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A network consists of two or more computers that are linked in order to share resources (such as printers and CDs), exchange files, or allow electronic communications.

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A Local Area Network (LAN) is a network that is confined to a relatively small area. It is generally limited to a geographic area such as a writing lab, school, or building.

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Wide Area Networks (WANs) connect networks in larger geographic areas, such as Florida, the United States, or the world. A WAN is complicated. It uses multiplexers, bridges, and routers to connect local and metropolitan networks to global communications networks like the Internet.

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Advantages of Installing a School Network

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Advantages of Installing a School Network

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- User access control

- Information storing and sharing
- Connections
- Services
- Internet
- Computing resources
- Flexible access
- Workgroup computing

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Disadvantages of Installing a School Network

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Disadvantages of Installing a School Network

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- Expensive to install
- Requires administrative time
- Servers fail
- Cables may break
- Security and compliance

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A protocol is a set of rules that governs the communications between computers on a network. In order for two computers to talk to each other, they must be speaking the same language.

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The physical layer of the network focuses on hardware elements, such as cables, repeaters, and network interface cards. By far the most common protocol used at the physical layer is Ethernet.

The data link layer of the network addresses the way that data packets are sent from one node to another.

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The Fast Ethernet protocol supports transmission up to 100 Mbps. Fast Ethernet requires the use of different, more expensive network concentrators/hubs and network interface cards.

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Gigabit Ethernet standard is a protocol that has a transmission speed of 1 Gbps (1000 Mbps). It can be used with both fiber optic cabling and copper.

The Ethernet standards continue to evolve. with 10 Gigabit Ethernet (10,000 Mbps) and 100 Gigabit Ethernet (100,000 Mbps).

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The network layer is in charge of routing network messages (data) from one computer to another. The common protocols at this layer are IP (which is paired with TCP at the transport layer for Internet network) and IPX (which is paired with SPX at the transport layer for some older Macintosh, Linus, UNIX, Novell and Windows networks). Because of the growth in Internet-based networks, IP/TCP are becoming the leading protocols for most networks.

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The transport layer is concerned with efficient and reliable transportation of the data packets from one network to another. In most cases, a document, e-mail message or other piece of information is not sent as one unit. Instead, it is broken into small data packets, each with header information that identifies its correct sequence and document.

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HTTP, FTP, SMTP and DNS (Session/Presentation/Application Layers)

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HTTP, FTP, SMTP and DNS (Session/Presentation/Application Layers)

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Several protocols overlap the session, presentation, and application layers of networks. There protocols listed below are a few of the more well-known:

DNS - Domain Name System - translates network address (such as IP addresses) into terms understood by humans (such as Domain Names) and vice-versa

DHCP - Dynamic Host Configuration Protocol - can automatically assign Internet addresses to computers and users

FTP - File Transfer Protocol - a protocol that is used to transfer and manipulate files on the Internet

HTTP - HyperText Transfer Protocol - An Internet-based protocol for sending and receiving webpages

IMAP - Internet Message Access Protocol - A protocol for e-mail messages on the Internet

IRC - Internet Relay Chat - a protocol used for Internet chat and other communications

POP3 - Post Office protocol Version 3 - a protocol used by e-mail clients to retrieve messages from remote servers

SMTP - Simple Mail Transfer Protocol - A protocol for e-mail messages on the Internet

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Networking hardware includes all computers, peripherals, interface cards and other equipment needed to perform data-processing and communications within the network.

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Servers are generally not used by humans directly, but rather run continuously to provide "services" to the other computers (and their human users) on the network. Services provided can include printing and faxing, software hosting, file storage and sharing, messaging, data storage and retrieval, complete access control (security) for the network's resources, and many others.

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Computers that humans use are broadly categorized as workstations. A typical workstation is a computer that is configured with a network interface card, networking software, and the appropriate cables.

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These devices typically have modest internal storage, but enough power to serve as a workstation for users on the go.

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The network interface card (NIC) provides the physical connection between the network and the computer workstation. Most NICs are internal, and they are included in the purchase of most computers.

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Ethernet cards are usually included with a computer, although additional ethernet cards can be purchased and installed on most computers.

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An ethernet switch is a device that provides a central connection point for cables from workstations, servers, and peripherals.

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Since a signal loses strength as it passes along a cable, it is often necessary to boost the signal with a device called a repeater. The repeater electrically amplifies the signal it receives and rebroadcasts it.

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A bridge is a device that allows you to segment a large network into two smaller, more efficient networks.
A bridge monitors the information traffic on both sides of the network so that it can pass packets of information to the correct location.
The bridge manages the traffic to maintain optimum performance on both sides of the network.

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Routers are the traffic directors of the global internet. All routers maintain complex routing tables which allow them to determine appropriate paths for packets destined for any address.
While bridges know the addresses of all computers on each side of the network, routers know the addresses other routers which in turn know about their own networks.
So, routers are network gateways.

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A firewall is a networking device that is installed at the entrance to a LAN when connecting networks together, particularly when connecting a private network to a public network, such as the internet. The firewall uses rules to filter traffic into and out of the private network, to protect the private network users and data from malevolent hackers. Firewalls are either hardware or software, depending on their intended use.

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Cable is the medium through which information usually moves from one network device to another.

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Unshielded twisted pair (UTP) is the most popular and is generally the best option for school networks.

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Although UTP cable is the least expensive cable, it may be susceptible to radio and electrical frequency interference (it should not be too close to electric motors, fluorescent lights, etc.). If you must place cable in environments with lots of potential interference, or if you must place cable in extremely sensitive environments that may be susceptible to the electrical current in the UTP, shielded twisted pair may be the solution.

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Coaxial cabling has a single copper conductor at its center. A plastic layer provides insulation between the center conductor and a braided metal shield. The metal shield helps to block any outside interference from fluorescent lights, motors, and other computers. lthough coaxial cabling is difficult to install, it is highly resistant to signal interference.

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Fiber optic cabling consists of a center glass core surrounded by several layers of protective materials. It transmits light rather than electronic signals eliminating the problem of electrical interference. This makes it ideal for certain environments that contain a large amount of electrical interference.

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More and more networks are operating without cables, in the wireless mode. Wireless LANs use high frequency radio signals, infrared light beams, or lasers to communicate between the workstations, servers, or hubs.

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Three basic techniques are used to protect networks from unauthorized wireless use. Use any and all of these techniques when setting up your wireless access points:

- Encryption
- Isolation
- Hidden SSID (Service Set IDentifier)

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- Mobility
- Fast Setup
- Cost
- Expandability

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- Security
- Interference
- Inconsistent connections
- Speed

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The physical topology of a network refers to the configuration of cables, computers, and other peripherals. Physical topology should not be confused with logical topology which is the method used to pass information between workstations.

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A linear bus topology consists of a main run of cable with a terminator at each end. All nodes (file server, workstations, and peripherals) are connected to the linear cable.

Advantages

Easy to connect a computer or peripheral to a linear bus.

Requires less cable length than a star topology.

Disadvantages

Entire network shuts down if there is a break in the main cable.

Terminators are required at both ends of the backbone cable.

Difficult to identify the problem if the entire network shuts down.

Not meant to be used as a stand-alone solution in a large building.

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A star topology is designed with each node (file server, workstations, and peripherals) connected directly to a central network hub, switch, or concentrator.

Advantages

Easy to install and wire.

No disruptions to the network when connecting or removing devices.

Easy to detect faults and to remove parts.

Disadvantages

Requires more cable length than a linear topology.

If the hub, switch, or concentrator fails, nodes attached are disabled.

More expensive than linear bus topologies because of the cost of the hubs, etc.

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A tree topology combines characteristics of linear bus and star topologies. It consists of groups of star-configured workstations connected to a linear bus backbone cable. Tree topologies allow for the expansion of an existing network, and enable schools to configure a network to meet their needs.

Advantages

Point-to-point wiring for individual segments.

Supported by several hardware and software venders.

Disadvantages

Overall length of each segment is limited by the type of cabling used.

If the backbone line breaks, the entire segment goes down.

More difficult to configure and wire than other topologies.

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- Money
- Length of cable needed
- Future growth
- Cable type

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Unlike operating systems, such as Windows, that are designed for single users to control one computer, network operating systems (NOS) coordinate the activities of multiple computers across a network. The network operating system acts as a director to keep the network running smoothly.

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Peer-to-peer network operating systems allow users to share resources and files located on their computers and to access shared resources found on other computers. However, they do not have a file server or a centralized management source. In a peer-to-peer network, all computers are considered equal; they all have the same abilities to use the resources available on the network.

Advantages

Less initial expense - No need for a dedicated server.

Setup - An operating system (such as Windows XP) already in place may only need to be reconfigured for peer-to-peer operations.

Disadvantages

Decentralized - No central repository for files and applications.

Security - Does not provide the security available on a client/server network.

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Client/server network operating systems allow the network to centralize functions and applications in one or more dedicated file servers. The file servers become the heart of the system, providing access to resources and providing security. Individual workstations (clients) have access to the resources available on the file servers.

Advantages

Centralized - Resources and data security are controlled through the server.

Scalability - Any or all elements can be replaced individually as needs increase.

Flexibility - New technology can be easily integrated into system.

Interoperability - All components (client/network/server) work together.

Accessibility - Server can be accessed remotely and across multiple platforms.

Disadvantages

Expense - Requires initial investment in dedicated server.

Maintenance - Large networks will require a staff to ensure efficient operation.

Dependence - When server goes down, operations will cease across the network.