Transcript Hub

Networks
DEVICES
Repeater
device to amplify or regenerate digital
signals received while setting them from
one part of a network into another. Works
on OSI layer 1.
some time the signal becomes weak
or disappears due to the distance
that is sent to. Therefore, we need
to use repeater. The repeater
receives weak signal and then send
it after making it stronger.
While Repeater consider as a cheap
device that uses to expand LAN
networks, it may cause some matters.
For example, it does not filtrate bad
signal and it cause Broadcast Storm
which is accrued when the many
packets are sent to all users and reach
the maximum capability of the
network .
Hub
connects multiple Ethernet segments
together. When using a hub, every
attached device shares the same
broadcast domain. It provides
bandwidth which is shared among all
the objects.
It is used usually in stare networks to
connect all nodes together and send
signal to all of them. It treats data as
electric signals and does not
understand IP addresses.
Types of HUBs
Active HUB.
Passive HUB.
Hybrid HUB.
Active HUB
The majority of hubs consider as an active
hub. They activate signals and they are
called sometime multiport repeaters. Also,
They require electric power to be used.
Passive HUB:
It does not require electric power. It just
connect cables and nodes to each others.
Hybrid HUB
They are usually used to expand networks.
They could be two or more and they are
suitable to be connected to different kind of
cables.
Switch
a device that allocates traffic from one network
segment to certain lines (intended
destination(s)) which connect the segment to
another network segment. So unlike a hub a
switch splits the network traffic and sends it to
different destinations rather than to all systems
on the network. Works on OSI layer 2.
It transmit data depending on MAC
Address. It is easy to be installed to a
network, and it increases speed of
sending data.
We can classify switch in different
layers as following:
It could be in Physical layer which is named
switching hub and deal with bits only.
It could be in data link layer which is named LAN
switch as it has been described later.
It could be in Network layer which is named
Routing switch and doing Router jobs.
Bridge:
a device that connects multiple network
segments along the data link layer. Works on
OSI layer 2.
The main role of a bridge is connecting
different networks together. Each bridge
has a table that contains all nodes
addresses, so it allows signal to move on
another network if the address is in
another one. It does repeater’s job with
better performance . It transmit signal
depending on MAC address. Also it is
worthy to mention that there are internal
and external bridges. The internal bridges
are usually installed in servers computers.
Local bridges
Remote bridges
Local bridges connect to networks or more
directly by network cables. While Remote
bridges connect different networks that are away
from each other by phone links. So there should
be two bridges at least two modem devices.
Bridge learning:
Bridges could realize every addition or
cancelation by sending a messages to nodes or
recognizing each signal that passes through it.
Router:
a specialized network device that determines
the next network point to which to forward a
data packet toward its destination. Unlike a
gateway, it cannot interface different
protocols. Works on OSI layer 3.
It has an address table similar to the
bridge table but much better. It uses IP
Address to reach nodes and has a map
to reach different routers and
networks quickly.
The main purpose of using routers is to
choose the best way to send signal
through. Also it links the data link layer
devices. The router is considered as a
backbone of the networks.
There are two kind of Routers:
Static Router
Dynamic Router
The static router force networks
manager to set convenience tables to
transmit data. Also elect the tracks of
data that is allowed. While the
dynamic router require less attention
from the networks manager.
Gateway:
A device sit at a network node for interfacing
with another network that uses different
protocols. Works on OSI layers 4 to 7.