Computer Networks

Question 1

Computer Network definition

Answer 1

collection of nodes connected by a communication link

Question 2

Why setup a computer network?

Answer 2

Resource/Database/Software sharing

Question 3

Key performance parameters of Computer Networks

Answer 3

-Bandwidth
-Delays
-Error rate

Question 4

Components of Computer Networks?

Answer 4

-Hosts
-Central connecting devices
-Apps use the network to provide a service
-Links are channels that connect nodes

Question 5

Network Types

Answer 5

-Personal Area Networks
-Local Area Networks
-Metropolitan Area Networks
-Wide Area Networks

Question 6

Personal Area Networks factors?

Answer 6

-Smallest
-Bluetooth, infrared enabled devices
-Connect up to 10 meters
-Wireless mouse, keyboards, headphones, printers, tv remotes

Question 7

Local Area Network factors?

Answer 7

-Privately owned network - home, office, campus
-Connect up to a few kilometers
-Worst case transmission time bounded and known in advance
-Different topologies can be implemented
-LAN uses ethernet or wireless network(WLAN
-LAN is relatively fast

Question 8

Metropolitan Area Network factors?

Answer 8

-Connection over entire city
-MAN can connect several LANs
-Ex - interconnecting several LANs on campus
-MAN uses Asynchronous Transfer Mode (ATM) and Fiber Distributed Data Interface (FDDI)

Question 9

Wide Area Network factors?

Answer 9

-Long distance transmission of data, voice, image and information
-Connectivity range up to countries, continents, entire planet
-Slower than LAN
-Some WAN use ATM, Frame Relay, and synchronous optical network
-Enterprise network is a WAN owned by a company

Question 10

What is a Network Topology?

Answer 10

-Physical and logical layout of a computer network
-Determines how various components communicate and connect
-Choice of topology depends on the following factors:
- # of devices
- Application
- Data transfer rate
- Response time
- Cost

Question 11

What are the types of Network Topologies?

Answer 11

• Bus
• Star
• Tree
• Ring
• Mesh

Question 12

What is Bus Topology?

Answer 12

-Linear configuration in which all network devices are connected to a common bus
- Full duplex communication is possible between devices and taps
- Data sent by one node can be seen by others
- Example: Ethernet LAN

Question 13

Pros/Cons of Bus Topology?

Answer 13

Pros:
- Cheap, easy to implement
-less cabling required, shared link reduces cost
- Expandable - devices can be added/removed without disruption

Cons:
- One device can transfer data at a time
-access control required to avoid data collision
- Signal strength becomes an issue for long distances
- Common bus failure can crash network
- Security risk - other devices can see data

Question 14

What is Star Topology?

Answer 14

• Central device to which remaining nodes are connected
• Each node has direct access to the central device via point to point links
• Central device can operate in either broadcast mode (hub/multiport transmission of data to all nodes) or unicast/frame switching mode (perform switching/routing function using a switch)
• Example: High speed LAN
• looks like a snowflake (central device)

Question 15

What are the pros and cons of Star Topology?

Answer 15

Pros:
- Scalable, high speed, easy to maintain.
- # of links = # of nodes
- Individual node failure doesn’t impact overall network
- Troubleshooting, modification is easy

Cons:
- Single point of failure exists in the form of central device
- Network size is limited by number of I/O ports on device

Question 16

What is Tree Topology?

Answer 16

• (Hierarchical topology) a hybrid of star and bus
• Network divided into multiple layers
• Highest layer contains central node
• Middle layer contains distribution nodes
• Lower layer (access layer) contains end-nodes

Question 17

Pros/cons of Tree Topology?

Answer 17

Pros:
- Scalable
- Flexible
- Easy maintenance, layered control of devices

Cons:
- Expensive to implement
- Single point of failure in the form of central node

• looks like binary tree

Question 18

What is Ring Topology?

Answer 18

• Circular config
• Each network device is connected to the 2 adjacent devices
• Data is transmitted in one direction reducing chances of collision
• Implementation requires use of token passing protocol

Question 19

Pros/cons of Ring Topology?

Answer 19

Pros:
- Simple installation with less cabling
- Troubleshooting is easy
- All devices have equal network access

Cons:
- Not very scalable
- Single mode of failure possible
- Transmission of data is slower than star, data travels through loop

Question 20

What is Mesh Topology?

Answer 20

• Involves interconnecting all network devices with each other via point to point links
• Fully connected mesh with ‘n’ devices has n(n-1)/2 cables
• Each device must have (n-1) I/O ports

Question 21

Pros/Cons of Mesh Topology?

Answer 21

Pros:
- High speed, no congestion issues
- Very high reliability/redundancy/security
- Individual node failure doesn’t impact network

Cons:
- Very expensive (cabling expensive)
- Poor expandability - addition of new node requires multiple links
- Rarely used in practice