Topic 3 Networks

A computer system or set of systems which uses communication equipment in order to connect computers and share their resources and data

Device on a network

A Computer program, software or host computer fulfills requests from client programs and serves as a central repository of data and programs which are shared by these clients

Computer hardware or software device that accesses a service made available by a server, achieved by sending a request for service. (e.g. email software client requesting email server software to fetch new emails).

Unlike a server, the client does not share any of its resources but requests content

connection point for all devices on network, connected through ethernet cables. Data from one device goes direct to the Hub, which share this to all devices. The intended recipient accepts this data, all other devices ignore it.

Although transmission to every port ensures that data reaches its destination, the effect of this creates a lot of traffic on the network, which slows down transmission

Also the connection point for multiple devices on a single network’ however a switch can identify which device is connected to which port, so can send data to the target device directly. Because of this, networks connected using a switch have faster data transmission than those connected using a hub

used to join multiple networks ands is used as an intermediary between these so data may be exchanged efficiently between devices (e.g. connecting a home network to the internet)

computer network in which a “bus” connects all the devices together through a common cable

copper wire and fiber. Cables allow for the connection of computers over a network

extra digit added to numerical data that is used to check data integrity after input, transmission, storage and processing

the accuracy of data after input, transmission, storage or processing

error-detecting procedure that generates a sum from the digits of a number

portion of a message that is transmitted through a network. Contains data such as check digits and destination address

link that resides between computer networks and is responsible for converting data passing through into the appropriate format so it can be understood by the receiving network

exchange of predetermined signal to signify that a connection has been established between two systems

international communications standard that allows for the transmission of audio/video and other data over digital telephone lines

computer network where all the connected computer are within a limited geographical area. Connection between the computers may be through cables and/or microwave transmission

electronic communication without the need for cables

electronic equipment that converts computer digital signals into audio signals and back. the audio signals are transmitted over telephone lines, which allows for distant communication

computer system that are interconnected and can share resources and data

group of bits. may include control signals, error control bits, coded information, as well as the destination for the data

network communication method that creates and transmits small units of data, called packets, through a network, independently of the overall message

making use of a network

error-detecting procedure that appends a binary digit to a group of binary digits. The sum of all the digits, including the appended binary digit, establishes the accuracy of the data after input, transmission, storage or processing

international rules that ensure the transfer of data between systems. A protocol that is recognized as the standard for a specific type of transfer is called standard protocol. For example: TCP/IP is a standard protocol

communications protocols used to connect hosts on the internet

computer network where all the connected computers are in a larger geographic area than that served by a LAN or a MAN (metropolitan area network)

Different sections of a LAN may not want to access all the available shared data, as such a LAN can be split into separate VLANS, the new network is known as a logical separate network.

Each logical separate network cannot access the other shared resources without being granted special access.

Examples include printers, scanners, external hard drivers, which provide increased functionality

Type of LAN created so that large storage devices can be accessible from servers in a convenient and easy way and is able to hand large data transfers

Network covering individuals workspace, essentially a LAN which only supports one person, instead of a group of people

Network with no centralized server. All nodes are client and server at the same time, consuming and supplying resources from and to other peers. This makes resources more widely available and supports file sharing for collaborative work.

connects nodes in a limited geographical area but achieves this without the use of cabling and wires.

Requires a wireless router or modem; access points; switch; wireless repeaters and so on

• possibility of user collaboration and make access easier due to wireless transmission. Quick access with mobile devices; anywhere in the scope of the WLAN and therefore do not need to be present at a workstation.

• allows users to bring their own device which has a more familiar interface, could lead to great efficiencies and fewer usability issues

• Could lead to insecure devices, but could be resolved with clear company policy regarding use, Virtual Testing ‘Sandbox’ could protect against viruses, MAC address authentication and testing, other security features in order to address.

• No extra equipment is needed for expansion after the initial set-up; which will save time and money

• Reduces wiring therefore increases the safety for employees

• user-mobility and economical access points

• poorer security as devices from outside can access the network and intercept transmissions since transmission goes ‘through the air’

• Could be resolved by strong encryption/protocols, e.g. WPA-2 or use of trusted MAC addresses, and regular changes of the router password

• Open to misuse, An administrator cannot directly monitor a specific user or device

• Data Transfer will decrease because the number of computers using the network increases and because the WLAN has a lower bandwidth than a wired LAN

• intermittent connectivity due to physical barriers; this may result in lower transfer speed, weakening of signal and may reduce operations and efficiency'

• Wireless signal could be weak in some places; leading to frustrated/ineffective users.

A global WAN connected through an Internet service provider (ISP) to exchange for a monthly feed. The internet is decentralized by design, any independent computer able to access the internet and share resources becomes a server of its own.

Ethical issues include: some information presented online may be deliberately incorrect and not subjected to validation and scrutiny; further issues such as plaigarism and intellectual property.

Computer network that utilizes the internet. works like an external extension to a LAN. Part of a network that uses internet protocols to allow limited access by specific users to a LAN or WAN

Ethernet is more reliable as the strength of the signal is independent from the distance from the router (in comparison to Wireless Network transmission). There is also no issues with the network topology type and nature of the surroundings, so long as the user is connected. Connection does depend on the condition of the cables; any loose or broken cable connections will reduce or fail transmission.

provide a common internal language that enables compatibility for all computer systems throughout the globe

1. easy to manage

2. greater understanding of each layer

3. common language for each layer

4. makes protocol design easier

5. a manufacturer can focus on technologies of a particular layer

6. products of different manufacturers can work together

7. Technology advances of a layer are independent of technology advancements of other layers

the most-widely used networking standard. It is just a reference model

makes a tunneled network connection through the internet or any other public network. Considered ideal for establishing a secure connection between private networks with remote users and remote sites.

1. Internet access

2. VPN software

3. VPN routers

4. VPN appliances

5. VPN concentrators. a single device to handle a large number of incoming VPN tunnels

6. VPN servers

1. Internet protocol security protocol (IPSec) which functions in both transport and tunnel mode:

   1. Allows the secure transmission of data over public IP-based networks

   2. Uses standard encryption algorithm to provide confidentiality (AES)

   3. Provides authentication via digital certificates

   4. Secure Sockets Layer (SSL) 3.0 or transport layer security with encryption. SSL/TLS based VPNS are much simpler than IPSec based VPNs. The use of this technology does not require special client software because all web servers and web browsers support this method of providing a VPN.

1. Asynchronous Transfer Mode (ATM) Circuits

2. Frame relay circuits

3. Transport of layer 2 frames over MultiProtocol Label Switching (MPLS)

MultiProtocol Label Switching (MPLS) with constrained distribution of routing information through border gateway protocol

A combination of both secure and trusted technologies or a combination of two VPN technologies

Connects entire networks and facilitates secure data interchange between different sites

Connects individual hosts to private networks and facilitates teleworkers who need to access their company’s network securely using the Internet. Every host has VPN client software installed.

• Information can be accessed in remote places

• lower cost; no need for long-distance leased lines

• Enhanced Security; data intercepted is undecipherable and security properties of each tunnel are agreed by the administrators of the endpoints of the tunnel

• Nobody outside the VPN should be able to affect the security properties of the VPN

• Multiple exit nodes; makes it hard to distinguish where the data was generated and thus more secure

• can change working patterns; allowing employees to work from home and reduce traveling time, beneficial for workplace efficiency and reduces environmental costs.

• need professional with detailed understanding of security issues and configuration to ensure sufficient security and protection

• reliability of VPN is not directly under the organizations control but under the ISP

• Not all VPN products are compatible across different vendors

In a VPN, access and transmission are always encrypted, users have access to everything, authenticate the sender before establishing a tunnel

original file is divided into packets before transmission, each of these packets may follow a different path to the destination address

Set of tules for transmission; to faviliatate a process being carried out correctly. Rules that ensure data is transferred correctly between systems. Recognized as the standard for a certain type of transfer is called a ‘standard protocol’.

Ensures data is not changed or corrupted during transmission

Network infrastructures have limited memory and bandwidth, the transport layer is responsible for using protocols to manage situation where an overload of resources occurs

prevents situation where two or more network competing actions are each waiting for the other to finish and thus neither ever does

prevents requests on network resources from exceeding capacity

ensures the validity of data

the ability to repair the error

• Hypertext Transfer Protocol (HTTPS)

  • creates a secure transmission of data from client to server

• Secure Socket Layer (SSL) and Transport Layer Security (TLS)

  • Encryption protocols used on the internet. Allows for things like secure payment

• Internet Protocol Security (IPSec)

  • Encrypt and authenticate traffic to ensure secure transfer over VPN tunnel

• Dynamic Host Configuration Protocol (DHCP)

  • Allows the server to automatically assign IP address to client device

Theoretical speed of data in a medium and depends on the signaling technique used and the physical properties of the medium

the actual transfer rate

measures the transfer rate of usable data

1. Bandwidth of the network

2. Data Transfer rate of storage devices

3. Interferences

4. Malicious software

5. Number of connected devices

6. Number of users’ and users demand at any particular time

7. Packet lost and retransmission

8. Read speed of storage devices

Reduces the size of files to be transmitted over a network; which will take up less bandwidth and reduce overall transmission time. The recipient will have a program that can decompress the contents of the file.

• Copper Cable

• Coaxial Cable

• Unshielded Twisted Pair Cable (UTP)

• Shielded Twisted Pair Cable

• Microwave Radio

• Satellites

• Infared

• RFID

• Bluetooth

• Free Space Optics

Unit of information in a form suitable to travel between computers

the basic transfer unit and sometimes is used instead of the term data packet

Each packet contains the receiver address, The path that datagrams take between the same source and destination can be different

A route from source to destination is set up before any transmission takes place

Used for encryption and decryption; each device uses this to Encrypt a packet before it is sent over an untrusted network

Altering a message into undecipherable form to those unauthorized. Only a recipient with the correct key can decode the message and read it.

• Faster than using a public key

• uses less computer resources

• Keys must be shared before they are used

• Risk or Key becoming known by unauthorized

Public Key Encryption and a private key for decryption are both mathematically linked. SSL and TSL protocols use this form of encryption

Both sender and recipient don’t need to share key beforehand to communicate

• Messages take longer to Encrypt and decrypt.

• Authenticity of public key needs to be verified

Wireless data transmission extends beyond walls and window screens.

• THe MAC address identifies a specific device through its unique 12 characters which is check against a list of approved addresses if not on this whitelist then Access is denied

• This prevents unauthorized access very difficult, unless the NIC has been cloned, but generally provides an additional layer of security since data send to a specific MAC address can only be accessed on the specified Device

• Extra security

Against

• Danger of allowed list of MAC addresses being discovered

• Difficult to manage the list as it grows

uses password to access networking device and/or another password to access the web interface used to set up a wireless router or access point

For

• Easy to use

• Prevents unauthorized access

Against

• Entering password each time may be time consuming and inconvenient

• Weak passwords are easy to crack and gain access

Either as; software installed on each device, or router hardware firewall that protects from hackers accessing devices through wireless connection

Filters incoming traffic and can block some messages coming through as well as control/limit users own access to the internet. Extent of firewall use depends on an organization’s policy

• Software firewall monitors traffic between device and network and prevents unauthorized access

• Router hardware firewall prevents unauthorized persons getting access to the network

• May slow down the device

• Issues about censorship with software firewall, depending on the organization

• Giving each user appropriate login details and strong passwords

• Different access rights for students, teachers, admins, etc.

• Encryption of all passwords and files

• use of the latest WiFi protocol Security

• Require MAC address and authentication