Protocol The protocol used for VoIP services is SIP (as described in RFC 3261), which uses specific ports and protocols that must be enabled to use the service correctly. The VoIP service works both on standard port 5060 and 5061 (usable when the former is disabled). Codec The voice carried by the VoIP protocol uses encryption mechanisms (defined by the "codec") that can be changed for any communication, according to the protocol negotiations between the 2 heads of the call. The codec used determines the bandwidth that will be allocated to the phone call. The codecs supported by the VoIP-KQI service and the bandwidth used in every communication (including overhead, that is, the bandwidth used for reporting data and headers), are: | Codec | Kb/s | | G.711 | 87.2 | | G.729 | 31.2 | | iLBC | 27.7 | |