1969 UCLA became the first node on ARPANET (created by the Department of Defense) At the end of 1969, there were 4 hosts on this network.
Other networks: BITNET, CSNET, USENET, SPAN, among others
1984-5 NSFNET (and JANET in Britian) announced an initiative to create an “open” network to serve the entire higher education community (many earlier networks were designed for a limited collection of users)
NSFNET originally connected 5 super computer centers, but became the backbone for the Internet. In 1992, over 1 million computers were connected to the Internet.
NSFNET required the use of TCP/IP (Transmission Control Protocol/Internet Protocol) as the method for passing information between nodes.
1989-1991 development of the World Wide Web – client (browser) server (www server) technology using the Internet as the medium.
1993 MOSAIC, the first “browser” was publicly available from NCSA. They also released a free web server httpd.
Internet – collection of computer systems and the basic protocols for intersystem communication
WWW – collection of documents and retrieval methods utilizing client-server technologies.
IP Address – 32bit number (address) assigned to each node of the Internet
Arranged as a sequence of 4 bytes: eg 130.101.5.4 (University of Akron)
Actually, these addresses are in 2 parts network/host – the division point depends on the class of the address:
Class A - supports 16 million hosts on each of 127 networks (0.x.x.x to 127.x.x.x)
Class B - supports 65,000 hosts on each of 16,000 networks (128.0.x.x to 191.255.x.x) The University of Akron has 130.101.x.x Class B address
Class C - supports 254 hosts on each of 2 million networks (192.0.0.x to 223.255.255.x)
The first part of an IP address determines its class… 127 is reserved for local (loopback) tests
An IP Index may be found at http://flumps.org/ip/index.html
Domain Names (www.uakron.edu) are text versions of IP addresses. Domain Name Servers make the translations. The last part is the top-level domain (usually .edu, .org, .com, .net, or a country id such as .jp or .uk). The middle section is the domain (such as uakron) and the first part the actual host (machine) – such as www or vonneumann.
Ports – Each node identified by IP address has 65536 ports. TCP/IP messages are directed from a port to a port (using a particular communications protocol). Servers are programs running on a host that “listen” to one or more ports.
Common port assignments:
| Service | port |
| ftp | 21 |
| telnet | 23 |
| gopher | 70 |
| http | 80 |
| nntp | 119 |
| wais | 210 |
URL – Uniform Resource Locator – protocol:location
http://www.cs.uakron.edu:80/~margush/index.html
Partial URLs omit the host and assume the rest from the context of the URL.
Other URL protocols: file, ftp, gopher, telnet, mailto, news, and wais
Protocols (developed by the mid 80’s) telnet, ftp, gopher, smtp, nntp, wais, …
WWW servers often modify the path relative to a root directory. They also react differently when a directory or executable file is the resource.
MIME (Multipurpose Internet Mail Extensions) is part of the http protocol. WWW servers attach a MIME type to all returned resources. The browser reacts differently to different types.
Servers determine MIME types from the file system – for example by the file’s extension.
| .gif | image/gif |
| .jpg | image/jpeg |
| .ps | application/postscript |
| .html | text/html |
| .txt | text/plain |
Browsers display some of these internally. Others require external applications for proper display.
HTTP Protocol:
Request:
Get www.cs.uakron.edu/~margush/index.html
accept text/plain, text/html, image/gif
(blank line)
Response:
HTTP/1.1 200 OK
Date: Tue, 15 Jan 2002 19:07:21 GMT
Server: Apache/1.3.14 (Unix)
Last-Modified: Mon, 24 Sep 2001 15:02:40 GMT
ETag: "3187-153-3baf4b10"
Accept-Ranges: bytes
Content-Length: 339
Connection: close
Content-Type: text/html