works with SLAAC in the 1:1 VLAN model?

It seems like the router would need to find out which VLANs are in use, 
so that it can multicast a RA for all those VLANs, because the host gave 
up after sending three RSs.

Is that how it would work? Or is 1:1 VLAN as problematic as N:1 with 
rs-mark when it comes to handling SLAAC?

    Erik

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From: Ole Troan <[email-masked]>
Date: Wed, 15 Sep 2010 08:00:37 +0200

> I've finally caught up on the discussion about rs-mark and the N:1 VLAN model. One of the key technical issues is how a SLAAC host recovers should its three RS messages be lost.
> 
> It seems like the router would need to find out which VLANs are in use, so that it can multicast a RA for all those VLANs, because the host gave up after sending three RSs.
> 
> Is that how it would work? Or is 1:1 VLAN as problematic as N:1 with rs-mark when it comes to handling SLAAC?

in the 1:1 model the router will just advertise prefixes in RAs like on any other link.
there is a one to one mapping between VLAN and customer. imagine a VLAN modeled as an interface.

cheers,
Ole

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From: [email-masked]
Date: Wed, 15 Sep 2010 08:21:58 +0200 (CEST)

> there is a one to one mapping between VLAN and customer. imagine a VLAN modeled as an interface.

(not commenting on rs-mark, just the 1:1 VLAN model)

Indeed. And the router needs to send out an individual RA per interface.
So a router aggregating 20.000 customers will need to send out 20.000
RAs on a regular basis.

The 1:1 VLAN model is used a fair amount in DSL deployments, often
combined with VLAN stacking to get the necessary scaling. Having each
customer on his own interface (no common broadcast domain) is in many
ways very nice.

Steinar Haug, Nethelp consulting, [email-masked]

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From: Erik Nordmark <[email-masked]>
Date: Wed, 15 Sep 2010 11:11:58 -0700

> So a router aggregating 20.000 customers will need to send out 20.000

So the router is configured to know all the VLANs up front?
Or does the router somehow get notified when the customer on VLAN X 
brings up their DSL line?

The reason I'm asking is if there is a notification mechanism, couldn't 
that notification mechanism also be used to provide notifications for 
the N:1 VLAN model?

    Erik

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From: [email-masked]
Date: Wed, 15 Sep 2010 20:37:37 +0200 (CEST)

> brings up their DSL line?

Both models are used:

- All VLANs configured up front (static configuration),
- A notification mechanism (often involving a PPPoE/Radius login) which
results in the necessary interface being created dynamically.

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From: Tom Taylor <[email-masked]>
Date: Wed, 15 Sep 2010 15:53:04 -0400

... and notifications via ANCP if that is running.

On 15/09/2010 2:37 PM, [email-masked] wrote:
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