PSTN & CPS

[extremum]

Hello ,

I am little bit cofused about CPS  , for example 4431 supports 15 cps  so if I have E1 does it mean it can not handle more then 15 call at the same time .?

Thnks.

[b.winter]

No, the number refers to a call setup rate. So in your case, the router can set up max. 15 new calls per second.
The other number tells you, how many calls can be active max. at the same time.

On 1 E1, you can have max. 30 active calls at the same time.

[Jonathan Schulenberg]

I have not seen Cisco specify a CPS figure for TDM connectivity, only the maximum number of DS0 channels and related DSP requirements. To knowledge, CPS is strictly a CUBE metric. On that topic, CPS is not strictly setup/establishment of new calls though. The real metric, that AFAIK Cisco doesn’t publish, is how many SIP messages per second the chassis CPU can handle before exceeding 70%. CPS is derived from that under several assumptions, chiefly that calls will be connected at least three minutes and require a total of 14 messages total: INVITE, 100, 180/183, 200 OK, ACK, BYE, 200 OK. That’s seven so multiply by two for the two call legs. Every feature you invoke (eg SIPREC) or additional SIP message (eg hold/resume) raises the messages per second number and decreases the effective CPS figure. Under really impressive load requirements it’s worth working through the math with your Cisco TSA and partner SE but most of the time what’s in the data sheet is good enough.