We are going to focus the article on how the communication over a network has development from a few years ago to present day. At the beginning, the e-mail was the tool widely used for researchers all over the world to be in touch. In fact, it still is the most popular communication tool used in Internet. Sadly e-mail is not the perfect way for the communication. It is an asyncronous method of communication, without direct contact.

Many times what we need is the direct communication. We need to know that the other people are understanding what we say right at that moment, or simply we want to listen to the opinion of others. To fulfil this, "talk" was created. "Talk" is an old tool used for the first time in Unix machines to maintain conversations between two person at the same time. The screen is divided in two parts, one to write and the other one to read what the other person is writing. The only thing you need to know to reach the other person is the machine’s name where your partner is connected an his or her user name. "Talk" can be found in many systems, it is not exclusive to Unix. These solutions are limited to a one to one communication, but are not valid when we want to contact many people at a time. The equivalent to e-mail and talk , but for many people, are distribution lists and IRC.

Distribution lists and IRC are well-known tools too. We must point out that the network of computers of Uni-net and its administrators make the use of the net for work purposes or to have a meeting possible. All these tools (e-mail, talk, distribution lists and IRC) have in common that they do not require a big bandwidth to work. You can use them even if you do not have the latest computer system at home or you do not have a T1 connection to the Internet. No problems have surfaced using an old 486 with 8 Mb of RAM and Windows 3.1.

IVTS IN UNINET

The UniNet objective is to supply information and communication channels in the Internet whatever his/her field or discipline is. One of the critical issues of the project is to provide the best resources for the user with the smaller requirements related with a computer science experience, so that the user can have little and even no knowledge of computers. We are working in the development of other services, as databases, chat in webs, unicast and multicast audioconference, news, Mbone, etc. We want to offer to our community all the tools that Internet gives in a free way.

Two different Integrated Virtual Thematic Services (ITVS) are defined corresponding to the two planned phases of the UniNet project. The first one is less ambitious and corresponds to the first phase of the project (current phase) while the second is more complete and ambitious and is due to be launched in the second phase of the project (future phase) after the consolidation of the initiative.

The first Integrated Virtual Thematic Services is formed by the following services:
World Wide Web or WWW (Information service)
File Transfer Protocol or FTP (Information service)
List-service (Communication service)
Internet Relay Chat or IRC (Communication service)

The second Integrated Virtual Thematic Services is expected to be formed by the following Services:
World Wide Web or WWW (Information service)
Channels and DataBase (Information service)
File Transfer Protocol or FTP (Information service)
List-service (Communication service)
Internet Relay Chat or IRC (Communication service)
Audio-conferencing (Communication service)
Video-conferencing (Communication service)

Although character oriented applications work fine, I have been asked if it is possible to prepare a topic and use a voice system on Uni-net rather than typing on a keyboard. The answer is yes. There are several powerful software solutions that deliver file-based and live audio streams to clients over any TCP/IP network. TCP/IP networks include Local Area Networks (LANS), Wide Area Networks (WANS) with intranets, and the Internet.

These servers deliver real-time transmissions of MPEG audio data. In addition to the content created with specific encoding tools, these servers can deliver any content created within the MP3 standard. It can deliver audio content as a "stream" of data over a network. Streaming data is a method of playing content as it is being received, without waiting for long file downloads or transfers.

This overview summarizes the types of content we can deliver and shows a few examples of the methods for streaming data.

Streaming Data on Your Network. Unicast and Multicast.

The StreamWorks MP3 Server delivers streams to clients using two basic transmission methods - unicast and multicast.

Unicast Transmissions: A unicast transmission is the traditional method for sending data over a network to a single network node. Unicast transmissions are appropriate when sending data directly from a Server to a single client or only a few clients. Because unicast transmission sends data to a single network node, it is not an efficient method of streaming the source data to several clients.

Serving a number of clients using a unicast transmission consumes bandwidth for each stream delivered. For example, if you have a stream that is 28k, serving 10 clients uses 280k of bandwidth. Many routers (especially older ones) only support unicast transmission.

Multicast Transmissions: A multicast transmission is a more efficient method to send data over a network to multiple network nodes. Because a multicast transmission can be received simultaneously by multiple clients, network bandwidth is greatly conserved. However, many routers (especially older ones) do not support multicast transmissions.

Multicast Transport Protocols: There have been a fairly large number of multicast transport protocols developed in recent years. (Russell Clark and Ammar, Mostafa. Providing Scalable Web Service Using Multicast Delivery, Georgia Tech, College of Computing, Technical Report GIT-CC-95-03, January 1995. Proceedings of the IEEE Workshop on Services in Distributed and Networked Environments, Whistler, BC, June 1995).

Types of Streams.

Combining Unicast and Multicast Transmissions: On-Demand File, a Live File, and a Live Feed

The MP3 servers can deliver three types of Streams - an On-Demand File, a Live File, and a Live Feed. Each type of stream serves a different purpose. No one stream type is best, and we are not limited to using just one type.

On-Demand File

On-Demand File is a pre-recorded file that resides on your MP3 Server. It is delivered to a Player at the Player's request. For each Player's request, the MP3 server delivers another stream of the file. A Player listens to the stream from the specified start position and can control playback (start, stop, or seek). When a Player stops the stream, the Server no longer delivers the stream to that Player.

To deliver file-based content, you need a source MP3 file and a multiconference server with a network connection. Your clients need a multiconference player and a network connection.

Live File

When you include a Schedule parameter in a Play File for a Live File, the MP3 server waits for the first Player request to begin delivery of the stream. When a Player request is received, the Server calculates the elapsed time and delivers the stream as if it had been in progress. For example, a Live File is scheduled to begin at 5:00 P.M. The first Player requests the Live File at 5:05 P.M. The Player will not see the beginning of the stream, but joins the stream in progress. As other Players request the stream, they join the stream in progress.

If you do not include a Schedule parameter in a Play File for a Live File, the first Player requesting the stream actually starts the stream and views the stream from the beginning. As other Players request the stream, they join the stream in progress.

When any Player stops playing the stream, the Server continues delivering the stream to the other Players. When the end is reached, the stream is automatically played over from the beginning. Serving a Live File minimizes the use of your Server's resources.

Live Feed

A Live Feed is an audio stream originating from an MP3 Encoder. The MP3 server delivers the Live Feed to the Player upon a Player's request. A Live Feed is not a file and is only delivered as long as it being transmitted from the MP3 Encoder. Because the MP3 Encoders can accept audio input from a variety of sources (such as a CD player or cassette tape player), your Live Feed can actually originate from a pre-recorded analog source.

To deliver live content, an analog audio source such as a microphone or camera, an encoder to produce the Live Feed (MP3 audio file in real time), and a multiconference server with a network connection is needed. Your clients need a StreamWorks Player and a network connection to receive the source.

From a technical and technological point of view, the Internet has matured considerably and has grown from a revolution phase to a (more stable and more productive) evolution phase. However, from a human, intellectual and social point of view, the Internet is still a growing and unstable child who is just beginning to have full consciousness of his/her identity and possibilities

UniNet (www.uni-net.org) is like a Virtual City of Knowledge for Virtual User Community. The UniNet Project aims to be universal, linguistically and geographically, and open to all the members of the Knowledge Society, but it covers mainly scientific, academic and cultural topics. Currently the higher emphasis is posed on medical and health science Virtual Community Users.

The objective is to supply information and communication channels in the Internet for each member of the Knowledge Society whatever his/her field or discipline is. One of the critical issues of the project is to provide the best resources for the user with the smaller requirements related with a computer science experience, so that the user can have little and even no knowledge of computers. The different services must be integrated following integration schemas so that the end-point of one service corresponds to the beginning of another. By integrating different services (IRC, www, distribution lists, etc) and by promoting active collaboration we will be able to produce a high quality product.

_____________________________________________________

Casner, S., Deering, S."First IETF Internet Audiocast",ConneXions, No.6:10-17;1992.

Coma del Corral MJ; Martín-Alganza A; Hawa-Attourah M. Direct communication on the Internet. Uninet: the university link for Integrated Telematic Services. Rev Neurol, 154:992-5; 1998

Floyd, A., Jacobson, V., McCanne, S., "A Reliable Multicast Framework for Light-weight Sessions and Application Level Framing", ACM SIGCOMM 95, Boston, August, 1995.

Hofmann, M., Adding Scalability to Transport Level Multicast. Proceedings of "Third COST 237 Workshop - Multimedia Telecommunications and Applications" (Springer Verlag), Barcelona, Spain, November 25 - 27, 1996.

Kumar V. "MBone: Interactive Multimedia On The Internet", Macmillan Publishing, November 1995

Kumar V. "Audio Video Multicast Streaming". Microsoft Interactive Developer Magazine. 1997.

Macedonia, M. R., Brutzman, D. P.,"MBone Provides Audio and Video Across the Internet," IEEE Computer.27:4:30-36;1994.

Matthew T. Lucas, Bert J. Dempsey, and Alfred C. Weaver, MESH: Distributed Error Recovery for Multimedia Streams in Wide-Area Multicast Networks, IEEE ICC '97, Montreal, Canada, June 1997.

Moy J. "Multicast Routing Extensions for OSPF".Communications of the ACM 37:61-66;1994

Savetz, K., Randall, N., Lepage, Y., "MBone: Multicasting Tomorrow's Internet". IDG Books, 1996.

Satoh T; Takahashi K; Yahata K; Nakagawa S; Wojtczak A; Takizawa Y; Tajima N; Kohyama A; Akazawa S; Higashi T; Yamaguchi N; Sekikawa A (1997) Application of Internet technology in public health. Nippon Koshu Eisei Zasshi, Jul 44(7):518-22

Tenenbaum, Andrew, "Computer Networks", third edition, Prentice Hall, 1996

Tomás C. "Grupos de Trabajo en RedIRIS y su entorno internacional". Bol. de la Red Nacional de I+D. RedIRIS 1997; 41:2 (28-36).