Web Basics and Protocols CS 502 - PowerPoint PPT Presentation

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Web Basics and Protocols CS 502

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Web Basics and Protocols CS 502 20020129 Carl Lagoze Acks to McCracken Syracuse Univ. In the beginning . In the beginning ARPANET DoD funded through ... – PowerPoint PPT presentation

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Title: Web Basics and Protocols CS 502


1
Web Basics and ProtocolsCS 502 20020129Carl
Lagoze
Acks to McCrackenSyracuse Univ.
2
In the beginning.
3
In the beginning
4
ARPANET
  • DoD funded through leadership of Licklider
  • Inspired by move from batch to timesharing
  • Allowed remote login

5
Packet Switching
  • Invented in early 1960s by Baran, Davies,
    Kleinrock
  • digital, redundant, efficient, upgradeable
    (software)
  • 1969 ARPANET first network implementation

6
Packet Switching
  • Network messages broken up into packets
  • Each pocket has a destination address
  • Pass and forward model router gets packet,
    examine, decides where to send next
  • Message reassembled on other end

7
Layered Protocol Model
8
TCP/IP Protocol Suite
  • IP packet delivery
  • TCP virtual circuits, packet reassembly
  • ARP/RARP address resolution

9
Protocol Layers
10
Internet Issues (Internet 2)
  • Demands of multimedia applications
  • Virtual circuit reservations bandwidth and
    quality of service guarantees
  • Real time streaming protocols
  • State saving

11
Internet Governance
  • Internet Society (ISOC) Evolution, social
    political issues
  • Internet Architecture Board (IAB) Oversees
    standards process
  • Internet Engineering Task Force (IETF)
    standards development
  • Internet Assigned Names Authority (IANA)
    protocol assignment
  • Internet Corporation for Assigned Names and
    Numbers (ICANN) IP and DNS addresses
  • World Wide Web Consortium (W3C) web standards
    and evolution

12
Internet Documents
  • STDs Official IETF Internet standards
  • http//www.rfc-editor.org/rfcxx00.html
  • RFCs Requests for Comments to IETF community
    for information, standardization
  • http//www.ietf.org/rfc.html
  • Internet Drafts IETF working documents
  • http//www.ietf.org/ID.html
  • W3C Reports (recommendations, drafts, notes)
  • http//www.w3.org/TR/

13
Well-Known Protocols
  • Telnet external terminal interface, RFC 854
    (1983)
  • FTP file transfer, RFC 959 (1985)
  • SMTP mail transport, RFC 821 (1982)
  • HTTP distributed, collaborative hypermedia
    systems, RFC 1945 (1.0 1996), RFC 2616 (1.1 1999)

14
Daemons and Ports
telnetd
Socket (Virtual Circuit)
23
httpd
80
ftpd
21
15
Basic Socket ServerProgramming
16
HTTP
  • HTTP is
  • Designed for document transfer
  • Generic
  • not tied to web browsers exclusively
  • can serve any data type
  • Stateless
  • no persistent client/server connection

17
HTTP Session
  • An HTTP session consists of a client request
    followed by a server response
  • Requests and responses
  • are sent in plain text
  • conform to the HTTP syntax
  • consist of start line, headers, blank line, and
    message body

18
HTTP Request
  • Start line
  • Consists of method, URL, version
  • GET index.html HTTP/1.1
  • Valid methods include
  • GET, POST, HEAD, PUT, DELETE
  • Headers
  • HTTP/1.1 requires a Host header
  • Body content

19
HTTP Request Methods
  • Methods include
  • GET retrieve information identified by the URL
  • HEAD same as get but don't get message body
    (content)
  • POST accept the request content and send it to
    the URL
  • PUT store the request content as the given URL

20
HTTP Response
  • Start line
  • consists of HTTP version, status code, and
    description
  • HTTP/1.1 200 OK
  • HTTP/1.1 404 Not Found
  • Headers
  • Content-type text/html
  • Content

21
HTTP Response Codes
  • Respose coded by first digit
  • 1xx informational, request received
  • 2xx success, request accepted
  • 3xx redirection
  • 4xx client error
  • 5xx server error

22
HTTP Content Body
  • Header fields can affect content interpretation
  • required header field Content-type
  • others Content-Encoding, Content-Length,
    Expires, Last-Modified
  • added by web server - we will configure some of
    these later

23
Serving a Page
  • User of client machine types in a URL

24
Serving a Page
  • Server name is translated to an IP address via DNS

25
Serving a Page
  • Client connects to server using IP address and
    port number

26
Serving a Page
  • Client determines path and file to request

27
Serving a Page
  • Client sends HTTP request to server

28
Serving a Page
  • Server determines which file to send

29
Serving a Page
  • Server sends response code and the document

30
Serving a Page
  • Connection is broken
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