10/14/2015CST Computer Networks1 Introduction CST 415

10/14/2015CST Computer Networks2 Topics Definitions TCP/IP Internet Internet Services Networking History IAB RFC

10/14/2015CST Computer Networks3 Definitions Network Any collection of items tied together through some media allowing transfer from one item to the next.

10/14/2015CST Computer Networks4 Definitions What are some networks? –Telephone network –Utility Network –Satellite Network –Other?

10/14/2015CST Computer Networks5 Definition Computer Network A collection of computers tied together by some media to allow information exchange. What is the simplest computer network you can think of? What is the media used for information exchange in this network?

10/14/2015CST Computer Networks6 Definition Protocol The customs and regulations dealing with the ceremonies and etiquette of the diplomatic courts and others at a court or capital. How does protocol relate to network communications?

10/14/2015CST Computer Networks7 Definition Protocol In general, protocol deals with rules and regulations that must be followed for two parties to get along and communicate. In data communications, protocol deals with: –Message format –Message sequence –Rules governing message transfer

10/14/2015CST Computer Networks8 Definition To have a computer network, we must have: –At least two computers. –The two computers are tied together via some communication media. –The communications between the computers must behave according to some set of communication rules (the communication protocol).

10/14/2015CST Computer Networks9 Definition Exercise –Define a media –Given this media »Define a method of information encoding »Define a standard to allow u Unreliable exchange of information u Reliable exchange of information Write your message definitions, sequencing, and rules down. Hand this in at the beginning of next class.

10/14/2015CST Computer Networks10 TCP/IP Internet Although there are many computer communication protocols – »NetBEUI »ISO OSI »etc. The Internet is primarily based on the protocol TCP/IP (Transmission Connect Protocol/Internet Protocol)

10/14/2015CST Computer Networks11 TCP/IP Internet The TCP/IP Internet is an example of a “de-facto” standard. At the time of the Internet’s emergence, there was a competing standard ISO OSI (International Standards Organization Open Systems Interconnect). ISO OSI was defined by a standards committee. TCP/IP was developed and defined “in-place” as part of a research project.

10/14/2015CST Computer Networks12 TCP/IP Internet As has been seen in many other areas of computer technology, the ISO Standards Committee attempted to define a protocol that was “something for everybody”. This slowed the implementation of the standard as well as caused it to bloat. TCP/IP grew out of an implementation. TCP/IP won the Internet because it was already there.

10/14/2015CST Computer Networks13 Internet Services Internet Services are based on protocols. –Application-Level Services (Application Layer) »FTP (File Transfer Protocol) »Telnet (Remote Login) »HTTP (Hyper Text Transfer Protocol) »POP (Post Office Protocol) »SMTP (Simple Mail Transfer Protocol)

10/14/2015CST Computer Networks14 Internet Services Internet Services are based on protocols. –Network-Level Services (Network Layer) »Connectionless Packet Delivery u Packets are delivered through what is known as a virtual circuit. u This means the path between node A and B could change at any time during network based communication. u What are the ramifications of such a scheme? »Reliable Stream Transport u Delivery of information is guaranteed to arrive at the network destination end-point in the order in which it was sent. u Applications do not need to worry about checking delivery status and buffering data until it is all delivered.

10/14/2015CST Computer Networks15 Internet Services TCP/IP Features –Technology Independent : Drivers can be written for any underlying physical transport mechanism. –Universal Interconnect : Any computer on the network is recognized due to a standardized address mechanism. –End-to-end Connectivity : Messages pass from source to destination and are acknowledged as such. Intermediate routing does not change delivery. –Standardized Applications : , ftp, etc.

10/14/2015CST Computer Networks16 Historical Perspective YearEvent 1966ARPA packet-switching experimentation done 1969First ARPANET nodes go operational. 1972Network based written by Ray Tomlinson and brought on-line. 1973First non-US computer linked to the ARPANET 1975ARPANET transferred to the DOD to become DARPANET. 1980TCP/IP protocol experimentation begins 1981Every 20 days, a now host computer is added to the DARPANET. 1983DARPANET is switched over to use the new TCP/IP protocol suite. 1986NSF funds and creates the NSFnet to connect 6 supercomputer centers. 1990ARPANET is retired 1991Gopher introduced, WWW invented, PGP released 1992Mosaic released after being developed by Mark Andreasson et. al. at NCSA. 1995Internet backbone goes private. 1996OC-3 (155 Mbps) backbone built. 1998Number of registered domain names exceeds 2 million 2000Number of indexable web pages exceeds 1 billion. – currently at 11.5 billion

10/14/2015CST Computer Networks17 Historical Perspective Internet growth from 1981 through 2000 plotted on a log scale illustrates the exponential growth.

10/14/2015CST Computer Networks18 IAB The IAB (Internet Architecture Board) was founded in 1983 to oversee the coordination of the TCP/IP protocol suite. Goals: Encourage exchange of ideas. Focus common objectives for research activities. Control direction of network based technologies

10/14/2015CST Computer Networks19 RFC Internet Requests For Comments A series to technical papers covering the TCP/IP Protocol suite. These papers chronicle the work done on the TCP/IP protocol standard as well as work intended for future research. RFCs are located at

10/14/2015CST Computer Networks20 RFC By 1989, the work in networking had become so large that the informal RFC method for communication and standardization no longer worked. Two groups were introduced: IRTF (Internet Research Task Force) : concentrates on long term research. IETF (Internet Engineering Task Force) : concentrate on short-term engineering issues.

10/14/2015CST Computer Networks21 RFC To get a standard: 1.The basic idea must be explained in an RFC. 2.The RFC must generate enough interest to warrant consideration. 3.The RFC will then be advanced to a Draft Standard. 4.A reference implementation must be produced and tested. 5.If the software is sound and the idea works, the IAB will advance the Draft Standard to become a Standard.

10/14/2015CST Computer Networks22 RFC The 802 working groups. The important ones are marked with *. The ones marked with  are hibernating. The one marked with † gave up.