The Dial Fusion system uses two different protocols, known as SIP and IAX, to communicate with the Zoiper softphone running on the agent computers as well as with our phone providers. Both technologies work in a similar fashion but with slight differences between the two.
SIP stands for Session Initiation Protocol. This protocol communicates over UDP port 5060. SIP is the older of the two protocols. SIP provides more detailed diagnostic information when troubleshooting problems. It also uses standard HTTP status codes to communicate the status of a request as opposed to IAX which has its own set of status codes. SIP also provides more information about the agent's computer to the Dial Fusion servers when used. SIP is the default protocol for new agent setups and is what Dial Fusion uses to communicate with its carriers. SIP is a universal protocol which can be used between the vast majority of VoIP systems and providers.
IAX stands for Inter-Asterisk eXchange. This protocol communicates over UDP port 4569. IAX is a newer protocol and uses slightly less bandwith than SIP does when communicating. This protocol also communicates through a NAT better than SIP does. However, this protocol provides less logging and diagnostic ability when compared to SIP. Dial Fusion uses IAX as a secondary connection method when an agent PC has trouble with SIP, and also to connect calls internally between the agent servers.
The Dial Fusion team may make a recommendation to switch from one protocol to another if we notice an agent PC is having trouble connecting to the system under the current protocol. However, customers may not make this change on their own, a Dial Fusion team member has to change the registration protocol on the servers before the Zoiper settings can be updated.