Page 36 - Intelligent Communication Systems

20 INTELLIGENT COMMUNICATION SYSTEMS
The OSI reference model was implemented at the U.S. National Bureau of Standards
as OSINET. The Manufacturing Automation Protocol (MAP) was implemented by
the consortium of GM and Boeing.

33 INTERNET NETWORK ARCHITECTURE

On the Internet, local area networks (LANs) are interconnected via dedicated lines
or telephone networks. A local area network is installed in the intraoffice network.
In LAN, terminals such as workstations, personal computers, and/or computers as
file server or database server or mail server are linked to the bus or ring network.
The network provides 1.5-100Mbps transmission lines. The Internet is called the
network of networks. Local area networks are interconnected by telephone network
or dedicated lines to form the Internet.
There are ring and bus network structures in the local area network topology.
Using the Internet, various kinds of IT services are provided, including mail han-
dling, database access, file access, continuous acquisition and lifelong support
(CALS), electronic payment, and electronic commerce services. Security is intro-
duced to protect information transmitted over the Internet from hackers, dishonest
users, and wiretapping. Encryption and decryption are implemented to build secure
networks.
To achieve the high-speed Internet, advanced Internet projects, such as Internet
2, are going on.

3.3.1 TCP/IP Protocol
TCP/IP has been widely used in the Internet as a de facto standard protocol. The
TCP/IP protocol initially was developed as ARPA network protocols and was
improved to include the concept of network architecture. It was implemented as
the standard protocol in Unix 4.2 Berkeley software distribution (BSD). Because
it was used in the Unix operating system, it has been widely employed on the
Internet, where Unix was mainly used. The TCP/IP protocol is shown in Figure 2.4,
where it is compared with the OSI protocol.
In accordance with the advances on the Internet, workstations that have a
reduced instruction set computer (RISC) and run on the Unix operating system
have been developed and put into practical use. At the same time, local area net-
works have been widely used and have expanded throughout the globe. In order to
interconnect workstations, the TCP/IP protocol has been used as their standard pro-
tocol. Because TCP/IP has been used mainly in local area networks, it has been
recognized as the de facto standard protocol in the local area network environment.
The TCP/IP layer structure is shown in Figure 2.4. There are five layers from
bottom to top: physical, network interface, Internet, transport, and application.
The application layer includes such application programs as the Telecom-
munication Network Protocol (TELNET), the File Transfer Protocol (FTP), and
the Simple Mail Transfer Protocol (SMTP).