[65311] in North American Network Operators' Group
Re: [nsp] Re: Per VLAN Stats on MSFC2 - Complaints from the Field
daemon@ATHENA.MIT.EDU (Anthony Cennami)
Thu Nov 20 18:14:35 2003
Date: Thu, 20 Nov 2003 18:13:47 -0500
From: Anthony Cennami <narziss@cdardn.net>
To: Hudson Delbert J Contr 61 CS/SCBN <Delbert.Hudson@LOSANGELES.AF.MIL>
Cc: 'Gert Doering' <gert@greenie.muc.de>,
Nanog Mailing list <nanog@merit.edu>,
"Robert A. Hayden" <rhayden@geek.net>, cisco-nsp@puck.nether.net
In-Reply-To: <29F6FAF7F2C0D41190980002A513591E07513C52@FSNSAB30>
Errors-To: owner-nanog-outgoing@merit.edu
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 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.
Hudson Delbert J Contr 61 CS/SCBN wrote:
> cisco long ago made the decision that counting packets was NOT as important
> processing them. i've seen this thread in discussions about IOS since
> Version
> 9. they arent going to change the methodology right now because we need to
> bill off
> of it. why use the overhead involved with passing info about L2 to L3
> if 'train is still moving the cattle'. who cares?
>
>
> ~v/r
> Del Hudson
> 61CS/SCBN - LAAFB NCC
> Network Architecture & Engineering Group
> delbert.hudson@losangeles.af.mil
>
>
>
> -----Original Message-----
> From: Gert Doering [mailto:gert@greenie.muc.de]
> Sent: Thursday, November 20, 2003 1:43 PM
> To: Anthony Cennami
> Cc: Nanog Mailing list; Robert A. Hayden; cisco-nsp@puck.nether.net
> Subject: Re: [nsp] Re: Per VLAN Stats on MSFC2 - Complaints from the
> Field
>
>
> Hi,
>
> On Thu, Nov 20, 2003 at 12:52:02PM -0500, Anthony Cennami wrote:
>
>>This is because in 1996 you were likely not dealing with 'Switch
>>Routers'; today's 'routers' perform some form of flow switching/caching,
>>meaning once the traffic enters the VLAN routed interface and an
>>appropriate path is found it is sent down the the Layer 2 fabric.
>
>
> This is all nice and shiny, but having shortcuts doesn't mean "the L2
> fabric can't export the resulting numbers up to the L3 brain".
>
> They just botched it. Counters and Cisco boxes seem to be fundamentally
> incompatible.
>
> gert
