OSI – 7 Layer model
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.
Ethernet switches, Frame relay
1 Physical Cables/wireless encoding of bits of data
Layer 4 switch Explained:
A network device that integrates routing and switching by forwarding traffic at
layer 2 speed using layer 4 and layer 3 information. When packets are inspected
at layer 4, the sockets can be analyzed and decisions can be made based on the
type of application being serviced.
Research further into the OSI seven layered model and find out some information on
each layer as discussed in the presentation.
Application Layer 7
Presentation Layer 6
Session Layer 5
Transport Layer 4
Network Layer 3
Data link Layer 2
Physical Layer 1
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Get into pairs and find out what the following protocols are used for and discuss
what layer you think that they might be used.
What layer do the following devices operate at?
Looking at the network diagram below relate the design of the network to the seven
layered model. Please make notes on your findings as this will help you when
completing the assignment.
25th Sept 08
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