[nsp] Re: Per VLAN Stats on MSFC2 - Complaints from the Field

[Gert Doering]

Hi,

On Thu, Nov 20, 2003 at 06:13:47PM -0500, Anthony Cennami wrote:
> If you want to bill accurately, bill off the Layer 2 ports; that's what 
> is always churning the traffic.  I've not looked at the accuracy on a 
> scientific level, but I've never found what I believed to be a serious 
> discrepency when billing/polling the physical ports.

The difference comes when you have a customer VLAN with multiple machines,
happily talking to each other (think "SQL server" or "backup"), but your
contract says "only traffic leaving the VLAN is billed".

So you can either buy a dedicated switch per routed VLAN, and bill on
the link between the single port on your Cat6500 and the dedicated switch
(which sounds like "somebody didn't understand VLAN technology"), or you
get some decent piece of hardware that can count frames on L3 interfaces.

[..]
> The reporting of the Layer 2 and 3 devices, virtual or otherwise appears 
> to be correct; I argue that Cisco attempting to 'populate' the SVI 
> counters with information they are actually not seeing would be 
> 'breaking' the implementation.  Remember folks, we're talking about 
> multi layer switching/routing here; the SVI isn't processing all of the 
> traffic and should not lie and say that it is.

As mentioned before: so what?  On a flow based engine (as "old" MLS is):
just export the flow data from the L2 engine to the L3 part as soon as the
flow is expired.  Not exactly rocket science.

gert
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Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de