Layer 2 Data Link Layer by ewghwehws


									                   Layer 1
• Physical channel
  • To move bits of data between systems
  • Hubs
     • Passive
  • Repeater
  • 1 and 0
  • cabling
                    Layer 2
                Data Link Layer
• Sub layers
  • Logical Link Layer
  • Media Access Control
• Media Access Control
  • Remembers NICs MAC address
  • communicates with the adapter card
  • controls the type of media being used:
     • 802.3 CSMA/CD (Ethernet)
                    Layer 2
                Data Link Layer
• Logical Link Layer
  • NIC talks to the operating system
  • Places data from the software into frames
     • Bridge
     • Switch
     • NIC
                              Layer 3
• translates logical network address and names to their physical address
  (e.g. computername ==> MAC address)
• responsible for
    • addressing
    • determining routes for sending
    • managing network problems such as packet switching, data congestion and
• if router can’t send data frame as large as the source computer sends, the
  network layer compensates by breaking the data into smaller units. At the
  receiving end, the network layer reassembles the data
• Routers
• brouters
                         Layer 4
• Transport layer manages end to end message delivery in a
  network and also provides the error checking and hence
  guarantees that no duplication or errors are occurring in the
  data transfers across the network.
• Transport layer also provides the acknowledgement of the
  successful data transmission and retransmits the data if no
  error free data was transferred.
• It also provides and error handling and connectionless
  oriented data deliver in the network.
                      Layer 6
• Session layer establish and manages the session
  between the two users at different ends in a network.
• Session layer also manages who can transfer the data
  in a certain amount of time and for how long.
• The examples of session layers and the interactive
  logins and file transfer sessions.
• Session layer reconnect the session if it disconnects.
  It also reports and logs and upper layer errors.
                    Layer 5
• The presentation layer presents the data into a
  uniform format and masks the difference of data
  format between two dissimilar systems.
• It also translates the data from application to the
  network format.
• Presentation layer is also responsible for the
  protocol conversion, encryption, decryption and data
                    Layer 7
• The application layer defines the interfaces for
  communication and data transfer.
• This layer also provides and support services such as
  job transfer, handles network access, e-mail,
  supports user applications and error recovery.
• Protocols: FTP, DNS, SMTP, FINGER, Network
  Devices: Gateway network device is operated on the
  application layer.

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