An overview of Voice Communications over IP

This article gives an overview of voice communications, why IP is a preferred medium to carry voice, basic components involved in setting up voice communications over IP, introduction to IP phones, introduction to IP PBX, introduction to IP Trunks, introduction to Analog/Digital trunks and why Voice Communications over IP is exciting.

Why is voice communications over IP Exciting?

¤ Every company has a LAN network. When the same network is able to handle voice communications – both internal and external, it becomes easy to set up and maintain.
¤ IP is the global standard in data communications. When voice packets are compatible with IP standards, it enables a lot of applications – like integration with email client, sending a voice mail as an mp3 attachment, recording the voice conversations in a server etc.
¤ Most of the offices of enterprises and large organizations are already connected via IP bandwidth for data transfer. This bandwidth could be used for voice as well and hence the cost of internal and long distance communications can be brought down.

Overview of Voice Communications over IP:

Voice has always been synonymous with the single pair copper cable. This has been the medium to carry voice for quite some time. The analogue phones, analogue PBX and analogue voice cables and voice networking are even popular today. But with the increase in the usage of IP networks for data and with the increase in the bandwidth and reliability of such networks, voice is increasingly travelling as data packets in data networks. This is done to reduce costs and enable newer applications. The following are the components used to enable IP Voice Communications over LAN:

Introduction to IP PBX/ Soft switch:

IP PBX / IP Soft switch is the controlling element of voice communications over LAN. The IP phones are registered here, the trunk lines terminate here and the features, facilities, authority, applications etc. are allowed and dis-allowed by the IP switch. It oversees the voice communications that happens in the network. IP PBX are sometimes custom hardware built with an interface to LAN, supporting analog trunks and extensions as well. But some of the IP PBX come in the form of soft switch which can be installed in any server and thereby making the server as the IP Switch. In both the cases, the actual switching of the voice packets are done by the data switches installed in the LAN and not by the IP PBX or soft switch. It is for that reason that every IP phone connecting to the IP PBX should be connected to a single port of the data switch.

Introduction to IP Phones:

IP phones are just like the analog phones but it has an RJ-45 interface jack to connect to the IP network instead of the RJ-11 jack to connect to the telecom network. Most of the IP phones come with a 2-port mini switch inbuilt so that even the PC could be connected through the IP phone itself without the seperate port and cable from the data switch. The IP phone has most of the features of an analog phone like the call pickup, speaker, dialling keys, special keys etc. IP phones are also available as soft phones (software downloaded from the internet) which can be utilized from the PC with a headphone and a mike.

Introduction to IP trunks/ Analog trunks/ Digital trunks:

Analog trunks: Trunk lines are basically required to connect to the external world. To the places outside the organization or the offices. The most common trunk is the analog trunk which is given as a single line from the public telephone exchanges to homes and offices. You can dial out to any phone number (depending on your subscription) through a phone.

Digital Trunks: Digital trunks like ISDN lines and PRI lines are similar to analog trunks and allow you to dial out to other numbers but they generally have more capacity. An ISDN line can handle upto two calls simultaneously and a PRI line can handle upto 30 calls simultaneously. They generally provide multiple services and since they are digital lines, troubleshooting of these lines are easier.

IP Trunks: The IP Data leased lines, Internet leased lines, IPSec VPN’s etc. can also be used as trunks for the IP PBX. The voice calls from the IP PBX travel through the data leased lines to provide voice calls to the various branches that are connected via these leased lines. There are also SIP trunks which provide exclusively voice services over data lines. Even the internet can provide voice services.