Category: 3 - Communication Technologies Subcategory: 1 - General Purpose Communication Technologies Audio quality; network quality/efficiency product; codec and transmission standards compliance; total cost impact. Industry Usage: Regardless of the products used, telephony traffic over a connectionless network demands high quality guarantees. It has quantifiable requirements and its value depends on these requirements being strictly met. One way to provide high quality guarantees is to significantly over-provision a network. This can lead to large inefficiencies and needless costs. A more cost-effective approach is to implement QoS (Quality of Service) mechanisms such as RSVP signaling, which sends service requirement metadata along with the voice data. H.323 developed by the ITU is considered the mature and stable protocol.
However, it has major limitations due to its lack of scalability and complexity.
Its leadership status is being challenged by newer protocols, such as H.248/Megaco,
MGCP, SIP and SIP+. Session-Initiated Protocol (SIP) is based on standards set by the Internet
Engineering Task Force (IETF) and is used to initiate and terminate interactive
sessions between Internet users. SIP is simpler, more scalable and goes beyond
H.323 in creating voice applications. Many consider it similar to HTML and find
it is easier for programmers to develop new applications. Its open design
supports interoperability with H.323 and offers a migration path for service
providers to deliver enhanced services. Many vendors are considering SIP+ but
regard it as relatively new and untested. Media Gateway Control Protocol (MGCP) is proposed by the IETF as the standard
to convert audio signals carried on the public switched telephone network (PSTN)
to Internet data packets. It has several variations based on different market
needs that have resulted in compatibility and interoperability issues with
equipment manufacturers. It is seen as losing ground to the emerging Megaco/H.248
standard. Megaco/H.248 offers a richer set of capabilities that also corresponds to
more complexity. It adds peer-to-peer interoperability capabilities and delivers
a control function for IP devices. The protocol allows low-cost gateways to
interface with signaling systems found in circuit-switched networks, reducing
expenditures. It is still considered a new and unproven technology. Interoperability between standards remains a major issue with vendors.
Implementing a standard in a product does not assure that this will interoperate
with another vendor’s product that uses the same standard. Only a few vendors,
such as Cisco, have announced other products that interoperate with their
products. Although many equipment manufacturers cite some interoperability based
on H.323, its impact as a leading protocol is declining. Interoperability based
on SIP+ and Megaco/H.248 is seen as increasing. Much more work by vendors and
standards committees on interoperability is needed before this issue is
resolved. Voice Extensible Markup Language (VoiceXML) is a computer language that is
quickly becoming the standard for creating Web content and services that are
accessible by the telephone. Leading providers of voice equipment and speech
engines, such as Lucent, Motorola, AT&T and IBM, have contributed their
markup language to the development of the open VoiceXML standard. Prior to the
VoiceXML Forum, application developers had to use proprietary languages that
were developed by each vendor. With the standardization of VoiceXML,
improvements in voice applications are simpler to develop, resulting in a
shorter time to market. Many consider phone access to the Internet the next big market. The rapid
rise in cell phone use and ubiquity of telephones create a demand for new
self-service applications that allow callers to interact with Web content for
information and transactions. With the use of natural-language speech
recognition and text-to-speech technology, a phone user can browse the Web
simply by talking and listening to responses, using many of the same basic
commands as browsing with a PC. While not a replacement for complex Web
searches, voice access to the Web supports anytime, anywhere communications. VoiceXML as defined by the VoiceXML Forum is designed for creating audio
dialogs that feature synthesized speech, digitized audio, recognition of spoken
and DTMF key input and recordings of spoken input. In May 2000, the VoiceXML
Forum announced the World Wide Web Consortium (W3C) acknowledged the submission
of Version 1.0 VoiceXML specifications. Acknowledgement by W3C helps accelerate
the reach of the Internet though voice-enabled Web content, and the W3C Voice
Browser Working Group will use VoiceXML as the basis for its dialog markup
language. The move toward using VoiceXML as the standard for dialog markup language is seen in the number of member companies supporting this language. VoiceXML Forum
now has more than 150 member companies and includes major voice recognition vendors and voice communication companies. The need to simplify the creation of Web-based applications is apparent, and VoiceXML appears to be the agreed upon standard going forward. SC Usage: Audio (and video) telecommunications in meeting rooms is provided by PictureTel systems. Analog telephone (POTS) service is provided by Verizon and funded at the departmental level, so there is no financial incentive to move to IP-based voice communications at this time. In the future, if higher-bandwidth audio and video communications are to be supported over TCP/IP, it is likely that new provisioning of the network will be needed. It is also recommended that network QoS (Quality of Service) mechanisms be established prior to heavy usage of Voice over IP to the desktops. SC Application Impacts: None in near term. Previous TPS ReportVision
Retirement Containment Current Tactical Strategic NetMeeting
RealPlayer Plus
Windows Media Player
Standards
Industry Usage SC Usage H.323
Performance Metrics
Usage and Dependencies
Last Update: Valid Until: 7/18/2001 3/1/2002 References
VoiceXML Gains Widespread Acceptance With Leading Vendors, Elizabeth Herrell, Giga, 7/5/2000.