1. Internet and Intranet Fundamentals
Class 4
Session A&B

2. HTTP Topics Overview Source Documentation How It Works Status
Future Directions

3. 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

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

5. 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

6. 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.

7. HTTP/1.0 Source Documentation
RFC 1945
HTTP/1.0 (deprecated)
May 1996
HTTP in use since 1990
Authors
Tim Berners-Lee
Roy Fielding
Henryk Frystyk

8. HTTP/1.0 HTTP/1.0 superceded HTTP/0.9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

9. 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

10. HTTP/1.1 Source Documentation
RFC 2068
HTTP/1.1
January 1997
addresses shortcomings of HTTP/1.0

11. 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

12. 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

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

14. How HTTP Works URIs Two Forms of URIs See RFC 1738: absolute
relative to some known base URI
Absolute
http: “//” host [: port] [abs_path]
Relative
[abs_path]
See RFC 1738:

15. 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

16. 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

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

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

19. 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

20. 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

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

22. HTTP Dynamic Pages: .pl, .asp, .jsp, .stm
Information from “environment” and from “forms”
examples:
{get syntax}

23. 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 =
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 =
REMOTE_USER =
AUTH_TYPE =
CONTENT_TYPE =
CONTENT_LENGTH =

24. HTTP https://secure1.csz.com/cgi-bin/ssienvirodump.pl
HTTP_USER_AGENT = Mozilla/4.72 [en] (Win95; U)
HTTP_REFERER =
HTTP_COOKIE = FALSE / FALSE Pass 1
SERVER_SOFTWARE = Apache/1.3.3 (Unix)
SERVER_NAME =
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 =
REMOTE_USER = mussatto
AUTH_TYPE = basic
CONTENT_TYPE =
CONTENT_LENGTH =

25. 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

26. 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

27. HTTP-XLM XML- Layout