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COMPUTER NETWORKS AND SECURITY

TUTORIAL I

1.What are the two types of transmission technology available?

(i) Broadcast and (ii) point-to-point

2.What are the possible ways of data exchange?

(i) Simplex (ii) Half-duplex (iii) Full-duplex.

3. What are the important topologies for networks?

BUS topology:

In this each computer is directly connected to primary network cable in a single line.

Advantages:

Inexpensive, easy to install, simple to understand, easy to extend.

STAR topology:

In this all computers are connected using a central hub.

Advantages:

Can be inexpensive, easy to install and reconfigure and easy to trouble shoot physical

problems.

RING topology:

In this all computers are connected in loop.

Advantages:

All computers have equal access to network media, installation can be simple, and signal

does not degrade as much as in other topologies because each computer regenerates it.

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4. What is mesh network?

A network in which there are multiple network links between computers to provide

multiple paths for data to travel.

5. What is difference between baseband and broadband transmission?

In a baseband transmission, the entire bandwidth of the cable is consumed by a single

signal. In broadband transmission, signals are sent on multiple frequencies, allowing

multiple signals to be sent simultaneously.

6. What are 10Base2, 10Base5 and 10BaseT Ethernet LANs ?

10Base2 An Ethernet term meaning a maximum transfer rate of 10 Megabits persecond that uses base band signaling, with a contiguous cable segment length of 100

meters and a maximum of 2 segments.

10Base5 An Ethernet term meaning a maximum transfer rate of 10 Megabits per

second that uses base band signaling, with 5 continuous segments not exceeding 100

meters per segment.

10BaseTAn Ethernet term meaning a maximum transfer rate of 10 Megabits persecond that uses base band signaling and twisted pair cabling.

7. What is a CAT 5 Cable?

Cat-5 cable, sometimes called Ethernet cable, is short for Category 5 cable, a currentpreferred industry standard for network and telephone wiring. Cat-5 cable is unshielded

wire containing four pairs of 24-gauge twisted copper pairs, terminating in an RJ-45 jack.

If a wire is certified as Cat-5 and not just a twisted pair wire, it will have "Cat-5" printedon the shielding.

The outer sheath of Cat-5 cable can come in many colors, with bright blue being quite

common. Inside, the twisted pairs are also sheathed in plastic with a standard colorscheme: Solid orange, blue, green and brown wires twisted around mates that are white

and striped with a solid color. The twisted pairs inside a Cat-5 cable reduce interferenceand crosstalk, and should be left twisted except at the termination point. Some expertsrecommend untwisting only inch (12.7 mm) of the pairs to strip and make connections.

Cat-5 cable can be purchased off a spool in varying lengths, or bought pre-cut to standard

lengths with RJ-45 jacks already attached.

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8. How to connect two computers :

How to connect two computers in Windows XP. This will let you share files and folders,

printers, play network games, etc...

Steps :

1. connect the two computers together either with a Crossover cable or a Hub/Switch

to the ethernet card in your computer.

2. Set the IP address on both computers. Goto Start > Control Panel > Network

Connections (choose switch to classic view if you cannot see network

connections)

3. Look for your Local Area Connection ethernet adapter, right-click and choose

properties.4. Select Internet Protocol TCP/IP and choose properties.

Setup the IP as 192.168.1.1 and the subnet maskof255.255.255.0 on the first

computer and 192.168.1.2 on the second with the same subnet mask.5. Choose OK then OK/close again.

Tips :

1. To share your files, right click on any folder and choose Sharing to make them

shared.2. You can also do this with your printers to be able to print from one computer

while the printer is connected to the other.

Things You'll Need :

1. A Crossover cable. This a Cat5 Ethernet Cable that the wires have been switchedaround to allow two computer only to talk to each other.

2. OR, you can purchase a switch/hub with two Standard "Straight-Through"

Ethernet Cables.3. Check to see if your computer has an Ethernet Adapter in the back of the

computer. Most new computers have this. You can tell by the documentation from

the computer or by looking at the back of the computer. It looks like a phone jack,but larger.

9 How to Build a Cat 5 Cable ?

The steps below are general Ethernet cat5 cable construction guidelines. They will work

for making any category of network cables. For our example we will be making acategory 5e patch cable. A key point to remember in making Ethernet patch cords is that

the twists in the individual pairs should remain entwined as long as possible until they

http://techhairball.com/interview-questions/networking-interview-questions/240-general/4186-how-to-build-a-cat-5-cablehttp://techhairball.com/interview-questions/networking-interview-questions/240-general/4186-how-to-build-a-cat-5-cable

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reach the RJ-45 plug termination. The twisting of the pairs in the network cable is what

helps to ensure good connectivity and keeps cross-talk interference to a minimum.

STEP 1 - StrippingStart by pulling out about 12 feet of bulk network cable to making the process a little

easier. Carefully remove the outer jacket of the cable exposing about 1 1/4" of the twistedpairs. Be careful when stripping the jacket as to not nick or cut the internal wiring. After

removing the outer case you will notice 8 wires twisted in pairs and a rip cord (whitethread).

STEP 2 - InspectingInspect the newly revealed wires for any cuts or scrapes that expose the copper wire

inside. If you have breached the protective sheath of any wire you will need to cut the

entire segment of wires off and start over at step one. Exposed copper wire will lead tocross-talk, poor performance or no connectivity at all. It is important that the jacket for all

network cables remains intact.

STEP 3 - PreparationTo prepare the wires and to make them easier to work with, you can untwist the pairs so

they will lay flat between your fingers. The white piece of thread can be cut off even with

the jacket and disposed.

STEP 4 - Layout

Now based on the wiring specifications you are following you will need arrange the wiresin a certain pattern. There are two methods set by the TIA, 568A and 568B. 568B is the

most common network cables, widely used for computer networks and digital phone

systems. So for our demonstration we will use that. Starting from the left-top side of the

RJ-45 plug, the wiring should be in the order shown at the right.

STEP 5 - Jack Preparation

Again, press all the wires flat between your thumb and forefinger as shown in step three.Verify the colors have remained in the correct order. Using a pair of scissors, cut the top

of the wires even with one another so that they are 1/2" long from the base of the jacket.

Ensure that the cut leaves the wires even and clean; failure to do so may cause the wirenot to make contact inside the jack.

STEP 6 - Wire InsertionEnsuring that the wires remain flat and in order, push them into the RJ-45 plug with the

flat surface of the plug on top. The white / orange wire should be on the left looking

down at the jack. You can tell if all the wires made it into the jack and maintain their

positions by looking head-on at the plug. You should be able to see a wire located in eachhole, as seen at the bottom right. You may have to use a little effort to push the pairs

firmly into the plug. The cabling jacket should also enter the rear of the jack about 3/16"

to help secure the cable once the plug is crimped.

STEP 7 - Crimping

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Now place the wired plug into the crimping tool. Give the handle a firm squeeze, you

should hear a ratcheting noise as you continue. Once you have completed the crimp, the

handle will reset to the open position.

STEP 8 - Testing

Once your new cable is completed, it is not a bad idea to test the cable to ensure that itwill function in the field. It is vital that all eight wires have connectivity and are in the

correct order. Mis-wired network cables could lead to headaches down the road. In

addition, with power-over-ethernet making its way into the market place, crossed wirepairs could lead to physical damage of computers or phone system equipment; making it

even more crucial that the pairs are in the correct order. A simple cable tester can quickly

verify that information for you.

10. How many cable segments do you need for mesh topology in a network having 7systems ?

The number of cable segments needed for mesh topology in a network ofN

systems isgiven by the formula N * (N-1) / 2