Computer Networks Review
Jeffrey M. Dorso
M.S. Information Technology, Strayer University
Abstract- The intent of this paper is to provide the reader with a brief overview of Chapter 9, Computer Networks. This paper will address some of the basics that go into the makeup of computer networks, the hardware that assists in those connections and some of the protocols that enable those connections.
I. Introduction
A lot of the technology and ideology of computer networks and protocols owe homage to research and development of the past. “Galactic Network”, in August of 1962, J.C.R Licklider of MIT had penned a series of memos that had envisioned the cultural collaboration that would be generated as a result of networking the computer. Lickliders vision would be the first ideology of the internet, where a global network of interconnected computers came together and where data and information could be accessed.
During the periods of 1964 -1967 research and developments to bring the internet to a reality started to happen. The ideas of packet switching were first publicized by Leonard Kleinrock at MIT. In order for the internet to work, the networked computers would need to come together as well having the ability to talk to each other. During this period and into 1965 Kleinrock at MIT had convinced Roberts of the idea and the need to develop this technology and so Roberts along with Thomas Merrill had connected two computers in separate geographic locations, the first computer being the TX-2 in Massachusetts and the second being the Q-32 in California, using a low speed dial up connection. This experiment validated Kleinrocks theory on packet switching and the concept of networked computers. While Roberts and Merrill were working on their project, without their knowledge, other teams were working on similar ideas. A team in the U.K headed by Ronald Davies and Roger Scantlebury of NPL and another team at the Rand Corporation head up by Paul Baran and his associates. What’s important about all three of these projects is that they were in agreement to develop the network line speed from 2.4 kbps to 50kbps.
During the periods of 1966 – 1968, Robert Lawrence in 1966 had gone to DARPA to continue the work on networked computers. The research department of DARPA called the IPTO or Information Processing Technologies Office which consisted of J.C.R Licklider, Ivan Sutherland, Robert Taylor and Lawrence Roberts had then created what is known as ARPANET. In 1968, Roberts and the DARPA team had streamlined the ARPANET structure and it’s at this time that contracts would be initiated for a series of packet switches called IMP’s or Interface Message Processors. Arpanet had splintered off its projects to various research centers. The IPM contract would be awarded to Bob Khan and the BBN team, Roberts worked on network topology (the study of limits in sets considered as collection points) and network measurements would be headed up by Kleinrock at UCLA’s Network Measurement Center. Another key player in the architecture of the internet was Douglas Englebert, he would transform the way in which computers and the internet would be utilized. Englebert would come to develop user friendly devices that normally would only be relegated to trained scientists. Englebert back in 1964 would develop what is known today as the mouse and in conjunction to what we know as a GUI interface or windows. What’s important about is that his team at the Human Augmentation Research Center at Stanford’s Research Institute in CA would play a key role in ARPANET coming online.
Connection, in 1969 we see the fruition of all the projects coming together and it’s at this point that we see ARPANET becoming a reality. The first to get the nod and connect was Leonard Kleinrock’s team at UCLA’s Network Measurement Center, it’s because of his earlier works on patch switch theory that he would be consulted first and BBN would install basically the first network protocol. Then came Douglas Englebert and his team at SRI, these two centers would be the first to connect to the ARPANET and the first to send a host to host message. The next two centers to be hooked up were UC at Santa Barbara and the University of Utah, and so by the end of 1969 we would have four host centers connected to the internet.
II. Computer Networks
Loosely termed, as a group of interconnected computers, by connecting the computers together we are able to share data, information, printers, storage and drives etc. On a small scaled down version our own home computer set up can be considered as a network, our desk top connected to an ISP modem connected to a wireless router with a wireless laptop sharing a connection and a printer with a print server and an external hard drive connected. On a more elaborate scale examine a large corporation or major university, what you will find would they would have many work stations, mini computers, servers, routers, tape drives, printers and even copiers all interconnected, sharing, storing and retrieving information, sending messages, and so on.
Figure 1 Computer Networks
III. Connections
Network topology is defined as the arrangement, implementation of a computer network including the physical cabling and how messages are sent and received. Network topology is broken down into to two platforms, physical and logical. Physical topology deals with the actual cabling and connections and the spacing and organization of hardware. Logical topology refers to how the end nodes will communicate with one another, what protocols that will be utilized and how data is transferred.
Figure 2 Network Mapping
A. Physical Topology
There many issues surrounding physical topology, hardware location, cabling, budget and physical location, which can affect the type of topology that would be installed. Physical topology is categorized in to the following types:
· Point to point
· Bus
· Ring
· Star
· Mesh
· Hybrids
Point to point topology is exactly what it means, each computer would be connected to each other to complete the circuit and if one failed they all failed. To figure out the number of connections we would need we would to solve using the following formula:
(n1)! = 1 +2 + 3…..+ (n-1)
Bus topology has a main line with which each computer is connected and when messages are sent they will go down the line until it reaches the computer that it was addressed to and at the end of each bus locates a resistor that prevents signals from bouncing back and forth. One of the pros of setting up a bus topology is that it’s easy and if one of the computers fails then the system is still intact, however if there is an issue to the main line then the system could crash.
Figure 3 Bus topology
Star topologies configuration represents its name, computers arranged in such a fashion with a central unit at its hub, the central unit can also be a work station. The star topology is relatively easy to set up however like the main line to the bus topology if the central unit fails then the system will crash as well.
Figure 4 star topology
Ring topology is configured where each user will be connected to two or three other users and the message will be sent around the ring repeatedly until it’s extracted by the user. Key advantages to a ring topology are the accuracy of the message delivery and the broad distance of the end node set up. Problems that arise are the difficulty of adding and removing end nodes and the reconfiguration once changes have been made.
Figure 5 ring topology
Hybrid topology takes advantage of using two or three different types of topologies for the physical configuration and for the logical topology of routing messages. By using different topologies together we take advantages of the differences and adapt as our needs see fit.
Figure 6 Hybrid topology (ring and bus)
B. Logical Topology
Logical topology is concerned with how messages are addressed and routed to end nodes. Depending on which physical topology you assembled will determine how the messages are sent and received. Logical topology affects the behavior of the signals and how it interacts within the network. Protocols are the rules by which the logical topology must adhere to in order to communicate along the network. When talking about logical topologies we also need to address LAN’s and WAN’s because as messages are sent along through these networks now these signals are sent are based on the hierarchy of the central units and nosed that are set up. A LAN composition can a small group of computer that are set up in an office or floor or building where as a WAN will travel over long distances or geographic locations.
IV. Network Hardware
At this point in our review we now need to bring everything together and there are many pieces to the computer network puzzle and the network hardware plays an intricate part in that puzzle. It is within the hardware that signals and messages are stored, send and receive messages. There many devices involved such as:
· Network Interface Cards
· Hubs
· Bridges
· Routers
· Switches
NIC/ NIU
· Connect an end node to the network
· The appropriate MAC and message forwarding functions are initiated
· Will act as bridge between the computer system bus and the LAN
Hub
· Is considered the central connection point for LAN wiring
· Puts into effect the logical network topology
· Typically will a LAN to a WAN
Bridge
· Connects two separate networks to create a virtual network
Router
· Connects two or more networks
· Forwards packets between networks
· Makes intelligent choices on alternative routes
Switches
· Quickly routes packets using hardware based switching
V. TCP/IP
TCP/IP which stands for Transmission Control Protocol and Internet Protocol, this protocol is what delivers the internet to us. This protocol was borne out of a research and development project that was commissioned by the Department of Defense known as ARPANET. (See introduction for further explanation) TC/IP uses layer dependency on the application that is being transmitted.
Figure 7 Network Connections
Figure 8 Encapsulation of apps
In essence what TCP/IP does is separate the message in to two layers the Top layer will breakdown the message into smaller packets to be transmitted and the IP portion will address the message to the proper location that it is assigned to.
VI. Network Standards
The IEEE802 Standards were developed by the (IEEE) Institute of Electrical and Electronic Engineers to address telecommunication and network standards and bring about uniformity and compatibility. These standards cover areas such as wireless, networking and telecommunications. One of the more prominent standards is the 802.11 wireless standards. We all are familiar with the wireless routers that are out there from Belkin and Linksys and even Cisco and the evolution that they have gone through over the years
VII. Conclusion
This brief overview was an attempt to explain in a more watered down version of how technical and complex computer networks are and all the areas that play a role in bringing communication to your computer. We also are seeing that this technology is constantly changing to make it better, faster, efficient and more reliable.
REFERENCES
[1] Stephen D. Burd, Systems Architecture fifth edition, Course Technology, 2006
[2] Jeffrey M. Dorso The Internet Technology for all, Works written for Technical Writing and Strategic Communication, May 2009
[3] Google Images
http://images.google.com/images?hl=en&source=hp&q=computer+networks&um=1&ie=UTF-8&ei=rPOjSuyBPOqz8QatncX0Dw&sa=X&oi=image_result_group&ct=title&resnum=13
[4] What is TCP/IP
http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci214173,00.html
[5] Wikipedia/ Internet Protocol Suite
[http://en.wikipedia.org/wiki/Internet_Protocol_Suite
[6] Webodedia, Logical topology
http://www.webopedia.com/TERM/L/logical_topology.html
[7] Wikipedia, Wide Area Network
http://en.wikipedia.org/wiki/Wide_area_network
REFERNCES
[8] What’s Up Gold, Network Mapping
http://www.whatsupgold.com/products/network-mapping.aspx?k_id=Google_topology&utm_source=google&utm_medium=cpc&utm_term=Topology&utm_content=1&utm_campaign=Functions&pi_ad_id=3875881637
[9] About.com, Wireless / Networking
http://compnetworking.about.com/od/networkdesign/a/topologies.htm
