Post on 13-Sep-2014
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CS 56 • Networking Essentials
Chapter 1 Introduction to Networking
Sonny Huang
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Chapter 1 Introduction to Networking
OutlineWhat is a Network
Network Configuration
Network Topology
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What Is a Network?
The Concept of Networking
A. Network is defined as a system in which a number of independent computers are linked together to share data and peripherals, such as hard disks and printers.
B. Sharing is the purpose of computer networking.
Centralized mainframes preceded networks. In a mainframe environment, all users on a mainframe share a single processor and use the same programs.
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What Is a Network?
The Introducing Computer NetworkingA. Stand-Alone Environment
Personal computers, most notably the IBM PC, were introduced in the late 1970s and early 1980s. A PC is a computer that has its own processor and programs.
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What Is a Network?
B. The Sneakernet
Since the early days, the cost of most PCs has dropped dramatically, as has the cost of peripherals such as hard drive disks and printers. Networks have developed because PC users need to share data and applications across short and long distances.
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What Is a Network?
C. A Simple Computer Network
It allowscomputer to sharing data, messages, graphics, fax capabilities, modems, and other hardware resources.
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What Is a Network?
Why Use a Computer Network? A.Sharing Information (or Data)
1. Documents (memos,spreadsheets, invoices, and so on)
2. E-mail messages3. Illustrations,
photographs, videos, and audio files
4. Live audio and video broadcasts
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What Is a Network?
B.Sharing Hardware and Software
1. Word-processing software2. Project-tracking software3. Printers4. Fax machines5. Modems6. CD-ROM drives and other removable drives, such as
Zip and Jaz drives7. Hard drives
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What Is a Network?
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What Is a Network?
C. Centralizing Administration and Support
1. Networking computers can simplify support tasks.2. Consistency in software across the network increases
support efficiency.
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What Is a Network?
Why Two Major Types of Networks: LANs and WANs
A. Local Area Network (LAN)1. Basic building block of any network.2. Confined to a limited geographical area.
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What Is a Network?
B. Wide Area Network (WAN)1. Number of interconnected LANs.2. No geographical limit.3. Ultimate WAN is the Internet.
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What Is a Network?
Since reasonably fast WAN links are becoming more affordable, the difference between a LAN and a WAN has become more blurred. Expand on the advantages of a network, including the benefits of sharing data and upgrading software
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Network Configuration
OverviewA. Components, functions, and features in common for all
networks:
1. Servers: Computers that provide shared resources to network users.
2. Clients: Computers that access shared network resources provided by a server.
3. Media: The wires that make the physical connections.4. Shared Data: Files provided to clients by servers across
the network.5. Shared Printers and Other Peripherals: Additional
resources provided by servers.
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Network Configuration
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Network Configuration
6. Resources: Any service or device, such as files, printers, or other items, made available for use by members of the network.
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Network Configuration
B. Type of network will depend on the following:
1. Size of organization2. Level of security required3. Type of business4. Level of administrative support available5. Amount of network traffic6. Needs of the network users7. Network budget
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Network Configuration
Peer-to-Peer Networks
A. Size1. Also called workgroups2. Typically ten or fewer computers
B. Cost1. Relatively simple2. Less expensive than server-based networks3. No central server
C. Operating Systems1. Servers do not function as clients.2. Peer-to-peer networking built into many operating
systems.
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Network Configuration
D. Implementation1. Computers located at user’s desk.2. User determines the data to be shared and is also
responsible for the security of the data.3. Simple, visible cabling system.
E. Where a Peer-to-Peer Network is Appropriate:1. Ten or fewer users.2. Users share resources, such as files and printers, but
no specialized servers exist.3. Security is not an issue.4. Organization and the network will experience only
limited growth within the foreseeable future.
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Network Configuration
Peer-to-peer networking is built into operating systems such as Microsoft Windows 3.11, Microsoft Windows 95, and Microsoft Windows NT Workstation; no additional software is needed.
F. Peer-to-Peer Network Considerations1. Administration tasks
a. Managing users and securityb. Making resources availablec. Maintaining applications and datad. Installing and upgrading application and operating system software
No system manager to oversee the entire network. Individual users administer their own network.
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Network Configuration
2. Sharing Resourcesa. Users share resources (directories, printers, fax cards, and so forth).b. Users control the manner in which these resources are shared.
3. Server RequirementsIn peer-to-peer environment, each computer must:a. Use a large percentage of its resources to support the user at the computer, known as the local user.b. Use additional resources such as hard disk space and memory, to support the user's accessing resources on the network, known as the remote user.
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Network Configuration
4. Securitya. Limited to resource password security.b. Each resource has its own password.c. Very little control over peer-to-peer networks.
5. Traininga. Users need training before they are able to function properly as both users and administrators of their computers.b. Users require more training than those in a server-based network.
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Network Configuration
Computers in a peer-to-peer network are not identical, but each has equal rank within the network. Note that the limit of ten computers in a peer-to-peer network is not an operating system limitation; it is an administrative recommendation. Therefore, user training is extremely important.
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Network Configuration
Server-Based NetworksA. Specialized Server(s)1. File and Print Servers2. Application Servers3. Mail Servers4. Fax Servers5. Communication Servers6. Directory Services Servers
Planning for specialized servers becomes important with an expanded network. The planner must take into account any anticipated network growth so that network use will not be disrupted if the role of a specific server needs to be changed.
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Network Configuration
It is possible to run more than one specialized function on a single computer that operates as the server. However, administrators should be particularly careful not to overload a single computer with too many functions.
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Network Configuration
B. Role of Software1. Network server hardware and its operating system
work together as a unit.2. Advanced server operating systems from Novell and
Microsoft are designed to take advantage of the most advanced server hardware.
3. No matter how powerful a server might be, it is useless without an operating system that can take advantage of its physical resources.
C. Advantages1. Sharing Resources: Centrally administered and controlled.
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Network Configuration
If more than one administrator manages a combined network, they should be sure to coordinate their work carefully to avoid a duplication of effort.
2. Security: Access to resources can be limited to
specific users.
Security is an important issue with server-based networks. Passwords are used for login security. Permissions, rights, and privileges are granted to users on a need-to-use basis.
3. Backup: Can be scheduled to occur automatically.
4. Redundancy: All data can be duplicated and kept online.
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Network Configuration
4. Redundancy: All data can be duplicated and kept online.
5. Number of Users: Can support a larger number of users and a larger network.
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Network Configuration
D. Hardware Considerations1. Limited to the needs of the user.2. Typical client has 32 MB of RAM.
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Network Topology
Designing Network TopologyA. Definition of Network Topology:1. Arrangement or physical layout of computers, cables,
and other components.2. Standard term that most network professionals use
for the network’s basic design.
B. Network topology determines the following:1. Physical layout of the network2. Design of the network (for example, star, bus, ring,
and mesh)3. Diagram of the network4. Map of the network
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Network Topology
C. Choice of topology influences the following:1. Type of equipment the network needs2. Capabilities of the network3. Future growth of the network4. Network management
Each network has a physical topology (layout of the network as if looking down at the network from above) and an electrical topology (how the electrical signals are passed through the network to accomplish communication). Most current physical topologies appear as stars, or modified stars, while the electrical topology may still be a bus or a ring.
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Network Topology
Costs of the various types of cables and devices such as routers, bridges, and connectors are important to consider because network managers are also constrained by budgets.
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Network Topology
Standard Topologies
Video Note c01dem01 video shows a bus topology connection.
A. Bus1. Communication on the Bus
a. Single trunk (backbone/segment) connects all computers in a single line.b. Computers communicate by addressing data to a particular computer and sending out that data on the cable as electronic signals.
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Network Topology
Video Note c01dem02 video shows how data is transferred in a bus topology.
2. Sending the Signal
a. Addressed data is put on network in the form of electronic signals.b. Signal goes to all computers on the bus.c. Information is accepted only by the computer with the correct address.
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Network Topology
d. Only one computer can send data at a time.e. If one computer fails, it does not affect the rest of the network.
Video Note c01dem03 video shows how a failed computer does not affect data transmission in a bus topology.
3. Signal Bounce
a. If the signal is allowed to continue uninterrupted, it will keep bouncing back and forth along the cable and prevent other computers from sending signals.b. The signal must be stopped after it has had a chance to reach the proper destination address.
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Network Topology
Video Note c01dem04 video shows a demonstration of signal bounce.
4. Terminator
a. Terminator required at each end of bus.b. Signal could bounce up and down the cable forever.c. "Break" in cable creates nonterminated ends.
Video Note c01dem05 and c01dem06 videos shoe a terminator component and a demonstration of how a terminator eliminates signal bounce.
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Network Topology
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Network Topology
5. Disrupting Network Communicationa. Break in the bus cable can bring down the network.b. Computers can still function as stand-alone computers, but they cannot communicate with each other.
A terminator’s resistance varies with the type of cable used.
Video Note c01dem07 and c01dem08 videos show a demonstration of what happens when there is a break in the cable of a bus topology network.
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Network Topology
6. Network Expansiona. Lengthen cable using BNC barrel connectors.b. Use a repeater to boost the signal.
Repeaters do more than amplify the signal; they also regenerate it, thus eliminating much of the noise or irregularities that the signal may have picked up. The bus topology has strict cable length limits, depending on the type of communications protocol used.
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Network Topology
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Network Topology
Video Note c01dem09 and c01dem10 videos show a demonstration of a star topology.
B. Star1. Computers are connected by cable segments to a hub;
signals are transmitted from sending computer through the hub to all computers on the network.
2. If a hub fails, all computers on that hub fail; but if a line from the hub to the computer is broken, only that computer is down. Remainder of network stays up.
3. If one computer fails, remainder of network stays up.4. More cable is required with a star than a bus.
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Network Topology
Video Note c01dem11 video shows what happens when a computer on a star topology network goes down.
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Network Topology
C. Ring1. Ring topology connects computers on a single circle of
cable.a. No terminated ends.b. Signals travel around the loop in one direction and pass through each computer.
2. Token Passing.
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Network Topology
Video Note c01dem12 and c01dem13 videos show demonstrations of logical and actual flows of data on a ring topology network.
Video Note c01dem14 and c01dem15 videos show demonstrations of logical and actual flows of token passing on a ring topology network.
Video Note c01dem16 video shows a demonstration of what happens when a computer on a token ring topology network goes down.
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Network Topology
a. Computers are connected on a single circle of cable in a ring or loop. Given that the cable is connected in a ring, no termination is required.b. The signal, or token, travels from computer to computer around the loop in one direction only until it reaches the destination computer with the address that matches the address on the data. Each computer boosts the signal and sends it on its way to the next computer. Upon delivery, a verification message is sent to the sender. The data is stripped from the signal and a new free signal is created by sender.c. Just as in the bus topology, one failed computer can affect the entire network if the physical topology is a ring.d. Token travels at approximately speed of light.
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Network Topology
Token passing is sometimes termed a "Mother, may I?" protocol, because a given computer cannot place a signal on the line until it has possession of the token. Contrast this with CSMA/CD and other contention protocols.
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Network Topology
D. Mesh1. Each computer is connected to every other computer
by separate cabling.2. Superior redundancy and reliability.3. Expensive to install because they use a lot of cabling.
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Network Topology
HubsA. Three types of Hubs:
1. Active Hub: Acts like a repeater by regenerating and retransmitting a signal (also called multiport repeaters)2. Passive Hub: A connecting point or switching station like a block3. Hybrid Hub: Supports different cable types
Video Note Run the c01dem17 video shows a discussion and demonstration of the role of hubs in network topologies.
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Network Topology
B. Hub Considerations1. Hubs segment the network; a break in any of the cables attached to the hub would bring only that segment down. The remainder of the network will continue to work.2. Wiring systems can be changed or expanded as needed.3. Different ports can be used to accommodate a variety of cabling types.4. Monitoring of network activity and traffic can be centralized.
Not all hubs are intelligent; some are merely connecting devices.
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Network Topology
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Network Topology
Variations on the Standard TopologiesA. Star Bus1. Bus backbone connects several star topologies in a
linear fashion.2. If one computer goes down, it will not affect the rest
of the network.
Video Note c01dem18, c01dem19, and c01dem20 show demonstrations of what happens when computers and hubs in a star-bus topology go down.
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Network Topology
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Network Topology
B. Star Ring1. Hubs all feed back to a main hub.2. The main hub contains the ring.
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Network Topology
C. Peer-to-Peer1. Configured as either a physical star or bus
topology.2. All computers on the network are equal.
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Network Topology
Selecting a TopologyA. Bus1. Advantages
a. Cable is economical.b. Media is inexpensive and easy to use.c. Simple to set up.d. Easy to extend.
2. Disadvantagesa. Network can slow down in heavy traffic.b. Problems are difficult to isolate.c. Cable break can affect many users.
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Network Topology
B. Ring1. Advantages
a. System provides equal access for all computers.b. Performance is even despite many users.
2. Disadvantagesa. Failure of one computer can impact the rest of the network.b. Problems are hard to isolate.c. Network reconfiguration disrupts operation.
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Network Topology
C. Star1. Advantages
a. Modifying system and adding new computers is easy.b. Centralized monitoring and management are possible.c. Failure of one computer does not affect the rest of the network.
2. Disadvantagesa. If the central point fails, the network fails.
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Network Topology
D. Mesh1. Advantages
a. Provides increased redundancy and reliability as well as ease of troubleshooting.
2. Disadvantages| a. Expensive to install because it uses a
lot of cabling.