Download Ch01

Chapter Overview

Network Communications
1
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.
2
Protocol Services







Packet acknowledgment
Segmentation
Flow control
Error detection
Error correction
Data compression
Data encryption
3
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.
4
Wide Area Networks (WAN)
WANs connect LANs through routers
Figure 1.3 gives another example
5
Three Common Network Components

Servers – a power computer providing
services and runs an NOS


Workstations – not necessary a client
machine, but have resources to provide.


File, Mail, Web, Printer, Fax, App, Telephone, etc.
In Unix world, a workstations has storage spaces
to share
Hosts – network devices with an IP address,
can be a server, workstation, or others
6
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).
7
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-topeer network operating systems.
Novell NetWare is a client/server network
operating system.
8
Cable Topologies






Bus
Star
Ring
Hierarchical star
Mesh
Wireless
9
Bus Topology
10
Star Topology
11
Ring Topology
12
Ring Network Types



Physical ring
Logical ring
Double ring (FDDI)
13
Hierarchical Star Topology
14
Mesh LAN Topology
15
Mesh Internetwork
16
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
17
Others

Hybrid



Physical start, logical rain or bus
Point-to-point
Point-to-multipoint
18
Topology selection consideration






Cost
Ease of installation
Ease of maintenance
Fault-tolerance requirement
Coverage area
Security, etc.
19
Backbone Network
Could be Switches
20