Home Technology What Is Voice Over IP?

 

What is it?

Voice over Internet Protocol, other names it goes by - VoIP, IP Telephony, Internet Telephony, Broadband Telephony and Voice over Broadband - is the routing of voice transmissions (generally telephone conversations) over the Internet or any other IP based network. There are 2 general methods to achieve this technology, either by using SIP or H.323, the most common of which is the SIP (Session Initiation Protocol). This technology is not to be confused with Skype or MSN Messenger, both of which have Voice capabilities (MSN does indeed have SIP capabilities) but are generally known as "closed proprietry systems" (meaning they won't interoperate with other SIP based hardware / software).

Session Initiation Protocol (commonly known as SIP) is used for the set-up (and breakdown) of sessions between one or more participants and can be used to create two-party, multiparty or multicast sessions (including, but not limited to telephone calls and conferencing). SIP was designed to run independantly of the underlying transport layer, therefore it can run over TCP, UDP or SCTP. This approach enables SIP to interoperate with other signalling protocols making it much more flexible then it's brother H.323.

How does it work?

Being an application in its own right, SIPs main purpose is to help session originators deliver invitations to potential session participants wherever they maybe. In less than 20 words, that is SIPs role. However there are two fundamental assumptions which need to be highlighted at this point.

Resusing existing protocols

SIP was designed to specifically reuse as many existing protocols and protocol concepts. For example SIP was modelled after the well known protocol HTTP, using URLs for addressing and legible error codes (remember that annoying 404?) along with SDP (Session Description Protocol) to convey information.

Maximising interoperability

With the reuse of existing protocols, SIP was also designed to be compliant in such a way that it could interoperate and bind to existing applications, such as e-mail and Web Browsers. SIP does this by limiting itself to a modular philosophy - just like many other common internet protocols, thereby focusing on a specific set of functions.

Myths of VoIP

As with any technology that it still "young" (for want of a better phrase) there's always postive and negative comments on it. Perhaps you've been a commentator on an emerging technology yourself? Well this section should dispel any myths surrounding Voice over IP that you may (or may not) have heard.

• Myth: VoIP isn't widely used
  
  • Truth: Although traditional phone systems are still the norm amongst businesses the majority of long-distance calls, and most mobile carriers are already using an IP backbone to carry calls. Industry experts tell us:
    • In 2005, orders for IP PBX systems surpassed sales for traditional TDM PBXs
    • By 2008, fifty percent of small to medium sized businesses in the US alone will be using VoIP
    • Simultaneously, the UK penetration will reach a similar level
    • More than 95% of Global Companies will have begun a programme of IP convergance by 2010

• Myth: You'll have to dump your current phone system to be able to fully utilise the benefits of VoIP
  • Truth: Manufacturers have developed a range of products to enable a gentle migration path from legacy PBXs to Voice over IP
    • Your business can still use the features that you are used to in the Legacy PBX system and still keep the existing desk handsets until they fall apart (the phones that is, not the employees!) and still take advantage of the cost benefits of using a VoIP gateway. The smartest applications can determine the best path for a particular call, on a per call basis

• Myth: Cost benefits only apply between VoIP Providers or similar systems
  • Truth: Calling other VoIP phones on a service plan is free between users on the same provider, and you can call any phone and save versus traditional charges
    • Your IP Phone (or IP-PBX) does not prohibit you from calling devices of any other type (landline, mobile, or satellite). Internet Service Providers (ISPs) offer myriad plans that include everything from flat monthly charges for unlimited calls to a schedule of charges for international calls to metered calls by the minute; even prepaid privileges. With your own IP Telephony network you have an almost unlimited choice of compatible services

• Myth: The sound quality of VoIP connections isn't as good as what I have at present
  • Truth: Depending on the codec (or compression program for voice converted to data on your system), sound quality can be significantly better than that of traditional telephony
    • Where traditional telephony transmitted sound as electrical signals, Voice over IP samples your voice hundreds of times per second and transmits the information digitally. It's possible (with the right decompression and sound reproduction equipment) to approach the sound available on MP3 or CD players.
    • The voice quality you get through a quality digital signal processor (DSP) is almost always better than that of conventional long distance calls.

• Myth: VoIP services are unreliable. The network or power can go down at anytime and leave my business without phones
  • With a DSL or cable connection, traffic congestion can still cause service issues at this stage in the technologies development. Power cuts do happen. Maintaining a traditional line (or lines) for emergencies is still a good practice.
  • A properly engineered network and Quality of Service providers can enhance call quality, prioritise voice traffic and minimise problems. Still, it doesn't hurt to have the benefits of a converged voice and data network, whilst keeping a traditional telephony backup (belt and braces anyone?). No matter which ISP you choose, any system you adopt should include provisions for a "lifeline" to the traditional PSTN (public switched telephone network).
  • Consider the impact of traditional telephony systems spread across the business in multiple locations. Resiliency and survivability can be better supported by IP Telephony than by traditional PBXs. Normally if Site B fails, B is normally cut off, with a Voice over IP system Site B can still operate via Site A

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