Network updated Mr Trofimczuk 29th Jan

3.1.5-Evaluate the use of a VPN
Refer back to VPN notes in Networks sub-section 3.14:
http://dpcsish.wikispaces.com/Network+Fundamentals

3.1.7-Explain why protocols are necessary:Computer Science Illuminated Page 495
Network Protocols

• Protocol is similar to an agreement that a particular type of data will be formatted in a particular manner
• Network protocols are layered such that each one relies on the protocols that underlie it. This is referred to as the protocol stack

TCP/IP-TCP is Transmission Control Protocol and IP is Internet protocol.

• Refers to a suite of protocols and utility programs that support low level network communication
• TCP-rests on top of the IP foundation
• IP software deals with the routing of packets through the maze of interconnected networks to their final destination
• UDP-User Datagram Protocol-Alternative to TCP. More faster than TCP, but less reliable.

Other Key Protocols:

• SMTP
• FTP
• Telnet
• HTTP

3.1.8-Explain why the speed of data transmission across a network can vary

• Data Transfer Rate (Bandwidth)-The speed with which data is moved from one place to the next.
• Bandwidth is usually measured in bits per second or multiples of it (bit/s, kbit/s, Mbit/s, Gbit/s, etc.).
• Latency: Term used to measure interference of network:http://compnetworking.about.com/od/speedtests/a/network_latency.htm
  
  

Possible Factors that can effect speed:

• Switches-type/speed and traffic
• Cabling Type & length
• Interference-electricity,
• Network use-eg: streaming
• Network topology type
• Structural limitations
• Compression techniques

http://en.wikipedia.org/wiki/Bandwidth_%28computing%29

3.1.9-Explain why compression of data is often necessary when transmitting across a network-(Computer Science Illuminated Page 54):

• Data Compression: Reducing the amount of space needed to store a piece of data.

http://en.wikipedia.org/wiki/Data_compression:
Compression can be either lossy or lossless. Lossless compression reduces bits by identifying and eliminating statistical redundancy. No information is lost in lossless compression. Lossy compression reduces bits by identifying marginally important information and removing it. The process of reducing the size of a data file is popularly referred to as data compression, although its formal name is source coding (coding done at the source of the data, before it is stored or transmitted).


3.1.11-Explain how data is transmitted by packet switching-Computer Science Illuminated Page 494
Packet-A unit of data sent across a network
Packet Switching-The approach to network communication in which packets are individually routed to their destination then reassembled.
Key Points-

• Packets may take up to several different routes, so can arrive in a different order
• Routers direct the packets as they move between networks
• On arrival the the final destination the packets are put back into the proper order.

3.1.16-Evaluate the advantages and disadvantages of each method of network security.

• Computer Science Illuminated Page 541
• http://en.wikipedia.org/wiki/Network_security#School

Advantages & Disadvantages of each point-Please add these to the list below

Firewalls

Pros:

• Easy to deploy
• Provides strong protection by physically blocking the transfer of malicious packets
• Can be implemented at a router or OS level, both of which are very secure.
• Advanced firewalls which perform deep packet inspection can identify malicious packets even more accurately.

Cons:

• Can wrongly identify malicious packets, resulting in a "vanishing" data.
• Requires proper configuration to stop malicious attacks, ergo, you need to be able to anticipate the kinds of attacks that will happen
• Software firewalls, especially those which perform deep packet inspection, are computationally intensive.

• Antivirus software
• Authentication: WEP, WEP2
• Policy Agreements
• Wi-Fi-range

Firewalls

Advantages

• Keeps unwanted traffic out
• Makes it possible to monitor

Disadvatages

• Delays in network speed
• May limit data flow.

Antivirus software

Advantages

• Removes virus and malware from the system
• Makes sure the system has integrity

Disadvantages

• It relies on virus definitions and if they are not up to date, the system doesn’t detect the newest viruses or malware.
• Can be tampered with or turned off.

Authentication

Advantages

• Ensures that the user accessing the data is in fact credible and allowed to access the data
• Extra layer of security on top of other systems.

Disadvantages

• Difficult to implement and requires a lot of knowledge about authentications systems
• If a user loses a password for this they can’t access anything

Policy Agreements

Advantages

• Ensures user loyalty and requires them by law to follow the policy agreement

Disadvantages

• Policy agreements tend to have loopholes that can be exploited

Wi-Fi-range

Advantages

• Limits the area from one can access the Wi-Fi therefore making it more secure

Disadvantages

• Difficult to implement and requires a lot of knowledge about Wi-Fi technologies

Security Method	Advantages	Disadvantages
Firewalls	Relatively inexpensive Monitor security alerts Can detect malicious software such as Trojans and viruses	Doesn’t protect from internal attacks from a shared network or other people who use the PC. Relatively weak in protecting against viruses
Antivirus	Reliable with regular updates Removes malicious software if present. If you think your PC is acting up, you can at anytime run a scan to see if a virus is involved.	Can use quite a bit of computer memory, which slows down performance. You are limited to one product as some antivirus software conflict with another.
Authentication
Policy Agreements
Wi-Fi-range

What can you do

Diffie–Hellman key exchange:

http://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exchange