FEATURE VOIP
An Overview of VoIP Technology, and Why it is Here to Stay The King is Speech By Giuseppe Venturini, Voispeed
VoIP stands for Voice over Internet Protocol and the acronym is commonly used to include all technologies enabling voice communication over IP networks. Most people are more familiar with VoIP as the technology used to ‘make a phone call using the internet’. Most telephone traffic is already
Prior to founding VOIspeed Limited, Giuseppe Venturini worked in innovation management consulting within the Cambridge industry cluster, helping technology companies to commercialise their intellectual property on international markets. With over 15 years of telecoms industry experience he advised SMEs and larger companies like Rolls Royce, MBDA and EADS Astrium to establish
strategic partnerships to launch new technologies.
routed over IP networks. Audio signals from more traditional analogue phones or legacy telephone systems are often converted into digital packets at some stage in the network and transferred over an IP backbone. In the past, a business’s telephone
system would most likely be connected to the PSTN (Public Switched Telephone Network) using either an analogue line or digital (ISDN) line. Both options are ‘circuit-switching’ connections meaning that for the entire duration of a phone conversation there are network resources that are entirely dedicated to the phone call, which nobody else can use. The important contribution brought
by VoIP technology is that it enables users to share network resources so that more than one phone call can be sustained on the same physical circuit. This concept of resource sharing is important in order to understand why VoIP offers significant cost savings to businesses who adopt it. For instance, all rental costs for network resources (e.g. copper wires, optical fibres, switches, routers, etc.) can be divided between many customers. Another advantage is that often there is no need for an engineer to go on-site to install additional lines, since most businesses already have at least one internet connection. So, the advantages of VoIP include:
Number portability: if you move office the number will move with you. Geographical presence: your office may be based in Aberdeen but you can have a London number. Reduced tariffs: by sharing the same IP resources the same connection can be used by multiple users, therefore reducing rental and call costs. Flexibility: phone lines can be added in no time and without an engineer visiting your office However, there are also some
disadvatages. The quality of voice calls can be negatively affected by
16 NETCOMMS Volume I, Issue 4 2011
poor broadband connection. It is also crucial to have a PBX with failover on traditional lines (ISDN or analogue) or by using a second broadband connection. There is a price to pay for sharing
the same resources. Whereas with a traditional telephone line the physical resource is fully dedicated to the phone call, with VoIP it is almost impossible to fully allocate network resources to each call. VoIP is a ‘Best-Effort’ service and it is not by chance that this wording is often present in the agreements with VoIP service providers. It is important that anybody adopting this technology understands that not all VoIP services are the same and there is a cost associated with achieving a higher level of service. Better quality tends to cost more as more network resources must be allocated. However, thanks to large economies of scale, VoIP is cheaper than traditional lines as the size of the installation grows.
Factors affecting VoIP quality
How physical resources are allocated to each user on an IP network is important. As a general guideline, the quality of a VoIP phone call is closely related to the quality of the broadband used. Some important parameters to
consider when assessing a broadband line include download and upload speed. The upload speed is often a bottleneck factor for VoIP on ADSL. It is also important to note that the bandwidth will tell you the maximum number of simultaneous calls that the DSL line can sustain, but will give very little information about their expected quality. Distance from the internet exchange is also important, as the signal degrades with distance. In addition, The lower the contention-ratio (for ADSL connections) is, the better. A lower priority level for ADSL2+ connections also corresponds to lower contention. Finally, low latency is also desirable.
VoIP technology enables users to share network resources, so that more than one phone call can be sustained on the same physical circuit.
www.netcommseurope.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60