Evolved from ARPANET (Advanced Research Projects Agency of the U.S. Department of Defense) Was the first operational packet-switching network Began operations in four locations Was so successful that ARPA applied the same packet-switching technology to tactical radio communication and to satellite communication (SATNET) Internetworking Communicating across arbitrary, multiple, packet- switched networks Led to a Transmission Control Protocol (TCP) and Internet Protocol (IP) Formed the basis for the TCP/IP suite

The term Internet refers to the global information system that: (i)is logically linked together by a globally unique address space based on the Internet Protocol (IP) or its subsequent extensions/follow-ons; (ii)is able to support communications using the Transmission Control Protocol/Internet Protocol (TCP/IP) suite or its subsequent extensions/follow-ons, and/or other IP-compatible protocols; and (iii)provides, uses or makes accessible, either publicly or privately, high level services layered on the communications and related infrastructure described herein

Circuit Switching Requires a dedicated communication path for duration of transmission Wastes bandwidth, but minimizes delays Message Switching Entire path is not dedicated, but long delays result from intermediate storage and repetition of message Packet Switching Specialized message switching with very little delay

Some of the early applications developed for the ARPANET also offered new functionality Telnet Provided a universal language for remote computer terminals FTP Allowed the transparent transfer of files from one computer to another over the network Distributed (1972)

In 1989 Tim Berners-Lee proposed the idea of a distributed hypermedia technology to facilitate the international exchange of research findings using the Internet Prototype WWW was developed at CERN in 1991 using the NeXT computer as a platform First graphical browser (Mosaic) was developed in 1993 by Mark Andreessen at NCSA The layout of the browser display is controlled by the HTML (Hypertext Markup Language) standard Uses HTTP (Hypertext Transfer Protocol) communications protocol in TCP/IP networks to fetch files from servers

Table 7.1 on page 191 of the text defines the following commonly used terms: Central Office (CO) Customer Premises Equipment (CPE) Internet Service Provider (ISP) Internet Exchange Point (IXP) Network Service Provider (NSP) Point of Presence (POP)

32-bit binary numbers Provides unique identification to devices attached to the Internet Has two components: A network number which identifies a network on the Internet A host identifier which identifies a unique host on that network Presents two problems: Routers devise a path through the Internet on the basis of the network number The 32-bit address is usually written as four decimal numbers, corresponding to the four octets of the address

Domain name space Tree-structured name space to identify resources on the Internet DNS database The collection of resource records is organized in a distributed database Name servers Server programs that hold information about a portion of the domain name tree structure and resource records Resolvers Programs that extract information from name servers based on client requests

Based on a hierarchical database containing resource records that include the name, IP address, and other information about hosts Key features: Variable-depth hierarchy for names Essentially unlimited levels and uses the period (.) as the level delimiter in printed names Distributed database: Resides in DNS servers throughout the Internet Distribution controlled by the database The DNS database is divided into thousands of separately managed zones which are managed by separate administrators Distribution and update of records is controlled by the database software

Query begins at a name resolver located in the user host system Each resolver is configured to know the IP address of a local DNS name server If the resolver does not have the requested name in its cache it sends a DNS query to the local DNS server and: Returns an address immediately, or Returns address after querying other servers Two possible types of queries: Recursive Query another name server for the desired result and then send the result back to the resolver Iterative Return to the resolver the address of the next server; the resolver then sends out a new DNS request

Internet protocol defined in RFC 2131 that enables dynamic allocation of IP addresses to hosts Developed to deal with the shortage of IP addresses Enables a local network, such as in a business enterprise, to assign IP addresses from a pool of available IP addresses to hosts currently in use When a host is not in use its IP address is returned to the pool managed by a DHCP server Can also assign permanent IP addresses to some systems, such as servers, so that the address remains the same when the system is rebooted

The structure of the Internet Business and the Internet The use of packet switching Key elements The World Wide Web Internet architecture Chapter 7: The Internet Internet domains Internet names and addresses Domain name system Dynamic host configuration protocol