1. What is a local area network?
Local area network (LAN) is a type of computer network that connects devices and computers within a limited geographical area, such as school, home, office building or computer laboratory (“Local area network,” n.d.). Its main distinguishing characteristics from wide area networks are smaller and limited geographic area, higher rates of data transfer and absence of need for leased telecommunication lines. It is convenient to use LANs in the areas with limited space, which can be as small as one apartment, or as large as a university campus. They are also often used for business purposes, as they have a number of benefits that are especially effective in this matter:
With their help it is convenient to share resources and hardware, in such a way reducing expenses and increasing productivity. Besides, file sharing allows multi-user access to different applications. There is also a possibility to communicate with other users by means of a messaging system.
Another convenient means of expenses economy is utilization of standard hardware for servers and workstations and common applications, thus allowing easy maintenance and installation on new computers.
Owing to the opportunity to store data on a central location, it is easy to perform network backups, thus reducing a chance of losing data in case of technical problems.
Moreover, there are a number of fault tolerance features supported by LANs, such as disk striping with parity (RAID5), disk mirroring, UPS (Uninterrupted Power Supply) and disk-duplexing. It additionally minimizes network downtime and increases reliability (“Benefits of LANs,” n.d.).
Along with the benefits, there are certain common problems that are spotted in LANs. They can be roughly subdivided into the following groups:
1. Problems with connection. They are often caused by wrong installation settings, incorrectly plugged network cables.
2. Problems with security, which are likely to occur if there are no effective security policies, methods and antivirus programs implemented within the network.
3. Problems with performance, which are often registered due to Windows registry errors, heavily installed applications, low physical memory and some other cases.
2. Prepare a simple cost report.
In order to buy cable in the quantity stated in the assignment, we need to purchase 1911 feet of cable and 80 connectors. For the convenience of purchase and so as to have some extra material, I will present pricing and recommendations for 2000 feet of cable and 100 connectors.
Results of the Internet search for the necessary cables, tools and connectors in CablesToGo.com Internet shop are presented in the table below.
In the case of the first vendor, CablesToGo.com, the required items will cost more and they are more numerous. In the latter case, everything will be cheaper and more convenient. So, I recommend LANShack.com, which also has many other interesting offers.
Category 5e cable is suitable for structured cabling of computer network, as well as for carrying other signals, such as video and telephony. Category 6 cable is a standard for Gigabit Ethernet standard. In comparison to the cables of categories 5, 5e, it has more stringent specifications for system noise and crosstalk.
3. Bridge, switch, and router.
Bridges connect network segments at the Layer 2 of the OSI model (data link layer). It works according to the standard IEEE 802.1D. It is very much alike switch, the latter having numerous ports. Layer 2 switch is often used interchangeably with bridge, but there are Layer 3 switches that additionally process data at the level of network (Layer 3 of the OSI model). Router forwards data packets between networks, creating an overlay internetwork (“Router,” n.d.). They work on the Layer 3 of the OSI model.
Among the advantages of bridge there are: low cost for simple bridges, isolate collision domains, bandwidth scaling along with network growing. At the same time, there are such disadvantages: often spotted delays in the course of buffering and processing, no limits for the broadcasts scope, problems with complex network topology. Among the advantages of switches there is greater flexibility in terms of supported layers, and as opposed to routers they are optimized for high-density Ethernet connectivity. The main difference between bridges and routers is that the first device directs frames according to hardware-assigned MAC address, while the latter one according to arbitrarily assigned IP addresses. So, bridge cannot distinguish networks, as opposed to routers (“Bridging,” n.d.).
4. Smith family network.
In the case of Smith family, when there are three different operation systems used, it is necessary to use TCP/IP protocol, as it is a standard basic protocol of computer connection and it doesn’t depend on OS and applications for this protocol setting are pre-installed in these systems.
5. The OSI reference model.
1. Layer Name: Physical
Function 1: Definition of physical means of data exchange between network devices.
Function 2: Serves as an interface between devices and network medium.
Unit of data: Bit
2. Layer Name: Data Link
Function 1: Definition of procedures for communication links operating.
Function 2: Framing packets, correcting and detecting errors in packets transmission.
Unit of data: Frame
3. Layer Name: Network
Function 1: Determination of the ways of data transmission between network devices.
Function 2: Packets routing in accordance with unique network device addresses.
Unit of data: Packet/Datagram
4. Layer Name: Transport
Function 1: Management of end-to-end delivery of messages in network.
Function 2: Flow control.
Unit of data: Segments
5. Layer Name: Session
Function 1: Management of user dialogues and sessions.
Function 2: Control of establishment and termination of logic links between users.
Unit of data: Data
6. Layer Name: Presentation
Function 1: Representation, encryption and decryption of data.
Function 2: Conversion of machine-dependent data into independent from machine.
Unit of data: Data
7. Layer Name: Application
Function 1: Definition of interface to user processes for data transfer and communication in network.
Function 2: Providing of standardized services.
Unit of data: Data (“OSI Model,” n.d.).
6. Why are fault tolerance and disaster recovery important?
Disaster recovery is a complex of procedures and processes related to preparing for recovery and continuation of technology infrastructure critical for some organization after some human-induced or natural disaster. Today disaster recovery is very important, as practically all large organizations heavily depend on the technological aspects. So, by allocating proper amount of money to disaster recovery planning, the company can avoid large losses, after which the majority of companies cease to exist (“Disaster recovery,” n.d.).
Fault tolerance is a system or component designed so that in case something fails, a backup component or process start and work can continue without interruption. It is also extremely important, as with its help system becomes much more reliable and can resist unexpected problems (McCarthy, 2000).
7. Troubleshooting
In case of troubleshooting the error when a person receives a message “The network path cannot be found”, it is necessary to understand what caused its appearance. In order to do it, it is necessary to check the following features and applications: Firewall (isn’t it blocking some processes), Windows services (either they are turned on or off), file system (access rights), WINS server (whether it is present in network). Depending on the received information, I will make all the necessary changes and the problem will be solved. If will use console utilities.
8. What are the different firewall methods and how do they differ?
There are four common firewall methods, which can be used separately or in complex:
Circuit Level Gateway – method applied to block all the incoming traffic to a host except for itself. It is useful when hiding information about the networks under protection. Its main function is monitoring of TCP handshaking between packets so as to determine whether requested sessions are legitimate.
Packet Filter – method applied to cut off traffic coming and going from network in order to assess it on the basis of selected principles. Its function is to evaluate and intercept the IP addresses of destination and source. It is recommended to use it to filter IP ports and addresses.
Application Gateway – it is kind of proxy server that monitors all the incoming traffic by means of traffic analysis and drawing conclusion – whether to allow session or not. They intercept packets travelling to and from applications.
Proxy Server – method used to increase network performance and hide the actual addresses. It can also be configured so as to block certain IP ports and addresses (“What is firewall,” n.d.).
9. Malware
Rimecud!mem is a computer worm of Win32 subtype that infects files in order to spread. It was discovered on October 9, 2009. The worm works by injecting malicious code into file explorer.exe and other non-explorer process. The main symptoms of the system infection are: frequent system crashes without user’s faults, unexpected connection to unsafe domains, new register key files or registry modification, reduction of system memory, malicious threads in explorer and non-explorer processes. Methods of infection: removable drives, Internet, P2P or MSN network.
There are the following stages in Rimecud!mem removal:
Disconnection from Internet and closing of all active browsers.
Scanning for virus with the help of any reliable virus detection system. In the majority of cases, these two stages are enough for virus removal, but if it is still present in the system, the following additional stages are required:
Restart computer in the Safe Mode.
Restore system under Safe Mode.
On the whole, the virus is considered to be of low threat level for computer and is easily spotted and eliminated from system.
References
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