Packetising voice

December 2001 While many forward-looking enterprises have already integrated their voice and data networks, it is only now that signs are emerging of convergence within wide-area systems

If the Internet is helping to nourish the commercial survival of a multitude of businesses today, then IP (Internet Protocol) is an essential vitamin. IP is the global, de facto standard for the Internet, which provides each device or server connected to the network with a unique number. This 'IP address' is critical, as it is used to pinpoint where on the network devices send and receive data.

IP also plays a crucial role in the ongoing process of convergence, under which computers, telephones and consumer electronics devices - for example, television sets - are increasingly able to exchange data with one another through a unified network.

As a result of the pervasive influence of IP, established standards designed for narrow instances of network use are inevitably giving way to IP. Many firms now use IP across their own local networks, rather than dedicated network protocols, for example, to identify PCs and other networked devices like printers with IP addresses.

In this way, these private networks can more easily be integrated with, so-called, public networks, larger-scale systems made available to a wide customer base by service providers and other carriers.

Convergence

Until recently, however, the rapid growth of the Internet, and its integration with the functions of local networks, had run in parallel to the use of PSTN (public switched telephone network) systems for voice-based communication.
Although PSTNs are capable of managing data-based traffic, such as faxes or modem-based Internet connections, they are fundamentally ill-equipped for data - as a dedicated circuit needs to be established between two points, which is both expensive and is waste of valuable bandwidth.

IP telephones combine voice and data

While consumers and small businesses - with minimal data transmission requirements - are prepared to accept PSTNs' data facilities and use their PSTN phone socket as a route for all their communication, SME and corporate customers have steadfastly maintained two separate networks throughout their operations, in order to strike a practical balance between quality of service (QoS) and cost for their voice and data traffic.

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This separation could be coming to an end, however, through the use of IP telephony systems that enable data networks to treat voice traffic as just another form of data. A defining characteristic of a PSTN voice or data transmission is that it relies on circuit-committed switching methods, where a set, and exclusive route is established for the duration of the connection.

Conversely, IP networks use packet-switching techniques, where data is separated into 'packets' that can each travel a different path, and then be reassembled at the destination. With IP telephony, voice calls are also broken into packets and travel through a network alongside other data formats.

Voice-over-IP or VoIP has become a generic term for the use of IP telephony, although it is technically a specific standard - ITU-T H.323 - promoted by the VoIP Forum, including Cisco, 3Com, Netspeak and others, as the best technology for sending audio and video over IP-based networks. Although VoIP currently provides poorer call quality than conventional voice networks, it does carry clear benefits, says Nortel Networks' IP telephony marketing manager Gavin McFadyen. "It can't be touched in terms of low cost of implementation."

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Carrier reluctance

Data formats, such as fax or Internet, have been relayed over public circuit-switched networks for many years. Enabling PSTN networks to use packet-switching, however, requires modification of every controlling switch in the network.

Up until now, therefore, carrier investment in VoIP has largely been confined to new infrastructure, particularly from start-up carriers that are building networks from scratch. The long-established telecom giants like BT and Deutsche Telecom have decades' worth of PSTN investment that will require significant upgrades to support packet voice transfer.

So, while some incumbents embrace IP as they enter new markets - McFadyen points to BT's IP-based network in Spain - they have been reluctant to embark on the large-scale domestic projects that changing from PSTN to IP demands.
But that resistance cannot hold, claims McFadyen, who sees signs that the old guard is starting to embrace the new realities. "The older companies are starting to risk looking like dinosaurs next to the alternative carriers," he says.

"Now we're seeing established carriers saying: 'Let's get IP telephony ourselves,'" he says. Nortel, itself, recently signed a deal with Sprint, the US-based international telecoms operator to supply the equipment it needs to begin converting its entire network to handle VoIP. The deal covers the first four-year phase and affects approximately 3.6 million telephone lines.

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Big business

A recent report from research group Frost & Sullivan estimates that as more carriers accept the need to convert legacy networks, 75 per cent of global voice traffic will travel over the Internet by 2007. McFadyen believes that even this figure could be conservative: "The levels of use are certainly low at the moment, but once carriers change their switches to IP, you have 50 million or 100 million people moving to IP in one go. It could potentially happen very quickly when it does."

As more established carriers join the alternative service providers already using IP networks, seamless interaction between networks will become crucial. One solution is the 'Telia Clearing House', from the Swedish network Telia.

This offers service providers a means to direct calls that start and terminate on PSTN systems through Telia's own IP network, enabling the carrier to offer low-cost communications packages to customers not yet converted to IP. Clearing House is able to track the call and make payments to each operator that handles part of the call transfer. Telia is initially looking to Eastern Europe as a key marketplace for the system, as the lower quality of PSTN in the region means switching to VoIP, as it stands now, is less jarring.

Inside the enterprise

While many incumbent telecom operators continue to weigh up the pros and cons of moving the mass of their customers onto IP voice networks, more nimble carriers are already targeting the lucrative enterprise market - which threatens to erode the incumbent's already precarious position.

VoIP is easy to integrate

At the most basic level, an enterprise is able to route its calls through a VoIP-enabled gateway server that sends calls through the firm's Internet service provider, rather than its telecoms carrier, making the calls much cheaper. However, this is far from straightforward.

The key to an effective corporate voice network is not bandwidth in itself - "even ten megabits a second is a lot when it comes to voice," says Nortel's McFadyen - but management of data traffic. "A well thought-out system allows the network to give priority to voice over other types of traffic," he says.

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Despite this additional layer of complexity, many firms choosing to integrate their communications typically regard the need to upgrade as an opportunity rather than an expense. "If people have a lot of digital phones, they add a gateway to their present system, but if they have an old PBX switchboard, customers are, by and large, upgrading their switches. We're seeing a lot of firms upgrading to Gigabit Ethernet. We don't see questions about achieving effective voice compression coming up anymore."

Using IP for all communications also enables firms to deploy advanced forms of computer and telephony integration. Replacing existing telephone handsets with new, IP-based handsets allows for greater operational flexibility, says McFadyen.
"You do see a difference when you start to deploy applications in parallel, from fairly simple applications like 'hot desking' through to unified messaging." Staff can route faxes, emails and voice calls through the same equipment, enabling them to share directory information, or have their equipment bring up a customer record automatically by recognising the caller's phone number.

An alternative to IP handsets is to provide staff with digital headsets that plug into their PCs, with software packages providing an on-screen 'softphone'. "The software is H.323 compatible to allow applications like video conferencing, whiteboarding and file sharing," says McFadyen. Because achieving clean-sounding audio through staff PCs may not have been a priority when ordering equipment originally, a USB-based headset adaptor can process the voice traffic offline.

McFadyen adds that enterprises' willingness to invest in high-bandwidth networks as they convert to VoIP is enabling operators to provide enhanced voice services. "The increase in bandwidth is going to impact telephony - perhaps in the very near future. We're looking at developing stereo sound, for instance."

Domestic use

The significant remaining sector of the market, so far untroubled by any consideration of IP telephony, is the family home. The growing momentum behind telecoms carriers upgrading their networks is only part of the equation here, says McFadyen.

"It all comes down to terminals. For the consumer, replacing an analogue phone with an IP telephone doesn't have a lot of potential. The thing that might change this is 3G, and its use of video and location-based services: it's possible that you'll see operators trying to move people towards using wireless terminals exclusively."

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