Internet and Intranet Fundamentals Class 4 Session A&B

HTTP Topics Overview Source Documentation How It Works Status Future Directions

HTTP Overview HyperText Transfer Protocol Applications Layer Protocol Generic Protocol gateway to SMTP, NNTP, FTP, Gopher, WAIS Uses TCP Port 80 (by default) presumes reliable transport

HTTP Overview Language of the World Wide Web Provides Open-Ended Set of Methods indicating purpose of request Builds on URI, URL, URN disciplines

HTTP Overview URI = Uniform Resource Identifier identifies points of content mechanism used to access resource specific computer housing the resource specific name of resource on computer formatted strings which indicate characteristics of a resource

HTTP Overview URL = Uniform Resource Locator a particular form of URI Web page address URN = Uniform Resource Name institutional persistence identifies agency responsible for a definition, for example, but not the location namable resource may exist at none or several locations.

HTTP/1.0 Source Documentation RFC 1945 HTTP/1.0 (deprecated) http://www.ics.uci.edu/pub/ietf/http/rfc1945 May 1996 HTTP in use since 1990 Authors Tim Berners-Lee Roy Fielding Henryk Frystyk

HTTP/1.0 HTTP/1.0 superceded HTTP/0.9 HTTP/0.9 allowed raw data transfer HTTP/1.0 introduced MIME types Multipurpose Internet Mail Extensions Content type: text/html Content type: text/plain modify request/response semantics

HTTP/1.0 Shortcomings of HTTP/1.0 weak on proxies, caching, persistent connections, and virtual hosts proliferation of imposters: incompletely implemented applications stateless new connection for each request/response exchange

HTTP/1.1 Source Documentation RFC 2068 HTTP/1.1 http://www.w3.org/Protocols/rfc2068/rfc2068 January 1997 addresses shortcomings of HTTP/1.0

How HTTP Works Request/Response Protocol Request from client contains ... request method URI protocol version MIME-like message with request modifiers, client info, possible body content

How HTTP Works Request/Response Protocol Response from server contains … status line message protocol version success or error code MIME-like message server info entity meta-information possible entity body content

How HTTP Works Request/Response Protocol More Sophisticated Interactions proxies forwarding agent gateways receiving agent tunnels relay point between two connections firewalls non-caching

How HTTP Works URIs Two Forms of URIs See RFC 1738: absolute relative to some known base URI Absolute http: “//” host [: port] [abs_path] http://www.csz.com:8023/directory/file.htm Relative [abs_path] See RFC 1738: http://www.ietf.org/rfc/rfc1738.txt

How HTTP Works Caching not all responses are cacheable national hierarchies of proxy caches to save transoceanic bandwidth systems that broadcast or multicast cache entries organizations that distribute subsets of cached data via CD-ROM

How HTTP Works Media Types Type / Subtype followed by 0 or more optional parameters delimited on the left by “;” parameter are of form attribute=value Content-type: text/html Content-type: text/plain (default) Content-Type: multipart/mixed; boundary=gc0p4Jq0M2Yt08jU534c0p Assigned by IANA

How HTTP Works Media Types Media Type Parameters: charset default is ISO-8859-1 Multipart Types multipart/form-data multipart/mixed multipart/parallel

HTTP Language Tags Identifies language Controlled by IANA en en-US en-cockney x-pig-latin I-cherokee

HTTP Messages Request or Response Use RFC 822 for Transferring Entities I.e., the payload of a message generic-message = start-line *message-header CRLF [ message-body ] start-line = Request-Line | Status-Line

HTTP Messages Methods GET, HEAD must be supported POST for sending data back to server although GET can also be used indirectly to pass parameter information back to the server

HTTP Authentication Secure Sockets Layer (SSL) .htaccess files https RSA Encryption public key / private key not really part of HTTP

HTTP Dynamic Pages: .pl, .asp, .jsp, .stm Information from “environment” and from “forms” examples: http://csz.com/cgi-bin/test-cgi?x=y {get syntax} https://secure1.csz.com/cgi-bin/ssienvirodump.pl

HTTP http://csz.com/cgi-bin/test-cgi?x=y HTTP_USER_AGENT = Mozilla/4.72 [en] (Win95; U) HTTP_REFERER = HTTP_COOKIE = SERVER_SOFTWARE = Apache/1.3.3 (Unix) SERVER_NAME = www.csz.com GATEWAY_INTERFACE = CGI/1.1 SERVER_PROTOCOL = HTTP/1.0 SERVER_PORT = 80 REQUEST_METHOD = GET HTTP_ACCEPT = image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, image/png, */* PATH_INFO = PATH_TRANSLATED = SCRIPT_NAME = /cgi-bin/test-cgi QUERY_STRING = x=y REMOTE_HOST = REMOTE_ADDR = 38.253.188.243 REMOTE_USER = AUTH_TYPE = CONTENT_TYPE = CONTENT_LENGTH =

HTTP https://secure1.csz.com/cgi-bin/ssienvirodump.pl HTTP_USER_AGENT = Mozilla/4.72 [en] (Win95; U) HTTP_REFERER = https://secure1.csz.com/vitafree/order.html HTTP_COOKIE = www.symantec.com FALSE / FALSE 972781498 Pass 1 SERVER_SOFTWARE = Apache/1.3.3 (Unix) SERVER_NAME = www.csz.com GATEWAY_INTERFACE = CGI/1.1 SERVER_PROTOCOL = HTTP/1.0 SERVER_PORT = 80 REQUEST_METHOD = GET HTTP_ACCEPT = image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, image/png, */* PATH_INFO = PATH_TRANSLATED = SCRIPT_NAME = /cgi-bin/test-cgi QUERY_STRING = x=y REMOTE_HOST = REMOTE_ADDR = 38.253.188.243 REMOTE_USER = mussatto AUTH_TYPE = basic CONTENT_TYPE = CONTENT_LENGTH =

HTTP-NG Limitations of HTTP/1.1 lack of modularity message transport, method invocation, document processing too tightly interwoven performance concerns HTTP accounts for too much of the load on the Net wireless at a disadvantage OBEd by XML

HTTP-XLM XML- Definitions XML is a method for putting structured data in a text file XML looks a bit like HTML but isn't HTML XML is text, but isn't meant to be read XML is a family of technologies XML is verbose, but that is not a problem XML is new, but not that new XML is license-free, platform-independent and well-supported

HTTP-XLM XML- Layout