Home page logo
/

nanog logo nanog mailing list archives

RE: ATM vs. DS3
From: "Chris A. Icide" <chris () nap net>
Date: Thu, 10 Jul 1997 15:57:25 -0500

I've heard (but have not verified) that Cisco has included
this capability via SNMP in at least one implementation of
their IOS code.  Perhaps someone may know if this in fact is
true, and what version(s) of IOS may contain this feature.

Chris

-----Original Message-----
From:   Stephen Balbach [SMTP:stephen () clark net]
Sent:   Thursday, July 10, 1997 3:36 PM
To:     Chris A. Icide
Cc:     Ben Black; Karl Denninger; Chris A. Icide; 'Josh Beck'; nanog () merit edu
Subject:        RE: ATM vs. DS3


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 () clark net]
Sent: Thursday, July 10, 1997 3:07 PM
To:   Ben Black
Cc:   Karl Denninger; Chris A. Icide; 'Josh Beck'; nanog () 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 () 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 () 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






  By Date           By Thread  

Current thread:
[ Nmap | Sec Tools | Mailing Lists | Site News | About/Contact | Advertising | Privacy ]
AlienVault