Cisa Exam Notes - Wan
Compiled by A.K.Asokan. (E-mail:asokanak@hotmail.com)
Page Nos.1 of 16
WIDE AREA NETWORK
Local Area Network can be easily understood since typically every office has a LAN. One could personally see the switches connecting various computer nodes and may be a router to which the switches are connected. Also we can see the Network Interface Card (NIC) at the back of the computer where we plug in the cable with the RJ45 connector, the blinking light etc. on the card. (Sometimes when it is not working, we pull out the cable from the card and plug it again to try our luck!!) All that we know. But how will you establish a connectivity between your Head office located in Chennai and the Branch office in Singapore? What are all the possibilities and whom to approach? We know that there is no way to lay a cable all the way to Singapore! That will be extremely difficult and not a good idea in terms of cost and feasibility also. So, let’s first understand what makes the difference between a LAN and a WAN. The general and immediate answer comes to our mind is that LAN is ‘local’ and WAN is a “wide” area network. The Distance!. But now-a-days we have the wireless LAN technology which can really cover a ‘wide’ area. Then is it the Bandwidth? Again we see the competition at our door step that we can get gigabit broadbands from various service providers at much, much cheaper rates. This is not either. What then? Generally, to set up a LAN, we buy computers, switches, cables, connectors, routers etc. But do you buy any equipment or wire to connect your Branch office located at Singapore or Delhi or Bombay? The answer is No. So we own the LAN infrastructure but we generally lease WAN infrastructure from any third party Service Providers or from a Telephone company. WANs generally carry a variety of traffic types such as voice, data and video. Imagine in your office there are 25 telephone extensions. So you have 25 telephone instruments placed on each officer’s desk wired and
Page Nos.1 of 16
WIDE AREA NETWORK
Local Area Network can be easily understood since typically every office has a LAN. One could personally see the switches connecting various computer nodes and may be a router to which the switches are connected. Also we can see the Network Interface Card (NIC) at the back of the computer where we plug in the cable with the RJ45 connector, the blinking light etc. on the card. (Sometimes when it is not working, we pull out the cable from the card and plug it again to try our luck!!) All that we know. But how will you establish a connectivity between your Head office located in Chennai and the Branch office in Singapore? What are all the possibilities and whom to approach? We know that there is no way to lay a cable all the way to Singapore! That will be extremely difficult and not a good idea in terms of cost and feasibility also. So, let’s first understand what makes the difference between a LAN and a WAN. The general and immediate answer comes to our mind is that LAN is ‘local’ and WAN is a “wide” area network. The Distance!. But now-a-days we have the wireless LAN technology which can really cover a ‘wide’ area. Then is it the Bandwidth? Again we see the competition at our door step that we can get gigabit broadbands from various service providers at much, much cheaper rates. This is not either. What then? Generally, to set up a LAN, we buy computers, switches, cables, connectors, routers etc. But do you buy any equipment or wire to connect your Branch office located at Singapore or Delhi or Bombay? The answer is No. So we own the LAN infrastructure but we generally lease WAN infrastructure from any third party Service Providers or from a Telephone company. WANs generally carry a variety of traffic types such as voice, data and video. Imagine in your office there are 25 telephone extensions. So you have 25 telephone instruments placed on each officer’s desk wired and