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TCP
Transmission Control Protocol (TCP) is a Layer 4 (Transport) protocol that evolved from the Network Control Protocol (NCP) of ARPANET. NCP was developed to provide reliable transmission across the essentially unreliable media of analog UTP and packet radio (AlohaNET). In support of higher level applications, TCP can be characterized as making use of virtual circuits in support of byte-stream oriented communications. TCP is a connection-oriented protocol that provides end-to-end flow control and error control. It also supports status exchange and synchronization [13-28] and [13-19].
IP
Internet Protocol (IP), the basic building block of the Internet, is a Layer 3 (Network) internetworking protocol for the routing of datagrams through gateways connecting networks and subnetworks. IP can be characterized as being datagram-orientedit provides for packet segmentation and reassembly and provides specific addressing conventions. IP supports routing control and status translation and communications. It also supports multiple service types, including low-delay, high-bandwidth, and high-reliability paths. Dialup IP access protocols include SLIP and PPP.
SLIP
SLIP (Serial Line Interface Protocol) was the original and remains the most basic protocol for handling IP packets across a voice-grade telephone connection. Installed on both the users workstation and the providers server, SLIP forwards packets created by TCP/IP software.
PPP
PPP (Point-to-Point Protocol) performs the same basic functions as SLIP. Additionally, it performs fairly sophisticated compression in order to eliminate unused or redundant data in the headers of long sequences of packets in a transmission stream. Further, PPP supports multiple native machine and network protocols and supports subnet routing. For instance, PPP installed on a telecommuters home PC will allow communication with the home office through a router connecting to a LAN based on AppleTalk or Novell. It will also support IP packet communication through the Internet [13-6].
Application-Level Protocols
Application-level protocols function above the TCP/IP protocol suite in support of specific Internet applications. Examples include Telnet and File Transfer Protocol (FTP).
Telnet
Perhaps the oldest Internet application protocol, Telnet provides terminal emulation, allowing the user to assume control over the applications that reside on a remote system. Virtual network terminal services allow the DTE to emulate other terminal devices, transparently, in a client/server environment.
FTP
File Transfer Protocol (FTP) supports the exchange of files between two hosts across the Internet. ACSII and binary file transfers are supported between a client and a server.
SMTP
Simple Mail Transfer Protocol (SMTP) supports text-oriented e-mail between any two devices that support MHS (Message Handling Service). Multipurpose Internet Mail Extension (MIME) is a SMTP extension that allows the attachment to textual e-mail of other types of files, including audio, graphics and video. Thereby, compound mail can be transmitted across the Net.
Internet applications are growing as fast as the imagination and technology will support. The applications include e-mail, file transfer, Bulletin Board Systems (BBSs), library catalogs, online banking, video and radio broadcasting, and even voice telephony.
E-mail clearly is the most popular application. More than one billion e-mail messages of over one trillion bytes (1TB) transverse the Internet each month. It is estimated that over 100 million people will use e-mail by the year 2000.
File transfer is accomplished through the File Transfer Protocol (FTP). Through any of over 8,000 FTP servers, any of the thousands of Net servers and their resident file resources be accessed and transferred in ASCII or binary code from the server to the users computer. While many FTP resources are privileged, others are unrestricted and available for public consumption. Such unrestricted resources can be accessed via the use of the account name anonymous. Large files ([ge]50 KB) generally will be in compressed format using compression techniques specific to the computer operating system; examples include .Z or .tar (UNIX), .zip (MS-DOS), and .hqx (Macintosh).
Bulletin Board Systems (BBSs) are specific to a region or area of topical interest. Each supports numbers of subcategories. Network News, or Usenet News, formed in 1979, is a collection of over 6,000 special-interest Bulletin Boards (BBSs). Example BBSs include the following:
Library catalogs for over 300 libraries are available through the Internet. Such catalogs include the U.S. Library of Congress, the Research Libraries Information Network and many major colleges and universities. Through the Interlibrary Loan program, Internet users may be able to have the document loaned to their local library.
Realtime applications are growing at significant rates. There are a number of legitimate applications, and many which are less so. Realtime applications include collaborative design and development, interactive role-playing, interactive remote education and chat lines (realtime BBSs). Other applications include voice and video conferencing, network games, gambling, and radio and video broadcasting (cybercasts).
Online banking has received a good deal of interest as a result of the failed acquisition talks between Microsoft and Intuit. While security issues abound, there is little doubt that this application has great promise.
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