VoIP uses SIP (Session Initiation Protocol), a peer-to-peer technology that allows computers to communicate with each other without having calls routed through some central station. Therefore, calling from one SIP enabled phone to another cuts call charges drastically.
The Asterisk System comes with an Asterisk server which manages things like teleconferencing, voice mails, queues and hold music. The hard phone is a digital phone that has an Ethernet jack to communicate with the server using the SIP protocol. They, including the wireless version, are not very expensive. The soft phone are implemented in software and can be attached to a PC. Asterisk runs predominantly on Linux, an open source operating system.
Cisco has telephony solutions that are network based and run on a router. They are scalable and work well in multi-user environments in mulitple locations. The UC500 suite is a bundle of services like router, switches, security, telephony and wireless functionality in a single device. This greatly reduces costs for a company which is planning on these services. The Cisco CallManager Express uses SIP to connect phones through the Internet and also has the features of UC 500 making it more viable for medium scale businesses. Additonal features are paging, intercom, ICMP and class of restrictions on a user's calls.
Avaya IP Office uses IP technology to deliver voice and data communication, messaging and customer management over multiple locations with 2 to 300 people. It allows you to work from anywhere, host conferences, integrate applications, measure and improve customer satisfaction at the touch of a button. It is cost effective as it lowers long-distance calls, conferencing fees, supports remote workers and helps keep your business collaborated and up-to-date.
The three products can be compared based on the following few criteria:
• Number of extensions: Asterix can support upto 100 extensions while Cisco and Avaya can go upto 360 extensions thereby suporting large organizations as well. This improves the scalability and helps to reduce costs in the long run.
• Freeware: Asterisk is freeware and runs on a Linux server. This makes the telephony solution cheaper than either Cisco or Avaya which make extensive use of routers and switches for communication.
• Installation and maintenance: Asterisk is a programmer's dream as it is open source and can be changed at his will. However, for an end-user, it may be a nightmare. Support and services are better with Cisco and Avaya which are established names in the industry.
The main thing going for Asterisk is its cost. However, it is not always advisable to look at the initial cost of things. Other criteria like scalability, integrating of one device with others already existing, interoperatability and long run costing should be considered while choosing one product over another.