1. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster Police Technology Police Technology Chapter Four Police Technology Networks

2. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster Learning Objectives Understand the importance and use of Networks Understand the importance and use of Networks Understand the different types of technologies necessary to establish a network Understand the different types of technologies necessary to establish a network Be exposed to several different types of networks Be exposed to several different types of networks Understand the necessity for network security and several of the means of providing network security. Understand the necessity for network security and several of the means of providing network security.

3. 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.

4. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster Network Basics Networks are founded on the concept of client-server architecture. Architecture refers to the design of a system or technology. Networks are founded on the concept of client-server architecture. Architecture refers to the design of a system or technology. The individual work station, called a node, is provided networking services by a server. The individual work station, called a node, is provided networking services by a server.

5. 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. 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.

6. 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.). 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.). Law enforcement Law enforcement

7. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster Networks also provide organizations with the capability to back up data. If one computer fails, the network can take over the processing load. Networks also provide organizations with the capability to back up data. If one computer fails, the network can take over the processing load. Why Network?

8. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster Back to ….. 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.

9. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster Digital signals are the primary means of transmitting data communications. Digital signals have several advantages over analog: Fewer errors; Fewer errors; Can be transmitted at higher speeds Can be transmitted at higher speeds Peripheral devices are less complex. Peripheral devices are less complex. Back to ….. Analog and Digital Signals

10. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster The analog wave is called a baud. Bits are essentially added to the analog wave. 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. Public networks tend to run at about 2,400 baud (waves) per second. Analog stuff

11. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster Our technology adds more bits to each baud generally in multiples of four. 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). 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). Analog stuff This about Modem Speed!

12. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster 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. 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. 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. The receiving computer compares the sum of the data stream to the bit parity digit. Error Detection

13. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster Information travels between computers in a network in one of three ways: Simplex transmission – information travels in one direction only Simplex transmission – information travels in one direction only Half-duplex – information travels in both directions, one way at a time Half-duplex – information travels in both directions, one way at a time Full duplex – data is transmitted in both directions simultaneously Full duplex – data is transmitted in both directions simultaneously Data Transmission

14. 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 fastest throughput and response time possible The least-cost path – the data flows through the fewest devices possible The least-cost path – the data flows through the fewest devices possible Design reliability Design reliability

15. 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 Unused (available) portions of a network are chosen Data passes through the most efficient available means Data passes through the most efficient available means

16. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster 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. Things That Connect

17. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster 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 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 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. The same line can transmit both a telephone conversation and the digital data. Asymmetric Digital Subscriber Line - DSL

18. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster Other ways of connecting to a network Use a hub 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 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 A router is like a switch. A router is a bridge between two networks. The router determines the best path between two different networks

19. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster A remote switch is one that is at your location but controlled by someone else at different location. 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. A trunk is a circuit between different types of switching equipment. Middleware describes a software that is used to connect different applications (the translator). Middleware describes a software that is used to connect different applications (the translator). Network Terms

20. 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. Techniques to reduce the size of data in order to improve storage and bandwidth (transmission) capacity.

21. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster Bandwidth Refers to the capacity of the medium that carries the signal. Refers to the capacity of the medium that carries the signal. Analog bandwidth is measured in Hz. Analog bandwidth is measured in Hz. Digital bandwidth is measured in the number of bits per second the medium can carry. 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 Determines the speed at which data can be moved through a network More bandwidth = more data, faster

22. 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 Transmission Control Protocol/Internet Protocol (TCP/IP). Your computer must use TCP/IP to go on the Internet.

23. 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.

24. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster LAN is a network that operates in one specific location. LAN is a network that operates in one specific location. Wide Area Network (WAN) is used to connect geographically separated networks together. Wide Area Network (WAN) is used to connect geographically separated networks together. Basic Network Types

25. 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.

26. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster Data Security Could be called Network security or Computer security. Could be called Network security or Computer security. Computer What we are most trying to protect is the information contained in the various systems. What we are most trying to protect is the information contained in the various systems.

27. 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 Placing servers, routers and switching equipment behind locked doors Backing up data in one or more location Backing up data in one or more location

28. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster Firewall - operates by controlling access to the network based upon the contents of the data packets being transmitted on the network. 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) Encryption - changing text or data into a form that is unreadable without a key (secret code) Virtual Security is…..

29. 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.

30. Copyright 2005-2009: Hi Tech Criminal Justice, Raymond E. Foster Police Technology Discuss law enforcement issues on the Criminal Justice Degree Forum law enforcement Criminal Justice Degreelaw enforcement Criminal Justice Degree