basic purpose and name the OSI layer where the following devices will be operating:

 Repeaters: repeters also called regenerator, are physical hardware device. They
connet two network segments and broadcast packets between them they have the
primary function to regenerate the electrical signal:

·        
Reshaping the wavefrom

·        
Amplifying the waveform

·        
Retiming the singnal, to
avoid collision on the network

As signal travels along a cable, its strength or
amplitude decreases. This is called attenuation. In other words, the signal
attenuates as it travels along  a cable.
This limits the length of a cable used to connect the computers together. Since
singnal is a factor in the maximum length of a segment, repeater can cable
length. A repeater has intelligence so that it takes a weak signal from one
cable segment, regenerates it and passes it on to the next segment. The
repeater does not amplift the original signal, it regenrates the original bit
pattern.

Hubs can also be called either MUlti port
Tepeaters or concentrators. They are physical hardware devices. A hub is
similar to a repeater, except that it broadcasts data received by any port to
all other ports on the hub. Intelligent Hubs can perform basic diagnostics, and
test the nodes to see if they are operating correctly. If they are not, the
samrt hubs(or Intelligents Hubs) will remove the node form the network. Hubs
are used to provide a physical star Topology the logical Topology is dependent
on the medium Access control Protocol.

A bridge sends the data frames only to the
concerned segment, thus preventing excess traffic. A bridge can split an
overloaded network into two separate network, reducing the amount to traffic on
each segment and thus making each network more efficient. Bridges can also be
used to connect dissimilar networks like Ethernet system to a Token Ring
system. Bridges are both hardware and software devices.

A router can connect network that use different
technologies, addressing methods, media type, frame formats and speeds. A
router keeps track of the address of all the segment of a network and can even
determine the best path for sending data. Routers do not pass broadcast
traffic.

A gateway is the Hardware software that is used
to interconnect LANs and WANs. Gateway are much more complex and powerful than
a router. They are slower than a router and are expensive. A grateway
incorporates the functions of routers and bridges, but it can translate
instruction set on sending network into corresponding instruction set of the
receiving network.