VoIP technology has become very significant these days. Though it has some commonality with the conventional telephone system, however, it offers some added advantages too. It facilitates domestic, local, long distance and international calls and all these at considerably low rates. VoIP technology is consistently progressing with new features and additional benefits.

Switching over to VoIP may result in tremendous call cost cuts along with a more comfortable experience of placing calls. Some attractive features of VoIP telephone system are: Three-way calling, advanced call forwarding, voicemail, speed dialing, caller ID block and last number redial.

VoIP only requires a broadband connection. Each IP phone is identified by an IP address and so it is only the IP address that is needed regardless of wherever the phone is plugged in. This makes the system moveable and flexible. If you make calls from your PC to another PC, then your calls will be free anywhere if the receiver too has VoIP. Therefore, VoIP is exceptionally cheap when compared to traditional telephone services.

However, VoIP has some disadvantages as well. Firstly, it is easy to listen to VoIP phones and make alterations in conversations. Then, when there is power failure, VoIP cannot work as it runs by power.

Despite these drawbacks, the advantages stand out far more prominently in terms of both cost and features making it a viable system of providing phone services.

Pic from: http://www.flickr.com/photos/camknows/3726757043/

Latency (also referred to as delay) is the time that it takes a packet to make its way through the network to the terminating device. In other words, latency is the time it takes the speaker’s voice to reach the listener’s ear. While large latency values do not necessarily degrade the sound quality of a phone call, they can disrupt the rhythm of conversation, making it difficult to interact.

Several factors contribute to latency in a multiservice network, including:

• The time it takes for the endpoints to create the packets used in voice services, known as packet creation latency
• The time it takes to serialize the digital data onto the physical links of the interconnecting equipment
• The time it takes an electrical (or photonic) signal to travel the length of a conductor, known as propagation delay
• The time that a packet remains buffered in a network element while it awaits transmission, referred to as the queuing delay
• The time it takes a network device (router, switch, firewall, etc.) to buffer a packet and make the forwarding decision, known as packet forwarding delay.

When designing a multiservice network, the total delay that a signal or packet exhibits is the sum of all the latency contributors. Generally, it is accepted that the end-to-end latency should be less than 150 ms for toll quality phone calls. The remainder of this section describes some basic steps network managers can take to assess and mitigate the impact of each latency contributor in a multiservice network.

Source: Juniper Networks, Inc. White Paper