All communication streams to workstations flow over an IP network. Audio to the PSTN is interworked to the LAN through the MMCX server. Quality of service is managed by proper engineering of the IP network and limiting router hops. For such products a local IP network has advantages in bandwidth and delay over a larger network. Additionally, since these products are introduced within an enterprise (typically within an engineering department) commonality of workstations and ability to properly configure the IP network can be arranged more easily than in a broader setting.
Communique! from Insoft (now part of Netscape), Intel Proshare (http://www.intel.com/comm-net/proshare/index.htm), PictureTel LiveLAN (http://www.picturetel.com) are some of the products in this area. These products have been built on proprietary protocols and interoperation is limited at best.
Communications products require standards to interoperate. Users are not willing to commit to large deployments of these products without assurance that different products can be used together with other communication devices (ordinary telephones, for example) and will not be made obsolete by technical changes or the failure of one particular product line. Properly conceived communications standards address all of these issues.
The lack of standards prevents a communication market from growing and thus limits investment in the technology. It is in the interest of vendors to cooperate in establishing at least a base level of interoperation among products.
Recently, standards for multimedia communications over an IP network have begun to emerge and products developed to them will begin to appear in the next few months. Most companies with products in this area have committed to supporting these standards (including all those mentioned above). The standards (H.323 and others) have been created by a study group of the ITU (study group 15) and represent the collective view of many of the companies with experience in this area. The standards take into account the nature LANs and also interworking with existing wide area collaborative standards (such as H.320 - a multimedia standard for ISDN lines) and ordinary telephones.
These protocols are available via ftp from ftp.gctech.co.jp login itu-t password sg15!avc. The site has (or did have) working versions of the specifications. Hunt around a bit. There is also a mail reflector for the H.323 implementers group - subscribe by sending mail to firstname.lastname@example.org; in the body of the message put subscribe h323implementors <you address or null>. This group discusses detailed implementation issues and does not deal in tutorial information.
H.323 calls for the T.120 suite of protocols to be the basis of collaborative data applications. T.120 includes a protocol for a multiparty shared white board and a multiparty binary file transfer protocol. A multiparty application share protocol has recently been presented for incorporation into the T.120 suite by Microsoft, PictureTel and Polycom (ftp://ftp.imtc-files.org sub-directory imtc-site/t120_napa96 file tshare.zip).
Much of the ubiquity of the web and its universal utility comes from standardization around formats and protocols (HTML and HTTP in particular). WWW multimedia protocols should interoperate with the "business" multimedia workstations based on H.323 standards. This would allow a web browser to collaborate in a multimedia session with one or more multimedia workstations sharing voice, video and data. For example DataBeam Corporation is testing a product that allows a web browser to participate in a T.120 based whiteboard collaboration (http://www.databeam.com/Products/neT.120/). Similarly, streaming media could be incorporated into a collaboration to serve as a training session or a review of audio or video material.
Integration of H.323 standards into WEB components will also enable the development of multimedia communication interfaces based entirely on standard web components. This greatly expands the number of endpoints that could be in a multimedia collaboration and will allow an "Internet Appliance" to collaborate as well. Imagine being able to retrieve your mail (voice, video and electronic) from an Internet Appliance in a hotel room or a library. A prototype of such a retrieval server has been built for the Intuity Message Manager from Lucent Technologies. Standardization of audio representation and the availability of a variety of codecs would make developing such services easier. A common way of representing terminal multimedia capabilities is also needed.
Voice over the Internet is growing rapidly. Unfortunately, there is little interoperability between products from different vendors. These products will remain "toys" until standards for interoperation are established. In this market as in any communications market a base level of interoperation is required. After this is established, competition based on features, price, etc. is good for the growth of the market.
There is much work to be done to improve the Internet as a base for real-time multimedia communication.
· Identification of media stream formats suitable for Internet bandwidths and delay characteristics will allow Internet users to communicate with H.323 users in enterprise settings via real-time multimedia. Careful consideration of the computation and delay needed for stream interworking is required, especially for video.
· Improving the delay characteristics and lowering the bandwidth requirements for RTP/RTCP headers will benefit H.323 based multimedia communications and is independent of the H.323 standards. This, along with a set of low bitrate media stream formats will enable H.323 to operate over 28.8 modems, greatly expanding the reach of real-time multimedia communication.
· Expanding the use of reservation protocols such as RSVP throughout the Internet will improve the quality of interactive multimedia.
· Augmenting WWW standards so that browsers can integrate cleanly with H.323 terminals will greatly increase the possibility of HTML to H.323 terminal interoperation and provide an exciting way to deliver and customize user interfaces for multimedia communications. This group along with a few others has particular experience with WWW standards and is uniquely situated to determine "the right way" to do this.
· Standardization of Internet voice products around H.323 will increase the utility of all these products.
· Modification of firewall technology must be done to allow these communication protocols through firewalls in a secure way.
Imagine a world where a student with nothing more than a web enabled device can visit a school's homework support desk and find help on the most recent assignment. If the published hints are not sufficient the student can consult via audio with a teacher who is in a pool of teachers providing consulting today. The teacher can see the students face and judge how the explanation is being understood. The teacher then augments the consultation with a short video clip. An expert can be added to the conversation and a three way whiteboard exposition made to further explain the concepts of the homework.
This scenario is within reach if we can focus on implementing and extending real-time multimedia communications standards.