Network Hardware
Hub :
An unintelligent network device that sends one
signal to all of the stations connected to it.
All computers/devices are competing for
attention because it takes the data that comes
into a port and sends it out all the other ports in
the hub.
Traditionally, hubs are used for star topology
networks, but they are often used with other
configurations to make it easy to add and
remove computers without bringing down the
network.
Resides on Layer 1 of the OSI model
Types of hubs:
There are several categories of hubs:
•"Active" hubs: They are connected to an
electrical power source and are used to
refresh the signal being sent to the ports.
•"Passive" hubs: They simply send the
signal to all the connected hosts, without
amplifying it. It acts as a connector.
• “Intelligent” Hub: It perform other intelligent
functions such as network management and
intelligent path selection.
A switching hub chooses only the port of the
device where the signal needs to go, rather
than sending the signal along all path.
A hierarchy of hubs
Bridge :
– Connects two LANs and forwards or
filters data packets between them.
– Creates an extended network in
which any two workstations on the
linked LANs can share data.
– Transparent to protocols and to
higher level devices like routers.
– Forward data depending on the
Hardware (MAC) address, not the
Network address (IP).
– Resides on Layer 2 of the OSI
model.
Bridge
Router
– A device that connects any
number of LANs.
– Uses standardized protocols to move packets
efficiently to their destination.
– More sophisticated than bridges, connecting
networks of different types (for example, star and
token ring)
– Forwards data depending on the Network
address (IP), not the Hardware (MAC) address.
– Routers are the only one of these four devices
that will allow you to share a single IP address
among multiple network clients.
– Resides on Layer 3 of the OSI model.
IP addresses
Routers connecting independent LANs and WANs
Routers
Switch :
– Split large networks into small
segments, decreasing the number
of users sharing the same network
resources and bandwidth.
– Understands when two devices want to
talk to each other, and gives them a
switched connection.
– Helps prevent data collisions and
reduces network congestion, increasing
network performance.
– Resides on Layer 2 of the OSI model.
▪ N-Port bridge where N is equal to number of
stations
▪ Usually used to connect individual computers
not LANs like bridge
• Allows more than one device connected to the
switch directly to transmit simultaneously.
• Can operates in Full-duplex mode (can send
and receive frames at the same time over the
same interface)
• Two types :
– Store-and-forward: switch receives the
whole a frame on the input line, buffers it
briefly , performs error checking, then
routes it to the appropriate output line
(similar to bridge). Buffering will cause
some delay.
– Cut-through: based on the fact that the
destination address appears at the beginning
of the MAC frame, so once the address is
recognized the frame is directly sent to the
appropriate output line if the output buffer
is empty (no need to buffer it). no
buffering delay NO ERROR
CHECKING
Full-Duplex
operation
Gateway
A network gateway is an internetworking
system capable of joining together two
networks that use different base protocols.
A network gateway can be implemented
completely in software, completely in
hardware, or as a combination of both.
Depending on the types of protocols they
support, network gateways can operate at
any level of the OSI model.
The main job of a gateway is to convert protocols
among communication network.
A gateway can accept a packet formatted for one
protocol and convert it into a packet formatted for
another protocol.
Repeater:
– Used to boost the signal
between two cable segments
or wireless access points.
– Can not connect different
network architecture.
– Does not simply amplify the
signal, it regenerates the packets
and retimes them.
– Resides on Layer 1 of the OSI
model.
– A signals that carry information within a
network can travel a fixed distance i.e
500m
– Repeaters do not understand Frames,
packets or header. They understand only
volts.
– Repeaters can extend the physical length
of a LAN.
– Repeaters does not actually connect two
LANs.
– It connect two segments of the same LAN.
Segment connected are still part of one
single LAN.
Function of a repeater
