Internet Telephony Developers:
Time to Answer the Call
BY DOMINIQUE LINDEN
By now, most of us have heard the arguments in favor of voice and fax over IP. Internet
telephony promises 14 times the efficiency of traditional voice transmissions, and can
digitize, compress, and prioritize voice, filling up unused bandwidth to stuff multiple
conversations over the same line that used to carry only one. The fundamental economics of
sending voice and data over a single network have transformed voice over IP from an
interesting technology into a proven business.
So far, Internet telephony is deployed mainly in the enterprise environment and by
service providers offering cheap phone calls. It works, but not for everybody. Big
companies and major telcos are still waiting for improved Quality of Service (QoS),
security, and manageability of integrated voice and data networks.
Still, now that developers have made Internet telephony work, the next challenge is to
make it work well. More importantly, developers need to understand the end user's point of
view and build smart products using today's Internet telephony technology.
CALLING THE MARKETPLACE
In the enterprise environment, the first customers to deploy VoIP gateways were small and
medium-sized companies with international sites. According to Probe Research Vice
President Hilary Mine, most of the 2,000 enterprise VoIP sales in 1997, as well as the
3,000 sold in the first half of 1998, were to those companies. Enterprise VoIP sales are
also expected to accelerate among other small to mid-sized companies where voice costs are
a major expense, especially those already experienced with call centers or computer
telephony. These companies often have an abundance of bandwidth because over-provisioning
is the easiest way to avoid end user complaints about throughput delays and, thus, about
carriers' private line pricing policies.
Big companies are already running VoIP trials and pilot projects, but holding off on
major deployments until they are convinced that QoS mechanisms can keep their voice and
data traffic from damaging one another on shared IP facilities. Reliability features are
not critical for super-cheap VoIP calling services, but if providers want customers to
depend on their VoIP services the way they depend on the PSTN today, they must provision
these services from more robust and reliable platforms. To the victor go the spoils, and
developers who figure out how to make voice and fax over IP work for large enterprises and
service providers with mission-critical applications will be the ones who succeed. The
objective is not necessarily to improve the fundamentals of IP telephony - it's enough to
build a solution that works today. There is no time to wait for better products. It took
the telephone 38 years and the fax machine 22 years to reach 10 million users. The
personal computer reached 10 million users in only nine years and the Internet took less
than two. Time is running out.
THE MYTHS OF INTERNET TELEPHONY
There are still many myths about Internet telephony, including voice quality problems
because of packet loss, delay, and a lack of sophisticated voice codecs. None of these are
true. Voice quality has improved dramatically and should no longer be of concern to
developers. Today's Internet telephony systems deliver voice quality in a box. In the
early days of geek-to-geek communications, IP packets could get lost. But those days are
gone. Intelligent gateways provide seamless voice and fax communications, and if lost
packets were really an issue with fax transmissions, you would see blank lines on the
page. Unlike our mind, a machine can not compensate for words that were not transmitted
correctly, and lost packets in fax over IP would show black on white. As the first
real-time fax over IP applications come to market, it is obvious that lost packets are a
myth of the past.
Another misconception is that the plain old telephone is the ultimate standard for
voice quality. Wrong again. The 64 Kbps compression mechanism in the phone network was
chosen randomly. Now we don't need 64 Kbps to achieve the same kind of voice quality. A
whole new generation of high bit-rate coders (higher than 64 Kbps) are delivering better
sound quality than the regular telephone with today's increased bandwidth availability. In
a few years, everybody will demand CD-quality digital sound, and people will complain
about the poor performance of the plain old telephone.
SO, WHAT'S THE PROBLEM?
If voice coders and packet loss are not causing voice quality problems, then what are the
big companies waiting for? First, delay is a function of the gateway and the network, and
people think they have to wait for better gateways before deploying Internet telephony. In
reality, they must redesign their network. There is an increasing need for people who
understand the whole system that makes up an IP voice and fax solution, and who understand
what QoS is all about. QoS has nothing to do with voice quality - it indicates how well
the system functions as a whole. What matters is how good the service is for the end user,
who will judge it based on voice quality, reliability, and manageability. Therefore, most
gateways already offer a variety of functions on Windows NT and UNIX servers, routers, and
remote access servers with a healthy selection of interfaces, compression algorithms, and
voice quality features like echo cancellation and jitter buffer.
Today's Internet telephony systems lack the system management tools to improve QoS.
There are no easy-to-use configuration and management tools for VoIP networks, no call
detail records (CDRs) for charge-back to customer departments, and no reasonable security
measures. Gateways do not support true redundancy or hot-swappable components, common
features of data switches and routers, and few have an SNMP agent onboard. This can be
problematic because end users of voice and fax over IP expect at least the same quality
and features they get from the PSTN network. But voice over IP solutions are implemented
by IT managers with only one thing on their minds: keeping their jobs. An IT manager's job
is not to be a pioneer, but to make sure that calls go through, no matter how the network
is configured. Both can be accomplished by focusing on QoS instead of only on voice
MANAGEMENT AND SECURITY SOLUTIONS
Network managers insist that any device connected to their networks be manageable via
SNMP, part of a more structural approach to QoS. Internet telephony platforms can be very
bandwidth-smart by fully supporting the RSVP and IP precedence specifications, which allow
for traffic prioritization and optimization. RSVP and IP precedence are features of the
router, not the gateway. The gateway, however, must be able to flag voice packets so that
they will be given priority over others when arriving in the router. IP Precedence and
RSVP are becoming the two most useful signaling mechanisms because both take advantage of
the end-to-end nature of Layer 3 protocol and the growing ubiquity of IP as the network
protocol of choice. IP precedence uses the three precedence bits in the Ipv4 header's QoS
field to specify calls of service for each packet. Managers can partition traffic in up to
six classes of service using IP precedence.
So far, security seems to have taken a back seat. But before Internet telephony becomes
mainstream, airtight security for Internet telephony connections needs to be addressed.
Authentication (are you who you say you are?), integrity (did anybody tamper with the
data?), privacy (did anybody tap into a conversation?), and non-repudiation (proof that
you really made a phone call) are all addressed through H.235, formerly known as H.Secure.
H.235 is a new member of the International Telecommunications Union's (ITU) H.323
standards umbrella for setting up VoIP calls. Firewalls should also be implemented with
H.323 proxies to allow H.323 calls through the firewall without opening it up to all kinds
DEVELOP FOR YOUR USERS
Having said all this, what's more important than QoS management techniques is taking the
end user's point of view when designing an Internet telephony solution. A good example is
choice of operating systems. Some developers think it's impossible to design reliable and
redundant systems based on Windows NT, so they develop on UNIX and are waiting for
CompactPCI hot-swappable hardware. But do end users really care which operating system is
used? No. All that matters is that the phone service doesn't go down. Some developers
believe in Windows NT because it's easy to program, and toolkits and management tools are
readily available. They, too, achieve redundant systems. It may not be graceful from an
engineering point of view, but in an emergency you can hot-swap an entire configured
server instead of taking out elements like voice boards. After all, we are living in the
throwaway society of complete product replacement.
What the IP telephony industry needs most is developers who can think like end users.
Instead of focusing on the technical difficulties of Internet telephony, developers should
work on end user solutions. Bill Buxton, human computer interaction specialist, once said
it very nicely, "Let's make smart products with the stupid technology of today,
instead of making stupid products with smart technology of tomorrow." There is no
industry for which this is more appropriate than for Internet telephony.
Dominique Linden is product marketing manager for Dialogic Corporation. Dialogic is
the leading manufacturer of high performance, standards-based computer telephony
components. Dialogic products are used in voice, fax, data, voice recognition, speech
synthesis, Internet telephony, and call center management telephony applications. For more
information, visit the Dialogic Web site at www.dialogic.com.