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 ‘Network Architecture’
Network Basics
January 30th, 2010Network Application Architectures
January 22nd, 2010
Before diving into software coding, you should have a broad architectural plan for your application. Keep in mind that an application’s architecture is distinctly different from the network architecture. From the application developer’s perspective, the network architecture is fixed and provides a specific set of services to applications. The application architecture, on the other hand, is designed by the application developer and dictates how the application is structured over the various end systems. In choosing the application architecture, an application developer will likely draw on one of the two predominant architectural paradigms used in modern network applications: the client-server architecture or the peer-to-peer (P2P) architecture.
In a client-server architecture, there is an always-on host, called the server, which services requests from many other hosts, called clients. The client hosts can be either sometimes-on or always-on. A classic example is the Web application for which an always-on Web server services requests from browsers running on client hosts. When a Web server receives a request for an object from a client host, it responds by sending the requested object to the client host. Note that with the client- server architecture, clients do not directly communicate with each other; for example, in the Web application, two browsers do not directly communicate. Another characteristic of the client-server architecture is that the server has a fixed, well- known address, called an IP address (which we’ll discuss soon). Because the server has a fixed, well-known address, and because the server is always on, a client can always contact the server by sending a packet to the server’s address. Some of the better-known applications with a client-server architecture include the Web, F1′R Telnet, and e-mail.
Often in a client-server application, a single server host is incapable of keeping up with all the requests from its clients. For example, a popular social-networking site can quickly become overwhelmed if it has only one server handling all of its requests. For this reason, a cluster of hosts-sometimes referred to as a server farm-is often used to create a powerful virtual server in client-server architectures. Application services that are based on the client-server architecture are often infrastructure intensive, since they require the service providers to purchase, install, and maintain server farms. Additionally, the service providers must pay recurring interconnection and bandwidth costs for sending an4 receiving data to and from the Internet. Popular services such as search engines (e.g., Google), Internet commerce (e.g., Amazon and e-Bay), Web- based v-mail (e.g, Yahoo Mail), social networking (e.g., MySpace and Facebook), and video sharing (e.g., YouTube) are infrastructure intensive and costly to provide.
In a P2P architecture, there is minimal (or no) reliance on always-on infrastructure servers. Instead the application exploits direct communication between pairs of intermittently connected hosts, called peers. The peers are not owned by the service provider, but are instead desktops and laptops controlled by users, with most of the peers residing in homes, universities, and offices. Because the peers communicate without passing through a dedicated server, the architecture is called peer-to-peer. Many of today’s most popular and traffic-intensiye applications are based on P2P architectures. These applications include file distribution (e.g., BitTorrent), file searching/sharing (e.g., eMule and LimeWire), Intemet telephony (e.g., Skype), and IPTV (e.g., PPLive).
By: Imran Rashid
