[afnog] ATM vs POS

Mark Tinka mark.tinka at seacom.mu
Sat Jan 12 20:16:03 UTC 2013

On Friday, January 11, 2013 09:05:19 AM Frank Habicht wrote:

> Hi,
> just to confirm / accelerate,
> can an ATM card like Cisco NM-1A-OC3-POM
> (http://www.cisco.com/en/US/docs/ios/12_4/12_4_mainline/a
> tm_oc3.html)
> be used to connect to a "normal" STM-1 circuit, with IP
> transit provider (upstream) at the other end, where we
> presume they use a POS interface?

Frank, POS is an alternative to ATM; so no, it won't work. 
POS will typically be used for Layer 2 protocols such as 
PPP, HDLC and Frame Relay.

ATM is a Layer 2 protocol unto itself, which can also run 
over SDH or SONET transmission networks. However, one would 
expect that for it to work, both ends of the circuit would 
need to run ATM. Assuming you're connecting to a service 
provider on the "other side", I'd be hard-pressed to hear of 
anyone still offering IP services over ATM - although I'm 
certain they do still exist :-).

With regard to efficiency, I'd recommend not wasting your 
time with ATM if you can help it. It will hit your IP 
throughput massively.

Try as much as you can to stick with either POS or Ethernet.


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