ATM vs. DS3

Thu Jul 10 20:36:05 UTC 1997

We go direct Cisco <-> Cisco DS3, no switch. Any variables to measure on the 
Cisco, assuming you only have access to 1 side?

On Thu, 10 Jul 1997, Chris A. Icide wrote:

> We monitor both the octet output of the cisco, and the received cells
> on our ATM switch.  One then would divide the cisco octet value by the 
> cell value * 53.  This would result in a percentage value that would
> indicate your "efficiency".
> 
> Efficiency (%) = octet rate / (cell rate * 53)
> 
> This assumes that you can measure both parameters.
> 
> Chris A. Icide
> Sr. Engineer
> Nap.Net, L.L.C.
> 
> -----Original Message-----
> From:	Stephen Balbach [SMTP:stephen at clark.net]
> Sent:	Thursday, July 10, 1997 3:07 PM
> To:	Ben Black
> Cc:	Karl Denninger; Chris A. Icide; 'Josh Beck'; nanog at merit.edu
> Subject:	Re: ATM vs. DS3
> 
> 
> Question: On a Cisco with an AIP card, how do you determain what the 
>           overhead is? We connect to our upstream provider via ATM.
> 
> .stb
> 
> On Thu, 10 Jul 1997, Ben Black wrote:
> 
> > i've never heard anything *less* than 20% loss in ATM overhead.
> > 
> > On Wed, 9 Jul 1997, Karl Denninger wrote:
> > 
> > > On Tue, Jul 09, 1996 at 10:38:57PM -0500, Chris A. Icide wrote:
> > > > On Wednesday, July 09, 1997 9:34 PM, Josh Beck [SMTP:jbeck at connectnet.com] 
> > > > wrote:
> > > > > Hello,
> > > > > 	I just thought of something. We are in the process of purchasing a
> > > > > 4 Mb CIR from another backbone. Now, we have the choice of ATM or standard
> > > > > T3 delivery (over a DS3 either way). Now, if we get ATM, that 4 Mb CIR
> > > > > turns into:
> > > > >
> > > > > [ (53-5)/53 ] * 4 Mb/s = 48/53 * 4 Mb/s = 3.62 Mb/s
> > > > 
> > > > Emperical data shows that we are currently losing about 20.5% of capacity
> > > > to IP over ATM overhead on fairly aggregated traffic.  This means that *IF*
> > > > your new connection is being measured as 4Mbps of cell bandwisth, you
> > > > will only be getting 3.18Mbps.  You may want to verify from the company
> > > > providing this link what exactly are they limiting you to?
> > > > 
> > > > btw, the extra overhead is lost in things like the last cell of a packet not
> > > > being full, etc.
> > > > 
> > > > Chris A. Icide
> > > > Sr. Engineer
> > > > Nap.Net, L.L.C.
> > > 
> > > My God, someone admits it?
> > > 
> > > I've used 20% as the general ATM overhead now for almost two years, and have
> > > been poo-pooed by lots of people claiming that it wasn't anywhere near that
> > > bad.
> > > 
> > > Funny how it all comes out in the end. :-)
> > > 
> > > --
> > > -- 
> > > Karl Denninger (karl at MCS.Net)| MCSNet - The Finest Internet Connectivity
> > > http://www.mcs.net/~karl     | T1's from $600 monthly to FULL DS-3 Service
> > > 			     | 99 Analog numbers, 77 ISDN, http://www.mcs.net/
> > > Voice: [+1 312 803-MCS1 x219]| NOW Serving 56kbps DIGITAL on our analog lines!
> > > Fax:   [+1 312 803-4929]     | 2 FULL DS-3 Internet links; 400Mbps B/W Internal
> > > 
> > 
> 