IP Telephony
What is it?
IP telephony is an aggregate term referring to the group of technologies that allow the transmission of voice using Internet protocol (IP) networks. Internet protocol has gained worldwide prominence and has become the de facto data transmission standard today, therefore using this protocol to transmit voice means taking advantage of the existing infrastructure and integrating voice with numerous applications.
Lexatel designs and implements end-to-end solutions based on IP telephony, and because of the flexibility and open standards, each IP telephony solutions in unique. Usually we consider 3 major types of IP telephony solutions: LAN, multi-site and Internet, described in more detail below.
LAN Based Solutions
LAN, which stands for Local Area Network, means your office or home IP network. Usually it is implemented in a concentrated area (entire floor or a complete building). This means that:
- cabling is protected
- distances are short
- throughput is anywhere between 10 and 1000 Mbps
- the entire network is managed in a centralized manner.
In other words, this is a network which, if managed well, will provide ample capacity, low variability and hence high quality of the telephony service that runs on top of it.
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| IP telephony implementation over the office IP network (inside dotted line). In this scenario the outgoing calls are sent via traditional telephone lines. | Both inside the office LAN and the outgoing lines are based on IP. This eliminates the need for gateway equipment which connects traditional and IP telephony environments. |
LAN based IP telephony carries virtually no risk:
- It cuts costs because it uses standard network equipment and eliminates the need for parallel telephony infrastructure.
- It has solid quality, as local network is usually stable and has enough capacity.
- It can grow painlessly farther beyond any traditional telephony implementation.
- Internal IP telephony implementation still leaves all options open on how to send your outbound traffic to the world -- via the traditional phone company or via an IP telephony service provider.
Multi-site Solutions
Multi-site solutions are in fact implementations where two or more geographically separate offices are connected via an IP route and thus send traffic among extensions inside each site without passing through the traditional telephone network.
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| Offices A and B are connected via an IP line. One office is connected to an IP Telephony service provider, the other to a traditional. This setup has three advantages: 1. Redundancy. If one outgoing line goes down, the other provides backup. 2. Least cost routing. Some destinations (typically international) are routed via the IP telephony provider while the local and national go via the traditional phone company. 3. No incremental investment in redundancy, because both nodes operate in an "active-active" mode. |
Benefits from multi-site solutions:
- Cost saving -- such architecture eliminates all telephony charges for calls between the sites
- No fancy technology - the sites can be connected using standard network equipment
- Take advantage of the pooling effect -- concentrate all outgoing traffic through one point -- thus you do not need to have monthly charges for half-idle phone lines at each office. Rather you can aggregate traffic through the phone lines of one central office which are busier and therefore give better allocation per minute of your fixed monthly line-rental costs.
- Spread the risk -- you can have a mirror installation (e.g. PBX, GW, etc.) and in case one fails, the other one takes over immediately. What's more you can have both nodes in "active-active" mode.
- Least cost routing -- if you choose to have two outgoing pipes, use different providers and route the traffic accordingly.
The IP route between the offices can be either a dedicated point-to-point IP line or simply the public internet.
IP Telephony over Public Routes
Unlike the two scenarios described above, here part of the traffic is routed via public IP networks. For example:
- Two remote offices exchange voice calls, each one connected via its own Internet connection (and not with a dedicated point-to-point IP line)
- One office is connected with its IP Telephony provider via the public Internet (e.g. a small office on ADSL).
The only reason why this scenario is singled out, is that public internet may introduce variance, which in its turn will affect the quality of voice. Public internet has lower price, so for applications where quality of the phone calls may bear variance or where the internet line is consistently stable, it might make more business sense to go down that route, especially for small offices.