NetWork Device

Networking Devices
• Punch_down panels
• Hubs
• Switches
• Bridges
• Routes
• Gateways
• Network Interface Cards (NICs)
• Wireless access points
• Modems

Hubs
• The bottom of the networking food chain
• Connect device and create larger networks
• Small hubs 5-8 ports (workgroup hubs)
• Some hubs have more ports, up to 32 normally
• Direct data packets to all devices connected to the
hub – shared bandwidth
animation
• Scalability, Collision, inefficient

Bridges
• Divide larger networks into smaller sections
• Check MAC address, forward or block the data
• Learning bridge builds list of MAC address by watching
the traffic on the network.
• Two issues to consider:
– Placement 80/20 rule
– Bridging loops
• IEEE 802.1d Spanning tree protocol
• Types of bridges
– Transparent bridge
– Source route bridge
– Translational bridge

Bridges
• Source Route Bridge
– Used in Token Ring networks.
– The entire path (ring number and bridge
number) is embedded within Packet
• Search frame
• Route discovery frame
• Translational bridge
– Used to convert one networking data
format to another.
• For example, from Token Ring to Ethernet
and vice versa.

Switches
• Like hub, connectivity points of Ethernet network
• Forward only to the port that connects to the
destination device
– knows MAC address
– Match the MAC address in the data it receives.
• Fully switched network, a dedicated segment for
each device is connected to switch. Expensive.
Switch routing method
Packet-based switches use one of the following
method to route packet.
• Cut-through
– Forward as soon as it received the destination MAC –
first 14 bytes
– Can cause propagation of error
• Store-and-forward
– Error checked before being forwarded
– Errors are not propagated through network
• Bad frames are discarded
– Error checking takes time.
– Considerably slower

Hub and switch cabling
• To create larger networks, connect hubs and
switches using
– Standard port with special cable
– Special ports with a standard cable
• Standard port – Medium Dependent Interface-
Crossed (MDI-X)
– Two wires are crossed internally
• Medium Dependent Interface (MDI)
– To see each other as an extension, no signal to be
crossed
• Using crossover cable between two MDI-X ports
– To uncross the internal crossing

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