Network Concepts

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Network Concepts

• OSI 7 Layer model

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Aims

• Discuss what is meant by a Standard
• Look into the different aspects of OSI and
• discuss what devices relate to the 7 layers

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OSI

• What is a standard?
• A principle commonly agreed to by experts in the
  conduct and use of evaluation for the measure of
  the value or quality of an evaluation.
• ec.wmich.edu/glossary/prog-glossary.htf

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OSI

• What does OSI stand for?
• Open Systems Interconnection
• What is OSI for?
• Describe network communication between network
  devices.
• It is a standard that has been agreed by the ISO
  international standards organisation.
• Any two computers can communicate when connected
  regardless of underlying architecture

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OSI Cont.

• The OSI model is represented by seven layers.
• The seventh layer being the top which is nearest
  the user.
• One being the bottom for the communication medium
  (the data leaving the computer).

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Layer OSI Role Related to a Network
7 Application Email and web browsers many protocols associated to it.
6 Presentation Organisation of data into a format that can be used by humans ASCII - Plain text for web pages Doc Word documents
5 Session This allows you to have multiple browsers and resources open simultaneously without data conflicts in transmission.
4 Transport Firewalls, layer 4 switches operate at this level
3 Network Logical address for a server or workstation is managed here common protocol is TCP/IP. Routing takes place at this level
2 Data Link Physical address (Media access control (MAC)) Used to identify the device. Frame relay
1 Physical Cables/wireless encoding of bits of data 0001111010101, Hubs
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Application Layer 7

• The application layer is the OSI layer closest to
  the end user, which means that both the OSI
  application layer and the user interact directly
  with the software application.
• This layer interacts with software applications
  that implement a communicating component.
• Examples?
• Web browser, Email

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Presentation Layer 6

• Presents data to the user in understandable
  format
• Provides conversion functions for application
  layer data.
• Examples?
• Data representation graphic formats
• Character representation text / ASCII

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Session Layer 5

• Manages connections between machines
• Determines whether all data transmitted /
  received
• It provides for full-duplex, half-duplex, or
  simplex operation.
• Enables the use of multiple browser, chat and
  email to be opened simultaneously.

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Transport Layer 4

• The Transport Layer provides transparent transfer
  of data between end users, providing reliable
  data transfer services to the upper layers.
• Examples?
• Firewalls
• VOIP

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Network Layer 3

• Routing and addressing functions correct
  destinations
• Receives incoming packets of data
• Routing decides what route to use
• Forwarding sends on packets to other hosts

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Data Link Layer 2

• Organisation of data bits into frame structure
• The beginning and end of the data frame
• The address of the sender
• The address of the receiver
• Error checking of the data frame

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Physical Layer 1

• Transmits / receives data bits as electrical
  pulses
• Controls physical link between communicating
  systems
• Describes network topology
• Transmission media cabling / broadcasting
• Transmission devices NICs / modems
• Electrical or optical (fibre optic) signalling

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Conclusion

• Discussed what is meant by a Standard
• Look into the different aspects of OSI and
• discussed what devices relate to the 7 layers