Transcript Chapter Four - Networks - CRIMINAL JUSTICE ONLINE
Police Technology Chapter Four
Networks Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Learning Objectives
Understand the importance and use of Networks Understand the different types of technologies necessary to establish a network Be exposed to several different types of networks Understand the necessity for network security and several of the means of providing network security.
Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Network Basics
A network is about two or more people establishing a way to communicate.
There are formal and informal networks. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Network Basics
Networks are founded on the concept of client-server architecture technology. . Architecture refers to the design of a system or The individual work station, called a node , is provided networking services by a server. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Network Basics
The server is a computer that provides files, printers, and processing power to the individual workstations. The server is a special type of computer linked into a network. It is used only to manage the network, shared data, and shared resources. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Why Network?
Law enforcement agencies may have many buildings and offices in different physical locations. A network allows them to share computer, data, and information resources. Much of the information used by law enforcement comes from agencies outside their organization (e.g., DMV, Corrections, other agencies, etc.). Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Why Network?
Networks also provide organizations with the capability to back up data. If one computer fails, the network can take over the processing load. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
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Analog and Digital Signals
An analog signal weakens as it travels through wire because of the resistance the signal meets in the medium that is carrying it (air, wire, coaxial cable). Digital signals are subject to the same decrease in strength as analog signals. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
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Analog and Digital Signals
Digital signals are the primary means of transmitting data communications.
Digital signals have several advantages over analog: Fewer errors; Can be transmitted at higher speeds Peripheral devices are less complex .
Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Analog stuff
The analog wave is called a baud . Bits are essentially added to the analog wave. Public networks tend to run at about 2,400 baud (waves) per second. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Analog stuff
Our technology adds more bits to each baud generally in multiples of four.
A 2,400 baud analog signal that adds 12 bits to each baud would give an effective transmission rate of 28,800 bits per second (BPS).
This about Modem Speed!
Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Error Detection
One of the schemes commonly used to prevent data corruption is bit parity . Take a stream of binary, add up the numbers, you get an odd or an even number. Add a digit at the end of the data to indicate if the sum is odd or even. The receiving computer compares the sum of the data stream to the bit parity digit. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Data Transmission
Information travels between computers in a network in one of three ways: Simplex transmission – information travels in one direction only Half-duplex – information travels in both directions, one way at a time Full duplex – data is transmitted in both directions simultaneously Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Designing a Network
Look at three things: The fastest throughput and response time possible The least-cost path – the data flows through the fewest devices possible Design reliability Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Things That Connect
Networks accomplish data transfer with a concept called packet switching . Unused (available) portions of a network are chosen Data passes through the most efficient available means Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Things That Connect
In networks, the connection point between your computer and the network is commonly a modem . Modems have become asymmetric digital subscriber line (ADSL).
The word asymmetrical is used because these modems send data faster in one direction than the other. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Asymmetric Digital Subscriber Line -
DSL Most homes and offices have a dedicated copper wire running between them and the telephone company’s central office. The copper wire can carry far more data than the 3,000 Hz signal of a typical telephone conversation The copper wire can act as a purely digital high-speed transmission channel (1 million bps). The same line can transmit both a telephone conversation and the digital data. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Other ways of connecting to a network
Use a hub Most hubs include a switch . A switch determines how data will travel along its path to the intended destination – to look for the optimal route A router is like a switch. A router is a bridge between two networks. The router determines the best path between two different networks Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Network Terms
A remote switch is one that is at your location but controlled by someone else at different location. A trunk is a circuit between different types of switching equipment. Middleware used to connect different applications (the translator). describes a software that is Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Data Compression
Techniques to reduce the size of data in order to improve storage and bandwidth (transmission) capacity.
Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Bandwidth
Refers to the the medium that carries the signal. capacity of Analog bandwidth is measured in Hz. Digital bandwidth is measured in the number of bits per second the medium can carry. Determines the speed at which data can be moved through a network
More bandwidth = more data, faster
Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Protocols
An agreement between people on how a transaction should take place. Many networks use the (TCP/IP).
Transmission Control Protocol/Internet Protocol Your computer must use TCP/IP to go on the Internet. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Basic Network Types
Hierarchical - vertical or tree structure Local Area Network (LAN) - horizontal network. Allows each device on the network to receive every network transmission. Star Configuration – All transmissions come from a hub.
Justice, Raymond E. Foster
Basic Network Types
LAN
is a network that operates in
one
specific location.
Wide Area Network (WAN)
connect geographically separated networks together. is used to Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Basic Network Types
Wireless Local Area Network (WLAN) uses radio waves to connect among the mobile node, mobile computer, and the hardwired network.
Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Data Security
Could be called Network security or Computer security. What we are most trying to protect is the information contained in the various systems. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Physical Security is . . .
Anything we do to physically protect our systems and information: Placing servers, routers and switching equipment behind locked doors Backing up data in one or more location Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Virtual Security is…..
Firewall
- operates by controlling access to the network based upon the contents of the data packets being transmitted on the network.
Encryption
- changing text or data into a form that is unreadable without a key (secret code) Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster
Virtual Security is…..
Intrusion Detection security management system that gathers and analyses info from different part of the network. Scans network looking for user and system activity and any pattern of abnormal behavior. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster –
Police Technology
Discuss law enforcement issues on the Criminal Justice Degree Forum Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster