Voice over Internet Protocol, or VoIP, architecture consists of end-user devices, gateways, gatekeepers and the IP network. The software for VoIP is a collection of programs, applications and protocols to manage the architecture. The significance of VoIP software is underlined by the increasing demand for higher quality of service from consumers. Effective software programming translates into effective management of callsin terms of routing of the calls through the least congested pathsand clarity of voice.

VoIP software can be classified according to the different functionalities in the VoIP network. These functionalities include the management of user interfaces, call processing, network management and billing. User interface software handles the interface to the user of IP telephone. The important features of the user interface include algorithms to compress voice data, echo cancellation and encryption.

Call processing servers are run by software to map the destination of the call. The software is a database program called soft switch. The software translates the phone number into a unique IP address after checking the validity of the number. It connects the two devices on both ends, after alerting the called party of the incoming call through a ring.

Call administration software, called consoles, are applications that manage the state of the calls and the distribution. This software provides bandwidth management. Some of the standard protocols are H.323 session initiation protocol. In order to maintain the quality of service, real time protocol (RTP) is employed. The software also manages the networks.

Some of the customer-oriented services managed by software are billing services. This includes pre- and post-paid services. Some provide voicemail services that synthesize voice for mails. IP soft phones are managed by software that lets the user directly connect with the VoIP provider through a computer. Skype software is rapidly capturing the market with millions of phone minutes.

Another area where software provides services is in the call-monitoring systems for call offices to manage the calls and Computer telephony Integration for businesses.

Software development is accelerated by the need to solve various issues such as loss of packets and sequencing of packets.