Which of the current crop of "standards du
jour" have shown the most promise? Which standard(s) do you feel is (are) the most
significant for the successful implementation of Internet telephony? (Part II)
[Click here to read
Part I in the February issue of Internet Telephony�]
We asked several industry-leading vendors for their views on the Internet telephony
industry. Their responses appear below.
In order to enable the successful deployment of public Internet telephony services, the
Internet and Public Switched Telephone Network (PSTN) infrastructures must comply with a
number of Internet Engineering Task Force (IETF) and International Telecommunications
Union (ITU) standards. These standards address several technical issues to ensure that a
voice call traversing the Internet (or any combination of the Internet and PSTN) has the
same perceived quality of service, security, and reliability as a "traditional"
Effective and complete deployment of Internet telephony services will depend on the
successful end-to-end implementation of many complementary standards, including the
- The IETF differentiated service (Diff-Serv) standards, which support the service types
and priorities needed to meet delay and jitter requirements;
- The IETF Multi-Protocol Label Switching (MPLS) standards, which enable the efficient
routing and forwarding of packets to further meet these requirements;
- The IETF IP Security (IPSec) and other Virtual Private Network (VPN) protocols, which
provide the necessary security and privacy; and
- The ITU H.323 Recommendations, which are currently used to support call setup and media
H.323 will be supplemented in the future by the Session Initiation Protocol (SIP),
Media Gateway Control Protocol (MGCP) or variations thereof, and SS7-over-IP (sigtran)
protocols as a means of reducing complexity and allowing easier distribution of functions
within the network. In addition to the standards mentioned above, the integration of
Internet and PSTN services will require the definition of interworking functions that map
between the Internet, SS7, and ISDN protocols.
- Jeff Lawrence, President and CEO, Trillium Digital Systems, Inc.
"Standard" is defined in Webster's Dictionary as "something established
by authority, custom, or general consent as a model or example." Though not
word-specific to Internet telephony, the spirit is apparent and true. Right now, I find
the sudden abundance of "standards" less than clear and view the motive of some
creators warily. VocalTec is an industry pioneer, but it would be laughable to claim
ourselves and a few close associates as sole authorities. We gladly sit at the same table
with competitors, working to arrive at general consent, which is good for all. It is the
most effective way for this industry to realize its full potential.
ITU H.323 easily has more product in compliance than any standard and the most industry
support. Service providers are today serving customers with products that are fully H.323
compliant. Has it been perfected? Of course not, but it is the most advanced and solid of
the existing proposals, one which all parties are welcome to build upon. So if it is not
etched in stone - if this proven standard can be influenced by all - is the influx of new
standards from "the few" sincerely aimed at bettering our entire industry?
Furthermore, where should our global industry place its trust: In the inherent
objectiveness of the ITU - a body of the United Nations - or the isolated strategy rooms
of organizations with subjective agendas?
Webster's says a standard is established "as a model or example." VocalTec
has been at Internet telephony awhile and yet we believe the industry is just emerging
from infancy. At this critical stage, as we all take these first steps, it's important
"this child" receive a few strong guidelines. And the less unnecessary
distractions the better.
- Dr. Elon Ganor, Chairman, VocalTec Communications
There can be little doubt that the most significant standard for Internet telephony is
H.323. Indeed, in a recent ITXC announcement, Ascend, Cisco, VocalTec, Lucent, Dialogic,
Natural Microsystems, and Siemens all committed to interoperability based on this
Gateway control protocols, of which IP Device Control (IPDC) is currently the most
significant, also represent an important new direction in standards. Ascend anticipates
that an evolution of IPDC will be standardized in the ITU-T (where it is being worked
under the name H.GCP), or in the IETF. This protocol offers many advantages to
manufacturers and customers seeking IP to SS7 integration, and complements - rather than
competes - with H.323. We anticipate that H.GCP will contain technical content from IPDC,
Simple Gateway Control Protocol (SGCP), MGCP, and a highly developed Lucent/Intel
proposal, as well as contributions from other major industry players. The current schedule
for H.GCP calls for a May 1999 technical freeze. There has been some confusion regarding
MGCP, which has created the mistaken impression that it is an actual standard. In fact, it
is simply a draft being promoted by particular vendors. MGCP was discussed for the first
time by the ITU-T and the IETF just months ago, and is only one of many industry
- Dale Skran, Director of Engineering, Enterprise Networking
Division, Ascend Communications
Adoption and deployment of Internet telephony will accelerate when the cost of Internet
telephony solutions becomes attractive. In today's circuit-switched telephony networks,
the switch is intelligent and terminals are simple (and thus, inexpensive). Internet
telephony, on the other hand, requires terminals with some built-in intelligence because
the terminals are not physically tethered to an intelligent switch. Therefore, IP phones
have the potential to become complex and expensive even prior to matching conventional
phone systems in terms of features and quality. To avoid this, it is up to standards
bodies to adopt simple standards, particularly in the areas of voice coders and signaling
Although voice coders are not a standards issue, choice of voice coders by vendors has
a significant impact on the deployment of Internet telephony solutions. Today, there are a
large number of voice coders on the market. If IP phone vendors have to implement a large
variety of coders to ensure compatibility with all the other IP phones on the market, the
complexity and cost of IP phones will skyrocket. Thus, one can safely assume that the
industry will gravitate towards a small number of voice coder standards. In addition to
G.711 (3.7 KHz, uncompressed toll-quality voice), G.729 (not G.729a) is particularly
- From a voice quality perspective, G.729 scores a Mean Opinion Score (MOS) of 3.9 which
is almost equal to the G.711 (toll quality) MOS of 4.1.
- From a Dual Tone Multi-Frequency (DTMF) preservation perspective, G.729 and G.711 are
able to forward DTMF unchanged. Some of the other coders and G.729 variations are known to
corrupt some of the tones. Considering that a significant number of business applications
rely on DTMF (e.g., phone banking, voice mail, call center operations), preservation of
DTMF is a significant requirement for the coders.
- The Frame Relay Forum (www.frforum.com) has
standardized on G.729. Therefore, IP phones can interwork with voice over frame relay
without additional compression cycles.
The other area of IP terminal complexity (no pun intended) is the requirement for IP
phones to participate in call control and signaling. Currently, H.323 (specifically,
H.225) is the only mature public standard in this space. H.323 is the right choice for
many of the software-based terminals such as PC phones, NetMeeting, etc. However, from an
IP phone implementation perspective, H.323 has a few shortcomings:
- H.323 is a blend of the signaling protocols from video, multimedia, and ISDN. H.323 call
control and signaling require several packets to be exchanged and many state transitions
to be performed that make the terminal design complex and the call setup times long.
- H.323 does not distinguish between gateways and terminals, which forces the terminal
designers to design complex terminals and consequently increases the cost of terminals.
Nortel Networks believes that MGCP, which is a blend of SGCP and IPDC, will evolve to
be a simpler and more telephony-optimized control and signaling standard. MGCP is also
expected to encompass a simpler variation of the protocol aimed at IP phone
implementation, which will allow vendors to create inexpensive terminals and accelerate
adoption of Internet telephony solutions.
- Ravi Narayanan, Director, IP Telephony Strategy, Nortel Networks
It's ironic that in the space of less than two years we've gone from disbelief in the
concept of Internet telephony to the question of why it isn't growing faster. By most
measures, including Internet measures, Internet telephony is growing very quickly. On the
vendor side, we've seen growth in excess of 100% per quarter over the last five quarters.
The real question is: "Are there sufficient standards to make Internet telephony
robust and ubiquitous?" There are not too many standards; there's very little
competition between them and lots of work going on to interoperate them.
There is still important standards work going on to make Internet telephony more robust
and ubiquitous in the future, and this will complement what exists. The best example of
this is MGCP. This simple protocol will allow simpler Internet telephony devices to be
built, without the need for the more complex and processor-intensive H.323 protocol, used
by computers for multimedia. MGCP is in advanced discussion at IETF, it combines the best
of earlier SGCP and IPDC proposals, and will interoperate with H.323 in the network.
MGCP will join standards like G.729 (8 Kbps voice compression) as the staples of
Internet telephony in the future. Vendors must remain committed to standards and
interoperability for adoption to reach the next level. Most will.
- Peter Alexander, Vice President, Enterprise Marketing, Cisco
It is not an either/or situation. To achieve wide deployment of Internet telephony,
there needs to be compromise and cooperation instead of competition among different
Who is going to make the decision as to which standard(s) is (are) best? For that
answer, we can look at examples from other network scenarios where vendors left the
"best standard" decision to the marketplace. The cellular phone example is an
appropriate scenario. Europe has one standard (GSM) while in the US, there are numerous,
heterogeneous, incompatible networks. From personal experience, GSM is a much better
solution for the customer. It works everywhere and cellular GSM phones are now used as a
key business tool in Europe.
I fear that, right now, VoIP is heading towards a situation reminiscent of the US
cellular networks and the biggest losers will be the customers.
All the people involved should converge and work as a team. Let the ITU and the IETF
agree to divide the labor. Let the IETF do what it does best - work on solving network
issues regarding reservations, quality of service, and packet-based security and billing.
Let the ITU contribute their know-how and expertise in telephony and user services. Let
- Dr. Michelle Blank, President, RADVision, Inc.