Functionality of SIP mainly consists of 3 phases.
High-level overview of the 3 phases:
Phase 1: SIP Registration - Phones are registered on the SIP VOIP Server (SIP_Register)
Phase 2: SIP Call Invite - Calls are initiated and phones are ringed/notified (SIP_Invite)
Phase 3: SIP RTP Session - Calls are established and conversations are made before ending the call (RTP)
General Points to note when troubleshooting SIP:
- Identify the IPs of Phones/endpoints and SIP VOIP Server
- Verify access to Phone logs and SIP VOIP Server logs are available
- Allow traffic packet capture (pcap) on Phones/endpoints, SIP VOIP Server and network devices to facilitate analytic/investigation efforts
Tips on troubleshooting SIP Registration:
- Check phones are able to connect and register on SIP server
- Verify phones logs and SIP Server logs that phone is registered successfully
- Perform pcap to analyse the traffic on phone, server, network device to analyse further (look for SIP_REGISTER)
Tips on troubleshooting SIP Call Invite:
- Check phones are registered on SIP Server and SIP invite logs are seen on Phone and Server
- Attempt a phone call and Perform pcap to analyse the traffic on phone, server, network device to analyse further (look for SIP_INVITE)
Tips on troubleshooting SIP RTP Calls (Call Dropped, One-way sound, Jittering, delay...):
- Verify the issue seen (Call Drop, One-way sound, Jittering, delay...)
For Call Drop, perform a pcap of the Call (RTP) and identify the time and events before Call was dropped. Match the events on network devices and identify possible cause (e.g. session timeout, keepalives not seen). Reach out to VOIP vendor for more details, if required.
For one-way sound encountered. perform a pcap of the Call (RTP) and identify the ports used. Disabling SIP ACL or SIP ALG may be considered. Reach out to VOIP vendor for more details, if required.
For Jitterring and Delay, check on Server logs on the timings of the occurrence(s). Perform a pcap as required. QoS and BW Management may be considered/reviewed to resolve this issue.
For additional troubleshooting on SIP issues, we may consider using bypass and/or configure Egress IP to further isolate the issue.
Please reach out to Cato support for more details, if required.