SIP

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”

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”

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#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”