CORDIS Archive : ACTS Handbook Objectives


	ACTS The Handbook on Communication Services [ Previous Chapter \| Next Chapter \| Table of Contents ]

2.	Definition of Communication Services The four most important means of communication are: 2.1 LS1 Electronic Mail 2.2 LS2 Archiving and retrieval 2.3 LS3 Co-operative work 2.4 LS4 Voice conference A short summary of the proposed approaches and solutions is given below. Due to the importance of security aspects in all communication types, security is dealt with as a separate subject in Section 2.5.

2.1	LS1 - Electronic Mail The three most important means of information transfer today are: Electronic Mail ISDN file transfer goto 2.2 and 3.2 Internet file-transfer goto 2.2 and 3.2 ISDN and Internet file transfer fit better with LS2 - Archive and Retrieval and are described there. In this section and in section 3.1 only electronic mail together with appropriate rendering tools and formats is dealt with. Electronic mail systems are used to exchange messages between users on a store and forward basis. A message submitted by one user is conveyed by a message transfer system, and subsequently delivered to the recipient mailbox. The mail transport service hides the addressing scheme and information transfer protocols that interface to the lower network layers. Figure 2: Electronic Mail The two main schemes that can currently implement this service are Internet - SMTP and X.400. In addition, there are several manufacturer-specific e-mail systems, but they usually have gateways towards SMTP and/or X.400. Thus, from a user point of view, e-mail systems form a common interconnected world and the users do not need to know which technology they are using to send a message. Multimedia mail is explained briefly below. Multimedia Mail is the exchange of messages consisting of at least two media within a message using the mail transport service. In the Internet world MM-Mail is represented by MIME-tools on the top of the SMTP-architecture. Berkom-MM-Mail is an example of the X400 world. Also other manufacturer specific MM-Mail systems are available. A simple way of achieving multimedia mail is using attachments, where MM components (sound, pictures or video) are added as separate files 'attached' to plain text mail messages. This is not ideal since MM messages using attachments are still unrelated collections of multimedia information. In addition, the receiver of the message may not have the necessary manipulation and rendering tools (those tools that are required for viewing or hearing the attachments) on his machine. For effective multimedia information transfer, an agreement must be reached between the sender and the receiver as to which encoding schemes they will use for the various media (e.g. JPEG for still images, MPEG for movies, etc.). However, using attachments has the advantage of being simple and can be extended to all future encoding standards. This openness also allows the transmission of arbitrarily formatted docu-ments, such as those produced by word processors, spreadsheets and other packages. The MIME standard, which can be supported on the Internet mail transport service, operates in this way. It should be noted that there are also difficulties with the message transport system which result from the introduction of multimedia information into a message. Unlike text messages, the size of multimedia messages may range from a few hundred bytes to many megabytes, especially when large video sequences are included. The message transfer system can restrict the overall message size to a particular value, which makes the exchange of video messages cumbersome.

2.2	LS2 - Archive and Search-Retrieval Archiving means the storage of information so that it can be retrieved efficiently. In addition to the physical storage of information on a computer ( known as a server ) this also means having a good referencing system, i.e. one that at least gives details of information location and preferably of the content of that information, in the form of an abstract or keywords, etc.. Search-Retrieval consists, typically, of selecting and locating the information, receiving an overview of the information (e.g. showing text abstracts or thumbnails of pictures), and finally downloading the desired information to your local computer. Archive and Retrieval in this guide are based on Internet solutions (except ISDN file transfer). The information repository of the Internet is available worldwide using a PC, a modem and with an account at an Internet provider. The World Wide Web (WWW) including customised navigators such as Netscape has simplified the accessibility to databases and information servers. The main information servers and services are depicted below. Figure 3: Internet Information Resources The WWW is the most visible facet and interface of the Internet today consisting of client and server computers which can handle multimedia documents. It was developed at CERN between 1989-1991 as a set of protocols and conventions and has become a universe of network accessible information. The client/server communication is based on the Hypertext Transfer Protocol (HTTP). More information see section 2.2.1. Gopher is a powerful navigator which provides menu controlled access to Internet databases. FTP is a protocol for file transfer. Information on FTP servers can be down- and uploaded and exchanged between clients and servers. Users can subcribe News servers with information about nearly every topic. WAIS (Wide Area Information System) is a software package for sharing indexed information on documents across the network. WAIS servers offer directories of indexed information. Telnet offers remote login to Internet connected sites. Three possible approaches for implementing these operations have been identified in the service definition phase, namely: using links, using menus, and using queries. The logical organisation of the Archive and Search-Retrieve operations is illustrated in the figure below. Figure 4:Archive, Search and Retrieval Ftp-kermit is a UNIX program to assist the archiving and searchability of information. The three main schemes that could currently implement this service are: Archive and Retrieval based on (Hyper)Links 2.2.1 Archive and Retrieval based on Menus 2.2.2 Archive and Retrieval based on Queries 2.2.3 2.2.1 Archive and Retrieval based on Links An easy way to grasp the idea of archive and retrieval service is to compare it to hypertext and hypermedia documents. Hypertext allows the users to navigate through the documents available in any server (independently of the physical location of the server) simply by clicking with the mouse in any of the cross-references indicated in the document they are currently looking at. Browsing is the usual term used for looking at documents in this way. Hypermedia is an extension of hypertext to include graphics, audio, and short video clips in the hypertext documents. A good system for providing such a service is the World Wide Web (WWW, W3 or Web). The WWW provides an archive and retrieval service based on hypertext and hypermedia documents. WWW documents are written in the Hypertext Mark-up Language (HTML). Conversion and authoring tools (HTML editors) are available for the production and conversion of wordprocessed documents to be placed on the server. Documents are transmitted between the information server and the client (the users desktop computer) using a simple file transfer protocol called Hypertext Transfer Protocol (HTTP). Besides the HTTP protocol, the WWW clients normally support protocols such as FTP, Gopher, etc., so the information available in those servers can also be accessed through the WWW client. All documents are referred to by means of a consistent naming scheme called Uniform Resource Locator (URL). 2.2.2 Archive and Retrieval based on Menus Selection of documents from a server can also be made via a menu system. Examples of systems supporting this approach are Gopher and WWW (discussed above). Among the protocols that support file retrieval, FTP is the most well-known. FTP services can be replicated and mirrored to speed up access and increase availability and user convenience. Please note that the recommendations dedicate a specific chapter to File Transfer via ISDN. 2.2.3 Archive and Retrieval based on Queries When a piece of information is stored on an electronic repository, it is obvious to store it so that it can be found and retrieved. To assist in this process you may register and maintain catalogue information. Sometimes systems go one step further into a third level of information in which there is a 3-level concept of: data database data dictionary (or meta database). The sophistication catalogue information design depends on retrieval needs. For private information on your own computer, it may be sufficient to use the facilities of the standard operating system, e.g. building file directories, using good naming conventions, and using various tools such as Find or Grep. However, when you have a situation in which the stored information needs to be available to a large audience of people, more sophisticated utilities are needed. Services such as Archie and WAIS may be considered as extensions to Find and Grep. The catalogue-like service can be integrated with several of the proposed tools for accessing the documents once they have been located, e.g. the WWW browsers, electronic mail, or file transfer.

2.3	LS3 - Co-operative Work Figure 5: Multimedia Collaboration (MMC) Co-operative work tools can enhance the management of projects, decision-making processes among international partners and telework (working from home or away from the office using a computer to communicate with others working on the same project using a centralised server) in a distributed environment. The objective of this handbook is to define a workable subset of tools that can be installed easily on remote computers. Co-operative work is defined by a set of key functionalities which provide a feeling of proximity among users at different locations. These features are: high resolution videoconferencing (telepresence) multicast (videoconferencing with more than 2 participants) file transfer further teleservices (e.g. fax, Internet access) co-operative work (incl. application sharing / joint editing) Among the variety of existing solutions for co-operative work, there are two which come close to being able to satisfy the requirements for co-operative work, namely narrowband solutions, based on Euro-ISDN and broadband solutions based on IP over ATM. The main distinction is the bandwidth consumption and the user groups. Due to the fact that only a subset of users can access broadband services, these are defined as optional. Broadband solutions need about 10-20 times more bandwidth than Euro-ISDN (2x64kbit/s) desktop videoconferencing solutions. The main advantages of ATM based solutions are the much better video quality (telepresence); processing speed in shared applications; real multicast; and interoperability between heterogeneous platforms. The main drawbacks are the price; the limited number of users and the fact that most solutions are currently only prototypes with poor support. Nevertheless many research organisations and European telcos offer IP over ATM. Broadband solutions for co-operative work are expected to substitute for Euro-ISDN solutions in the next decade. Since Euro-ISDN is available in all capital cities and trading places worldwide, PC-based videoconferencing has become one of the most powerful means of communication in business, industry and research. Much progress has been made since the standardisation of Euro-ISDN and H.320 as the de facto standard for videotelephony. The installation of desktop videoconferencing is as simple as any other hard- and software installation and the usability is as easy as an analogue telephone. Currently only Euro-ISDN video-conferencing solutions offer dial-up connectivity with network operators providing the access. Tariffs for installation, monthly fee and communication costs are still not uniform in the countries of the EU. The main drawbacks of desktop video-conferencing are related to the bandwidth limitations, i.e. the poor image resolution vs. low frame rates.

2.4	LS4 - Voice Conference Voice conferencing is currently a standard service offering from most network operators in Europe. In section 3.4 a detailed overview of operator services is given by country.

2.5	Security Security of information systems is rapidly becoming an issue. The questions of authenticity (is the information authentic and created by the stated issue?), and confidentiality will need to be addressed. The protection of intellectual property is also of great importance for some of the material that is accessible from archives and video libraries. The provision of a full set of security functions exceeds the scope of this handbook but an attempt has been made to establish the essential requirements in the context of ACTS. For further information go to 3.5. As a result of tests, some recommendations on utilisation of security services are given in section 3.1.2.