Lecture#05 Data transmission networks The Bonch-Bruevich Saint-Petersburg State University of Telecommunications Series of lectures “Telecommunication networks” Instructor: Prof. Nikolay Sokolov,

Definition At present time "data transmission" term is often used for description of the different information exchange processes. Earlier this term was used for information intended for processing in the computer or for information already processed by the computer techniques means. In the ITU-T X.902 Recommendation (edition of the 1995) the "data" term definition was given as follows: "The representation forms of information dealt with by information systems and users thereof". Transformation of the term is related to processes of integration and convergence in the modern infocommunication system. In some cases, term "information and communications technology" (ICT) is used instead of infocommunications".

First data transmission systems for the mainframe

Internet Engineering Task Force (IETF) The Internet Engineering Task Force (IETF) is a large open international community of network designers, operators, vendors, and researchers concerned with the evolution of the Internet architecture and the smooth operation of the Internet. It is open to any interested individual. The IETF Mission Statement is documented in RFC 3935 (RFC – Request for Comments). The goal of the IETF is to make the Internet work better. The mission of the IETF is to produce high quality, relevant technical and engineering documents that influence the way people design, use, and manage the Internet in such a way as to make the Internet work better. These documents include protocol standards, best current practices, and informational documents of various kinds.

Internet (RFC 3935 ) The Internet: A large, heterogeneous collection of interconnected systems that can be used for communication of many different types between any interested parties connected to it. The term includes both the "core Internet" (ISP networks) and "edge Internet" (corporate and private networks, often connected via firewalls, NAT boxes, application layer gateways and similar devices). The Internet is a truly global network, reaching into just about every country in the world. The IETF community wants the Internet to succeed because we believe that the existence of the Internet, and its influence on economics, communication, and education, will help us to build a better human society.

Definition related to Internet (1) 1. Domain. Every country is assigned a certain code marking two-three Latin letters long, which is called first level domain. If the address ends with letters "ru", then corresponding site is situated in the Russia’s domain. There are also first level domains, which are related not with geography, but to the site orientation. For example, letters "com" are used for the commercial organizations, and letters "edu" are used for the educational institutes. Domains of the second level are rented to the organizations and private persons. Domain of the second level, as well as the next levels, must consist of the digits and Latin letters. When choosing domain of the second level for their site, as a rule, one usually strives to find a word that will correspond to the organization’s name, produced goods or orientation of activity, and also is easy to read and remember. Second level domain possessor has a capability of creating unlimited number of third and so on level addresses. 2. Search engine. This system serves as an instrument for the information search in the Internet. Search engines differ in scope on local (for example, limited to national domain or certain language) and global (in particular, they qualitatively conduct USA sites search, where the significant part of the information resources is placed). Most part of the search engines does not require knowledge of the special request language. It’s enough to point out in the inquiry line a few key words determining the area of the user’s interest. Texts are the main object for the search engines.

Definition related to Internet (2) 3. Site, Web-site. Site is the place in the Internet, which is determined by its address, has its own possessor and consists of several web-pages, which are apprehended as a single whole. Usually web-pages have identical design. There is no strict definition to the term “site”. For example, some parts of the big sites can be perceived and even defined by their possessors as individual sites. 4. Server, web-server. This term is used in three different meanings. Firstly, sometimes it is equivalent to the term "site". Secondly, computer, which provides site operation, is called server. Thirdly, sometimes the program which provides Web-site operation is called so. Server’s main task is the transmission of the site’s pages via http protocol. 5. Web-page. Web page represents independent part of the Web-site. This document has unique address, which is well known by the abbreviation URL. 6. Host. There are several interpretations of this term. Mostly, any device (including PC), connected to the Internet and using TCP/IP protocol stack is called host. Rarely, by host mainframe is meant. 7. Web-browser. This program provides user with abilities of navigating and reviewing the Web-resources, downloading files and also with a number of other operations. 8. HTTP. Http protocol determines principles of the Web-pages transmission via the Internet network. At first http protocol was used only for transmission of the html-documents. At the present time, it is possible to transmit any information, including static images, sound and video by means of the http.

Definition related to Internet (3) 9. HTML. In that language browser (navigator) is informed just what the text and other elements (pictures, tables and etc) exactly and how should be shown on the page. HTML is not programming language; it’s used for the special markup of the text, meant for the publishing in the Internet. HTML language allows cohering pages by means of links. Existence of the links is an important property of the Web pages. 10. IP-address. This address is used for the identification of the node in the network and for determining routing principles. Address consists of the network and host identifications (network and host ID), assigned by the network administrator. Network ID is a part of the IP-address, which determines group of the computers and devices of one logic network. Host ID is a part of the IP-address, which determines belonging of the computer to the certain network. Usually IP address is written in form of the four numbers with values from 0 to 255, separated by dots. 11. DNS-server. Main function of these special Web-servers is the storage of information about IP addresses and its transformation. 12. URL (Universal Resource Locator). This term is interpreted as the address of the page in the Internet. URL consists of domain name, path to the page on the site and the name of the page file. As a rule files containing Web-pages have "htm" or "html" extensions.

Example of the Internet network structure AS – Internet autonomous system

Interconnection of two local networks R – router, LAN – Local Area Network

Internet influence on the infocommunication system

Some aspects of the Internet evolution

Internet2 (1) Who We Are Internet2 is a not-for-profit advanced networking consortium comprising more than 200 U.S. universities in cooperation with 70 leading corporations, 45 government agencies, laboratories and other institutions of higher learning as well as over 50 international partner organizations. Our organization is governed by an executive Board of Trustees and strategic councils consisting of leaders who represent our broad membership.

Internet2 (2) What We Do Internet2 members leverage our high-performance network and worldwide partnerships to support and enhance their educational and research missions. Beyond just providing network capacity, Internet2 actively engages our community in the development of important new technology including middleware, security, network research and performance measurement capabilities which are critical to the progress of the Internet.

Internet2 (3) Why We Do It We have only begun to discover the potential of Internet technology, not only to the important work of the research and education community, but to commerce and business, to healthcare and science, to the arts and humanities and beyond. Unlike any other organization of its kind, the Internet2 community pioneers the use of advanced network applications and technologies, from their academic inception through their evolution to the commercial Internet.

Internet2 (4) Structure of the network Abilene OC-48c – Mbit/s, OC-192c – Mbit/s, (OC – Optical Carrier)

Protocols (1) DoD – Department of Defense

Protocols (2)

Protocols (3)

Access to Internet (1)

Access to Internet (2)

Wide area network connection (1)

Wide area network connection (2) NTE – Network terminal equipment

Switching equipment

Examples of network structure (1)

Examples of network structure (2)

Traffic growth

Traffic distribution In 2010, approximately 140x10 18 bytes will be transmitted via networks.

Forecast of the access demands

Cost of Internet services

Internet in our life Research company “Yougov” carried out survey among broadband Internet users in Great Brittan. The main goal was to define goods and services that citizens will be eager to sacrifice during economic depression. Approximately 3% of the respondents were ready to save money by limiting expenses on Internet access. About 30% of respondents (near 5 million) were ready to cut down expenses related to newspapers & magazines, alcohol, cigarettes but will use Internet. On the other hand, only 60% of respondents were going to use services from their Provider. Remainder will find Provider with inexpensive services.

Note Some pictures used in this presentation may be found in “Handbook of Data Communications and Networks” written by William Buchanan.

Instructor: Prof. Nikolay Sokolov, Questions? Data transmission networks