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Chapter Overview

Network Communications

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Signals and Protocols

A data network is a group of computers connected by some network mediums.

The network medium carries signals between computers.

Signals reduce complex information to the simplest possible form.

Computers communicate by following rules defined in a protocol.

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Protocol Services

Packet acknowledgment Segmentation Flow control Error detection Error correction Data compression Data encryption

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Local Area Networks A local area network (LAN) is a collection of

computers located in a relatively small area. The pattern in which computers in a LAN are

connected is called the topology. The basic LAN topologies include bus, star,

and ring.

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Wide Area Networks (WAN)

Figure 1.3 gives another example

WANs connect LANs through routers

Three Common Network Components

Servers – a power computer providing services and runs an NOS File, Mail, Web, Printer, Fax, App, Telephone,

etc. Workstations – not necessary a client

machine, but have resources to provide. In Unix world, a workstations has storage spaces

to share Hosts – network devices with an IP address,

can be a server, workstation, or others

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Virtual LANs and Virtual Private Networks

A virtual LAN (VLAN), is a group of hosts communicate as if they were on the same broadcast domain, regardless of their physical location. A VLAN has the same attributes as a physical LAN, but it allows for end stations not located on the same network switch. Network reconfiguration is done through software (more on chapter 11, if we go that far).

A virtual private network (VPN) is a network that uses a public telecommunication infrastructure, such as the Internet, to provide secure access to a user’s intranet (more on chapter 13, if we get that far).

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Client/Server and Peer-to-Peer Networking

Clients request services; servers provide services

On a client/server network, computers function as either clients or servers.

On a peer-to-peer network, computers can function as both clients and servers.

Microsoft Windows, UNIX, and Linux are peer-to-peer network operating systems.

Novell NetWare is a client/server network operating system.

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Cable Topologies

Bus Star Ring Hierarchical star Mesh Wireless

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Bus Topology

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Star Topology

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Ring Topology

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Ring Network Types

Physical ring Logical ring Double ring (FDDI)

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Hierarchical Star Topology

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Mesh LAN Topology

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Mesh Internetwork

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Wireless Topologies

Ad hoc topology: Connects two or more wireless computers communicating with each other only

Infrastructure network: Connects wireless computers communicating with a network access point that provides access to a standard cabled network

Others

Hybrid Physical start, logical rain or bus

Point-to-point Point-to-multipoint

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Topology selection consideration

Cost Ease of installation Ease of maintenance Fault-tolerance requirement Coverage area Security, etc.

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Backbone Network

Could be Switches