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					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
                                   0001111010101, Hubs

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.


Task 1
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




HNC Computing                                                              Page 1 of 2
Task 2

Get into pairs and find out what the following protocols are used for and discuss
what layer you think that they might be used.

          FTP
          DNS
          TCP
          IP
          ARP

Task 3

What layer do the following devices operate at?

          Ethernet Switch
          Router
          Cables
          Firewall

Task 4

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
                                       Network Concepts

                                        Network Diagram

                                                                                            Internet


                                               Printer




                         Laptop                                                Firewal
                                      Switch




                                                                  Router




                 Computers
                                                                           Scanner




                                                         Server




HNC Computing                                                                 Page 2 of 2

				
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