2 Voice over IP Network VOIP, Version 1.6e T.O.P. BusinessInteractive GmbH Page 1 of 8
2.1 VoIP Network Elements...3 2.2 Single-Site VoIP Location...4 2.3 Multi-Site VoIP Location...5 2.4 PBX Networking via IP...6 2.5 PBX Migration towards VoIP...7 2.6 VOIP and ISP...8 VOIP, Version 1.6e T.O.P. BusinessInteractive GmbH Page 2 of 8
2.1 VoIP Network Elements In order to create a Voice over IP infrastructure, three basic components are needed. The end user needs an IP phone, also known as terminal. This can either be an IP phone or an IP client installed on user's PC. The centre element is an IP public branch exchange server (IP-PBX server) together with a gatekeeper. They are responsible for connection request management and switching. Finally, a gateway is needed as a third component to establish a packet-oriented connection between the IP network elements and the Public Switched Telecommunication Network, PSTN. Additionally, a Multi-point Control Unit, MCU, can be implemented to support voice and video conferences with more than two terminals. VOIP, Version 1.6e T.O.P. BusinessInteractive GmbH Page 3 of 8
2.2 Single-Site VoIP Location A company's organizational structure strongly determines the requirements for an IP-PBX. A single site location only requires a stand-alone solution with one central IP-PBX server and gateway. The IP-PBX hosts all subscriber data whereas the gateway connects the company to the legacy PSTN or to other IP networks. An integration of the IP-PBX with an existing standard PBX creates no problems for the IP-PBX hardware. VOIP, Version 1.6e T.O.P. BusinessInteractive GmbH Page 4 of 8
2.3 Multi-Site VoIP Location Multi-site solutions have different requirements for a convergent infrastructure. Both, IP-PBX and gateway have to support multi-site environments. This could lead to dedicated IP-PBX servers and gateways at each location. All components are interconnected all the time to constantly align server data and states as a common numbering plan and common phone directory are used. For cost efficiency reasons, the IP-PBX servers route the call as long as possible within the IP network and deliver the call to the PSTN as close as possible to its final destination. Additionally, the IP gateways must support dialling-in from any PSTN signaling point to any branch office and call delivery to the PSTN gateway according to a least cost routing plan in order to save costs. VOIP, Version 1.6e T.O.P. BusinessInteractive GmbH Page 5 of 8
2.4 PBX Networking via IP The interconnection of legacy PBXs in different branch offices using a company intranet is a major domain of IP-based telephony. One of the most significant features is the independence from any time-based cost structures and the parallel use of resources for data traffic. Hence, IP-based PBX networking provides a lot of economic advantages. A Voice over IP gateway is the heart of IP networking. It compresses a synchronous stream of speech data, encapsulates these speech data in IP packets and transmits them with a low data rate via the packet-oriented IP network. This transmission is a transparent one, with the gateway neither analyses the signaling info nor making any routing decisions. From the PBX's view, the gateway only acts as an additional switching node. VOIP, Version 1.6e T.O.P. BusinessInteractive GmbH Page 6 of 8
2.5 PBX Migration towards VoIP Many companies own a quite powerful legacy PBX infrastructure with long-term service agreements and a defined period for capex depreciation. Therefor, it is uneconomic to put it out-of-service and replace it by new IP-PBX equipment. In many cases, IP-PBXs are used to complement an existing PBX, also known as "PBX migration towards VoIP". A gateway is used to connect the local area network to the existing internal telephone network. Step by step, different departments are equipped with IP-PBXs as a subset of the existing switchboard and with IP phones instead of standard terminals. Branch offices and home offices can be integrated easily using IP-dial-in access to the company' s network. As IP telephony is accepted by the users, new extensions are activated directly within the IP- PBX. Step by step, the legacy PBX can be replaced totally by the IP-PBX using teh company's experience with the new technology and with copeing network load problems or system break-down periods. VOIP, Version 1.6e T.O.P. BusinessInteractive GmbH Page 7 of 8
2.6 VOIP and ISP Internet services providers (ISPs) have already achieved a good position in a tough market fighting for end users. Unfortunately, the ISPs' margins have gone down as the fight for subscribers has been price-driven and is still continuing. Hence, value added services are badly need to assure additional revenue. This services could include access to non-data communication, e.g., voice and fax services. This requires an upgrade of the backbone infrastructure to be able to support this kind of service and assures a proper connection to the PSTN using the gateways used. VOIP, Version 1.6e T.O.P. BusinessInteractive GmbH Page 8 of 8