Download pdf - Definition/Overview: · PDF file · 2015-09-22... such as Bus network, Star network, Ring network, Mesh network, Star-bus network, Tree or Hierarchical topology network, ... the logical

INTRODUCTION TO TELECOMMUNICATION NETWORKS

Topic Objective:

At the end of this topic students will be able to:

Discuss By scale

Discuss By connection method

Discuss By functional relationship (Network Architectures)

Discuss By network topology

Discuss By protocol

Discuss Common Types Of Computer Networks

Definition/Overview:

Computer Network: A computer network is an interconnected group of computers.

Networks may be classified by the network layer at which they operate according to basic

reference models considered as standards in the industry, such as the five-layer Internet

Protocol Suite model. While the seven-layer Open Systems Interconnection (OSI) reference

model is better known in academia, the majority of networks use the Internet Protocol Suite

(IP).

Key Points:

1. Computer Networks Classification

1.1. By scale

Computer networks may be classified according to the scale: Personal area network

(PAN), Local Area Network (LAN), Campus Area Network (CAN), Metropolitan area

network (MAN), or Wide area network (WAN). As Ethernet increasingly is the standard

interface for networks, these distinctions are more important to the network administrator

than the user. Network administrators may have to tune the network, to correct delay

issues and achieve the desired performance level.

1.2. By connection method

Computer networks can also be classified according to the hardware technology that is

used to connect the individual devices in the network such as Optical fibre, Ethernet,

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Wireless LAN, HomePNA, or Power line communication. Ethernets use physical wiring

to connect devices. Often they employ hubs, switches, bridges, and/or routers. Wireless

LAN technology is built to connect devices without wiring. These devices use a radio

frequency to connect.

1.3. By functional relationship (Network Architectures)

Computer networks may be classified according to the functional relationships which

exist between the elements of the network, e.g., Active Networking, Client-server and

Peer-to-peer (workgroup) architecture.

1.4. By network topology

Computer networks may be classified according to the network topology upon which the

network is based, such as Bus network, Star network, Ring network, Mesh network, Star-

bus network, Tree or Hierarchical topology network, etc. Network Topology signifies the

way in which intelligent devices in the network see their logical relations to one another.

The use of the term "logical" here is significant. That is, network topology is independent

of the "physical" layout of the network. Even if networked computers are physically

placed in a linear arrangement, if they are connected via a hub, the network has a Star

topology, rather than a Bus Topology. In this regard the visual and operational

characteristics of a network are distinct; the logical network topology is not necessarily

the same as the physical layout.

1.5. By protocol

Computer networks may be classified according to the communications protocol that is

being used on the network. See the articles on List of network protocol stacks and List of

network protocols for more information. For a development of the foundations of

protocol design.

2. Common Types Of Computer Networks

Below is a list of the most common types of computer networks in order of scale.

2.1. Personal Area Network (PAN)

A personal area network (PAN) is a computer network used for communication among

computer devices close to one person. Some examples of devices that are used in a PAN

are printers, fax machines, telephones, PDAs or scanners. The reach of a PAN is typically

within about 20-30 feet (approximately 6-9 meters).



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Personal area networks may be wired with computer buses such as USB and FireWire. A

wireless personal area network (WPAN) can also be made possible with network

technologies such as IrDA and Bluetooth.

2.2. Local Area Network (LAN)

A network covering a small geographic area, like a home, office, or building. Current

LANs are most likely to be based on Ethernet technology. For example, a library will

have a wired or wireless LAN for users to interconnect local devices (e.g., printers and

servers) and to connect to the internet. All of the PCs in the library are connected by

category 5 (Cat5) cable, running the IEEE 802.3 protocol through a system of

interconnection devices and eventually connect to the internet. The cables to the servers

are on Cat 5e enhanced cable, which will support IEEE 802.3 at 1 Gbit/s.

The staff computers can get to the color printer, checkout records, and the academic

network and the Internet. All user computers can get to the Internet and the card catalog.

Each workgroup can get to its local printer. Note that the printers are not accessible from

outside their workgroup.

All interconnected devices must understand the network layer, because they are handling

multiple subnets (the different colors). Those inside the library, which have only 10/100

Mbit/s Ethernet connections to the user device and a Gigabit Ethernet connection to the

central router, could be called "layer 3 switches" because they only have Ethernet

interfaces and must understand IP. It would be more correct to call them access routers,

where the router at the top is a distribution router that connects to the Internet and

academic networks' customer access routers.

The defining characteristics of LANs, in contrast to WANs (wide area networks), include

their higher data transfer rates, smaller geographic range, and lack of a need for leased

telecommunication lines. Current Ethernet or other IEEE 802.3 LAN technologies operate

at speeds up to 10 Gbit/s. This is the data transfer rate. IEEE has projects investigating the

standardization of 100 Gbit/s, and possibly 40 Gbit/s.

2.3. Campus Area Network (CAN)

A network that connects two or more LANs but that is limited to a specific and

contiguous geographical area such as a college campus, industrial complex, or a military

base. A CAN may be considered a type of MAN (metropolitan area network), but is

generally limited to an area that is smaller than a typical MAN. This term is most often

used to discuss the implementation of networks for a contiguous area. This should not be

confused with a Controller Area Network.



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2.4. Metropolitan Area Network (MAN)

A Metropolitan Area Network is a network that connects two or more Local Area

Networks or Campus Area Networks together but does not extend beyond the boundaries

of the immediate town, city, routers, switches & hubs are connected to create a MAN.

2.5. Wide Area Network (WAN)

A WAN is a data communications network that covers a relatively broad geographic area

(i.e. one city to another and one country to another country) and that often uses

transmission facilities provided by common carriers, such as telephone companies. WAN

technologies generally function at the lower three layers of the OSI reference model: the

physical layer, the data link layer, and the network layer.

2.6. Global Area Network (GAN)

Global area networks (GAN) specifications are in development by several groups, and

there is no common definition. In general, however, a GAN is a model for supporting

mobile communications across an arbitrary number of wireless LANs, satellite coverage

areas, etc. The key challenge in mobile communications is "handing off" the user

communications from one local coverage area to the next. In IEEE Project 802, this

involves a succession of terrestrial Wireless local area networks (WLAN).

2.7. Internetwork

Two or more networks or network segments connected using devices that operate at layer

3 (the 'network' layer) of the OSI Basic Reference Model, such as a router. Any

interconnection among or between public, private, commercial, industrial, or

governmental networks may also be defined as an internetwork.

In modern practice, the interconnected networks use the Internet Protocol. There are at

least three variants of internetwork, depending on who administers and who participates

in them:

o Intranet

o Extranet

o Internet

Intranets and extranets may or may not have connections to the Internet. If connected to

the Internet, the intranet or extranet is normally protected from being accessed from the

Internet without proper authorization. The Internet is not considered to be a part of the

intranet or extranet, although it may serve as a portal for access to portions of an extranet.



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2.8. Intranet

An intranet is a set of interconnected networks, using the Internet Protocol and uses IP-

based tools such as web browsers and ftp tools, that isunder the control of a single

administrative entity. That administrative entity closes the intranet to the rest of the

world, and allows only specific users. Most commonly, an intranet is the internal network

of a company or other enterprise. A large intranet will typically have its own web server

to provide users with browseable information.

2.9. Extranet

An extranet is a network or internetwork that is limited in scope to a single organization

or entity but which also has limited connections to the networks of one or more other

usually, but not necessarily, trusted organizations or entities (e.g. a company's customers

may be given access to some part of its intranet creating in this way an extranet, while at

the same time the customers may not be considered 'trusted' from a security standpoint).

Technically, an extranet may also be categorized as a CAN, MAN, WAN, or other type of

network, although, by definition, an extranet cannot consist of a single LAN; it must have

at least one connection with an external network.

2.10. Internet

A specific internetwork, consisting of a worldwide interconnection of governmental,

academic, public, and private networks based upon the Advanced Research Projects

Agency Network (ARPANET) developed by ARPA of the U.S. Department of Defense

also home to the World Wide Web (WWW) and referred to as the 'Internet' with a capital

'I' to distinguish it from other generic internetworks.

Participants in the Internet, or their service providers, use IP Addresses obtained from

address registries that control assignments. Service providers and large enterprises also

exchange information on the reachability of their address ranges through the Border

Gateway Protocol (BGP).



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Topic : Network Standards

Topic Objective:


Discuss Standards govern the semantics and syntax of messages

Discuss Reliability

Discuss Connection-oriented versus connectionless

Discuss Hybrid TCP/IP-OSI Architecture

Discuss Hybrid TCP/IP-OSI Standards Architecture

Discuss Ethernet

Discuss Internet Protocol (IP)

Discuss Vertical Communication on the Source Host

Discuss Vertical Communication on the Destination Host

Discuss Not All Devices Have All Layers

Discuss OSI Architecture

Discuss Other Standards Architectures


All networking technologies have standards associated with them. These are usually highly

technical documents, and often presume that the reader has a fair bit of knowledge about

networking. If you aren't an expert, you will probably have some difficulty understanding

networking standards. (Some people seem to think I am an expert, but I too have trouble with

most of the details in a typical networking standard.)

Key Points:

1. Overview

An Internet Standard is a special Request for Comments (RFC) or set of RFCs. An RFC that

is to become a Standard or part of a Standard begins as an Internet Draft, and is later (usually

after several revisions) accepted and published by the RFC Editor as a RFC and labeled a

Proposed Standard. Later, an RFC is labelled a Draft Standard, and finally a Standard.



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Collectively, these stages are known as the standards track, and are defined in RFC 2026. The

label Historic (sic) is applied to deprecated standards-track documents or obsolete RFCs that

were published before the standards track was established.

Only the IETF, represented by the Internet Engineering Steering Group (IESG), can approve

standards-track RFCs. Each RFC is static; if the document is changed, it is submitted again

and assigned a new RFC number. If an RFC becomes an Internet Standard (STD), it is

assigned an STD number but retains its RFC number. When an Internet Standard is updated,

its number stays the same and it simply refers to a different RFC or set of RFCs. A given

Internet Standard, STD n, may be RFCs x and y at a given time, but later the same standard

may be updated to be RFC z instead. For example, in 2007 RFC 3700 was an Internet

StandardSTD 1and in May 2008 it was replaced with RFC 5000, so RFC 3700 changed to

Historic status, and now STD 1 is RFC 5000. When STD 1 is updated again, it will simply

refer to a newer RFC, but it will still be STD 1. Note that not all RFCs are standards-track

documents, but all Internet Standards and other standards-track documents are RFCs.

In fact, many technologies have quite a number of standards associated with them. A

networking technology may have more than one standard for any or all of the following

reasons:

The original standard has been revised or updated;

The technology is sufficiently complex that it needs to be described in more than one

document;

The technology borrows from or builds on documents used in related technologies;

More than one organization has been involved in developing the technology.

Standards documents created in the United Statesare usually developed in English, but are

also routinely translated into other languages. European standards are often published

simultaneously in English, French and German, and perhaps other languages as well.

2. Standards govern the semantics and syntax of messages

HTTP: Text request and response messages

Data field, header, and trailer

Header and trailer subdivided into fields



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3. Reliability

In TCP, receiver sends ACKs

Senders retransmit non-acknowledged segments

4. Connection-oriented versus connectionless

TCP is connection-oriented

HTTP is connectionless

5. Hybrid TCP/IP-OSI Architecture

OSI is nearly 100% dominant at Layers 1 and 2

TCP/IP is 70% to 80% dominant at Layers 3 and 4

Situation at Layer 5 is complex

6. Hybrid TCP/IP-OSI Standards Architecture

Application layer (application-to-application)

Transport layer (host-to-host)

Internet layer (across an internet)

Data link layer (across a switched network)

Physical layer (between adjacent devices)

7. Ethernet

Source and destination addresses are 48 bits long

Switches forward packets by destination addresses

Data field encapsulates an IP packet

Unreliable: if detects an error, drops the frame

8. Internet Protocol (IP)

32-bit addresses

Show 32 bits on each line

Unreliable: checks headers for errors but discards



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9. Vertical Communication on the Source Host

Layer process creates message and then sends the message to the next-lower layer

Next-lower layer encapsulates the message in its own message

This continues until the final frame at the data link layer

10. Vertical Communication on the Destination Host

Decapsulation and passing up

11. Not All Devices Have All Layers

Hosts have all five

Routers have only the lowest three

Switches have only the lowest two

12. OSI Architecture

Divides application layer into three layers

o Session

o Presentation

o Application

13. Other Standards Architectures

IPX/SPX

SNA

AppleTalk



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Topic : Physical Layer Propagation: Utp And Optical Fiber

Topic Objective:


Discuss Solid-Wire Versus Stranded-Wire UTP

Discuss Patch Cords Versus Bulk Wire

Discuss Cutting UTP

Discuss Stripping the Cord

Discuss Putting Wires in Order

Discuss Connectorize the Cord

Discuss RJ-45 Connector (Side View)

Discuss Crimp the Wire into the Connector

Discuss Connectorize Both Ends

Discuss Test Your Cord


The propagation speed of a medium refers to the speed that the data travels through that

medium. Propagation delays differ between mediums, which affect the maximum possible

length of the Ethernet topology running on that medium.

Key Points:

1. Overview

The maximum propagation delay through the network can be calculated by dividing the

maximum length by the speed. For 10Base2 thin coax network, this is 185 meters divided by

195,000 km/sec, or 950 nanoseconds. If the actual propagation delay from one end of the

network to the other is greater than 950 nanoseconds, latecollisions may occur.

In the following table, c refers to the speed of light in a vacuum, or 300,000 kilometers per

second.



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Medium Propagation Speed

Thick Coax .77c (231

Thin Coax .65c (195

Twisted Pair .59c (177

Fiber .66c (198

AUI Cable .65c (195

Table 1: The Maximum Propagation Delay ThroughThe Network

From these values, the size of a bit on 10BaseT can be calculated. 10BaseT is twisted pair,

which has a propagation delay of 177,000 km/sec. 177,000 km/sec divided by 10 million bits

per second is 17.7 meters, or the size of a single bit on a 10BaseT network.

2. Solid-WireVersus Stranded-Wire UTP

Solid-Wire UTP

o Each of the eight wires is a solid wire surrounded by insulation

o Solid wires have low attenuation and so can reach 100 meters

o Easy to connectorize (add connectors to)

o Brittle and easy to break if handled roughly. Not good for runs through open office

areas

Stranded-Wire UTP

o Each of the eight wires is really several thin strands of wire surrounded by

insulation

o Flexible and rugged: ideal for running around an office area



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o Higher attenuation than solid-wire UTP so can only be used in short runsup to about

10 meters

3. Patch Cords Versus Bulk Wire

Patch Cords

o Cut to popular lengths and connectorized at the factory

o Tested for quality

o Use stranded-wire UTP, which is sufficiently rugged for open office areas

o TIA/EIA-568 specifies patch cords for the run from the wall jack to the desktop

because it is rugged and flexible

Bulk Wire

o Comes in spools of 50 meters or more

o Can be cut to precise lengths needed to connect devices

o Solid-wire UTP for longer distance and to make connectorization easier

o Cut, connectorized, and tested by the user, by the organization, or by a LAN

installer

4. Cutting UTP

Cut a desired length of UTP

Make it a little longer than you need

o Adding a connector can take a few inches

o If the connectorization doesnt test well, you will have to cut the end and install a

new connector

o UTP cord should never be pulled tautly; it can beak if subjected to pulls. Should be

slack after installation



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5. Stripping the Cord

You must strip the jacket 3 to 5 cm (1 to 2 inches) at each end

Stripper scores the jacket (cuts into the jacket without cutting through it) to avoid damaging

the wires inside the jacket

Stripper is rotated once around the cord to score it evenly

The tip of the cord is pulled off after the scoring, exposing 3 to 5 cm (one to two inches) of

the wires

6. Putting Wires in Order

There are orange, green, blue, and brown pairs

Each pair has one wire with solid-color insulation and one wire that is white with bands of

the pairs color

These wires will be placed in a particular order in the RJ-45 connector

There are two popular color schemes in TIA/EIA-568

o T568A and T568B

o T568B is the most commonly used color scheme in the United States we will use it

Note that T568A is a part of the TIA/EIA-568 standard, as is T568B

7. Connectorize the Cord

Cut the wires straight across so that no more than 1.25 cm (a half inch) of wires are exposed

from the jacket

o This controls terminal cross-talk interference

Be sure to cut straight across or the wires will not all reach the pins when you push them into

the connector in the next step!

8. RJ-45 Connector (Side View)

Hold the RJ-45 connector away from you (with the hole in the back toward you) and the

spring clip down



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Insert your wires into the connector, white-orange on left

Push the wires all the way to the end

Examine the Connector

o Are the wires in the correct order?

o Hint: as a rough first check, the 1st, 3rd, 5th, and 7th wires from the left should be

mostly white

o If not, reinsertthem in the correct order

9. Crimp the Wire into the Connector

Get a good crimper

Cheap ones often fail to make a good connection

Should have a ratchet for tightening without breaking the connector

Press down to make a good connection. If you press too lightly, the connection will not work

Crimping forces the pins on the front of the RJ-45 connector though the insulation, into each

wire

o Insulation displacementconnection (IDC)

This also crimps the cord at the back end of the connector for strain relief to keep the cord

from pulling out if the cord is pulled

10. Connectorize Both Ends

White-orange is on the left (in Pin 1) at BOTH ENDS of the cord

o You do not reverse the order at the other end!

11. Test Your Cord

After you have connectorized both ends, test your cord

Misconnection is very common, so every cord must be checked

Inexpensive continuity testers make sure wires are connected electrically and in the right

order



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Expensive performance testers test for the quality of propagation

Continuity Tester

o Test for wires being in right slots and making good contact

o Place connectors of cord into two ends

o Hit Test button

o Did it work?

If It Didnt Work

o Be sure you understand the problem

o If an open connection, one or more of the wires was not pushed all the way to the

end or the crimping did not push the pin all the way through the insulation. Next

time, cut the wires straight across and crimp very firmly

o If miswired, see where it was miswired

o Cut off theends of the cord and reconnectorize

Signal Testers

o Expensive testers

o Test for signal quality

o Test for breaks with time domain reflectometry (TDR), which sends signals and

looks for reflections that indicate breaks.

In Section 2 of this course you will cover these topics:Ethernet Lans

Wireless Lans



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Topic : Ethernet Lans

Topic Objective:


Discuss Ethernet Standards Setting

Discuss Physical Layer Standards

Discuss Ethernet MAC Layer Standards

Discuss Ethernet MAC Layer Standards

Discuss Switch Purchasing Considerations

Discuss Advanced Switch Purchasing Considerations


Ethernet: Ethernet was developed by the Xerox Corporation's Palo Alto Research

Centre (known colloquially as Xerox PARC) in 1972 and was probably the first true

LAN to be introduced.

Key Points:

1. Overview

In 1985, the Instituteof Electrical and Electronic Engineers (IEEE) in the United

States of America, produced a series of standards for Local Area Networks (LANs)

called the IEEE 802 standards. These have found widespread acceptability and now

form the core of most LANs. One of the IEEE 802 standards, IEEE 802.3, is a

standard known as "Ethernet". This is the most widely used LAN technology in the

world today. Although IEEE 802.3 differs somewhat from the original standard (the

"blue book" defined in September 1980) it is very similar, and both sets of standards

may be used with the same LAN.

The IEEE standards have been adopted by the International Standards Organisation

(ISO), and is standardised in a series of standards known as ISO 8802-3. ISO was

created in 1947 to construct world-wide standards for a wide variety of Engineering

tasks. Adoption of ISO standards allows manufacturers to produce equipment which



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is guarented to operate anywhere it is finally used. ISO standards tend to be based on

other standards (such as those produced by the IEEE), the only problem is that the

ISO standards tend to be issued later, and are therefore less up to date.

The simplest form of Ethernet uses a passive bus operated at 10 Mbps. The bus is

formed from a 50 Ohm co-axial cable which connects all the computers in the LAN.

A single LAN may have up to 1024 attached systems, although in practice most

LANs have far fewer. One or more pieces of coaxial cable are joined end to end to

create the bus, known as an "Ethernet Cable Segment". Each segment is terminated

at both ends by 50 Ohm resistors (to prevent reflections from the discontinuity at the

end of the cable) and is also normally earthed at one end (for electrical safety).

Computers may attach to the cable using transceivers and network interface cards.

Frames of data are formed using a protocol called Medium Access Control (MAC),

and encoded using Manchesterline encoding. Ethernet uses a simple Carrier-Sense

Multiple Access protocol with Collision Detection (CSMA/CD) to prevent two

computers trying to transmit at the same time (or more correctly to ensure both

computers retransmit any frames which are corrupted by simultaneous

transmission).

100 Mbps networks may operate full duplex (using a Fast Ethernet Switch) or half

duplex (using a Fast Ethernet Hub). 1 Gbps networks usually operate between a pair

of Ethernet Switches. (N.B.It is not possible to have a dual-speed hub, since a hub

does not store and forward frames, however a number of manufacturers sell products

they call "dual-speed hubs". In fact, such devices contain both a 10 Mbps and a 100

Mbps hubs, interconnected by a store-and-forward bridge.)

Ethernet LANs may be implemented using a variety of media (not just the coaxial

cable described above). The types of media segments supported by Ethernet are:

10B5 Low loss coaxial cable (also known as "thick" Ethernet)

10B2 Low cost coaxial cable (also known as "thin" Ethernet)

10BT Low cost twisted pair copper cable (also known as Unshielded Twisted Pair

(UTP), Category-5)

10BF Fibre optic cable




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(UTP), Category-5)

100BF Fibre Fast Ethernet


(UTP), Category-5)

1000BF Fibre Gigabit Ethernet

10000BT Category 6 (Unshielded Twisted Pair (UTP), Category-6)

10000BT Fibre 10 Gigabit Ethernet

The network design rules for 10 Mbps using these types of media are summarized

below:

Segment type Max Number of

systems per cable

segment

Max Distance of a

cable segment

10B5 (Thick Coax) 100 500 m

10B2 (Thin Coax) 30 185 m

10BT (Twisted Pair) 2 100 m

10BFL (Fibre Optic) 2 2000 m

Table 1: Network Design Rules for Different types of Cable

There is also a version of Ethernet which operates fibre optic links at 40 Gbps and at

100 Gbps. Many LANs combine the various speeds of operation using dual-speed

switches which allow the same switch to connect some ports to one speed of

network, and other ports at another speed. The higher speed ports are usually used to

connect switches to one another.

2. Ethernet Standards Setting

802.3 Working Group

Physical and data link layer standards

OSI standards

3. Physical Layer Standards

BASE means baseband



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100BASE-TX dominates for access lines

10GBASE-SX dominates for trunk lines

Link aggregation for small capacity increases

Regeneration to carry signals across multiple switches

4. Ethernet MAC Layer Standards

Data link layer subdivided into the LLC and MAC layers

The Ethernet MAC Layer Frame

o Preamble and Start of Frame Delimiter fields

o Destination and Source MAC addresses fields

▪ Hexadecimal notation

o Length field

o Data field

▪ LLC subheader

▪ Packet

▪ PAD if needed

o Frame Check Sequence field

5. Ethernet MAC Layer Standards

Switch operation

o Operation of a hierarchy of switches

▪ Single possible path between any two computers

▪ Hierarchy gives low price per frame transmitted

▪ Single points of failure and the Spanning Tree Protocol



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o VLANs and frame tagging to reduce broadcasting

o Momentary traffic peaks: addressed by overprovisioning and priority

o Hubs and CSMA/CD

6. Switch Purchasing Considerations

Number and speed of ports

Switching matrix (nonblocking)

Store-and-forward versus cut-through switches

Managed switches

Ethernet security

o 802.1X Port-Based Access Control

o 802.1AE MACsec

7. Advanced Switch Purchasing Considerations

Physical size

Fixed-Port-Speeches

Stackable Switches

Modular Switches

Chassis Switches

Pins in SwitchPorts and Uplink Ports

Electrical Power (802.3af)

Topic : Wireless Lans

Topic Objective:


Discuss Benefits Of Wireless LANs

Discuss Local Wireless Technologies



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Discuss Radio Propagation

Discuss Radio Propagation

Discuss 802.11 Operation

Discuss 802.11 WLAN Security

Discuss WLAN Management

Discuss Bluetooth


Wireless LAN: A wireless LAN or WLAN is a wireless local area network, which

is the linking of two or more computers or devices without using wires. WLAN

utilizes spread-spectrum or OFDM modulation technology based on radio waves to

enable communication between devices in a limited area, also known as the basic

service set. This gives users the mobility to move around within a broad coverage

area and still be connected to the network.

Key Points:

1. Overview

The popularity of wireless LANs is a testament primarily to their convenience, cost

efficiency, and ease of integration with other networks and network components.

The majority of computers sold to consumers today come pre-equipped with all

necessary wireless LAN technology.

For the home user, wireless has become popular due to ease of installation, and

location freedom with the gaining popularity of laptops. Public businesses such as

coffee shops or malls have begun to offer wireless access to their customers; some

are even provided as a free service. Large wireless network projects are being put up

in many major cities. Google is even providing a free service to Mountain View,

California and has entered a bid to do the same for San Francisco. New York City

has also begun a pilot program to cover all five boroughs of the city with wireless

Internet access.

2. Benefits Of Wireless LANs

The benefits of wireless LANs include:



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Convenience: The wireless nature of such networks allows users to access network

resources from nearly any convenient location within their primary networking

environment (home or office). With the increasing saturation of laptop-style

computers, this is particularly relevant.

Mobility: With the emergence of public wireless networks, users can access the

internet even outside their normal work environment. Most chain coffee shops, for

example, offer their customers a wireless connection to the internet at little or no

cost.

Productivity: Users connected to a wireless network can maintain a nearly constant

affiliation with their desired network as they move from place to place. For a

business, this implies that an employee can potentially be more productive as his or

her work can be accomplished from any convenient location.

Deployment: Initial setup of an infrastructure-based wireless network requires little

more than a single access point. Wired networks, on the other hand, have the

additional cost and complexity of actual physical cables being run to numerous

locations (which can even be impossible for hard-to-reach locations within a

building).

Expandability: Wireless networks can serve a suddenly-increased number of clients

with the existing equipment. In a wired network, additional clients would require

additional wiring.

Cost: Wireless networking hardware is at worst a modest increase from wired

counterparts. This potentially increased cost is almost always more than outweighed

by the savings in cost and labor associated to running physical cables.

3. Local Wireless Technologies

802.11 for Corporate WLANs

Bluetooth for PANs

Ultrawideband (UWB)



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RFIDs

ZigBee

Mesh Networks

4. Radio Propagation

Frequencies and Channels

Antennas

Propagation Problems

o Inverse square law attenuation

o Dead spots / shadow zones

o Electromagnetic interference

o Multipath interference

o Attenuation and shadow zone problems increase with frequency

5. Radio Propagation

Shannons Equation and the Importance of Channel Bandwidth

o C = B Log2(1+S/N)

WLANs use unlicensed Radio Bands

Spread Spectrum Transmission to Reduce Propagation Problems

o FHSS (up to 4 Mbps)

o DSSS (up to 11 Mbps)

o OFDM (up to 54 Mbps)

o MIMO (100 Mbps to 600 Mbps)



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6. 802.11 Operation

Wireless Access PointBridge to the Main Wired Ethernet LAN

o To reach servers and Internet access routers

o Transfers packet between 802.11 and 802.3 frames

Need for Media Access Control (Box)

o CSMA/CA and RTS/CTS

o Throughput is aggregate throughput

Bands

o 2.4 GHz band: Only 3 channels, lower attenuation

o 5 GHz band: Around 24 channels, higher attenuation

o More channels means less interference between nearby access points

Standards

o 802.11b: 11 Mbps, DSSS, 2.4 GHz band

o 802.11a: 54 Mbps, OFDM, 2.4 GHz band

o 802.11g: 54 Mbps, OFDM, 5 GHz band

o 802.11n: 100 Mbps 600 Mbps, MIMO, Dual-Band

7. 802.11 WLAN Security

Wardrivers and Drive-By Hackers

Core Security

o WEP (Unacceptably Weak)



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o WPA (Lightened form of 802.11i)

o 802.11i (The gold standard today)

o 802.1X and PSK modes for WPA and 802.11i

Rogue Access Points and Evil Twin Access Points

8. WLAN Management

Surprisingly Expensive

Access Point Placement

o Approximate layout

o Site survey for more precise layout and power

Remote Access Point Management

o Smart access points or WLAN switches and dumb access points

9. Bluetooth

PANs

Cable Replacement Technology

Limited Speeds and Distance

Application Profiles

UWB in the Future?

In Section 3 of this course you will cover these topics:Telecommunications

Wide Area Networks Wans



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Topic : Telecommunications

Topic Objective:


Discuss Modulation

Discuss Channels

Discuss Networks

Discuss Analogue or digital


Telecommunication: Telecommunication is the assisted transmission of signals

over a distance for the purpose of communication. In earlier times, this may have

involved the use of smoke signals, drums, semaphore, flags, or heliograph. In

modern times, telecommunication typically involves the use of electronic

transmitters such as the telephone, television, radio or computer. Early inventors in

the field of telecommunication include Antonio Meucci, Alexander Graham Bell,

Guglielmo Marconi and John Logie Baird. Telecommunication is an important part

of the world economy and the telecommunication industry's revenue has been placed

at just under 3 percent of the gross world product.

Key Points:

1. Overview

A telecommunication system consists of three basic elements:

A transmitter that takes information and converts it to a signal;

A transmission medium that carries the signal; and,

A receiver that receives the signal and converts it back into usable information.

For example, in a radio broadcast the broadcast tower is the transmitter, free space is

the transmission medium and the radio is the receiver. Often telecommunication

systems are two-way with a single device acting as both a transmitter and receiver or

transceiver. For example, a mobile phone is a transceiver.



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Telecommunication over a phone line is called point-to-point communication

because it is between one transmitter and one receiver. Telecommunication through

radio broadcasts is called broadcast communication because it is between one

powerful transmitter and numerous receivers.

2. Analogue or digital

Signals can be either analogue or digital. In an analogue signal, the signal is varied

continuously with respect to the information. In a digital signal, the information is

encoded as a set of discrete values (for example ones and zeros). During

transmission the information contained in analogue signals will be degraded by

noise. Conversely, unless the noise exceeds a certain threshold, the information

contained in digital signals will remain intact. This noise resistance represents a key

advantage of digital signals over analogue signals.

3. Networks

A collection of transmitters, receivers or transceivers that communicate with each

other is known as a network. Digital networks may consist of one or more routers

that route information to the correct user. An analogue network may consist of one

or more switches that establish a connection between two or more users. For both

types of network, repeaters may be necessary to amplify or recreate the signal when

it is being transmitted over long distances. This is to combat attenuation that can

render the signal indistinguishable from noise.

4. Channels

A channel is a division in a transmission medium so that it can be used to send

multiple streams of information. For example, a radio station may broadcast at 96.1

MHz while another radio station may broadcast at 94.5 MHz. In this case, the

medium has been divided by frequency and each channel has received a separate

frequency to broadcast on. Alternatively, one could allocate each channel a recurring

segment of time over which to broadcastthis is known as time-division multiplexing

and is sometimes used in digital communication.



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5. Modulation

The shaping of a signal to convey information is known as modulation. Modulation

can be used to represent a digital message as an analogue waveform. This is known

as keying and several keying techniques exist (these include phase-shift keying,

frequency-shift keying and amplitude-shift keying). Bluetooth, for example, uses

phase-shift keying to exchange information between devices.

Modulation can also be used to transmit the information of analogue signals at

higher frequencies. This is helpful because low-frequency analogue signals cannot

be effectively transmitted over free space. Hence the information from a low-

frequency analogue signal must be superimposed on a higher-frequency signal

(known as a carrier wave) before transmission. There are several different

modulation schemes available to achieve this (two of the most basic being amplitude

modulation and frequency modulation). An example of this process is a DJ's voice

being superimposed on a 96 MHz carrier wave using frequency modulation (the

voice would then be received on a radio as the channel 96 FM).

Topic : Wide Area Networks Wans

Topic Objective:


Discuss Virtual Private Networks (PVCs)

Discuss Other PSDNs

Discuss Frame Relay PSDNs

Discuss Public Switched Data Networks

Discuss Leased Line Networks

Discuss WANs


Wide Area Network: Wide Area Network (WAN) is a computer network that

covers a broad area (i.e., any network whose communications links cross

metropolitan, regional, or national boundaries ).



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Key Points:

1. Overview

Wide Area Network (WAN) are less formally, a network that uses routers and public

communications links .Contrast with personal area networks (PANs), local area

networks (LANs), campus area networks (CANs), or metropolitan area networks

(MANs) which are usually limited to a room, building, campus or specific

metropolitan area (e.g., a city) respectively. The largest and most well-known

example of a WAN is the Internet.

WANs are used to connect LANs and other types of networks together, so that users

and computers in one location can communicate with users and computers in other

locations. Many WANs are built for one particular organization and are private.

Others, built by Internet service providers, provide connections from an

organization's LAN to the Internet. WANs are often built using leased lines. At each

end of the leased line, a router connects to the LAN on one side and a hub within the

WAN on the other. Leased lines can be very expensive. Instead of using leased

lines, WANs can also be built using less costly circuit switching or packet switching

methods. Network protocols including TCP/IP deliver transport and addressing

functions. Protocols including Packet over SONET/SDH, MPLS, ATM and Frame

relay are often used by service providers to deliver the links that are used in WANs.

X.25 was an important early WAN protocol, and is often considered to be the

"grandfather" of Frame Relay as many of the underlying protocols and functions of

X.25 are still in use today (with upgrades) by Frame Relay.

Academic research into wide area networks can be broken down into three areas:

Mathematical models, network emulation and network simulation. Performance

improvements are sometimes delivered via WAFS or WAN Optimization.

Transmission rate usually range from 1200 bits/second to 6 Mbit/s, although some

connections such as ATM and Leased lines can reach speeds greater than 156

Mbit/s. Typical communication links used in WANs are telephone lines, microwave

links & satellite channels.

Recently with the proliferation of low cost of Internet connectivity many companies

and organizations have turned to VPN to interconnect their networks, creating a



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WAN in that way. Companies such as Cisco, New Edge Networks and Check Point

offer solutions to create VPN networks.

Option: Description Advantages Disadvantage

s

Bandwidt

h range

Sample

protocol

s used

Leased

line

Point-to-

Point

connection

between two

computers

or Local

Area

Networks

(LANs)

Most secure Expensive PPP,

HDLC,

SDLC,

HNAS

Circuit

switchin

g

A dedicated

circuit path

is created

between end

points. Best

example is

dialup

connections

Less

Expensive

Call Setup 28 Kb/s -

144 Kb/s

PPP,

ISDN

Packet

switchin

g

Devices

transport

packets via

a shared

single point-

to-point or

point-to-

multipoint

link across a

carrier

internetwork

Shared media

across link

X.25

Frame-

Relay



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. Variable

length

packets are

transmitted

over

Permanent

Virtual

Circuits

(PVC) or

Switched

Virtual

Circuits

(SVC)

Cell

relay

Similar to

packet

switching,

but uses

fixed length

cells instead

of variable

length

packets.

Data is

divided into

fixed-length

cells and

then

transported

across

virtual

circuits

best for

simultaneou

s use of

Voice and

data

Overhead can

be

considerable

ATM

Table 1 : Several options are available for WAN connectivity



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2. WANs

Wide Area Networks

o Carry data between different sites, usually within a corporation

o High-cost and low-speed lines

▪ 128 kbps to a few megabits per second

o Carriers

o Purposes

▪ Internet access, site-to-site connections, and remote access for

Individuals

o Technologies

▪ Leased line networks, public switched data networks, and

virtual private networks

3. Leased Line Networks

Leased Lines are Long-Term Circuits

o Point-to-Point

o Always On

o High-speeds

▪ Device at Each Site

o PBX for leased line voice networks

o Router for leased line data networks

▪ Pure Hub-and-Spoke, Full Mesh, and Mixed Topologies



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▪ Many Leased Line Speeds

o Fractional T1, T1, and bonded T1 dominate

o Slowest leased lines run over 2-pair data-grade UTP

o Above 3 Mbps, run over optical fiber

o Below about 3 Mbps, 2-pair data grade UTP

o Above 3 Mbps, optical fiber

o North American Digital Hierarchy, CEPT, and other standards below 50

Mbps

o SONET/SDH above 50 Mbps

o Symmetrical DSL lines with QoS

4. Public Switched Data Networks

PSDNs

o Services offered by carriers

o Customer does not have to operate or manage

o One leased line per site from the site to the nearest POP

o By reducing corporate labor, typically cheaper than leased line networks

o Service Level Agreements

o Virtual circuits

5. Frame Relay PSDNs

Frame Relay

o Most popular PSDN



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o 56 kbps to about 40 Mbps

o Access devices, CSU/DSUs, leased access lines, POP ports, virtual

circuits, management

▪ Usually POP port speed charges are the biggest cost component

▪ Second usually are PVC charges

o Leased line must be fast enough to handle the speeds of all of the PVCs

multiplexed over it

6. Other PSDNs

ATM

o High speed and cost

o Cell switching

o Low use

Metro Ethernet

o Extending Ethernet to MANs

o Very attractive speeds and prices

o Small but growing rapidly

Carrier IP Networks

o Essentially, private Internets with QoS and security

o Carriers want to use it to replace Frame Relay

7. Virtual Private Networks (PVCs)

The Internet is inexpensive and universal



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o VPNs add security to transmission over the Internet (or any other untrusted

network)

IPsec

o The strongest security for VPNs

o Tunnel mode between sites is inexpensive

o Transport mode between computers is expensive

SSL/TLS

o First for browser communication with a single webserver

o SSL/TLS gateways make it a full remote access VPN

In Section 4 of this course you will cover these topics:Tcp/Ip Internetworking

Security

Topic : Tcp/Ip Internetworking

Topic Objective:


Discuss Layer 3 Switches

Discuss Port Numbers and Sockets in TCP and UDP

Discuss The User Datagram Protocol (UDP), Transmission Control Protocol (TCP) ,

Internet Protocol (IP) and Internet Control Message Protocol (ICMP)

Discuss Domain Name System (DNS)

Discuss Multiprotocol Label Switching



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Discuss Address Resolution Protocol and Dynamic Routing Protocols

Discuss Routing Decisions and Routing of Packets

Discuss Router Operation

Discuss Hierarchical IP Address parts

Discuss Internetworking


The Internet evolved from the ARPANET , an early wide-area network developed

by the USmilitary for military and academic communication. Amongst the design

aims was the ability to provide a scalable internetwork of heterogeneous networks.

The result was the TCP/IP-based Internet, which is based on several fundamental

principles:

Hosts in the Internet are identified by unique (32-bit) addresses assigned by a

number of central authorities. The address consists of a network part and a host part.

All hosts on the same network have the same network part to their address, but

unique host parts. Clearly, a host which is connected to more than one network

(called a multi-homed host) has more than one address. A drawback of this approach

is that moving hosts between networks requires their addresses to be changed. On

the other hand, the approach has numerous advantages that more than compensate

for this.

Interconnection among networks is provided by multi-homed hosts called gateways

or routers (a firewall is a special type of gateway). A gateway relays network traffic

between two or more networks. These networks may have further gateways,

resulting in further relaying. To reduce the amount of information needed by

gateways, decisions about where to relay traffic (called routing decisions) are based

on the network part of the destination address; the host part is only used to route

traffic once it reaches the destination network.

All networks are treated equally. LANs, WANs and point-to-point links are each

separate networks and are treated in a uniform fashion.

The network protocol used for transferring traffic across the Internet is IP (Internet

Protocol), and the 32-bit addresses are known as IP addresses.



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Key Points:

1. Overview

The TCP/IP model is a specification for computer network protocols created in the

1970s by DARPA, an agency of the United States Department of Defense. It laid the

foundations for ARPANET, which was the world's first wide area network and a

predecessor of the Internet. The TCP/IP Model is sometimes called the Internet

Reference Model, the DoD Model or the ARPANET Reference Model.

The TCP/IP Suite defines a set of rules to enable computers to communicate over a

network. TCP/IP provides end to end connectivity specifying how data should be

formatted, addressed, shipped, routed and delivered to the right destination. The

specification defines protocols for different types of communication between

computers and provides a framework for more detailed standards.

TCP/IP is generally described as having four abstraction layers (five if the bottom

physical layer is included). The layer view of TCP/IP is based on the seven-layer

OSI Reference Model written after the original TCP/IP specifications, and is not

officially recognized. Regardless, it provides an analogy for understanding the

operation of TCP/IP, and comparison of the models is common.

The TCP/IP model and related protocols are currently maintained by the Internet

Engineering Task Force (IETF).

An early architectural document, RFC 1122, emphasizes architectural principles

over layering.

End-to-End Principle: This principle has evolved over time. Its original expression

put the maintenance of state and overall intelligence at the edges, and assumed the

Internet that connected the edges retained no state and concentrated on speed and

simplicity. Real-world needs for firewalls, network address translators, web content

caches and the like have forced changes in this Principle.

Robustness Principle: "Be liberal in what you accept, and conservative in what you

send. Software on other hosts may contain deficiencies that make it unwise to



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exploit legal but obscure protocol features".

Even when the layers are examined, the assorted architectural documentsthere is no

single architectural model such as ISO 7498, the OSI reference modelhave fewer,

less rigidly defined layers than the commonly referenced OSI model, and thus

provides an easier fit for real-world protocols. In point of fact, one frequently

referenced document does not contain a stack of layers. The lack of emphasis on

layering is a strong difference between the IETF and OSI approaches. It only refers

to the existence of the "internetworking layer" and generally to "upper layers"; this

document was intended as a 1996 "snapshot" of the architecture: "The Internet and

its architecture have grown in evolutionary fashion from modest beginnings, rather

than from a Grand Plan. While this process of evolution is one of the main reasons

for the technology's success, it nevertheless seems useful to record a snapshot of the

current principles of the Internet architecture."

No document officially specifies the model, another reason to deemphasize the

emphasis on layering. Different names are given to the layers by different

documents, and different numbers of layers are shown by different documents.

There are versions of this model with four layers and with five layers. RFC 1122 on

Host Requirements makes general reference to layering, but refers to many other

architectural principles not emphasizing layering. It loosely defines a four-layer

version, with the layers having names, not numbers, as follows:

Process Layer or Application Layer: this is where the "higher level" protocols such

as SMTP, FTP, SSH, HTTP, etc. operate.

Host-To-Host (Transport) Layer: this is where flow-control and connection

protocols exist, such as TCP. This layer deals with opening and maintaining

connections, ensuring that packets are in fact received.

Internet or Internetworking Layer: this layer defines IP addresses, with many routing

schemes for navigating packets from one IP address to another.

Network Access Layer: this layer describes both the protocols (i.e., the OSI Data

Link Layer) used to mediate access to shared media, and the physical protocols and

technologies necessary for communications from individual hosts to a medium.

The Internet protocol suite (and corresponding protocol stack), and its layering



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model, were in use before the OSI model was established. Since then, the TCP/IP

model has been compared with the OSI model numerous times in topics, which

often results in confusion because the two models use different assumptions,

including about the relative importance of strict layering.

2. Internetworking

Internetworking involves the internet and transport layers

Packets are encapsulated in frames in single networks.

Transport layer is end-to-end

Internet layer is hop-by-hop between routers

IP, TCP, and UDP are the heart of TCP/IP internetworking

3. Hierarchical IP Address parts

Network, subnet, and host parts

4. Router Operation

Border routers connect networks

Internal routers connect subnets

We focused on TCP/IP routing, but multiprotocol routing is crucial

Router meshes give alternative routes, making routing very expensive

5. Routing of Packets

Routing tables

IP address range governed by a rowusually a route to a network or subnet

Metric to help select best matches

Next-hop router to be sent the packet next

o Can be a local host on one of the routers subnets

Process

o Final all possible routes through row matching



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o Select by length of match, then metric if tie

o Send out to next-hop router in the best-match row

6. Detailed Look at Routing Decisions

IP address range

o Destination

o Mask

o If the masked destination IP address in an arriving packet matches the

destination value, the row is a match

Next-Hop Router

o Interface

o Next-hop router or destination host

7. Dynamic Routing Protocols

Interior dynamic routing protocols within an autonomous system

o RIP, OSPF, EIGRP

Exterior dynamic routing protocols between autonomous systems

o BGP

8. Address Resolution Protocol

Router knows the IP address of the next-hop router or destination host

Must learn the data link layer address as well

9. Multiprotocol Label Switching

Routing decisions are based on labels rather than destination IP addresses



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Reduces routing costs

10. Domain Name System (DNS)

General hierarchical naming system for the Internet

11. Internet Control Message Protocol (ICMP)

General supervisory protocol at the internet layer

Error advisements and Pings (echo requests/replies)

12. The Internet Protocol (IP)

Detailed look at key fields

Protocol field lists contents of the data field

32-bit IP addresses

IPv4 is the current version

IPv6 offers 128-bit IP addresses to allow many more IP addresses to serve the world

13. The Transmission Control Protocol (TCP)

Sequence and acknowledgement numbers

Flag fields that are set or not set

Window size field allows flow control

Options are common

Three-way openings (SYN, SYN/ACK, and ACK)

Four-way normal closings (FIN, ACK, FIN, ACK)

One-way abrupt closing (RST)

14. The User Datagram Protocol (UDP)

Simple four-field header

15. Port Numbers and Sockets in TCP and UDP

Applications get well-known port numbers on servers

Connections get ephemeral port numbers on clients



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Socket is an IP address, a colon, and a port number

This designates a specific application (or connection) on a specific server (or client)

16. Layer 3 Switches

Fast, inexpensive, and limited routers

Topic : Security

Topic Objective:


Discuss Cryptographic Systems

Discuss Firewalls

Discuss Security Management

Discuss The Threat Environment

Discuss Attributes of a secure network

Discuss Comparison with computer security


Network security: Network security consists of the provisions made in an

underlying computer network infrastructure, policies adopted by the network

administrator to protect the network and the network-accessible resources from

unauthorized access and the effectiveness (or lack) of these measures combined

together.

Key Points:

1. Comparison with computer security

Securing network infrastructure is like securing possible entry points of attacks on a

country by deploying appropriate defense. Computer security is more like providing

means to protect a single PC against outside intrusion. The former is better and



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practical to protect the civilians from getting exposed to the attacks. The preventive

measures attempt to secure the access to individual computers--the network itself--

thereby protecting the computers and other shared resources such as printers,

network-attached storage connected by the network. Attacks could be stopped at

their entry points before they spread. As opposed to this, in computer security the

measures taken are focused on securing individual computer hosts. A computer host

whose security is compromised is likely to infect other hosts connected to a

potentially unsecured network. A computer host's security is vulnerable to users

with higher access privileges to those hosts.

2. Attributes of a secure network

Network security starts from authenticating any user, most likelyan username and a

password. Once authenticated, a state firewall enforces access policies such as what

services are allowed to be accessed by the network users. Though effective to

prevent unauthorized access, this component fails to check potentially harmful

contents such as computer worms being transmitted over the network. An intrusion

prevention system (IPS) helps detect and prevent such malware. IPS also monitors

for suspicious network traffic for contents, volume and anomalies to protect the

network from attacks such as denial of service. Communication between two hosts

using the network could be encrypted to maintain privacy. Individual events

occurring on the network could be tracked for audit purposes and for a later high

level analysis.

Honeypots, essentially decoy network-accessible resources, could be deployed in a

network as surveillance and early-warning tools. Techniques used by the attackers

that attempt to compromise these decoy resources are studied during and after an

attack to keep an eye on new exploitation techniques. Such analysis could be used to

further tighten security of the actual network being protected by the honeypot.

3. The Threat Environment

Many threats

Malware: viruses versus worms, payloads, etc.

Social engineering



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Spam, credit card theft, identity theft, adware, spyware

Human Break-Ins

o Definition of hackingauthorization

o Scanning phase; the exploit

o After the Break-in: deleting log files, backdoors, damage at leisure

Human attacks

o Denial-of-Service (DoS) Attack with zombies

o Bots

Traditional attackers

o Hackers, virus writers, script kiddies

o Disgruntled employees and ex-employees

Criminal attackers now dominate on the Internet

Cybercrime and cyberwar

4. Security Management

Security is a management issue, not a technical issue

Comprehensive security and centralized management

Defense in depth

Enumerating and prioritizing assets

o Asset control plans: authentication, authorization, and auditing

Authentication

o Applicant and verifier

▪ Central authentication server for consistency



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o Password authentication

▪ Poor password discipline is common

▪ Passwords need to be long and complex

o Biometrics

▪ Fingerprint, iris, face, etc.

▪ Error rates and deception

o Digital certificate authentication

▪ Public key / private key pairs, digital certificates

▪ The strongest form of authentication

▪ Need both an applicant calculation and a digital certificate for

authorization

5. Firewalls

Filter, drop, or pass incoming and outgoing packets

Stateful inspection firewalls

o Default rules for connection-opening attempts

o ACLs to modify the default rules

o Other packetsaccept if part of connection

Firewalls, IDSs and IPSs

IPSs have the strongest filtering ability



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6. Cryptographic Systems

To protect streams of messages

Initial authentication

Message-by-message protections: encryption for confidentiality, digital signature for

authentication and message integrity

Symmetric key encryption

Public key encryption

o Hardening Clients and Servers

o Vulnerability Testing

o Incident Response

▪ Detecting the attack, stopping the attack, repairing the damage,

punishing the attacker

▪ Major attacks and CSIRTs

▪ Disasters and disaster recovery

In Section 5 of this course you will cover these topics:Network Management

Networked Applications

Topic : Network Management

Topic Objective:


Discuss Network Simulation



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Discuss IP Subnetting

Discuss Directory Servers

Discuss Configuring Routers

Discuss Network Management Utilities

Discuss Simple Network Management Protocol (SNMP)

Discuss Traffic Management


Network management: Network management refers to the activities, methods,

procedures, and tools that pertain to the operation, administration, maintenance, and

provisioning of networked systems.

Key Points:

1. Overview

Functions that are performed as part of network management accordingly include

controlling, planning, allocating, deploying, coordinating, and monitoring the

resources of a network, network planning, frequency allocation, predetermined

traffic routing to support load balancing, cryptographic key distribution

authorization, configuration management, fault management, security management,

performance management, bandwidth management, and accounting management.

A large number of access methods exist to support network and network device

management. Access methods include the SNMP, Command Line Interfaces (CLIs),

custom XML, CMIP, Windows Management Instrumentation (WMI), Transaction

Language 1, CORBA, netconf, and the Java Management Extensions - JMX.

Schemas include the WBEM and the Common Information Model amongst others.

Data for network management is collected through several mechanisms, including

agents installed on infrastructure, synthetic monitoring that simulates transactions,

logs of activity, sniffers and real user monitoring. In the past network management

mainly consisted of monitoring whether devices were up or down; today

performance management has become a crucial part of the IT team's role which



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brings about a host of challenges -- especially for global organizations.

Operation deals with keeping the network (and the services that the network

provides) up and running smoothly. It includes monitoring the network to spot

problems as soon as possible, ideally before users are affected.

Administration deals with keeping track of resources in the network and how they

are assigned. It includes all the "housekeeping" that is necessary to keep the network

under control.

Maintenance is concerned with performing repairs and upgrades - for example,

when equipment must be replaced, when a router needs a patch for an operating

system image, when a new switch is added to a network. Maintenance also involves

corrective and preventive measures to make the managed network run "better", such

as adjusting device configuration parameters.

Provisioning is concerned with configuring resources in the network to support a

given service. For example, this might include setting up the network so that a new

customer can receive voice service.

2. Network Simulation

Study before you install equipment

There is a process to follow

What Is versus What If

3. IP Subnetting

Must balance number of subnets with number of hosts per subnet

A part with N bits can support 2N-2 subnets or hosts

4. Directory Servers

Centralized storage of information

Hierarchical organization

LDAP is the protocol for data queries



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5. Configuring Routers

Cisco IOS command line interface (CLI)

Worked through a simple example

6. Network Management Utilities

Diagnose a network connection for a client PC

7. Simple Network Management Protocol (SNMP)

Protocol for managing network devices remotely

Manager, managed device, agent, RMON probe

Management information base (MIB)

SNMP messages: commands and responses, traps

8. Traffic Management

Overprovisioning

Priority

QoS reservations

Traffic shaping: prevent congestion from occurring

Topic : Networked Applications

Topic Objective:


Discuss Application Architectures

Discuss E-Mail

Discuss HTTP and HTML



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Discuss E-Commerce

Discuss Software as a Service (SAS)


Network applications: Network applications are simply the things networks are

used for.

Key Points:

1. Overview

There are many ways we can classify and talk about network applications, for

example:

Who created the application content? Is the content created by users, a company

running a Web site, a third party? Who creates the content on MySpace? Who

creates the content on Amazon? An increasing proportion of Internet content is

created by users.

How much did it cost to create and deliver the content? An email is nearly free. A

studio movie or recording is quite expensive. The Internet is disrupting many

industries by bringing the cost of content creation and delivery down rapidly.

Who was the application intended for? The general public? A small group with a

common interest? An individual?

What was the content creator's goal? To sell something? To teach? To persuade?

How is the application paid for? Subscription? One time sales? Advertising?

Is the application on the public Internet or a restricted-access intranet or extranet?



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Type Definition Example

Internet a global, public TCP/IP network used by

over a billion people

Sending email to a friend

Intranet a TCP/IP network with access restricted

to members or employees of a single

organization

Accessing your record in

the employee personnel

file

Extranet a TCP/IP network with access restricted

to members or employees of a two or

more organizations

Checking availability of

inventory from an outside

supplier

Table 1: Client-Server Applications That Use The TCP/IPCommunication

Protocols

2. Application Architectures

Terminal-host

Client/server

o File server program access

o Client/server processing with request/response cycle

Peer-to-peer (P2P)

Evolution of architectures driven by growing desktop computer power

3. E-Mail

Sending: Simple Mail Transfer Protocol (SNMP)

Retrieving: POP and IMAP

Document format standards: RFC 822/2822, HTML, and UNICODE

Viruses, worms, and Trojan horses

o Where to do antivirus filtering?

Spam



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4. HTTP and HTML

Webpages consist of an HTML document and multiple graphics, etc. files

Message transfer: HTTP

o Multiple downloads for the multiple files in a webpage

MIME

5. E-Commerce

E-Commerce : webservice with additional functionality

Webserver interacts with customer browser

Application server interacts with back-end databases, passes webified response to

the webserver for delivery to the customer

DMZ and SSL/TLS security

6. Software as a Service (SAS)

Regular webservice: retrieve stored files

SAS: use HTTP and extended HTML to handle program-to-program interactions on

different machines

SOAP request message passes parameters to a service object on another machine

SOAP response message brings the reply

SOAP messages are written in XML



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