Networking Protocols

Updated By Patrik Weiland

Uppdaterad May 14th, 2021

Below are the protocols used by equipment supplied by Telavox, as well as a description of their functionality. Different terminal types use different protocols so, for example, while HTTPS is preferred over TFTP and HTTP for downloading software, there are cases where the terminal does not support HTTPS where the other protocols are used instead. Telavox does not recommend blocking traffic to and from terminals based on ports and / or protocols, but that you rather choose to trust all traffic to and from the Telavox network. Please note that Telavox does not commit to only using the protocols mentioned below in the future. 

Note: that the ports listed are receiver ports. As a rule the equipment uses randomly selected sender ports.


File Transfer Protocol, RFC959, TCP ports 21 and 20. Used to retrieve terminal configuration and software.


Domain Name Server, RFC1035, TCP / UDP port 53. DNS functionality is part of a functioning IP network and the terminals provided by Telavox will not work if they do not have access to a working DNS.

In cases where the DNS server is located outside the firewall, the firewall must be configured to allow the terminals to make DNS lookup requests against it.

Our provisioned phones are configured with Google's DNS and


Hyper Text Transfer Protocol, RFC2616, TCP port 80. Used to retrieve terminal configuration and software. Normally, no special configuration is required for HTTP to work satisfactorily.


Hyper Text Transfer Protocol over Secure Socket Layer, RFC2818, TCP port 443. Used to retrieve terminal configuration and software as well as Softphone Telavox Desktop.


Trivial File Transfer Protocol, RFC1350, UDP port 69 and dynamically allocated ports for data transfer. Used to retrieve terminal configuration and software.


Simple Network Time Protocol, RFC1305 / RFC1361, UDP port 123. Used to set the time / clock in the terminal.


Session Initiation Protocol, RFC3261, UDP port 5060, websocket / tcp. Used to connect up and down calls. SIP traffic goes between our SIP server and the phone. This is by far the most important protocol for your telephony to work. 


Real Time Transfer Protocol, RFC1889, UDP port 1024-65535 (Telavox uses UDP port 10,000-20,000). During a call the sound goes via RTP. The port used is randomized when a call is initiated. All supplied Telavox terminals use symmetrical RTP, which means that the receiver and sender ports for the RTP stream are the same for both incoming and outgoing audio streams. This means that the audio stream that goes from the terminal to us opens the session in the firewall to allow incoming voice streaming over the same session.


Real Time Control Protocol, RFC3550, UDP port 1024-65535. Some terminals generate RTCP packets used in the communication between RTP endpoints to convey local statistics and call data such as information about jitter and any packet loss.

WSS websocket

WSS used by the softphone "Telavox desktop" port 8443 against "push servers" and port 443 for SIP.