• LAN is stand for Local Area Network.
• LANs make it possible for businesses that use
computer technology to share efficiently such
items as files and printers, and to make
possible communications such as e-mail.
• LANs are designed to do the following:
- operate within a limited geographic area
- allow many users to access high-bandwidth media
- provide full-time connectivity to local services
- connect physically adjacent devices
• LANs consist of:
- Network interface cards (NIC)s
- Networking media.
- Network traffic control devices
- and peripheral devices.
Network Interface Card Device (NIC)
• A network interface card (NIC card or NIC) is a
printed circuit board that fits into the
expansion slot on a computer’s motherboard
or peripheral device.
• It is also called a network adapter. On
• Its function is to adapt the host device to the
Network Interface Card Device (NIC)
• NICs are considered unique devices because
each individual NIC in the world carries a
unique code, called a Media Access Control
• This address is used to control data
communication for the host on the network.
• One of the disadvantages of any cable type that is
used is there is a limit of segment length that the
signal runs through the cable without
• For example: we primarily use (CAT5 UTP) which
can support up to 100 meters without any
• If we need to extend our network beyond that
limit, we must add a device to our network. This
device is called a repeater.
• The purpose of a repeater is regenerate and
retime network signals at the bit level to allow
them to travel a longer distance on the media.
• Repeaters are single-port quot;inquot; and single-port
• The purpose of a hub is to regenerate and retime
network signals . This is done at the bit level to a
large number of hosts (e.g. 4, 8, or even 24) using a
process known as concentration.
• Hub is also known as a multi-port repeater. The
difference is the number of cables that connect to the
• The reasons for using hubs are to create a central
connection point for the wiring media, and increase
the reliability of the network by allowing any single
cable to fail without disrupting the entire network.
• The HUB is classified as active or passive.
• Most modern hubs are active, they take energy from a
power supply to regenerate network signals. Some
hubs are classified as passive devices because they
merely split the signal to multiple users, passive hubs
do not regenerate bits.
• So which one increase the length of the cable?
• A bridge is a device that designed to connect two
• The purpose of a bridge is to filter traffic on a
LAN, to keep local traffic local, yet allow
connectivity to other part (segment) of the LAN
for traffic that has been directed there.
• How does the bridge know which traffic is local
and which is not?
• The answer is the same one that the postal
service uses when asked how it knows which mail
is local. It looks at the local address. Every
networking device has a unique MAC address on
• The bridge keeps track of which MAC addresses
are on each side of the bridge and makes its
decisions based on this MAC address list.
• A switch is a device just like a bridge is. In fact a switch
is called a multi-port bridge, just like a hub is called a
• The difference between the hub and switch is that
switches make decisions based on MAC addresses and
hubs don't make decisions at all.
• Because of the decisions that switches make, they
make a LAN much more efficient. They do this by
quot;switchingquot; data only out the port to which the proper
host is connected. In contrast, a hub will send the data
out all of its ports so that all of the hosts have to see
and process (accept or reject) all of the data.
• The router makes decisions based on groups
of network addresses (Classes)
• Routers can also connect different
technologies, such as Ethernet, Token-
ring, and FDDI (Fiber Distributed Data
• However, because of their ability to route
packets of information, routers have become
the backbone of the Internet, and running the
• The purpose of a router is to examine incoming
packets, choose the best path for them through
the network, and then switch them to the proper
• Routers are the most important traffic-regulating
devices on large networks. They enable virtually
any type of computer to communicate with any
other computer anywhere in the world!