The Internet and Network Protocols Review

1
The Internet and Network Protocols(Review)
2
Objectives

• Review the services provided and the operation
  of the internets, intranets and the Internet
• Find out information on Internet protocols via
  the use of RFCs

3
The Internet

• Developed in 1969 as ARPANET
• (Advanced Research Projects Agency Network)
• US defense initiative to develop packet switching
  to produce a network which would be robust
  against hardware failure
• 1973 TCP/IP were adopted as the Internets
  standard protocols
• The Internet is now a global network

4
The Internet, internetsand intranets

• In this module the following terms will be used
  -
• The Internet global network developed from
  ARPANET
• an internet any network using the
  TCP/IP protocols to move traffic
• an intranet TCP/IP network within 1 site or
  organisation

5
Request For Comments RFCs

• RFCs are the documents that give information on
  Internet standards
• Can be downloaded from the web
• RFC 821 Simple Mail Transfer
  Protocol
• RFC 2068 Hypertext Transfer protocol
• RFC 2045-2049 Multipurpose Internet Mail
  Extensions
• For RFCs try -
• http//www.faqs.org/rfcs/ or
• http//www.soc.staffs.ac.uk/ps1/

6
Computer Networking

• Stacks and layers
• The Internet
• TCP Transaction Control Protocol
• UDP user datagram protocol
• The TCP/IP family of services

7
Network Layers

• In network communication a number of services are
  required to move data reliably from 1 point to
  another e.g.
• move bits across a link
• move data reliably across a link, controlling
  errors
• relay data across a network
• move data from 1 host to another, controlling
  errors
• Each of these set of services is called a layer
• The TCP/IP network has 4 layers

8
TCP 4 layers model

• Layer 1 Physical Layer
• moves bits down a wire
• Layer 2 Data Link Layer
• uses layer 1 to move data across the link with
  error control
• Layer 3 Network Layer
• uses a number of layer 2 links to move data
  across a multi-hop network
• Layer 4 Transport Layer
• uses 1 or more layer 3 links to move data
  reliably from 1 host to another

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Layer 1 Physical Layer

• Responsible for moving bits down a link
• Layer 1 is defined by a set of standards for the
  physical connection on a link e.g.
• shape of signal for 1 and 0
• voltage for 1 and 0
• shape of connectors
• type of wire
• data rates
• Note layer 1 does not provide any form of error
  control

10
Layer 2 Data Link layer

• Responsible for moving data across a link with
  some degree of error control
• Layer 2 provides the following services
• structure the data into a frame
• address the data so that it goes to the correct
  recipient
• control access to the media
• do some error detection or error control (Note
  error control is not always provided)
• Examples of layer 1,2 combinations
• Token-Ring
• Ethernet
• Frame-relay

11
Layer 3 Network Layer

• For The Internet, layer 3, or the network layer
  is called IP or Internet Protocol
• It is responsible for
• delivering packets to the correct destination
  over a series of intermediary routers
• fragmenting packets that are too large to cross a
  particular subnet

12
Layer 4 Transport Layer

• For The Internet, layer 4, or the transport layer
  is called TCP or Transmission Control Protocol
• It is responsible for
• moving data from host to host reliably (error
  control)
• flow control between hosts and between host and
  network
• delivering data for a particular application end
  point

13
TCP/IP stack

• When you add the 4 layers together you get the
  TCP/IP stack, layers 1 2 are usually provided
  in hardware and layers 3 4 in software (as part
  of UNIX or Windows OS)

14
Application layer (layer 5)

• When using TCP/IP a 5th layer called the
  application layer is often used as well. This
  consists of a number of protocols which provide
  user services such as HTTP (Web Access), SMTP
  (Mail Service) and FTP (File transfer)

15
Encapsulation and De-capsulation

• Each layer talks to the layers immediately above
  or below it.
• This is accomplished by encapsulation and
  de-capsulation.
• Encapsulation is the process of embedding each
  layers packets into the packets of the layer
  immediately below it
• De-capsulation is the reverse process- stripping
  lower level packets as the data moves up the
  receiving machine's protocol stack.

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Example of encapsulation between protocol layers

• The application generates a stream of data in
  this example a request for a web page

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Encapsulation (cont.)

• The stream is handed to Transport layer which
  encapsulates the packet into a TCP packet.

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Encapsulation (cont.)

• The TCP layer then passes the packet to the IP
  layer which puts them into IP Datagrams.

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Encapsulation (cont.)

• The IP datagrams next go to datalink layer
  (Ethernet) which encapsulates them into Ethernet
  frames

20
De-capsulation

• When the Ethernet frame is received at the other
  end it is passed up the protocol stack with each
  layer stripping of its own header