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
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
Stephen, Cisco doesn't have a lot of ATM stats avaiable yet. We have been beating the ATM developers to try to get better stats.. but no luck yet. We have had a lot of problems the way the SAR chip accounts for VBR traffic.. and they don't even do CBR. The output/input counters on the interfaces are not valid ways of measuring traffic either, they don't take ATM Traffic shaping into account. This is because the interface counters are calculated before the actual SAR chip segments/reassembles the ATM Cells. This can be proven by using an ATM traffic generator and flooding the interface... According to the interface stats I was pushing over 200 mb through and OC-3. I wish!! So, in a nutshell, there isn't a real good way to measure performance/effieciency on a Cisco.. yet. Eric _______________________________________________________ Eric D. Madison - Senior Network Engineer - ACSI - Advanced Data Services - ATM/IP Backbone Group 24 Hour NMC/NOC (800)291-7889 Email: noc@acsi.net On Thu, 10 Jul 1997, Stephen Balbach wrote:
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
participants (3)
-
Chris A. Icide -
Eric D. Madison -
Stephen Balbach