When dealing with networks one has to understand the different types and how they are used along with the advantages and disadvantages of each.
A mesh network allows for redundancy in that if one node goes down all terminals are able to still communicate with
other terminals and networks by taking several possible paths. The mesh network will be more complex and time consuming
to install, but is also the more reliable than other topologies. If each terminal having reliable connectivity is mission
critical, the knowledge is available and cost is not really a factor then a mesh would be the preferred network.
Bus topology is probably the least preferred topology to implement. If one node is removed or non-operational on the bus
then all terminals will not be able to utilize the network. According to Annabel Dodd (2005) “Prior to hubs, each device
in a LAN was wired to another device in a “bus” arrangement.”(p. 26)
Circumstances that may play a factor in this use of this particular topology would be cost savings in regards to cable and
the importance of that particular network to the department’s mission, as well as the network’s size as well as security.
Required speed, number of attachments, cable length, and use play a factor in determining the use of the bus topology.
Bates & Gregory (2000) tell us that bus speed is limited to “10Mbits/s with effective throughput of 3.3-4 Mbits/s” and that
attachments cannot exceed “1024 addressable nodes” and are “limited to cable lengths of 1500 meters.” They continue on to
say that “collisions when the network gets 40% busy, resulting in less throughput.” It seems that the bus topology is also
the least secure in respect to the fact that all transmissions are a broadcast to the entire network.
The star topology is another network architecture. Circumstances to install this type of network would be similar to those of the bus topology. The star topology would be
primarily used with hubs and switches. This topology allows for all terminals to continually communicate on the network
when a terminal is dropped or goes down. This type of topology is important when connectivity of each terminal in the
network is important and is mission critical to operations.
Combinations of all the various topologies will be seen in MAN, WAN, and even some larger LANs. An example would be a
college campus in which each department uses a star topology internally, but meshes with all the other outlying departments.
So in the case of a college campus all departments would still be able to access records from other departments on campus
when one or more departments lose connectivity.
By: Joseph Brochin
Posts Tagged ‘Node’
Network Basics
January 30th, 2010Understanding Your Home Network
October 19th, 2009
A home network is a very complex thing. Taking information from one place to another place which might not eve be on the same continent is a pretty big deal. This article will not go into too much technical jargon, but will do a thorough job of answering general (and some complex) questions about networking, especially wireless networking. Let us look at the most basic aspects of a wireless network in a question/answer format.
How does the signal get from my computer to my router, the Internet and back again?
When a computer user is connected to the internet, they are almost constantly sending signals to multiple places. The way this is achieved begins with binary code. Everything the user does is broken down into binary code and sent (in this case, wirelessly) to the router and then towards the destination you have given it. In the case of a wireless connection, it is sent from the wireless card to the router using a protocol called CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) which only allows one node (or computer) to access the router at once. If one computer is using the router and a second computer wants to use it too, the second system is sent a sort of “busy signal” and must wait a specified amount of time. Once the time is up, the computer may resend the request. For reference, a wired connection uses CSMA/CD (Carrier Sense Multiple Access with Collision Detection), which enables the computer to sense when another node is using the router. This way the request is not sent in the first place.
This, of course, makes more sense, but it is not possible with a wireless connection as there is no permanent connection to the router. The connections imply stops when the request has been fulfilled unlike the wired connection which always has the cable connected. The router now relies on the 7-layer OSI model (which is too elaborate and advanced to fit into in this article, but Google can e your friend) in order to get the information to and from the destination host.Basically, the router (which for the sake of argument will work as a DNS server in this scenario) finds Google’s assigned IP address and throws your request for Google out to their web server. The connection is directed at port 80 for access to a web page and is then processed by Google’s web server. The signal is then sent back the same way it was sent out from the computer. When it arrives back, the user sees the display from Google. This process is done very quickly as you get your display sometimes in a matter of less than a second. If the user lives in the US and the web server is in China (again, only for the sake of argument), the speed at which all this is done is quite impressive to the uninitiated. This is a very brief description of how the process works.
What Kind of Protection is Available for Wireless Networks?
There are a few options for wireless encryption. Encryption is very useful as it helps keep people off your wireless network if they aren’t supposed to be on. This is basically a password-protection for your connection. Some of the more popular choices are as follows:
WEP (Wired Equivalent Privacy)
WEP typically uses a 128-bit encryption scheme using using a string of 26 hexadecimal (base 16) characters. 256-bit is available, but historically has been quite uncommon. This method of encryption is a bit outdated but is still used by some. This has been replaced by the more secure WAP and WAP2, discussed next. The way a computer is authenticated is by receiving a plain-text challenge from the router, encrypting the challenge and sending it back.
WPA and WPA2 (Wi-Fi Protected Access)
WPA2 is preferred by many as it is arguably the most secure connection available to home users. A 256-bit key is used to encrypt all network traffic. There are two forms of WPA, which are TKIP and PSK. Let us discuss these a little:
TKIP
Temporal Key Integrity Protocol (TKIP) was designed originally designed to replace WEP without having to replace the WEP hardware. It repaired many of the errors from WEP, but had problems of its own such as its ability to be decrypted by a third-party in short bursts. This was a problem with WEP that carried over to TKIP.
PSK
Pre-Shared Key mode (PSK) was designed for those who don’t need complex security, such as home users. Some smaller businesses use this as well. It offers entirely decent password-protected security while not being as strong as a large corporation might have. Many home users implement this because of its ease-of-use. The only real vulnerability in this protocol that a home user should be worried about is a weak password. Weak passwords are the primary reason these sometimes lose some effectiveness.
Advice on Network Security
There are a few things the average home user can do to secure their network and computer from intrusion. With the network, setting a strong password is absolutely vital. This should be placed high on one’s list. Secondly, hiding the router’s Service Set Identifier (SSID) works quite well. If the would-be hacker can’t find the network, they can’t penetrate the network. As far as one’s personal computer, immediately change the Administrator account to another name. Hackers try to this account more often than not in order to get administrative access on the user’s system. If the user name is still Administrator the would-be hacker has won half the battle. The only unknown is the password. If, however, the Administrator user name is FozzyBear, neither the user name or password is known and the hacker has to spend much more time and will likely just give up even if they do manage to get inside the network. As a side note, a good Anti-virus and firewall cannot be forgotten. These are vital to general computer security.
If you have further question, please contact me through my website below and I will gladly answer.
By: Drew Meigs
