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March 1999


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" voice call.

Effective and complete deployment of Internet telephony services will depend on the successful end-to-end implementation of many complementary standards, including the following:

  1. The IETF differentiated service (Diff-Serv) standards, which support the service types and priorities needed to meet delay and jitter requirements;
  2. The IETF Multi-Protocol Label Switching (MPLS) standards, which enable the efficient routing and forwarding of packets to further meet these requirements;
  3. The IETF IP Security (IPSec) and other Virtual Private Network (VPN) protocols, which provide the necessary security and privacy; and
  4. The ITU H.323 Recommendations, which are currently used to support call setup and media mapping.

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 standard.

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 contributions.

- 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 and control.

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 attractive because:

  • 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 Systems, Inc.


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 standards bodies.

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 reason prevail.

- Dr. Michelle Blank, President, RADVision, Inc.







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