A number of organisations are already reaping the benefits of
carrying their voice and data traffic on the same network, and
analysts believe every enterprise should be looking ahead to the
day when it will become the most cost-effective option, writes
Philip Hunter.
Carrying voice communications in IP (Internet Protocol) packets on
the same network as data makes sense because having one network
rather than two saves money and makes it easier to implement
computer-telephony applications. The question is whether now is the
right time for enterprises to begin migrating telephony to IP
networks.
The answer depends largely on whether existing private branch
exchanges (PBXs) and data networks need replacing or still have
some time to run.
"If you have already got a large investment in high-end legacy PBXs
and have a pretty smart data network, then although there are still
benefits in migrating to voice over IP [VoIP], it is not as
justifiable in terms of cost," said Matt Winckless, the RSPCA's IT
architecture and standards manager.
Animal charity the RSPCA was an early adopter, going live with full
end-to-end VoIP in August 2001. Its network is based on Cisco
equipment.
"We were running on 14-year-old PBXs, which were up for replacement
anyway," explained Winckless. So, to an extent, the RSPCA was a
"greenfield" site. In those circumstances the case for VoIP is
overwhelming, according to Paul Strauss, research manager for
enterprise networks at analyst firm IDC.
Even sites that are not looking to upgrade in the near future
should ensure that they are prepared for VoIP and that all future
purchases of equipment are made with that aim in mind, said
Strauss. "The strategic benefits of VoIP are so enormous that
anybody who is not ready for them is making a terrible mistake," he
said.
Nevertheless, Strauss believes it would also be a mistake to rush
in and replace legacy systems that are working well, especially as
there are still some technical issues with VoIP to be resolved.
"There are still compelling reasons to be cautious, and you don't
necessarily have to jump in," he said.
Strauss cited feedback from suppliers such as Cisco, which has 40%
of the market for enterprise VoIP systems, that suggests companies
are heeding this advice to prepare. "Cisco tells me it is selling
enormous numbers of Lan [local area network] nodes equipped with
electrical power so that telephones can be put in - many times more
than the number of actual VoIP systems installed," he said. Strauss
believes this is evidence that the market is ready for a dramatic
acceleration.
At present, the VoIP field is being led by small and medium-sized
businesses and branch offices rather than large enterprise sites,
said Strauss. This is largely because suppliers such as 3Com have
been successful in promoting smaller-scale "tactical" systems sold
for telephony, without emphasising the fact that they are actually
sending voice communications as IP packets.
However these systems achieve the benefits of IP transmission,
avoiding the need for dedicated bandwidth which is idle when no
calls are being made, and stopping the transmission of pauses in a
conversation.
"Over a traditional circuit-switched call with 64kbps of reserved
bandwidth, utilisation is only about 35%," said Rufus Grig, chief
technology officer at VoIP supplier Convergent Systems. With a
shared IP network, this wastage is avoided, because spare bandwidth
can be soaked up by less-urgent data traffic such as e-mails and
file transfers.
Savings
There are also savings to be made in
administration through having just one network to manage. According
to Ben Anrep, network
manager at the Consumers Association, the ongoing maintenance cost
of a VoIP network comprising purely suitably configured IP routers
will usually work out at less than half the combined cost of the
routers, PBXs and multiplexers necessary to run separate voice and
data networks.
The extent of these savings naturally depends on how much is being
spent on the networks in the first place, and works out greater
when there are many sites or there is a substantial amount of
international traffic. This suggests that multinationals have the
most to gain from VoIP, but at the same time they are hindered from
migrating by legacy PBXs that only support circuit-switched
voice.
Quality
Quality is often cited as an impediment to
adopting VoIP, but this no longer applies to private IP networks,
because it is possible to allocate and reserve guaranteed bandwidth
for voice at the temporary expense of non-real-time data.
Voice over the Internet is another matter, for at present it is
impossible to guarantee quality when there is no control over the
whole of the end-to-end transmission path. For this there needs to
be a protocol for signalling and negotiating quality of service
between successive networks along an end-to-end path.
But for enterprises with private networks, the greater technical
concerns are over security and availability. With VoIP, voice is
just a type of data and so becomes exposed to the same risks and
threats as other data. The systems tend to run on ordinary servers
and PCs and so are vulnerable to external hackers and viruses to
which traditional circuit-switched voice networks are immune.
A related issue is the fact that, generally, lower levels of
availability have prevailed - and been tolerated - on data networks
than for telephony. But, as Steve Cramoysan, Gartner Group's EMEA
team leader for enterprise networking, pointed out, the problem for
VoIP is as much perception as reality. "It may well be that VoIP
will be just as secure and reliable, but until it has been
installed for some time it will be impossible to prove that," he
said.
For these reasons the RSPCA was assiduous in piloting VoIP before
full roll out. "We needed to ensure that we could obtain from an IP
data network the 99.999% level of availability of a traditional
voice system," said Winckless. This was achieved through network
and system redundancy, and the use of servers dedicated to VoIP. So
far there have been no failures.
In some cases, as at the Consumers Association, the use of VoIP is
restricted to inter-site traffic to exploit the bandwidth and
management cost savings. In others, such as the RSPCA, voice is
also carried over the Lan, which confers additional benefits by
having just one physical network, reducing costs and also making it
easier to integrate voice and telephony for applications such as
unified messaging and screen popping in call centres.
Cost
Implementing VoIP over the Lan will usually
require an upgrade to the existing network to guarantee voice
quality, and IP phones will have to be supplied to users. IP phones
still cost considerably more than conventional handsets, and in
practice most sites will wait until they need an upgrade
anyway.
VoIP can also score significantly for teleworking, making it easier
to include homeworkers in workgroups. At this level VoIP leads to
immediate capital cost savings.
Winckless said, "Our homeworkers can log on and take calls at home
as if they were part of their call centre group without having
thousands of pounds worth of call distribution equipment in their
living room. They can also access their unified messaging mailboxes
and do not need answerphones or fax machines. This is quite a
saving as we have 500 people working this way."
According to Strauss, in the longer term the real prizes that VoIP
will bring are strategic, while the impediments are merely
tactical. "Ultimately it will make the telephone a much more
productive tool than it is today," he said. It will also act as an
enabler for deeper levels of interaction between computing and
telephony, and some enterprises, such as the RSPCA, are already
reaping the rewards.
The pros and cons of voice over IP
Pros- It saves Wan communications costs by using bandwidth more
efficiently. This is particularly significant for multiple sites
and international traffic
- It reduces administration costs and saves IT staff costs by
having just one network to manage
- It reduces the cost of moves, adds and changes within the Lan
because each user has just one connection point
- VoIP over the Lan reduces cabling costs because telephony
wiring is eliminated
- End-to-end VoIP makes it easier and less costly to implement
computer telephony applications because there is no need to
integrate and synchronise separate voice and data networks
- VoIP makes it easier to implement distributed workgroups across
multiple sites, including homeworkers
- It reduces the cost of teleworking, especially in call centre
applications, because the need for telephony equipment in the home
is avoided
- The cost of telephony management is reduced by having a single
consolidated bill spanning all sites.
Cons
- It is hard to justify the expenditure, particularly in the Lan,
if existing networks still have some time to go before they would
otherwise need replacing
- There is a perception that quality is not so good, and further
progress is needed with the transmission of the silences that
naturally occur in telephone conversations
- There are fears that telephony services could be threatened by
viruses and denial of service attacks
- If not managed correctly, availability levels could be closer
to those of traditional data networks rather than the higher
standards expected for voice
- A lack of agreement over standards means interoperability is an
issue.
Case study: VoIP on the Consumers Association's Wan
The
Consumers Association is implementing VoIP on the wide area network
(Wan) that connects its three sites, but it has not yet rolled it
out to its local area networks (Lans).
As is the case for many businesses, it is a largely a matter of
timing, for there is still some life left in the existing PBX at
one of the sites and until this is replaced it would be impossible
to transmit data over the Lan there.
Over the Wan, an eight-year-old multiplexer network is being
replaced by a router-based IP network. The change is motivated by
the prospect of reducing ongoing communications costs by more than
half.
The main technical issue being resolved at present is whether to go
for G.729 encoding of the voice, which compresses it down to 8kbps
per channel, or whether to make do with the more mature but less
efficient G.711 encoding which transmits at 64kbps. In either case,
the use of packetised voice will avoid the need to transmit the
pauses between words. "It is a question of ensuring that G.729 is
reliable enough, which it probably is," said the association's
network manager Ben Anrep.
The main concern, as for many of the present crop of relatively
early adopters, is service availability, given the very high
standards that have long prevailed for circuit-switched voice - and
which business users have come to expect.
Ironically, the lingering quality issues concern the transmission
of the silences rather than the speech. Normally during a
conversation there is some background hiss which is heard during
the pauses, but VoIP saves bandwidth by not transmitting this. To
compensate, some systems attempt to regenerate this at the
receiving end. According to Anrep, they fail dismally so the
Consumers Association turned this option off. "We found this
'comfort noise' actually made the quality worse," he explained.