1. NETWORKING TECHNOLOGIES

2. Telecommunications Systems
Purpose – to transmit data from one location to another
Voice data
Computer data
Video data
Any data
Major components
Transmission media
Network topology
Data communications hardware
Protocols used in system
Network software
Telecommunications services

3. Data Format for Network Transmission
Data inside computers is in digital form
Networks transmit two forms of data
Analog – voice over telephone
Digital – data over ISDN telephone line
Analog network cannot carry digital data
Most of existing telephone system is an analog network
Conversion of digital data to analog format (when necessary)
Modulation
Amplitude modulation
Frequency modulation
Convert on one end of transmission; de-convert on other end
Modulation–demodulation, or modem for short

4. How Modems Work

5. Bandwidth The measure of capacity of transmission media
Bits per second (bps)
Kilobits per second
Modem communications over telephone lines
Megabits per second
Most existing local area networks
Gigabits per second
High speed data networks
Internet backbone

6. Network Media Physical media Electrical signal Optical signal
Wire
Twisted pair
Phone System
LAN
Coaxial
Signal interference
Optical signal
Fiber optic cable
Thin glass fibers surrounded by coating
Uses lasers for light source
Very fast
Physical media require installation of cable
Expensive
Time consuming

8. Network Media Wireless media Radio frequency Terrestrial microwave
Low power radio waves
Affected by electromagnetic interference
Highly vulnerable to snooping
Conflicting standards
IEEE a, b, and G
Limited distance
Terrestrial microwave
Tower
Satellite
Geosynchronous – GEO
Medium earth orbit – MEO
Low earth orbit – LEO
Infrared
Close proximity and “line of sight” location required

9. Media Types and Speed

10. Computer Networks
Two or more computers that are connected for the purpose of sharing data
File sharing (e.g. MP3s)
Database sharing
Computer must be connected to the network media
Network interface card (NIC)
Each NIC has its own unique address
Once connected to the network, the computer (or other device) becomes a network node

11. Transmitting Data in a Network
Circuit switched network
Entire circuit from end to end must be open and available
Guarantees message goes through
Any one segment along the way goes down, the circuit is disabled
Packet switched network
Message data divided into small pieces called packets, each with destination address and packet id
Special network hardware routes packets to destination where message is reassembled
More fault tolerant than circuit switched networks

12. Network Topologies The configurations of network components
Widely used network topologies
Bus
Star
Ring
Mesh
Tree
Hybrid

13. Bus Network Topology Most simple network topology
All devices connected to a common central cable
Inexpensive
Easily expanded
If cable fails, the entire network will shut down
Bus is topology used most widely in businesses

14. Bus Network Topology (Continued)

15. Star Network Topology
Star topology is centered around central routing device called a hub
All network nodes connect to the hub
Easy to install and update
If hub fails, network fails
Hub can also be a bottleneck

17. Ring Network Topology Each node connected to two other nodes in a ring
Similar to the buss, but with the ends of the buss connected together
More reliable than buss or star
If one node fails, data rerouted around failed node
Expensive and difficult to install
Usually used by larger organizations who can afford the expense and to whom the reliability is very important

18. Ring Network Topology (Continued)

19. Mesh Network Topology Every node connected to every other node Fast
Reliable
No hub or bus to fail
If one device goes down, it is the only node affected
Expensive
Every node must be wired to every other node
Difficult to add nodes
If there are 32 nodes in a mesh network and you wish to add a new node, how many new cables must you add?
32 nodes
Add new 33rd node
New node must connect to all 32 existing nodes, therefore 32 cables to add

21. Tree Network Topology Combination of bus and star
Two or more star networks connected using a bus for the backbone

23. Hybrid Topologies Combine two or more of the other topologies
Bus used for LANs and ring used for campus backbone linking LANs together

25. Network Architecture Defines how network functions at a logical level
Two primary types
Client-server
Peer-to-peer (P2P)

26. Client-server Network Architecture
Nodes are either clients or servers
Clients use services
Servers provide services
Access to shared data
Printing
FAX
Client software on client node cooperates with server software on server node
WWW is largest client server application

27. Peer-to-Peer Network Architecture
All nodes on the network are equal.
Any node can be both a client and a server.
Napster was an example of a P2P network used to share MP3 files.
Windows printer and file sharing use P2P.

29. Local Area Networks (LANs)
Computer network where the nodes are all in close proximity
Department
Floor in office building
Small business building
Provides access to shared resources
Servers
Printers
Databases
Internet access

30. Larger Networks Campus area network (CAN)
Connects LANs within a limited geographic area
School
Corporate campus
Military installation
Metropolitan area network (MAN)
Within a town or city
Wide area network (WAN)
Two or more LANs that are geographically separate but linked through a public telephone network

31. Data Communications Hardware
Hub
Modem
Router – special hardware in packet switched networks that determines optimal routing path for packets
Gateway – converts data from one standard to another; allows connections of disparate networks

32. Protocols
An agreed upon set of rules that govern communications in a network
TCP/IP
The protocol suite for the Internet
Transmission Control Protocol (TCP)
Provides a reliable byte-stream transfer service between two endpoints on an internet
Internet Protocol (IP)
Defines a delivery mechanism for packets of data sent between all systems on an Internet
Widely used by business, even for internal networks

33. Protocols (Continued)
Ethernet
A set of rules for constructing message in a local network
Most widely used protocol for transmitting data over LANs
Listen before talk
Simple
Inexpensive
Flexible
Collisions
High message volume greatly reduces transmission speed

34. Protocols (Continued)
Token Ring
Also a set of rules for constructing message in a local network
Only one node “talks” at a time
Complex
Expensive
More fault tolerant than Ethernet
No collisions
Transmission speed unaffected by message volume

35. Network Software Network operating system Network management software
Novell NetWare
Microsoft Windows Server 2003
Network management software
Helps ensure security of network
Monitors performance
Helps administrators reconfigure network
Remote administration via push technology
Network monitoring software
Packet sniffers – see data as it moves over network
Keystroke monitors – see what users are doing

36. Telecommunications Services
Value Added Networks (VANs)
Proprietary networks built using common carriers
Provide enhanced services
Video conferencing
Electronic data interchange (EDI)
Virtual Private Networks (VPNs)
Use encryption to provide a secure end-to-end connection over common carriers or the Internet
Remote access to internal networks w/o dialup
Leased lines
High speed, long distance data transfer

37. Leased Line Comparisons