Explanation of call with CCM.

[johnleeee]

Hi all,

I have very basic question.

Could someone explain me way of call

from local network with IP phone to

PSTN.

I know that when I do call from IP phone

to IP phone lacally, call signalization goes to CCM, CCM contacts opposite IP phone and call itself goes only between

both phones.

What Im interested in is how does it function when I want to call number in PSTN. IP phone contacts CCM, CCM contacts

voice gateway and gateway contacts local CO if it is connected for instance with E1(T1). And call is after that routed directly from IP phone to voice GW?

Thanks for help.

BR

jl

[Chris Deren]

Just like you said ip phone to ip phone SCCP signling goes thru callmanager, and RTP goes directly between the phones.

For PSTN call the Geteway is configured either as MGCP or H.323, the MGCP or H.323 goes between the gateway and the CallManager, and SCCP traffic from CallManager to IP phone, the RTP stream goes between IP phone and Gateway. Voice GW converts the voice signaling into your digital or analog signaling such as PRI, CAS, etc.

Chris

[Brandon Buffin]

That is correct. There is an RTP stream setup between the phone and the gateway. This is the VoIP Call Leg. The connection from the gateway to the PSTN is the POTS Call Leg.

Brandon