Study Unit 1 - Chapter One Introduction to Computer Networks and Data Communications

Question 1

What does properly designing a computer network entail?

Answer 1

It requires planning and analysis, feasibility studies, capacity
planning, and baseline creation skills
PAFSCPBCS

Question 2

What does a network manager do?

Answer 2

Network manager must possess computer and people skills,
management skills, financial skills, and be able to keep up with
changing technology

Question 3

What do system planners and management personnel do?

Answer 3

within the company try to generate set of questions, or problems, to help company achieve those goals

Question 4

What is the SDLC

Answer 4

methodology, or plan, for a structured approach to the
development of a business system

Question 5

What are the phases involved in the SDLC, and what are the phases characterized as?

Answer 5

• Planning
  – Analysis
  – Design
  – Implementation
  – Maintenance

phases are cyclical and usually never-ending

Question 6

What are system analysts usually responsible for?

Answer 6

typically responsible for managing a project and following the SDLC phases

Question 7

Planning phase?

Answer 7

Identify problems, opportunities, and objectives

Question 8

Analysis phase?

Answer 8

Determine information requirements
– Information requirements can be gathered by sampling and collecting hard data, interviewing, questionnaires, observing environments, and prototyping

Question 9

Design phase

Answer 9

Design the system that was recommended and approved at the end
of the analysis phase

Question 10

Implementation phase?

Answer 10

The system is installed and preparations are made to move from the
old system to the new

Question 11

Maintenance phase?

Answer 11

The longest phase, involves the ongoing maintenance of the project
– May require personnel to return to an earlier phase to perform an
update

Question 12

What is network modelling and what does it demonstrate?

Answer 12

When updating or creating a new computer system, analyst will create set of models for both existing system and
proposed system.
* Network models can either:
– Demonstrate current state of network
– Model desired computer network
* Series of connectivity maps are network modeling tools that
depict various locations involved over wide and local areas
and interconnections between those locations

Question 13

What is a wide area connectivity map?

Answer 13

Shows big picture of geographic locations of network
facilities
* External users and mobile users can be identified, as well as
the locations primary to a business

Question 14

How do we identify the connections between sites?

Answer 14

– d = distance of the connection (usually shown in either miles or
kilometers)
– s = security level (high, medium, low, or none)
– du = duplexity (full duplex, half duplex, or simplex)
– dr = data rate desired (in bps)
– l = latency, or acceptable delay time across the network (usually in
milliseconds, or ms)
– QoS = Quality of Service
* CBR - constant bit rate, VBR - variable bit rate, ABR - available bit rate,
UBR - unreliable bit rate, or none
– de = delivery rate (sometimes called throughput percentage)

Question 15

What is a metropolitan connectivity map?

Answer 15

Shows the design of a metropolitan area and its network
facilities.

Question 16

How do we identify the connections between sites?

Answer 16

QoS = VBR
* dr = 100 Mbps
* s = high
* d = 5 km
* failover = 50 ms
* de = 99.9%

Question 17

Local area connectivity map?

Answer 17

Local area overview connectivity map – shows the big
picture design of a local area network

Question 18

How do we identify between sites in a LAN?

Answer 18

QoS = none
– dr = 100 Mbps
– s = none
– d = 85 m
– du = full
– thru = 50%

Question 19

Local area connectivity detailed map?

Answer 19

– shows the close-up design of a local area network, including switches, routers, hubs, and servers
– Much like the homework we did earlier showing LAN connections

Question 20

What are feasibility studies?

Answer 20

There are a number of ways to determine if a proposed
system is going to be feasible
* Technically feasible – proposed system can be created and
implemented using currently existing technology
* Financially feasible – proposed system can be built given the
company’s current financial ability
* Operationally feasible – system operates as designed and
implemented

Question 21

Time feasibility?

Answer 21

system can be constructed in an agreed
upon time frame

Question 22

Whats a good technique to determine financial feasibility?

Answer 22

Payback analysis:
To calculate payback analysis, you must know all expenses that will
be incurred to create and maintain system, as well as all possible
income derived from system
– You must also be aware of time value of money
* A dollar today is worth more than one dollar promised a year from now
because dollar can be invested

Question 23

What is capacity planning?

Answer 23

• Involves trying to determine the amount of network
  bandwidth necessary to support an application or a set of
  applications
• A number of techniques exist for performing capacity
  planning, including linear projection, computer simulation,
  benchmarking, and analytical modeling

Question 24

What is linear projection?

Answer 24

Linear projection involves predicting one or more network
capacities based on the current network parameters and
multiplying by some constant

Question 25

What is a computer simulation, benchmarking and analytical modeling?

Answer 25

A computer simulation involves modeling an existing system
or proposed system using a computer-based simulation tool
* Benchmarking involves generating system statistics under a
controlled environment and then comparing those statistics
against known measurements
* Analytical modeling involves the creation of mathematical
equations to calculate various network values

Question 26

What is creating a baseline?

Answer 26

Involves measurement and recording of a network’s state of
operation over given period of time
* Baseline can be used to determine current network
performance and to help determine future network needs
* Baseline studies should be ongoing projects, and not
something started and stopped every so many years

Question 27

What should you do in order to perform a baseline study?

Answer 27

Collect information on number and type of system nodes, including
workstations, routers, bridges, switches, hubs, and servers
– Create an up-to-date roadmap of all nodes along with model
numbers, serial numbers and any address information such as IP or
Ethernet addresses
– Collect information on operational protocols used throughout the
system
List all network applications, including the number, type and utilization
level
– Create a fairly extensive list of statistics to help meet your goals
* These statistics can include average network utilization, peak network utilization, average frame size, peak frame size, average frames per
second, peak frames per second, total network collisions, network
collisions per second, total runts, total jabbers, total CRC errors, and
nodes with highest percentage of utilization

Question 28

What are some skills a good network manager has?

Answer 28

Computer skills
– People skills
– Management skills
– Financial planning skills
– Knowledge of statistics
– Speaking and writing skills

Question 29

What are some certifications a good network manager will posses?

Answer 29

Microsoft Certified Systems Engineer (MCSE)
– Cisco Certified Network Associate (CCNA)
– IBM Certified Systems Expert (CSE)
– IBM Certified Administrator (CA)
– Many others

Question 30

Generating usable statistics, as well as MTBF and MTTR.
Availability%?

Answer 30

Statistics, properly generated, can be an invaluable aid to
demonstrating current system demands and predicting future
needs
* Mean time between failures (MTBF) – average time a device
or system will operate before it fails
* Mean time to repair (MTTR) – average time necessary to
repair a failure within the computer system
Availability – probability that a particular component or
system will be available during a fixed time period
* Availability % =
– (Total available time – Downtime) / Total available time

Question 31

Quick example: Suppose we want to calculate the availability of a modem for
one month (24 hours per day for 30 days, or 720 hours),
knowing the modem will be down for two hours during that
period:

Answer 31

Answer: Availability % = (720 – 2) / 720
» = 0.997

Question 32

Reliability equation?

Answer 32

R(t) = e -bt
In which:
b = 1/MTBF
t = the time interval of the operation

Question 33

Example on reliability: What is the reliability of a modem if the MTBF is 3000 hours
and a transaction takes 20 minutes, or 1/3 of an hour (0.333
hours):

Answer 33

R(0.333 hours)
= e -(1/3000)*(0.333)
= e -0.000111
= 0.99989

Question 34

Managing operations? and SNMP?

Answer 34

There are many services and functions available to assist an
individual in managing computer network operations
– One of the more useful is Simple Network Management Protocol
(SNMP)
* SNMP is industry standard designed to manage network
components from a remote location
– Currently in version 3, SNMP supports agents, managers, and the
Management Information Base (MIB)

Question 35

More on managing operations?

Answer 35

A managed element has management software, called an
agent, running in it
* A second object, SNMP manager, controls operations of a
managed element and maintains a database of information
about all managed elements
* A manager can query an agent to return current operating
values, or can instruct an agent to perform a particular action
* Management Information Base (MIB) – collection of
information that is organized hierarchically and describes the
operating parameters of all managed agents

Question 36

To assist a network support person, a number of diagnostic
tools are available:

Answer 36

Electrical testers
– Cable testers
– Network testers
– Protocol analyzers

Question 37

What is a better box corporation?

Answer 37

Returning to Better Box Corporation from an earlier chapter,
let’s complete our design, including e-mail and Internet
access for each of the four sites
* A linear projection can be used to estimate the amount of
Internet traffic at each site
* A wide area connectivity map gives us a big picture of the
network interconnections