1. Suitable data connection
- Minimal bandwidth both up and down per voip call: >100Kbit/s
- Latency: <70ms
- Jitter: <10ms
- Packet loss: <0,5%
2. Suitable router
- User friendly webportal
- Option to enable remote access
- No VoIP/SIP functionality enabled on router
- No POTS/PSTN ports
- No Active firewalls
- No SIP stacks (Software that simulates ATA on modems)
- No SIP-ALG
3. The right configuration
- The NAT should be symmetric and NAT keep Alive on the phone should be switched on (4-byte packet, NOTIFY or OPTIONS)
- In case of NAT the SIP packet should, upon arrival at the registrar, contain IP addresses following the rfc1918 range in the following places: 1st Via header, Contact header and All c= addresses in the SDP.
- Do not allow Fragmented packets
- Have the ability to set up QOS on all (network) devices so that VoIP traffic is given priority.
- Firewall: Allow port 5060 and 8060. All traffic goes over UDP. (allow both inbound and outbound)
- Firewall: RTP is used for the transport of the audio data. The traffic can come from any IP address. Many times the voip device dictates which range is being used. In a firewall, this can therefore only be filtered by the local destination port, not on the remote IP. Configure your phones and/or firewall with two ports per concurrent call and allow inbound and outbound traffic to / from these ports to / from any IP address (0.0.0.0/0). RTP is using exclusively UDP (1024 - 65535)
- Firewall: Always block inbound and outbound http/https ports to phones.
- Check the attendant console and/or voip phone logs and make a brief summary of your findings.
- Make a pcap trace and a brief summary of your findings
5. Check for existing problems
- Check our helpcenter for existing problems, solutions and workarounds.
Escalation IPerity Support
- If conditions 1–5 are met please provide a report of these points. Also include the following data.
- Client name
- From which number is dialed
- To which number is dialed
- Date & Time (24 hour format and timezone)
- Exact steps to reproduce the issue
- Possible screen recording / movie of the behaviour
- Precise version of any hardware, firmware and software used (phone, browser, device)
Email this to: firstname.lastname@example.org