Voice over IP, or just VoIP as it is commonly known, is a series of technologies and communication protocols to enable voice traffic to be transmitted of an IP (Internet Protocol) network. IP networks were developed to enable computers from different manufacturers to communicate with each other using a common “language”. The internet is an enormous IP network which allows all types of different data devices to successfully communicate with each other. Indeed a significant proportion of the population of the planet use the internet to communicate. With the development of VoIP technologies, the internet can now also be used to communicate using the human voice.
Cisco is a global networking company and was founded in 1984, employs over 70,000 personnel worldwide and has sales of over $40 billion. The Internet was literally built in large part using Cisco routers and switches so when it comes to networking, Cisco are the experts and world leaders. Cisco uses the term IP telephony rather than the more generic term VoIP. Before IP telephony and the GSM (Global System for Mobile Communications) network used by mobile phone providers, all telephone calls had to travels over the public switched telephone network (PSTN) which is usually owned and run by one provider per country and so therefore they tend to hold a monopoly. In the UK this was obviously BT although Kingston Communications were given the rights to cable up Hull and if you live in HULL you are therefore forced to use Kingston instead of BT.
With the emergence of the mobile phone providers using the GSM network, there was a cost effective alternative to using landlines to make telephone calls. However because licenses had to be purchased from the government to operate as a mobile provider and because the infrastructure had to be built covering the vast majority of the UK, there were large cost barriers to entry. In the UK there are only five providers, Vodafone, o2, Orange, T-mobile and 3.
IP telephony or VoIP lowers the barriers to entry significantly. No licenses have to be purchased to become a provider of VoIP services and the infrastructure costs are significantly lower because the calls use the internet. Therefore over the last few years there has been an explosion of companies offering VoIP services. With increased competition usually comes lower prices and therefore cost savings for the customer. Typically our customers find a 20% decrease in the phone charges when they move from BT to a VoIP providers like VoIP.co.uk.
The most common protocols used in providing a VoIP service are H.323, Media Gateway Control Protocol (MGCP), Session Initiation Protocol (SIP), Real-time Transport Protocol (RTP) and Inter-Asterisk eXchange (IAX). However the two protocols that are probably gaining the greatest traction are SIP and RTP. These two protocols work together to delivery VoIP.
SIP is a signalling protocol used to set up the call between the two end points. It is an application layer protocol and can run on TCP (transmission control protocol) or UDP (user datagram protocol). It is a text-based protocol in a similar way to HTTP (hypertext transfer protocol). Once the call has been established between the two end points, the media stream needs to be created to actually carry the voice. For this RTP is used. Of course the human voice is analogue and therefore to be transmitted over a digital medium like an IP network, it needs to be digitised. To do this a codec is used to encode the voice payload and turn it into a data packet. There are many different codecs but two of the most popular are G.711 and G.729. Without going into all the details of these codecs and how an analogue signal is digitised, it is sufficient to know that the main difference between these codecs is the size of the payload. The G.711 is a larger payload and therefore requires more bandwidth whereas the G.729 is a smaller payload and so requires less bandwidth. The G.729 codec is therefore better for operating VoIP over smaller bandwidth connections, like ADSL for example. So why use G.711 at all? Because there is always a price to pay in compressing the data packets, one is in quality and the other is it takes more compute cycles. So if there is enough bandwidth like in a LAN then G.711 tends to be used whereas G.729 would be used over the internet.
So in a typical setup where our customer has Cisco IP phones in their office on a LAN, the phones will be using the G.711 codec to communicate with each other and with the Cisco UC500 PBX. If the company has home workers with Cisco IP phones that connect to the office network using a VPN across the internet, then these phones would be configured to use the G.729 codec.
If the Cisco UC500 series was a standard PBX then it would only connect to BT’s PSTN either using analogue, ISDN BRI or ISDN PRI. However the Cisco UC500 series can also connect to a VoIP service provider like VoIP.co.uk using a SIP trunk. This gives you more flexibility. You can have all your incoming and outgoing calls using a SIP trunk while using an analogue or ISDN line as a backup.
VoIP is undoubtedly the future of telephony, now offering capability, flexibility, quality and resilience that are a far cry from the limitations of earlier systems.
Many features and advantages make it the ideal business solution:
- VoIP provides a lower cost alternative to the traditional networks.
- Call costs for businesses systems are substantially lower than ISDN.
- VoIP is scalable on an individual channel basis and extra phones can be added without additional telephone cabling.
- For multi-site organisations all internal phones can be on the same network, so calls between sites within the organisation are potentially toll free.
- Number portability is assured and simple, even when moving long distance.
- Disaster recovery is fast, with same day line switching to an alternate location.
- Conference calling, call forwarding and caller ID are all low-cost features.
- Integration with other services such as voicemail, email and SMS is straightforward.
- Advanced features such as videoconferencing are easier and cheaper to implement.
- Advanced DDI offers comprehensive management and analysis tools.
- Emergency services are supported.
- VoIP is ideally suited all businesses, and higher volume customers financially benefit even further, as the capacity requirements increase without linear increase in connectivity charges.
The bottom line is VoIP technology has now matured to offer comparable if not more dependability than traditional ISDN-type services. This, combined with low lifetime cost and fast ROI, is presenting decision makers with an overwhelmingly compelling business case.
