Network Components

Introduction to Network Components

• There are two main types of networks Peer to Peer  and client server

• Peer to peer networks may only be used in small sized networks and client server  networks should be used in large sized networks.

• There are different access methods to a network  including token  ring and CSMA/CD .

• The devices  used in a network  include NIC cards, Hubs, Switches , Routers and Gateways .

Key Topics

Types of Networks Peer To Peer Networks Client Server  Networks Authentication Server Operating System Access Method CSMA/CD

Token Ring Network Hardware Hubs Bridges Routers Gateways

Types of networks

• There are two main logical types of network , Peer to Peer , Client Server

·        These Logical networks  have nothing to do with topology.

 

Peer to Peer  networks

• Peer-to-Peer networks are a number of computers connected together using client workstation software  competent of sharing  files  and folders

·        Each computer acts as both client and server computer.

• Operating systems  offering client side networking include Windows95, Windows 98, Windows NT  workstation, Windows Professional , Windows XP

• Peer to peer networks offer very little security and are only desirable in a limited size network  usually recommended to be less then 10 computers.

·        Each user must set their own local computers security settings in a peer-to-peer network

 

• Backing up data from this type of network  is slow and tedious work because all clients need to be backed up individually.

 

 

 

Client Server  Networks

• There exists a centralized  server that interacts with the workstations on the network

• All users on the network  must log on the server (become authenticated) before they can access the resources  of the network including files  and printers .

• Security  is centralized  on the network  and managed by a dedicated network administrator

• Servers are suitable for networks of all sizes from several computers to several thousand computers.

• Backing up of data is centralized  and made easy on a client server  network

• Operating systems  with server side software  include Novell  OS, Windows NT , Windows 2000 , and Unix .

• Server Operating System is a lot more expensive then workstation software

• All server operating systems are subject to license agreement, as to the number of users per server. 

Access Method

• Access method  is the process that is used by the networking operating system  to transmit data on the networking medium from the network  card.

• Ethernet network  that are both the BUS and STAR topologies  use CSMA/CD  access method.

• Carrier Sense Multiple Access with Collision Detections  (CSMA/CD ).

• Another access method is the Token Ring .

CSMA/CD  Steps

·        The transmitting computer checks to see if there is data on the network  bus.

• If there is data on the medium the card will not transmit any data.

• As soon as it finds a empty gap it start to transmit its own data packet.

• It listens while it is transmitting to make sure only its data is on the bus.

• If it detects another data packet on the bus, it presumes that a data collision has occurred.

• If data collision occurs the transmitting machine waits a random period of time before it retransmits of the same packet

Token Ring

• Sometimes referred as Token Ring  because there is a digital token  sent around the network  which any computer within the loop  can pickup, and only the computer with the token can talk.

• The token  ensures that only one computer transmits at any time and there are no packet collisions  on the network .

• The Token Ring  contention method ensures that the network  is fairly fast because there is no packet collision, and packets don’t have to be retransmitted on the network.

 

Network Hardware

• A network  can contain any number of equipment used for communication , network expansion and network segmentation from the simple network card to the routers  and gateways used for segmenting networks.

• Lets take a closer look at all the components that make up our network

 

Network Card (NIC)

·       Network card is the physical device on the computer responsible for transmitting the data pulses of 5V and 0V on the network  for 1’s and 0’s. Each network card has a unique ID code burned on the card itself.

 

Bus topology  Network cards

Physical installation  of BUS Topology

Connecting NIC to system

Connecting the cable to the card

Terminating the cable

 

Star Topology Network Card

Installation of the Star Topology

Connecting NIC to system

The RJ45 connector on the twisted pair cable

Connecting the cable to the NIC

 

Medium

• Medium is the cable  that transfers the data, there are many different cables associated with different topologies  including Thinnet , Thicknet , twisted pair , fiber optic, etc.

Network Expansion

• Repeaters, Hubs, and MAU ’s are responsible for expanding a network  with the limitations of the topology.

Repeaters

• Repeater are devices , which read  the data that comes in and then reproduces the data and outputs it to the network , thereby removing the noise from the data and expanding the network.

Hubs

• Hubs or concentrators are a central point of connection between all PC’s on the network

• There are three types of hubs:

–Active Hubs  

–Passive Hubs  

–Hybrid Hubs .

 

• Active hubs require power to operate and also amplify the signal they receive before retransmission that extend the cable  length limitation. 

• Passive hubs do not require power to operate and perform no data amplification.

• Hybrid Hubs  have the capability of connecting two separate topologies  together such as STAR and BUS.

Network Segmentation

• Bridges/Switches  are responsible for reducing network  traffic significantly by using network segmentation either on a single port or multiport.

Bridge/ Switch

• Bridge/switches are an intelligent component of the network  responsible for storing all physical card ID’s linked to the port, either directly or via a hub  in its memory

• It controls network  traffics by checking if the ID of the source PC and Destination PC network cards  are on the same port. If the two PC’s are on the same port (e.g. PC1 and PC2), the data is blocked from all other ports.

• If the addresses of the two communicating PC’s are on two separate ports (e.g.. PC1 and PC2), then a route is opened directly only between the two ports and all other ports are blocked.

Bridges V Switches

• Bridges can link networks that use different access methods, but switch can only use one access method.

• Switches  can allow maximum bandwidth  through each port.

Routers

• Routers are responsible controlling network  traffic by routing data between networks using the network cards  logical address called the IP  address

• Routers can communicate with each other to dynamically route network  traffic depending on network congestion, broken links.

Gateways

• Gateways  can do all that routers  can do and more

• Gateways  are very expensive and highly specialized.

• Gateways  perform the job of the translator and achieve the goal of ensuring the packet gets to its destination overcoming all barriers of protocol , topology, and access method variations.

Questions

 

1) What are the advantages of a Peer-to-Peer network ? (Choose all the apply)

a) Centralized security

b) Forced authentication

c) Cheap

d) Centralized backup

e) Unlimited network  size

 

2) What are the advantages of a client server  network ? (Choose all the apply)

a) Centralized security

b) Forced authentication

c) Cheap

d) Centralized backup

e) Unlimited network  size

 

3) What is the contention method used in the star topology?

a) CSMA/CD

b) CSMA/CA

c) Token

d) CSMT/TD

 

4) What is the contention method used in the bus topology?

a) CSMA/CD

b) CSMA/CA

c) Token

d) CSMT/TD

5) What is the contention method used in the ring topology?

a) CSMA/CD

b) CSMA/CA

c) Token

d) CSMT/TD

 

6) What are the features of a network  card? (Choose all that apply)

a) Sends pulses of 1's and 0's on to the network

b) Its identified by an network  assigned address

c) It is the link between the computer and the network

d) Its identified by a unique fixed hardware address

e) A ROM  chip can be installed on them that enable booting from the card

 

7) What devices  can be used to expand a network ?(choose all that apply)

a) Network card

b) Barrel connector

c) Switch/Bridge

d) Hub

e) Repeater

f) Router

 

8) What devices  can be used to segment a network ? (Choose all that apply)

a) Network card

b) Barrel connector

c) Switch/Bridge

d) Hub

e) Repeater

f) Router

 

9) Gateways  can overcome which of the following network  restrictions? (Choose all that apply)

a) Topology

b) Protocol

c) Contention method

d) Routing problems

e) Slow links

 

10) Which of the following are variations of hubs? (Choose all that apply)

a) Passive hub

b) Slow hub

c) Contact hub

d) Active hub

e) Hybrid hub  

 

Answers

1. C

2. A,B,D,E

3. A

4. A

5. C

6. A,B,C,D,E

7. B,D,E

8. C,F

9. A,B,C

10. A,D,E