Topic 3: Networks
Error Checking
Data transmitted across network subject to noise/interference, so if error detected, then device will ask sender to resend data. Redundancy is the central concept behind error checking.
Outline the advantages of wireless networks
Deployment- much easier to set up wireless network than physically assemble a wired network Convenience- easy access to Internet, convenient for emergence of PCs Cost- labor cost of maintaining wiring is saved Expandability- easy to add more clients v. wired networks require additional wiring Mobility- don't have to be at home or work to use net, can access for free at coffee shops Productivity- employees can work during travel time
3G Mobile
"3rd Generation" cell phone technology first avaliable in cell phones in 2003. Depending upon carrier 3G networks use either EDGE, EV-DO or HSPA data protocols. Speeds range between 400 kilobits and 2Mbps, depending on the carrier and region.
Checksum
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Parity checking
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Identify different types of networks
1) LAN: Local area network 2) VLAN: Virtual local area network 3) WAN: Wide area network 4) SAN: Storage area network 5) WLAN: Wireless local area network 6) Internet 7) Extranet 8) VPN: Virtual private network 9) PAN: Personal area network 10) P2P: Peer-to-peer
SSID
A SSID is a unique name given to a wireless network that is broadcast so that clients can connect to it. Each packet sent over a wireless network includes the SSID, which ensures that the data being sent over the air arrives at the correct location.
Data packet
A data packet contains data traveling over a network. It is a basic unit of binary data for communication over a digital network.
Protocol
A set of rules that defines how data is formatted and processed on a network A protocol is, in one sense, nothing more than an agreement that a particular type of data will be formatted in a particular manner. Specifically, a network protocol is used by computers to communicate with one another.HTTP and TCP are examples of network protocols for Internet communication.
Outline the importance of standards in the construction of networks
All programs should be written in same format so that computers can communicate with one another: -Pointless to write a communications program in which the programmer invents his own series of codes and messages; program receiving the output of this original program would be unable to decipher the messages -Compatibility of software and hardware through a common language -Open standards encourage diversity of production
Latency
Amount of time it takes for data to travel from sender to receiver in a network connection
Authentication
Authentication: determining whether someone or something is, in fact, who or what it is declared to be. In a wireless network, logon passwords or passphrase are forms of authentication. WPA/WPA2 utilize two different protocols for network authentication: WPA2- PSK: Intended for home and small office networks, uses 256 bit key to authenticate each wireless device, encyrption passphrase must be entered for each user connected to network and for each device. WPA-ENT: Enterprise and business network provides security against more attacks than WPA2-PSK and separates users from the router's passphrase to the network b/c creates new encryption keys each time users log on to the network with their unique passwords, and the passphrase to the network is not stored locally. It also allows for centralized control over users' access to the wireless network, which makes management easier than with the WPA2-PSK mode.
Redundancy
Central concept behind error checking Error detection codes send extra bits to see if incorrect data can be detected Includes 2 forms: parity checking and checksum
Internet
Combination of many small networks that have agreed to communicate and share data by obeying a standard protocol and passing on messages until they reach the final destination
Explain why compression of data is often necessary when transmitting across a network
Data compression enables information to be disseminated more quickly. It is the process of encoding to decrease bandwidth used for transmission and decrease amount of storage space required. Graphics: compresses 20-90% of original size, text: compressed 40% of original size; think zip files How it works Identify patterns of repeating bits (binary digits- 0 or 1) More repeats, more compression Better compression algorithm, more compression
Flow Control
Different devices have varying rates of transmission (sender may pass on message faster than receiver can digest) Flow control protocol such as XON-XOFF is used to sync sender and receiver. Transmit off if no more data can be taken in buffer (where incoming data is taken in). Transmit on to resume data uptake.
Benefits of diverse production
Drives competition, lowers prices and generates innovation.
Evaluate the advantages and disadvantages of each method of network security.
ENT V. PSK: All users share a locally stored passphrase, which can be found and copied from a computer by anyone. This makes WPA2-PSK less secure than the WPA2-ENT mode. MAC Address filtering discourages the casual user from accessing your network but does little to deter knowledgeable hackers who can use software to scan for MAC Addresses of legitimate devices currently accessing your network and then spoof their own MAC into a validated one. The best way to secure a wireless network is combine both encryption and authentication technology using the WPA2 standard. However, for authentication to be effective a strong password must be used.
Explain how data is transmitted by packet switching
Each packet has a destination address and may follow a dynamic route to the destination; packets may not even arrive in order, so destination computer has to reassemble packets in proper sequence Steps of Packet Switching 1. Sender computer chops up data into packets and gives each one the destination address 2. Each packet is assembled with a piece of particular data (email, music file, etc.) 3. Different routers along the way move packet from sender to receiver (each successive router is closer and closer to the receiver)- hot potato! 4. Receiver computer assembles data by using instructions from the packets so that data can return to original state
WiFi
Easy setup Short range, but higher average data speeds Uses radiowaves to transmit and receive data
Methods of network security
Encryption types, userID, trusted media access control (MAC) addresses Remember, wireless networks have led to concerns about the security of the user's data
ESP
Enterprise service provider; manages NAS for a business
Data Integrity
Error checking and correction protocols used by computers to ensure that data sent over is complete and accurate
Benefits of Packet Switching
Frees up 2 computers communicating with one another, so they can communicate with other computers Efficient in transmission of data- Data packets will got through least congested and cheapest routes
Describe the hardware and software components of a wireless network
Hardware... Wireless router- Sends packets through most efficient routes, uses radio waves to transmit data Wireless adapter-Connects computer to wireless network so they can communicate; that way, computer can become a wireless unit Extender- Captures router signal and rebroadcasts it to increase the range of the signal Software... Router software- Software built in to router; can be accessed using any web browser; software used to configure router; software enables one to assign SSID to router and set security and firewall parameters
Future Networks
LTE-Advanced (Long Term Evolution-Advanced)... Next generation cellular networking standard that offers higher throughput than its predecessor, LTE standard. LTE-Advanced networks can deliver up to 1 GBps of data, compared to a maximum of 300 MBps over LTE networks. Uses multiple-input, multiple-output (MIMO) technology to deliver data faster via more than one signal. MIMO requires multiple antennas to receive those signals, which can limit its use in compact mobile devices such as smartphones and tablets.
How do businesses manage VPNs?
Large corporations or businesses with knowledgeable IT staff typically purchase, deploy and maintain their own remote-access VPNs. Businesses can also choose to outsource their remote-access VPN services through an enterprise service provider (ESP). The ESP sets up a NAS for the business and keeps that NAS running smoothly.
LAN
Local area network- set of computers and peripheral devices housed in physical proximity of one another (either in the same building or buildings in the same area); usually exclusive to a company/home
Buffer
Memory location in networking device
Identify the technologies required to provide a VPN
NAS (Network Access Server) Client software (either installed as separate application or built in to operating system)
NAS
Network Access Server (nazz)- could be dedicate server or application software on shared server -User connects to NAS from Internet in order to use VPN -User provides credentials to sign into VPN -NAS autheticates access (Either NAS or another designated security server on the network can authenticate)
Computer network
Network of computing devices (nodes/hosts) that share resources and can communicate with one another; can be wired or wireless (radiowaves, infrared signals)
Intranet
Network that is local to a company. In other words, users from within this company can find all of their resources without having to go outside of the company. Ex: LANs and private WANs
Diagrams/Charts
OSI Model
Deadlock
PROBLEM: Both computers wait for signals from each other, so neither ever sends a message due to lost or corrupt signals Protocols to determine order of communication and handle situations such as deadlock so that communication does not break down
P2P
Peer to Peer Network- users from different computers can share files on each others computers by all connecting to the Internet (Bearshare, Limewire, etc.) Pros: easy, convenient file sharing Cons: could lead to illegal software and music sharing (Internet piracy) Remember, a peer is a computer system
PAN
Personal area network; personal devices within 10m of each other connected w/o wires (phone, printer, laptop)
Encryption
Process of coding messages so only authorized parties can read it; process of encoding data sent wirelessly between your device and the router, essentially scrambling the information and restricting open access. Wired Equivalent Privacy (WEP): Older security- only used for older devices; no longer used b/c keys are easy to crack; set up security that encrypts info sent from one computer to another Wi-Fi Protected Access (WPA): Stronger encryption that corrects weaknesses of WEP WPA2: Upgrade to WPA b/c does not allow security holes in WPA; implements AES (advanced encryption standard) instead of TKIP algorithm; AES is better b/c even skilled hackers cannot crack the code and has government-grade, stronger encryption
Outline the characterstics of different transmission media
Refer to chart on Wagner website
Outline the disadvantages of wireless networks
Security- Encryption methods for wireless networks have weaknesses Range- Network range is enough for a home, but to extend network repeaters or additional access points have to be purchased Reliability- Interference in transmission Speed- Fastest wireless networks are slower than slowest wired networks!
Client software
Software maintains and secures connection to VPN Stores IP addresses of computers that are permitted to login to VPN; sets up the tunneled connection to a NAS, which the user indicates by its Internet address The software also manages the encryption required to keep the connection secure.
Congestion
Source sends more data than destination buffer can hold, degrading performance TCP protocol decides which packets traveling over the Internet will be dropped and which ones will be kept in memory buffer (old or new)
SAN
Storage area network- multiple computers that share the same hard drive that contains important information (esp. for a company), so that only new servers have to be added (instead of new computers holding the same information on a local disk) Increases network's storage capacity
Explain why protocols are necessary
To resolve communication problems concerning data integrity, flow control, deadlock, congestion and error checking
Extranet
Type of extended intranet where certain internal services are made available to known external users or external business partners at remote locations
VLAN
Virtual local area network- computers connected to each other through software in wireless fashion; VLANs map workstations according to departments or otherwise instead of physical proximity; if computers were to physically move, it would not affect the organization of the VLAN... flexibility is their big plus "behave as if they are connected to the same wire"
VPN
Virtual private network: company provides secured access to part of public telecommunications network to users In other words, technology that provides secure and reliable connection over a public network such as the Internet Costs less than buying physical technology and wires to ensure private access
Types of wireless networks
WiFi, WiMax, 3G Mobile, Future Networks
WAN
Wide area network- two or more local networks that span a greater geographical area; ex: Internet Modes of transmission: radio waves, satellite dishes, telephone lines
WLAN
Wireless local area network
WiMax
Worldwide Interoperability for Microwave Access Similar to WiFi, but can provide longer range Wireless broadband alternative to cable, DSL and satellite Internet service Higher cost, so does not replace WiFi Limited availability b/c lost to LTE technology in cell phone industry
Describe how communications over networks is broken down into different layers
7 Layers of OSI model
Evaluate the use of a VPN
A VPN is a way for companies to allow their employees to access company resources outside the office. -Work patterns are changing b/c people can work from home (telecommuting) -VPN's enable people to access company resources (files, application software, database, printers) while traveling People subscribe to VPN services at home to protect their online privacy
Explain why the speed of data transmissions across a network can vary
Slow speed of data transmission- degrades user experience; people perceive this as lag; latency period varies and can increase due to several reasons... -Time of day (slower @ peek times), traffic load (how many people are using network) -Weather (satellite and wireless signal interferences) -Medium of transmission (fiber optics, satellite, wireless, metal wiring) -Network congestion: if so, packets may have to be resent -Length of route between sender and receiver
MAC Address Filtering
Media Access Control Address: Unique identifier assigned to a network adapter by the manufacturer for identification MAC address filtering allows only machines with specific MAC addresses access to a network. You specify which addresses are allowed in the router software.
Packet switching
Network technology that processes data in packets, breaking up data in smaller chunks for transmission Examples: Transport Control Protocol/Internet Protocol (TCP/IP) is an example of a packet switching protocol. Some mobile phone technologies also use packet switching technologies.
