Data Communication And Networking Worksheet Final Correct A
Content
Running head: ABC AUDITING FIRM
1
Network Case Scenario Shane Thompson Andrew Smith Vernon Brighton Mark Green Excelsior Community College Amis 1A (Evening) July 23, 2010
Running head: ABC AUDITING FIRM
2
Table of Contents Introduction…..………………………………………………………………………………3 Network Architecture………………………………………………………….……………..4 Topology used for network………………………………………………………………….5-6 Storage Systems……………………………………………………………………………..6-7 How information will be secured and recovered on the network…….……………………....7 Technology for transmitting information……………………………………………………8-9 Data Security……………………………………………………………………………......9-10 Protocols……………………………………………………………………………..……..10-11 Applications and System Software used on the Network…………………………;………..11 Conclusion……………………………………………………………………………………12 Appendix……………………………………………………………………………………13-14 Reference……………………………………………………………………………………..15
Running head: ABC AUDITING FIRM
3
Introduction Network which is the interconnection of computing devices consists of computer hardware and software. This paper explains the types of networks to be implemented to complement an existing network to provide e-training and e-tutoring to students. Representing the Auditing firm ABC we wish to use the most effective and efficient networking system to complement the network of the Head Office which is located in Canada. We aim to justify the use of equipments, hardware and software chosen for the locations in Jamaica and Tanzania. This network will allow students to pay for training online and have private conferences with course coordinators.
Running head: ABC AUDITING FIRM
4
Network Architecture The Network specialists have proposed to use Local area Network (LAN), Wireless Area Network (WAN) and a server based network architecture for the networks to be developed. Both Local area Network and Wireless area Network will be implemented to transfer data across the network. The Local Area Network will be used mostly for administrative and class purposes while the Wireless Area Network will be used frequently by students to access the internet. The Server based or Client server is a network architecture in which a computer or process on the network is either a client or server. Servers are computers dedicated to managing disk drives, printers or network traffic. Clients are PCs or workstations on which users run applications. The clients will rely on servers for resources, such as files devices and processing power. Due to the environment consisting of more than 10 users a client/server is ideal for this type of network. The servers will be acting as dedicated servers. The server based networks is advantageous to use in sharing, security, backup, redundancy and number of users on the network. It is designed to provide access to many files and printers while the performance and security of the network is maintained. Sharing is centrally administered and controlled. Being centrally administered one administrator can set policies and apply them to the uses of the network. Server backup can be set automatically even if servers are located on different parts of the network. Through redundancy system the data on server can be duplicated and kept online.
Running head: ABC AUDITING FIRM
5
Topology used for Network The topologies to be used on the network to be developed by the ABC Auditing Firm’s Data Communications and Networks specialists are Bus and Star Topology accompanied by communication equipments such as router, switch, file, domain and storage server, unshielded twisted pair copper cabling, work stations and network interface cards. Bus topology refers to a single cable that connects all work stations, servers, printers and other devices on the network. In this type of topology, long backbone cable is used to link all the devices in the network. Drop lines and taps are used to connect node to this backbone. This type of topology is easy to install requires less cabling than other topologies. This is very cheap and cost effective. In a star topology, each network device has a home run of cabling back to a network hub, giving each device a separate connection to the network. If there is a problem with a cable, it will generally not affect the rest of the network. The advantages of using star are it is easy to install, no disruptions to the network when connecting or removing devices. The most common cable media in use for star topologies is unshielded twisted pair copper cabling. This we have chosen for both topologies. Internal Transmission type will be linked using combination copper wired; cat5 or cat6 cables and unshielded twisted pair copper cabling to be connected routers to switches – servers to workstations (clients). Routers translate information from one network to another; it is similar to a super intelligent bridge. Routers select the best path to route a message, based on the destination address and origin. The router can direct traffic to prevent head-on collisions, and is smart enough to know when to direct traffic along back roads and shortcuts.
Running head: ABC AUDITING FIRM
6
Switch is a device that provides a central connection point for cables from workstations, servers, and peripherals. In a star topology, twisted-pair wire is run from each workstation to a central switch/hub. Most switches are active, that is they electrically amplify the signal as it moves from one device to another. Switches no longer broadcast network packets as hubs did in the past, they memorize addressing of computers and send the information to the correct location directly. The NIC is used to connect the workstations to the network. Network interface cards are a major factor in determining the speed and performance of a network. The network will be linked external using the Public Network .We chose Flow which is Fiber to Fiber. This might not be the cheapest but fewer signals are lost using this network and the speed of this type is the best. LIME will be used as a backup in case the main Public network goes down. The diagrams of the topologies show how these devices are connected on the network. Careful planning and thought has led to these devices and topologies being chosen. Set up cost, time and the amount of cabling have influenced our decision.
Storage Systems The network will use both online and offline storage. File and Storage servers will be used at each location to store files. Files are loaded into your computer’s memory so that you can edit or use it logically. This is ideal for file and data storage as it can store information automatically. The use of data center will be used also for storage. Its separate location makes it ideal for storing files of the company for archiving. If the locations in Jamaica and Tanzania have server problems and failure then the files can be retrieved from the data center. These are all physical types of storage. Logically they will be stored using a Relation database management system, which is SQL for areas where student information will be stored, that is the E-learning
Running head: ABC AUDITING FIRM
7
Tutorial. For staff Combination of Microsoft Access, Excess and SQL data and information. Online backing up will also be implemented in case the server goes down.
How will information will be secured and recovered on the network. Data will be secured on the network effectively to maintain security. We have implemented the Palo Alto Firewall device and Kaspersky antivirus which will allow us to mitigate outside threats through IPS and content filtering. Our Virtual Private Network data transfer will be difficult to compromise because it will be heavily encrypted. Data will be backed up often to ensure that data loss does not happen. The use of file-level and share –level security to keep unauthorized person from accessing data files and folders that are shared on the network. In addition, Password- protect documents such as Microsoft office applications and Adobe acrobat will allow us to set passwords on documents. The use of disk encryption will enable us to encrypt and decrypt data on disk drives also the use of a public key infrastructure to manage public or private key pairs and digital certificates as to share data through our public network safely. Data in transit can also be protected with Internet Protocol security (IPsec) to encrypt data for confidentiality. Wireless network will use encryption such as Wi-Fi protected access. We have user rights management to retain control of data through the use of Windows Rights management Services (RMS). This will control what the recipient is able to do with documents. Finally, all computers will be protected by passwords and users are managed by the server.
Data will be easily recovered on the network because we have used Quantum Backup Exec to backup and restore data on our storage and client servers. This software manages up to 100GB per job can be backed up to a hard drive. This software also supports various languages easy to use and very effective.
Running head: ABC AUDITING FIRM
8
Technology for Transmitting Information There will be a combination of LAN and WAN technologies used for data transmission. Internally we will use CSMA/CD and externally we will use Virtual Private Network (VPN) which is secured connection using a Public network as the medium. CSMA/CD which stands for Carrier-Sense Multiple Access with Collision Detection when used each computer on the network, including clients and servers, checks the cable for network traffic. Only when a computer "senses" that the cable is free and that there is no traffic on the cable can it send data. Once the computer has transmitted data on the cable, no other computer can transmit data until the original data has reached its destination and the cable is free again. This might seem like a cumbersome way to put data on the cable, but current implementations of CSMA/CD are so fast that users are not even aware they are using a contention access method. With the distance of network traffic being less than 2500 meters this type of access is ideal for the locations. The level of network activity and the type of network being Ethernet also has led to the use of CSMA/CD. The VPN is a solution to establishing long-distance and/or secured network connections. For our organization which is looking to provide a secured network infrastructure for its client base, a VPN offers two main advantages over alternative technologies: cost savings, and network scalability. To the clients (students) accessing these networks, VPNs also bring some benefits of ease of use. VPN technology also works well with Wi-Fi local area networking. We will also organizations use VPNs to secure wireless connections to local access points when working inside the office. These solutions provide strong protection without affecting performance excessively. With FLOW as our Public network first choice because its more sophisticated and offers more messages at cheaper rate we will also have LIME as our second choice network as back incase FLOW goes down.
Running head: ABC AUDITING FIRM
9
Data Security The data in our network will be secured through software safe guards such as firewall and virus protections. The use of Palo Alto firewall device will allow us to mitigate outside threat through IPsec and content filtering. These include (Kaspersky) antivirus to enhance security. In addition to firewall there is logical security through the use of VLAN to separate the server network from client network to ensure breach on any particular network does not affect each other such as virus attack. There will also be a user id and passwords for each account on our network and a password authentication system to control access of any particular user wishing to use our network. Through the use of NOS, Networking Operating System features; that is the Username and Password Access to the Network, along a two way authentication system. Using active directory to groups and setting Security Polices example rights such as being able to write to file and privilege to access certain folder. This ensures that users gaining access are doing so for a legitimate reason. By configuring the switches to operate VLAN, this would segment the network into separate networks and applying Access control list at the ports of the switches that will filter the traffic the goes out and comes in the network. The VLAN will be equipped with IPsec (Internet Protocol Security) IPsec is said to be especially useful for implementing virtual private networks and for remote user access through dial-up connection to private networks. A big advantage of IPsec is that security arrangements can be handled without requiring changes to individual user computers. For the physical security there will be locks on every computer to protect it from unauthorized use and locks on the doors that house our equipment. The usage of port security will avoid people from plugging things on the computer. Also preventing any unauthorized individuals from gaining unauthorized entry to your network. There will be a use of locked cabinets to prevent severs from being accessed. Another type of security to be
Running head: ABC AUDITING FIRM
10
implemented is the use of DMZ or demilitarized zone, its purpose is to add an additional layer of security to an organization’s LAN. An external attacker only has access to equipment in the DMZ, rather than the other part of the network. If you look at the Tanzania topology you will see the DMZ servers, all web info go on these servers and we have layer 3 switch to send channel information. We keep the DMZ by themselves for security threats while other servers for students and administration are on a switch.
Protocols
The protocols we will be using are one TCP/IP suite, HTTP, .FTP, Ethernet and fast Ethernet. Ethernet is a system where each computer listens to the cable before sending anything through the network if it is clear then the computer will transmit but if some other node is already Transmitting on the cable the computer will wait and then try again when the line is clear. Fast Ethernet this allows for an increased speed of transmission which supports up to 100 Mbps through the use of more expensive connectors such as hubs and NICs it basically works the same as Ethernet but with increased speed. This uses a method called CSMA/CD (Carrier Sense Multiple Access with Collision Detection). TCP/IP suite of protocols has been chosen by the company as strategic business transport protocol for windows 2003.This suite is designed to make it easy to integrate the Microsoft software into the Our network and provide the ability to operate over our network in a secure manner. HTTP protocols defines how messages are formatted and transmitted and what action the network web servers should take in response to various command.FTP File Transfer Protocol provides Bi-directional file transfer between computers running Windows Server 2003 and any host running FTP.
Running head: ABC AUDITING FIRM
11
Application and System Software used on the network The system software used are as follows: i. The Client Server Networking Operating System is Windows Server 2003.
ii. For the Client Operating System is Windows 7 Ultimate Edition OEM.
The application software being used areas follows: i. Ms SQL Relational Database Management System ii. Microsoft Office 2007 Suite
iii. Kaspersky Antivirus Network Edition iv. Microsoft SharePoint. v. Student E-learning
Running head: ABC AUDITING FIRM
12
Conclusion The Data Communications and Networks Team of ABC have taken into consideration the type of operations and communications to be done on this network, such as e-learning and private conferencing along with other factors such as, the size and distances between the LANs to put together a very effective and efficient networking system. The uses of various necessary protocols, networking devices, security systems and security measures which are state of the art, have proven their necessity. This necessity allows the users of this network to have ease of use internally on the LANs and externally on the WANs of the network. A lot of careful considerations were taken in the areas of cost and set up time. We also made an extra effort to select the best security, methods of backing up and data retrieval. We have also given justifications for all decisions made in the selection of devices, protocols backing up and transmission. We believe that these decisions are in the best interest of the company and the users of the network.
Running head: ABC AUDITING FIRM
13
Appendix
Running head: ABC AUDITING FIRM
14
Running head: ABC AUDITING FIRM
15
Running head: ABC AUDITING FIRM
16
References
The computer Technology documentation project. Network Operating System, N.D. retrieved from, http://www.comptechdoc.org/independent/networking/guide/netnos.html
Hallberg, B, (2010) Networking, A Beginner's Guide, Fifth Edition Larry L. Peterson, Bruce S. Davie: Computer Networks* A Systems Approach Lowe, D, (2010) Networking for Dummies, 9th Edition Maggiora, D. & Doherty, J, Cisco Networking Simplified Virtual Lan retrieved from, http://en.wikipedia.org/wiki/Virtual_LAN July 25, 2010 William R. Cheswick, et al.: Firewalls and Internet Security Repelling the Wily Hacker
1
Network Case Scenario Shane Thompson Andrew Smith Vernon Brighton Mark Green Excelsior Community College Amis 1A (Evening) July 23, 2010
Running head: ABC AUDITING FIRM
2
Table of Contents Introduction…..………………………………………………………………………………3 Network Architecture………………………………………………………….……………..4 Topology used for network………………………………………………………………….5-6 Storage Systems……………………………………………………………………………..6-7 How information will be secured and recovered on the network…….……………………....7 Technology for transmitting information……………………………………………………8-9 Data Security……………………………………………………………………………......9-10 Protocols……………………………………………………………………………..……..10-11 Applications and System Software used on the Network…………………………;………..11 Conclusion……………………………………………………………………………………12 Appendix……………………………………………………………………………………13-14 Reference……………………………………………………………………………………..15
Running head: ABC AUDITING FIRM
3
Introduction Network which is the interconnection of computing devices consists of computer hardware and software. This paper explains the types of networks to be implemented to complement an existing network to provide e-training and e-tutoring to students. Representing the Auditing firm ABC we wish to use the most effective and efficient networking system to complement the network of the Head Office which is located in Canada. We aim to justify the use of equipments, hardware and software chosen for the locations in Jamaica and Tanzania. This network will allow students to pay for training online and have private conferences with course coordinators.
Running head: ABC AUDITING FIRM
4
Network Architecture The Network specialists have proposed to use Local area Network (LAN), Wireless Area Network (WAN) and a server based network architecture for the networks to be developed. Both Local area Network and Wireless area Network will be implemented to transfer data across the network. The Local Area Network will be used mostly for administrative and class purposes while the Wireless Area Network will be used frequently by students to access the internet. The Server based or Client server is a network architecture in which a computer or process on the network is either a client or server. Servers are computers dedicated to managing disk drives, printers or network traffic. Clients are PCs or workstations on which users run applications. The clients will rely on servers for resources, such as files devices and processing power. Due to the environment consisting of more than 10 users a client/server is ideal for this type of network. The servers will be acting as dedicated servers. The server based networks is advantageous to use in sharing, security, backup, redundancy and number of users on the network. It is designed to provide access to many files and printers while the performance and security of the network is maintained. Sharing is centrally administered and controlled. Being centrally administered one administrator can set policies and apply them to the uses of the network. Server backup can be set automatically even if servers are located on different parts of the network. Through redundancy system the data on server can be duplicated and kept online.
Running head: ABC AUDITING FIRM
5
Topology used for Network The topologies to be used on the network to be developed by the ABC Auditing Firm’s Data Communications and Networks specialists are Bus and Star Topology accompanied by communication equipments such as router, switch, file, domain and storage server, unshielded twisted pair copper cabling, work stations and network interface cards. Bus topology refers to a single cable that connects all work stations, servers, printers and other devices on the network. In this type of topology, long backbone cable is used to link all the devices in the network. Drop lines and taps are used to connect node to this backbone. This type of topology is easy to install requires less cabling than other topologies. This is very cheap and cost effective. In a star topology, each network device has a home run of cabling back to a network hub, giving each device a separate connection to the network. If there is a problem with a cable, it will generally not affect the rest of the network. The advantages of using star are it is easy to install, no disruptions to the network when connecting or removing devices. The most common cable media in use for star topologies is unshielded twisted pair copper cabling. This we have chosen for both topologies. Internal Transmission type will be linked using combination copper wired; cat5 or cat6 cables and unshielded twisted pair copper cabling to be connected routers to switches – servers to workstations (clients). Routers translate information from one network to another; it is similar to a super intelligent bridge. Routers select the best path to route a message, based on the destination address and origin. The router can direct traffic to prevent head-on collisions, and is smart enough to know when to direct traffic along back roads and shortcuts.
Running head: ABC AUDITING FIRM
6
Switch is a device that provides a central connection point for cables from workstations, servers, and peripherals. In a star topology, twisted-pair wire is run from each workstation to a central switch/hub. Most switches are active, that is they electrically amplify the signal as it moves from one device to another. Switches no longer broadcast network packets as hubs did in the past, they memorize addressing of computers and send the information to the correct location directly. The NIC is used to connect the workstations to the network. Network interface cards are a major factor in determining the speed and performance of a network. The network will be linked external using the Public Network .We chose Flow which is Fiber to Fiber. This might not be the cheapest but fewer signals are lost using this network and the speed of this type is the best. LIME will be used as a backup in case the main Public network goes down. The diagrams of the topologies show how these devices are connected on the network. Careful planning and thought has led to these devices and topologies being chosen. Set up cost, time and the amount of cabling have influenced our decision.
Storage Systems The network will use both online and offline storage. File and Storage servers will be used at each location to store files. Files are loaded into your computer’s memory so that you can edit or use it logically. This is ideal for file and data storage as it can store information automatically. The use of data center will be used also for storage. Its separate location makes it ideal for storing files of the company for archiving. If the locations in Jamaica and Tanzania have server problems and failure then the files can be retrieved from the data center. These are all physical types of storage. Logically they will be stored using a Relation database management system, which is SQL for areas where student information will be stored, that is the E-learning
Running head: ABC AUDITING FIRM
7
Tutorial. For staff Combination of Microsoft Access, Excess and SQL data and information. Online backing up will also be implemented in case the server goes down.
How will information will be secured and recovered on the network. Data will be secured on the network effectively to maintain security. We have implemented the Palo Alto Firewall device and Kaspersky antivirus which will allow us to mitigate outside threats through IPS and content filtering. Our Virtual Private Network data transfer will be difficult to compromise because it will be heavily encrypted. Data will be backed up often to ensure that data loss does not happen. The use of file-level and share –level security to keep unauthorized person from accessing data files and folders that are shared on the network. In addition, Password- protect documents such as Microsoft office applications and Adobe acrobat will allow us to set passwords on documents. The use of disk encryption will enable us to encrypt and decrypt data on disk drives also the use of a public key infrastructure to manage public or private key pairs and digital certificates as to share data through our public network safely. Data in transit can also be protected with Internet Protocol security (IPsec) to encrypt data for confidentiality. Wireless network will use encryption such as Wi-Fi protected access. We have user rights management to retain control of data through the use of Windows Rights management Services (RMS). This will control what the recipient is able to do with documents. Finally, all computers will be protected by passwords and users are managed by the server.
Data will be easily recovered on the network because we have used Quantum Backup Exec to backup and restore data on our storage and client servers. This software manages up to 100GB per job can be backed up to a hard drive. This software also supports various languages easy to use and very effective.
Running head: ABC AUDITING FIRM
8
Technology for Transmitting Information There will be a combination of LAN and WAN technologies used for data transmission. Internally we will use CSMA/CD and externally we will use Virtual Private Network (VPN) which is secured connection using a Public network as the medium. CSMA/CD which stands for Carrier-Sense Multiple Access with Collision Detection when used each computer on the network, including clients and servers, checks the cable for network traffic. Only when a computer "senses" that the cable is free and that there is no traffic on the cable can it send data. Once the computer has transmitted data on the cable, no other computer can transmit data until the original data has reached its destination and the cable is free again. This might seem like a cumbersome way to put data on the cable, but current implementations of CSMA/CD are so fast that users are not even aware they are using a contention access method. With the distance of network traffic being less than 2500 meters this type of access is ideal for the locations. The level of network activity and the type of network being Ethernet also has led to the use of CSMA/CD. The VPN is a solution to establishing long-distance and/or secured network connections. For our organization which is looking to provide a secured network infrastructure for its client base, a VPN offers two main advantages over alternative technologies: cost savings, and network scalability. To the clients (students) accessing these networks, VPNs also bring some benefits of ease of use. VPN technology also works well with Wi-Fi local area networking. We will also organizations use VPNs to secure wireless connections to local access points when working inside the office. These solutions provide strong protection without affecting performance excessively. With FLOW as our Public network first choice because its more sophisticated and offers more messages at cheaper rate we will also have LIME as our second choice network as back incase FLOW goes down.
Running head: ABC AUDITING FIRM
9
Data Security The data in our network will be secured through software safe guards such as firewall and virus protections. The use of Palo Alto firewall device will allow us to mitigate outside threat through IPsec and content filtering. These include (Kaspersky) antivirus to enhance security. In addition to firewall there is logical security through the use of VLAN to separate the server network from client network to ensure breach on any particular network does not affect each other such as virus attack. There will also be a user id and passwords for each account on our network and a password authentication system to control access of any particular user wishing to use our network. Through the use of NOS, Networking Operating System features; that is the Username and Password Access to the Network, along a two way authentication system. Using active directory to groups and setting Security Polices example rights such as being able to write to file and privilege to access certain folder. This ensures that users gaining access are doing so for a legitimate reason. By configuring the switches to operate VLAN, this would segment the network into separate networks and applying Access control list at the ports of the switches that will filter the traffic the goes out and comes in the network. The VLAN will be equipped with IPsec (Internet Protocol Security) IPsec is said to be especially useful for implementing virtual private networks and for remote user access through dial-up connection to private networks. A big advantage of IPsec is that security arrangements can be handled without requiring changes to individual user computers. For the physical security there will be locks on every computer to protect it from unauthorized use and locks on the doors that house our equipment. The usage of port security will avoid people from plugging things on the computer. Also preventing any unauthorized individuals from gaining unauthorized entry to your network. There will be a use of locked cabinets to prevent severs from being accessed. Another type of security to be
Running head: ABC AUDITING FIRM
10
implemented is the use of DMZ or demilitarized zone, its purpose is to add an additional layer of security to an organization’s LAN. An external attacker only has access to equipment in the DMZ, rather than the other part of the network. If you look at the Tanzania topology you will see the DMZ servers, all web info go on these servers and we have layer 3 switch to send channel information. We keep the DMZ by themselves for security threats while other servers for students and administration are on a switch.
Protocols
The protocols we will be using are one TCP/IP suite, HTTP, .FTP, Ethernet and fast Ethernet. Ethernet is a system where each computer listens to the cable before sending anything through the network if it is clear then the computer will transmit but if some other node is already Transmitting on the cable the computer will wait and then try again when the line is clear. Fast Ethernet this allows for an increased speed of transmission which supports up to 100 Mbps through the use of more expensive connectors such as hubs and NICs it basically works the same as Ethernet but with increased speed. This uses a method called CSMA/CD (Carrier Sense Multiple Access with Collision Detection). TCP/IP suite of protocols has been chosen by the company as strategic business transport protocol for windows 2003.This suite is designed to make it easy to integrate the Microsoft software into the Our network and provide the ability to operate over our network in a secure manner. HTTP protocols defines how messages are formatted and transmitted and what action the network web servers should take in response to various command.FTP File Transfer Protocol provides Bi-directional file transfer between computers running Windows Server 2003 and any host running FTP.
Running head: ABC AUDITING FIRM
11
Application and System Software used on the network The system software used are as follows: i. The Client Server Networking Operating System is Windows Server 2003.
ii. For the Client Operating System is Windows 7 Ultimate Edition OEM.
The application software being used areas follows: i. Ms SQL Relational Database Management System ii. Microsoft Office 2007 Suite
iii. Kaspersky Antivirus Network Edition iv. Microsoft SharePoint. v. Student E-learning
Running head: ABC AUDITING FIRM
12
Conclusion The Data Communications and Networks Team of ABC have taken into consideration the type of operations and communications to be done on this network, such as e-learning and private conferencing along with other factors such as, the size and distances between the LANs to put together a very effective and efficient networking system. The uses of various necessary protocols, networking devices, security systems and security measures which are state of the art, have proven their necessity. This necessity allows the users of this network to have ease of use internally on the LANs and externally on the WANs of the network. A lot of careful considerations were taken in the areas of cost and set up time. We also made an extra effort to select the best security, methods of backing up and data retrieval. We have also given justifications for all decisions made in the selection of devices, protocols backing up and transmission. We believe that these decisions are in the best interest of the company and the users of the network.
Running head: ABC AUDITING FIRM
13
Appendix
Running head: ABC AUDITING FIRM
14
Running head: ABC AUDITING FIRM
15
Running head: ABC AUDITING FIRM
16
References
The computer Technology documentation project. Network Operating System, N.D. retrieved from, http://www.comptechdoc.org/independent/networking/guide/netnos.html
Hallberg, B, (2010) Networking, A Beginner's Guide, Fifth Edition Larry L. Peterson, Bruce S. Davie: Computer Networks* A Systems Approach Lowe, D, (2010) Networking for Dummies, 9th Edition Maggiora, D. & Doherty, J, Cisco Networking Simplified Virtual Lan retrieved from, http://en.wikipedia.org/wiki/Virtual_LAN July 25, 2010 William R. Cheswick, et al.: Firewalls and Internet Security Repelling the Wily Hacker
