Teleconferencing service.
Telecom operators
A teleconference is a system for exchanging electronic messages on a specific topic between network subscribers (in delayed communication mode - offline). Each participant receives all materials to his or her email address (E:mail). Each subscriber's e-mail is published on the teleconference server and reaches all participants. (Fig.3).
Rice. 3. Teleconference operation scheme
Unlike e-mail, when a user sends his letter personally to a subscriber or group of subscribers, in teleconferences the letter is sent simultaneously to all its participants. In turn, all messages that arrive at the conference will be sent to the user's mailbox and downloaded to his computer during the communication session.
To participate in the teleconference, you must subscribe to it. There are specific addresses for these purposes. Every conference is devoted to a specific topic, so correspondence in it occurs only within the framework of the topic. According to some estimates, the number of ongoing online conferences has exceeded 50,000.
The newsgroup service is called by many names: newsgroups, Usenet service. At Network nodes, news servers service teleconferences. A news client program must be installed on the user's PC. The MS Outlook Express program mentioned above is both an email client and a news client.
Information services provide users with the ability to access certain information resources stored on the Internet. Such resources are either files in one of the generally accepted formats or various documents.
The use of these resources is provided through the corresponding services.
File Transfer Service
This service is often referred to by the name of the protocol it uses: FTP (File Transfer Protocol). On the Network side, the service is provided by so-called FTP servers, and on the user side by FTP clients. The purpose of an FTP server is to store a set of files for a wide variety of purposes (usually in archived form). Most often these are program files: system and application software.
But sets can store files of any other formats: graphic, audio, MS Word, MS Excel documents, etc. All this information forms a hierarchical structure of folders (directories and subdirectories).
After connecting the FTP client to the server, a file interface for storing folders and files on the server opens on the user’s screen (similar to Windows Explorer). Further work occurs in the same way as with the file system on a PC: folders and files can be viewed, sorted, and copied to your disks. The FTP client is included in Internet Explorer and is therefore always available on a PC running MS Windows. In the field of video conferencing, the term teleconferencing is used as a synonym for the concept. Teleconference is a type of meeting in which communication is carried out at a distance using specialized telecommunications means.
A teleconference primarily involves communication between a large number of users at a distance, united by a common topic or question. Messaging mode
teleconferences
Both video images of participants and audio information are transmitted in real time. Participants can also use collaboration tools on the documents being discussed.
Newsgroups
The term teleconference is closely associated with communication and data exchange at a distance, and therefore it is often used as a synonym for the concept of “newsgroup”. As part of this event, communication is carried out both in real time and with various time delays (that is, offline). Using a specialized client program, the user connects to the news server and selects teleconference, in which he wants to participate. As a result, the user subscribes to a newsletter related to the selected topic, gets access to all conference materials: can read texts, comment, view messages from other participants, take part and start discussions, etc.
Not so long ago, people who wanted to discuss any problem were forced to gather in one place. Nowadays, with the development of teleconferencing technology, people located at a considerable distance from each other can participate in a computerized version of the conference as easily as if they were gathered in the same room.
The microphones of an audio teleconferencing system like the one shown here pick up the voices of people in two offices located in different cities. Simple devices installed at both ends of a telephone line convert the sound waves of outgoing voices into digital impulses, and then carry out the reverse conversion, feeding the voice into an amplifier. Special electronic circuits remove the echo effect and squeaks that occur when sound enters the microphone from the amplifier. A fax machine and electronic sketchbook complete the teleconference equipment list, ensuring the exchange of notes and illustrations throughout the meeting.
With the advancement of telephony, companies can discuss problems directly without having to send their employees on expensive and tedious business trips. The same method allows students to take a course of study. while located a considerable distance" from a college or university. When they have a question for a teacher, they simply raise their hand - electronically - by pressing the keys on their personal computer. Many educational institutions, corporations and government organizations have appreciated the speed and ease of audio and computer teleconferencing. And the day is not far off when specially designed video conferencing rooms, which currently cost about $200,000 but are projected to fall in price, will replace long trips domestically and internationally.
Types of teleconferencing
Both individuals and entire groups can participate in a teleconference. The illustration shows examples of possible combinations of conference participants, as well as the equipment and communications required in each specific case.
Coursework on the topic :
"Computer networks"
Pyatigorsk 2002
1. What is a computer network?
A certain number of computers connected to each other and having special hardware and software designed to be used together.
A computer network may also have a server or host machine, or be globalized (i.e. be part of Internet).
2. How is a local network organized?
The network structure is designed so that each subscriber can connect to another. For example, networks serving any industry are called sectoral, there are networks that exist within one region - regional networks. A local network usually has connections with other networks; for this, one of the servers acts as a gateway; it connects to similar servers of other networks.
3. What functions does it perform?
Local networks perform quite a lot of functions, the main ones being: email, file transfer, etc. A wide variety of information can be transmitted over the network, in particular, the exchange of letters is possible. All information is in the form of files stored on magnetic disks of PCs or servers.
4. What is a global network?
Global computer network- a set of servers, local networks that form a single “seamless” network and use various IP protocols, as well as providing certain services to their users.
You can also give this definition: Global computer network- technology of network interaction between computers of different types.
5. What are sectoral and regional?
See question 2.
6. What is the name of the worldwide network that connects most computers?
Internet.
7. Come up with different ways to connect 4 computer servers. Find a way to communicate, the shortest route between two computers?
Types of connections are shown in the figure. The shortest route between two computers will be when connected by bus.
8. What is email?
The main type of network services is electronic mail (E-mail). When registering on the network, each user receives a “mailbox” there. In reality, a mailbox is simply a subdirectory on the disk of a network host computer, and the user acquires the right to read files in this area. A special addressing system is used to exchange letters. There are a lot of email addressing systems, but increasingly the one that is accepted in Internet. This is due not only to the scale of the Internet, but also with the fact that many disparate networks are connected to each other not directly by mail, but via the Internet. In this system, addresses are written using Latin letters and numbers, and the address format is always the same:
9. What does an email consist of?
The computer name consists of several words or abbreviations separated by periods. The computer name must be read from right to left. This looks unusual for us, but those who corresponded with friends or colleagues from the USA will remember the sequence of writing an address in the West: first the name of the addressee, then the street, then the city, then the state... - and so it is here.
By e-mail you can conduct private correspondence (one-on-one), you can send copies of your letter to other network users, send faxes and telexes, and also work with information servers, requesting information from them that interests you. By the way, an email is not just text. An email can send a binary file, graphics, or sound.
After typing the address and message, we press the Send button. Using the Attach button, you can attach an arbitrary file to a message.
Email is designed to be read by a specific user. But what if you need to contact everyone or a large group of users at once? Of course, you can send a letter to a list, and this method is widely used in networks. But there is another, often more convenient approach - to place the message in some area of the network, which (unlike a mailbox) is accessible to all users. To make this area easier to navigate, it has a clear structure: it is divided into separate sections called teleconferences. Of course, each user decides for himself which conferences he is interested in viewing and which ones he is not. Conferences are usually built according to a single scheme: each conference consists of topics, and each topic contains sequentially numbered responses. You can think of a conference as a bulletin board divided into vertical columns with headings, each column containing a string of notes pinned one below the other.
Such teleconferences are classified as so-called “delayed”, when their participants communicate with each other over a short time interval. However, there is now another form of communication - Internet Relay Chat (IRC), which gives users the opportunity to chat with each other (by entering words directly from the keyboard) through one of thousands of constantly active IRC communication channels.
10. Where is the subscriber's mailbox located and what is stored in it?
See question 8.
11. What is an email address?
See question 8.
12.
See question 9.
13. What are teleconferences and how to become a participant?
Computer network services include: remote control, fax transmission, bulletin boards, software distribution and much more.
14. What is included in the technical means of computer networks?
By technical means are host computers, personal computers of subscribers (terminals), communication lines, modems.
15. Why are telephone lines used as a communication line?
Information in a computer has a discrete binary form, while telephone lines transmit a continuous electrical signal.
16. What is a modem? Its purpose in the network?
Modems(modulator - demodulator) is a device that connects a personal computer with a remote computer or server via telephone communication. A modem is used if the communication channel is a telephone line. The modem converts the computer's binary code into an analog electrical signal from the telephone information transmission network (modulation) and performs the reverse conversion while receiving information.
17. What quantity is the main characteristic of the modem and in what units is it measured?
The main characteristic of a modem is the speed of receiving and transmitting information, which is measured in bits/s or bot/s.
18. What capabilities does a smart modem have?
An intelligent modem can monitor and, in some cases, correct errors.
19. What is a network protocol?
Protocol network operation– this is a standard, a certain form of presentation and methods of sending information, procedures for their interpretation, rules for the compatible operation of various equipment.
20. What is the client-server model?
The organization of software adopted in modern networks is called "client-server technology". The client program prepares the user's request, transmits it over the network, and then receives the response and transmits it to the user.
21. What job does a mail server do?
Server - an e-mail program organizes the distribution of correspondence from subscribers' mailboxes over a network, as well as the reception of incoming information.
22. What work does an email client program do?
Purpose of the client program: preparation of sending subscriber letters, receiving incoming correspondence and a number of services.
23. What's happened Internet ?
Internet– worldwide global computer network.
24. How to translate World Wide Web ( WWW )?
World Wide Web- "The World Wide Web".
25. What's happened WWW ?
WWW is a hyperconnected information system distributed throughout the world, existing on the technical basis of the Internet.
26. What information can be obtained from WWW ?
The information can be very different: text, drawing, photograph, multimedia, advertising, background information, latest news, etc.
27. How is the connection between Internet pages?
The most important property of the WWW is the hypertext organization of connections between WEB pages. The connection between pages is organized through hyperlinks.
28. What's happened Hypertext?
Hypertext is a way of organizing text information within which semantic connections are established. Between its various fragments.
29. What is the analogy WWW and poutines?
WWW is an information system distributed throughout the world. In appearance it resembles a spider's web.
30. What is hypermedia?
Hypermedia– a system of connections between multimedia documents.
31. What's happened WEB- server?
WEB -server– a computer on the Internet that stores WEB pages and the corresponding software for working with them.
32. What method in WWW can I find the right page?
To find the desired page, you need to type the desired address on the keyboard, press the enter key and you will immediately be taken to the right place. Another way to search.
33. What is hyperspace?
Hyperspace is a set of world telecommunication systems and information circulating in them.
The most popular telecommunication technologies currently are videoconferencing and teleconferencing. Their popularity is due to the enormous technological potential of information interaction (information exchange) between subscribers, the ability to work in real time.
Video conference– information technology that simultaneously provides two-way transmission, processing, transformation and presentation of interactive information over a distance in real time using computer hardware and software. Video conferencing interaction is also called a video conferencing session.
Video conferencing(abbreviated VKS) is a telecommunication technology for the interactive interaction of two or more remote subscribers, in which they can exchange audio and video information in real time, taking into account the transfer of control data (Fig. 1).
Rice. 1. Example of a video conferencing session
Videoconferencing is used as a means of quickly making decisions in a given situation; in emergency situations; to reduce travel expenses in geographically distributed organizations, and also as one of the elements of distance learning technologies. To communicate in videoconference mode, the subscriber must have a videoconferencing terminal device (codec), a video phone or other computer equipment. As a rule, a set of devices for video conferencing includes: a central device - a codec with a video camera and microphone, which provides encoding/decoding of audio and video information, capturing and displaying content; device for displaying information and playing sound. A personal computer with video conferencing software can be used as a codec. Communication channels, that is, the data transport network, play a major role in videoconferencing. To connect to communication channels, IP or ISDN network protocols are used.
To implement video conferencing, the head (decision maker) of the organization needs to determine the main purpose of the application: holding meetings, recruiting personnel, efficiency in decision-making, monitoring, distance learning, consulting doctors, conducting court hearings, questioning witnesses, and so on. In this case, it is necessary to take into account the basic rules of video conferencing: equipment on the receiving/transmitting side must be from the same manufacturer; guaranteed high-speed communication service or dedicated communication channels only for video conferencing sessions; stable and reliable power supply for telecommunications equipment and video conferencing; optimal noise- and echo-absorbing features of the room in which the videoconferencing equipment will be installed; correct location of video conferencing equipment in relation to the light background of the room; correct configuration of telecommunications equipment and video conferencing to maintain the quality of communication services with prioritization of data transfer; competent operating technical personnel.
There are two video conferencing modes that allow you to conduct two-way (point-to-point mode) and multi-way (multipoint mode) video conferences. As a rule, point-to-point video conferencing meets the needs only at the initial stage of technology implementation, and quite soon the need for simultaneous interaction between several subscribers arises. This mode of operation is called “multipoint” or multipoint video conferencing. To implement this mode, you must have a multipoint license activated in the codec, provided that the device supports this function, or a special video server, or a hardware-software control system.
Video conferencing systems are based on advances in telecommunications and multimedia technologies. Image and sound are transmitted using computer technology via communication channels of local and global computer networks. The limiting factors for such systems will be the communication channel bandwidth and compression/decompression algorithms for digital image and sound. The typology of videoconferencing systems is presented in table. 1.
Table 1. Types of videoconferencing systems
|
Essence |
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Customized systems |
Provide the ability for individual video communication between the user in real time without leaving his/her workplace. Structurally, individual systems are usually implemented in the form of desktop terminals or software solutions. |
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|
Group systems |
Designed for conducting group video conferencing sessions in meeting rooms. The group system can turn any size room into a video conferencing studio for interactive meetings. |
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Group systems include set-top boxes with standard definition and high definition support). This category also includes TelePresence class systems, which provide a set of tools that provide the maximum effect of the presence of remote interlocutors in the same room. |
Industry systems |
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They are used directly in a specific industry to quickly present information. |
Mobile systems |
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|
Administrative systems |
They are a set of hardware and software tools for administering/managing multipoint video conferencing sessions using various terminal equipment. This category includes multipoint video conferencing servers, as well as software and hardware management systems (a set of accounting systems, configuration management, security, performance and errors of video conferencing nodes, lines and terminal equipment). |
A number of concepts are associated with videoconferencing as an information technology (Table 1). The last concept (distance learning) will be discussed in detail in the tenth chapter of this manual.
Table 1. Concepts related to videoconferencing
|
Concept |
Essence |
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|
Conference call |
Meeting in the form of a telephone conference. |
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|
As a rule, this occurs using a selector, that is, a device that allows you to divide the audience of a meeting into those who have two-way communication (i.e., they can listen and speak - as a rule, this is the host of the conference call) and those who have one-way communication ( who can only listen). |
Telepresence |
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|
Technology for conducting video conferencing sessions, providing the maximum possible effect of presence (a combination of high-definition video conference class in combination with other equipment) |
Situation center |
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Designed for decision makers and can be used in various fields of activity. |
Provides the opportunity to: express analysis of the current situation; |
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modeling scenarios of possible events; expert assessment of decisions made and their optimization; choosing the most effective management influence on a particular situation, and so on. |
Videophone |
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A hardware device that, in addition to transmitting and receiving an audio signal, provides transmission and reception of the subscriber's image. |
Teleconference |
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A set of technical and organizational measures aimed at ensuring two-way audio and video communication between two or more remote objects using television equipment and satellite communications, one of the types of group telecommunications. |
Multipoint Conference Server |
It is known that the larger the network, the more difficult it is to manage. To ensure reliability and increase fault tolerance and security of video conference networks, technologies called network management systems are used. The videoconferencing network management system includes five components (Table 1).
Table 1. Components of a video conferencing network management system
|
Component |
Essence |
|
|
Error handling and analysis |
Providing the necessary tools to detect failures and failures of network and terminal devices, determine their causes and take actions to restore functionality |
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Configuration management |
Monitoring and configuring network hardware and software |
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Measuring network resource usage and availability |
||
|
Performance Management |
Measuring network performance, collecting and analyzing statistical information about network behavior to maintain it at an acceptable level both for operational management of the network and for planning its development |
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|
Security Management |
Control access to equipment and network resources with access logs to detect, prevent and suppress unauthorized access |
Teleconferences (Netnews, Newsgroups), along with e-mail, belong to the “classic” types of service Internet. Teleconferences are a network service aimed at supporting collective discussions, in which thousands of users of global computer networks can take part, and the main purpose of teleconferences is to provide operational information. Teleconference is a user opportunity BBC or a subscriber of an information computer network to participate together with other users in discussing a specific topic. A teleconference in the classical sense can be thought of as a large bulletin board. A subscriber subscribed to a specific newsgroup receives articles on the selected topic written by other subscribers. In this sense, the teleconference resembles a periodical thematic publication. However, the subscriber can also send his own article to the conference, which will become available to all conference participants. So it's also a bulletin board where you can pin your note.
Unlike usual BBC– local bulletin boards, teleconferences in the information network are distributed across the servers of this network and cover all subscribers. Therefore, in the case of many servers, a teleconference is sometimes called an "echo teleconference" (information from one server echoes to another). Almost all commercial information networks have teleconferencing.
Currently in Internet there are discussions in more than ten thousand newsgroups. Each teleconference has its own unique name and is something like a club of interests. Newsgroup names are hierarchical and consist of several words separated by periods.
The name of a newsgroup begins with the name of a hierarchy (top-level category) that groups together a large number of newsgroups and often has several subsections. For example, in the worldwide teleconferencing system Usenet The following basic hierarchies exist: comp(issues related to computers and programming), news(issues of organization, operation and development of the teleconference system), rec(leisure, hobby), sci(the science), soc(social issues), talk(discussion of controversial issues, conversations), misc(topics not included in the listed categories). The most extensive hierarchy of Russian-language teleconferences is the hierarchy relcom, which brings together newsgroups created primarily on the Internet Relcom and widely used in other networks. After the name of the hierarchy, there are sequential names of subsections, narrowing the topic of the teleconference to a specific range of issues. For example, teleconference relcom.commerce.estate is dedicated to the purchase and sale of real estate, and relcom.commerce.food– food products, and both of them relate to network conferences Relcom commercial direction.
The teleconferencing system is implemented using special software - teleconference servers ( news servers), which solve the following tasks: providing users with information about available newsgroups and the ability to view their content, select and receive articles; receiving from users new articles and messages sent in response to previously published publications, and posting them in the appropriate newsgroups; exchange of information with other teleconference servers in order to receive and transmit new publications, that is, relay of teleconferences between nodes.
Teleconference as an information technology has gained immense popularity in many areas of human activity, incl. and in education. Teleconferences differ from each other in three important ways. According to the degree of accessibility and openness, they distinguish open and closed teleconferences. Private newsgroups differ from public newsgroups in that they are only available to a limited number of registered users. According to controllability they distinguish moderated, pre-moderated and unmoderated teleconferences. Moderated teleconferences are characterized by the presence of a moderator who is responsible for organizing and conducting the teleconference. In pre-moderated conferences, messages are also processed by the moderator, but after they are published in the teleconference. In this case, the moderator can delete or leave a message or make a comment. Unmoderated teleconferences are characterized by the absence of a moderator; participants themselves direct the development of the discussion during the exchange of messages. Based on their mode of operation, conferences are divided into delayed mode and in real time. For example, on the Internet, conferences in deferred mode are organized in the form of discussion groups (Newsgroups), mailing lists (Maillists), electronic mail (E-mail), etc. Here, communication between participants occurs through the exchange of messages via email. Real-time conferences include IRC (Internet Relay Chat), ICQ (I seek you), chat servers with a WWW interface, video teleconferences. In this case, communication between participants is carried out using special software and equipment. Real-time mode implies the immediacy of the processes of receiving and transmitting information, as well as responses.
The simplest ones from the point of view of organizing teleconferences are in delayed mode. However, if the number of participants is small and they are not in distant time zones, it makes sense to conduct teleconferences in real time.
Delayed conferences held via email using a mailing list, have their advantages. This type of conference is more preferable for organizing educational telecommunications among students, since most Russian universities do not have direct access to the Internet. Creating an educational mailing list in its various variants - free, moderated, with access restrictions, etc. - allows you to organize the work of students on the network in accordance with the educational tasks being solved. Depending on the chosen option for operating the mailing list, the educational structure of the electronic conference is also built. A significant advantage of such conferences over a real-time conversation is the greater period of time allotted for thinking through their questions, answers and judgments, which allows the participant to prepare his answer and bring it into line with the given requirements. In a chat conference, due to limited time, it is difficult to avoid making unsubstantial remarks. In addition, participants can send illustrative material and multimedia information by e-mail, which is currently impossible to present in conventional chat programs. The most common email programs are TheBat, Internet Mail, Outlook Express, Eudora, Exchange Mail, Beauty Mail, etc.
Another type of teleconference held in a delayed time mode is teleconferences held on a special news server. You also need to subscribe to them. In practice, this means that the user defines a list of newsgroup addresses that will be read during each network connection session (downloading and unloading mail). The most common network organized according to this principle is Usenet, an international newsgroup network. Discussion groups are called newsgroups or newsgroups. The material for teleconferences is new articles submitted by users and responses to previously published ones. To work with these newsgroups in Outlook Express, you must set up a news reader. The disadvantage is the difficulty in highlighting the main message and the responses received in the case of a large number of participants corresponding with each other in one teleconference on various topics. In the Outlook list, you can read only the main messages or just one message and all replies to it.
