Introduction to Networks

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Title

Introduction to Networks

Subject

Selected Topics from Communication

Course

ATSEP Basic Course

Author

Alex Moucha

Version

1.1

Date

10
th

October 2013

1.
Syllabus

In this chapter, we will study:


Network types


Network topologies


The most used network requirements and data integrity



Cable types and devices that you meet with



Redundancy, its uses and requirements



How to meet imposed requirements



How to measure parameters of the network



How to troubleshoot your network

ATSEP Basic Course
-

Data Processing

Introduction to Data Processing

2. Network Types

There are many classifications

Let us consider two:


Criterion: mobility


Implies: fixed / mobile / hybrid


Criterion: data propagation


Implies: unidirectional / bidirectional


Think about other classifications

You are right: it is almost impossible to take into account all the
classifications

Let us concentrate on the extension area of the network

Network Types

LAN = Local Area Network

WLAN = Wireless LAN

MAN = Metropolitan Area Network

WAN = Wide Area Network

SAN = Storage Area Network

PAN = Personal Area Network


Examples

3. Network Topologies

Think about a topology through different perspectives:


Physical arrangement


Logical function


All networks behave through both the aspects above introduced and
surprise: physically a network can have a topology, but logically
another.


But first, let us see some basic physical topologies:


Star, Ring, Bus, Tree, Mesh

Star

Where have you met such a
topology?

How does it work?

What inherent advantages and
disadvantages such a topology
presents?

Ring

Where have you met such a
topology?

How
does it work?

What inherent advantages and
disadvantages such a topology
presents?

Can a star work as a ring?

You now see the difference:
physical / logical

Bus

Where have you met such a
topology?

How does it work?

What inherent advantages and
disadvantages such a topology
presents?

Can a bus work as a ring?

Can a star work as a bus?

Can a ring work as a bus?

You now understood the
difference: physical / logical

Tree

Where have you met such a
topology?

How does it work?

What inherent advantages and
disadvantages such a topology
presents?

Mesh / Full Mesh

Where have you met such a
topology?

How does it work?

What inherent advantages and
disadvantages such a topology
presents?

4a. Network Requirements

There are many parameters which can be monitored / set / required

Do you know any? At GSM for example…

For you 3 are the most important:


Bandwidth / Speed


Delay / Latency


Jitter

Many tools and let me show you two:


Ping


Speedtest

(
www.speedtest.net
)

4b. Data Integrity

For me (the network guy) the safety of data is as important as it is
for you (the ATC guys) an airplane. With only one difference: in the
case of network guys some collisions are acceptable.

The data passing through a network has to encounter the same
“dangers” as an airplane passing through the busy airspace of an
airport… in Afghanistan.

Long story short: the bad guys (other data and errors) want to
destroy your data.

Let us see what we can do to ensure a safe journey. Stealth?
Maybe…

Data Integrity: Alpha, Bravo, Charlie and all the way
to Zulu

How do you know all your airplanes arrived to the destined …
destinations? You count them.

That is exactly what we do with the bits: we count them.

Simple way: parity


simply count ones. Example.

More complicated ways: CRC.

Even more complicated: data recovery (it requires redundancy =
more bits sent than the minimal requirement).


Base line: it is also important to know the error probability on the
line, something called BER. The lower the BER, the better the line.

Which is the safest data transport environment? But the worst?

5a. Cable Types

10Base5 = 10 Mbps @ 500 m, 50 Ohm, coax, thick

10Base2 = 10 Mbps @ 185 m, 50 Ohm, coax, thin, end
-
terminator

10Base
-
T = 10 Mbps @ 90+10 m, twisted

100Base
-
T = 100 Mbps @ 100 m, twisted (you know it)

100Base
-
TX
= 100 Mbps
@ extended range,
twisted

100Base
-
FX = the same but Fiber

1000Base
-
T = Gigabit Ethernet. You know already how to read.

10GBase
-
T = 10 Gigabit


Question: what happens beyond the maximal distances?

5b.
Wifi

standards

IEEE 802.11 standard

So many sub
-
standards that the alphabet ended long ago.

We discuss just a few, which you probably will meet in practice.

Wifi

802.11 base standard


1997 + 1999


1 or 2 Mbit = so funny


900 MHz, 2400 MHz


FHSS (
McGuyver

will explain this to you)

Wifi

802.11b


You know it


Year: 2000


2.4 GHz => higher range


10 Mbps (theory)


Encryption: WEP then WPA

Wifi

802.11a


Never heard of it



Much, much better than b


Year: 2000


54 Mbps


OFDM


5 GHz


Why do you think everybody chose the worse standard (b) and
not the good one (a)?

Wifi

802.11g


I am sure you all know it


Year: 2003


Child of b and backwards compatible


Magic: OFDM


54 Mbps


2.4 GHz

Wifi

802.11n


Hot and sexy


Magic: OFDM + modulation on more levels


Year: 2009


2.4 and/or 5 GHz

Wifi

802.11ac


Super hot and super sexy


Year: just around the corner


5 GHz


1
Gbps

Wifi

An image is more than 1000 words

5b. Devices

For this I would like to introduce you to the OSI Layered Architecture

OSI

The layers: application, presentation, session, transport, network,
datalink
, physical (APSTNDP)

I know you ATC guys love letters. Let me tell you a secret: the
networking world has more abbrev. than a. o. We have abbrev.
o
f
abbrev.

How to remember them: All People Seem To Need Data Processing

Or: Please Do Not Throw Sausage Pizza
Away (backwards)

OSI
AddOn

On my responsibility I added three layers to OSI, on top of the
existing ones

God (Saint Reboot, Saint Reload, Saint Restart)

Network Administrator

SFU (the most important component)

Application

Presentation

Session



Physical

OSI

Where do you think this model is used?




Repeater

Layer 1

Stupid, Stupid, Stupid

Collision, Collision Domain

Hub

Layer 1

The same at stupidity, though multiplied

Multiport repeater

How many collision domains?

How many broadcast domains?

Bridge / Switch

Layer 2

More intelligent

Switch = multiport bridge

MAC addresses

How many collision domains?

How many
bcast

domains?

The concept of VLANs

Router

Layer 3

The king of the hill

Goal: deliver from Alpha to Foxtrot

Tips

The presentation is not all true

In the real world we work with something called: L3S

Keywords: routing, routing table, protocol

6. Redundancy

Multihoming

= Backup line

What are the disadvantages and advantages?

Redundancy

Load Balancing

Advantages and disadvantages?

Redundancy

Spanning Tree Protocol

No loops

Why is it needed?

Router Redundancy

Master


Slave

HSRP / VRRP / GLBP

Routing

BGP

7
. How to meet imposed
requirements

QoS


Best effort


Do you know a best effort service?


Class of service


Qos

SLA


Service Level Agreement


Do you know an example?


QoS

tip: priority 0?

8. How to measure parameters of the
network

Many, many parameters

Packet analyzer


WireShark

Promiscuous

Security?

SNMP

WireShark

Image

NetScout

Image

Monitor

Image

9. Troubleshooting

ALWAYS: BOTTOM UP IN OSI !!!!!!!!

OSI: God, Net
Adm
, SFU, Application, Presentation, Session,
Transport, Network, DL, Physical

Verify Microsoft Internet Exploder before the cable is USELESS!!!
Got it?

Let us see and discuss

Practice lab

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