These different types of domains mean different things and when
designing a LAN both
of these domains can harm the performance of your network. If you are
not aware of the difference between these two, this tutorial should help
you out.
If you have a small network at your home there is usually the
router/modem that is connected via phone line or cable to the ISP that
router/modem is then connected to a switch or they even have a switch
built into the device. You connect a few cables turn on some devices and
you now have an internet connection ready to go. In larger networks you
have more choices that need to be taken like when to use a hub, a
switch, or a router? How much money do you want to spend usually the
more money spent you get more ports, performance increases and more
features are added. These are all types of components that need to be
thought of when designing a LAN.
This tutorial is going to be focusing on two major things collision
domains and broadcast domains. The definition of a collision domain is
a set of LAN devices whose frames could collide with one another. This
happens with hubs, bridges, repeaters and wireless access points as only
one device can send and receive at a time. If more than one device
tries sending or receiving, the information is lost and irrecoverable it
will need to be resent. This can slow down netwqork performance along with making it a security threat.
A hub is considered a layer one device of the OSI model; all it does
is send packets out on all ports including the port in which the packet
was received on. This causes a collision domain because only one device
can transmit at time. This also shares the bandwidth of all devices
connected to that collision domain. These devices can inefficiently use
that bandwidth because of the CSMA/CD and jamming signals that occur
when a collision happens.
A switch uses layer two of the OSI model, so the switch uses MAC addres to
send the packet to the correct device. Rather than sending it to all
ports a switch only sends the packet out one port, if it has the MAC
address in its MAC address table. If not the switch will send the packet
on all ports except for the port in which the packet was received on.
Switches provide separate collision domains on each port. This provides
dedicated bandwidth to that device. This also allows simultaneous
conversations between devices on different ports. Each port can be
operated at full-duplex so the device can send and receive information
at the same time.
A broadcast domain is
like a collision domain, the definition of a broadcast domain is a set
of devices that if one device sends a broadcast frame all other devices
will receive that frame in the same broadcast domain. So if devices are
in the same IP Networkthey
will be able to receive a broadcast message. Having a smaller broadcast
domain can improve network performance and improve against security
attacks. The more
PCs and
network devices connected to a single broadcast domain, the more
broadcast messages you will have. Remember a broadcast message goes to
every PC and network device. An example is when the router gets a packet
that is destined to a host (192.168.1.124) on its Ethernet interface
(192.168.1.0/24 network) the router will send an ARP request saying who
is 192.168.1.124? That packet will go to every PC on the network, each
PC has to look at the packet and then discard it if it is not
192.168.1.124. But only be processed by the PC that is 192.168.1.124. So
a broadcast message can be just like a collision domain and affect
network performance. The only devices that can block or not send
broadcast messages are routers because they separate networks. Each
interface on a router is a different network.
To find more information about collision domains and broadcast
domains do a simple web search, you will find a lot of information. You
can also go to the Cisco Learning Network to find
that and more information about the networking world. I hope this
tutorial was helpful.
Source :
http://ciscoskills.net/2011/03/30/collision-domains-vs-broadcast-domains/
