Gateways

Scenario#41 – No Ringback tone from H323 Gateway going to SIP trunk

One of our customer reported an issue with ring back tone when calling their Contact center. I made a test call and observed that as a caller when you call their main Contact center number all you hear is dead silence and then when agent picks up the phone you could hear them talk. ThereContinue reading “Scenario#41 – No Ringback tone from H323 Gateway going to SIP trunk”

Hair-pinning Or redirecting a call from Gateway

There are times when you would like to forward a call coming into your gateway out to PSTN before it goes to Call manager. Reason could be WAN outage to Call managers or Call manager down situation. This is how you can route out an incoming call out of the gateway. Let suppose the mainlineContinue reading “Hair-pinning Or redirecting a call from Gateway”

Scenario#34 – Cannot make International Calls from US gateway

One of our customer has multiple sites across the globe including sites in UK and US. Their initial design was to send all UK calls from US over a SIP trunk to break out from a UK gateway for LCR (least cost routing). For some reason they stopped using that trunk and configured local dialContinue reading “Scenario#34 – Cannot make International Calls from US gateway”

Scenario#32 – SIP Calls drop after 75 minutes

I had an interesting case where SIP calls over a SIP trunk were dropping after like 75 minutes. The duration was not confirmed as sometimes it use to drop even before 75 minutes. I looked into few CCSIP debugs (debug ccsip messages) and found that the ‘BYE’ message was actually coming from our end (CallContinue reading “Scenario#32 – SIP Calls drop after 75 minutes”

Scenario#31 – Calls over ICT have delayed Voice

I had an interesting case last week where calls over ICT trunk would connect but then either party will not hear each other for 8-10 seconds. The issue was first reported from US users trying to reach UK users over an Inter-cluster trunk (Non-GK). Both clusters had two call managers version 8.0.3. The whole issueContinue reading “Scenario#31 – Calls over ICT have delayed Voice”

Applying QoS for Voice Traffic

QoS is very important for Voice traffic which is delay sensitive. I won’t go into details of QoS over here and will just explain the configuration we normally use on a Voice gateway for QoS. class-map match-any Voice-RTP match ip precedence 5 match ip dscp ef match ip rtp 16384 16383 class-map match-any Voice-Cntl matchContinue reading “Applying QoS for Voice Traffic”

Scenario#29 – Interworking error -0x80FF

I came across this issue with one of our customer last week where a call was coming in to receptionist at Site ‘A’ but she was not able to transfer the call to someone at Site ‘B’. They had Centralized deployment and all phones on branch sites were registered to Central site. The call wasContinue reading “Scenario#29 – Interworking error -0x80FF”

Scenario#27 – RightFax Server not working – MGCP

I had an interesting scenario where customer logged a case with us regarding their RightFax server not working. Those of you who don’t know what is a RightFax server can read about it here. When you dial the fax number from outside, it reaches the gateway and you hear one ringback and then a fastContinue reading “Scenario#27 – RightFax Server not working – MGCP”

Scenario#24 – SIP Calls drop after Silence

Came across a complex situation where customer was using this SIP trunk as an alternative to ISDN-30 (if all channels are used or if ISDN goes down). The ISDN-30 link was working fine but they had issues on SIP trunk (how many times I have heard this?) …. their outbound calls over SIP were usingContinue reading “Scenario#24 – SIP Calls drop after Silence”

DSP, PVDM & Media Resources

The Cisco High-Density Packet Voice Digital Signal Processor (DSP) Module (PVDM2) enables Cisco Integrated Services Routers to provide high-density voice connectivity, conferencing, and transcoding capabilities in Cisco IP Communications solutions. PVDM stands for packet voice DSP module; it is the Cisco product name for the module that provides digital signal processing resources to a system.Continue reading “DSP, PVDM & Media Resources”