· pdf file · 2015-09-22... such as bus network, star network, ring network, mesh...
TRANSCRIPT
NETWORKS AND TELECOMMUNICATION
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
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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.
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).
Topic : Network Standards
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Topic Objective:
At the end of this topic students will be able to:
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
Definition/Overview:
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.
Collectively, these stages are known as the standards track, and are defined in RFC 2026. The
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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
Topic : Physical Layer Propagation: Utp And Optical Fiber
Topic Objective:
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At the end of this topic students will be able to:
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
Definition/Overview:
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.
Medium Propagation Speed
Thick Coax .77c (231
Thin Coax .65c (195
Twisted Pair .59c (177
Fiber .66c (198
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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
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
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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
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
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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
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?
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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
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
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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
Topic : Ethernet Lans
Topic Objective:
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At the end of this topic students will be able to:
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
Definition/Overview:
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 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
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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
100BT Low cost twisted pair copper cable (also known as Unshielded Twisted Pair (UTP),
Category-5)
100BF Fibre Fast Ethernet
1000BT Low cost twisted pair copper cable (also known as Unshielded Twisted Pair (UTP),
Category-5)
1000BF Fibre Gigabit Ethernet
10000BT Category 6 (Unshielded Twisted Pair (UTP), Category-6)
10000BT Fibre 10 Gigabit Ethernet
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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
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
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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
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
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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:
At the end of this topic students will be able to:
Discuss Benefits Of Wireless LANs
Discuss Local Wireless Technologies
Discuss Radio Propagation
Discuss Radio Propagation
Discuss 802.11 Operation
Discuss 802.11 WLAN Security
Discuss WLAN Management
Discuss Bluetooth
Definition/Overview:
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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:
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.
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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)
RFIDs
ZigBee
Mesh Networks
4. Radio Propagation
Frequencies and Channels
Antennas
Propagation Problems
o Inverse square law attenuation
o Dead spots / shadow zones
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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)
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
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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)
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
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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
Topic : Telecommunications
Topic Objective:
At the end of this topic students will be able to:
Discuss Modulation
Discuss Channels
Discuss Networks
Discuss Analogue or digital
Definition/Overview:
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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.
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.
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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.
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).
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Topic : Wide Area Networks Wans
Topic Objective:
At the end of this topic students will be able to:
Discuss Virtual Private Networks (PVCs)
Discuss Other PSDNs
Discuss Frame Relay PSDNs
Discuss Public Switched Data Networks
Discuss Leased Line Networks
Discuss WANs
Definition/Overview:
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 ).
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.
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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 WAN in that
way. Companies such as Cisco, New Edge Networks and Check Point offer solutions to
create VPN networks.
Option: Description Advantages Disadvantages Bandwidth
range
Sample
protocols
used
Leased
line
Point-to-Point
connection between
two computers or
Local Area
Networks (LANs)
Most secure Expensive PPP,
HDLC,
SDLC,
HNAS
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Circuit
switching
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
switching
Devices transport
packets via a
shared single point-
to-point or point-
to-multipoint link
across a carrier
internetwork.
Variable length
packets are
transmitted over
Permanent Virtual
Circuits (PVC) or
Switched Virtual
Circuits (SVC)
Shared media
across link
X.25
Frame-
Relay
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
simultaneous
use of Voice
and data
Overhead can
be considerable
ATM
Table 1 : Several options are available for WAN connectivity
2. WANs
Wide Area Networks
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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
▪ Many Leased Line Speeds
o Fractional T1, T1, and bonded T1 dominate
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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
o 56 kbps to about 40 Mbps
o Access devices, CSU/DSUs, leased access lines, POP ports, virtual circuits,
management
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▪ 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
o VPNs add security to transmission over the Internet (or any other untrusted
network)
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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:
At the end of this topic students will be able to:
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)
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Discuss Multiprotocol Label Switching
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
Definition/Overview:
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.
Key Points:
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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 exploit legal but
obscure protocol features".
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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 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
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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
o Select by length of match, then metric if tie
o Send out to next-hop router in the best-match row
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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
Reduces routing costs
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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
Socket is an IP address, a colon, and a port number
This designates a specific application (or connection) on a specific server (or client)
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16. Layer 3 Switches
Fast, inexpensive, and limited routers
Topic : Security
Topic Objective:
At the end of this topic students will be able to:
Discuss Cryptographic Systems
Discuss Firewalls
Discuss Security Management
Discuss The Threat Environment
Discuss Attributes of a secure network
Discuss Comparison with computer security
Definition/Overview:
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 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
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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
Spam, credit card theft, identity theft, adware, spyware
Human Break-Ins
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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
o Password authentication
▪ Poor password discipline is common
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▪ 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
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
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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:
At the end of this topic students will be able to:
Discuss Network Simulation
Discuss IP Subnetting
Discuss Directory Servers
Discuss Configuring Routers
Discuss Network Management Utilities
Discuss Simple Network Management Protocol (SNMP)
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Discuss Traffic Management
Definition/Overview:
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 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.
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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
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
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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:
At the end of this topic students will be able to:
Discuss Application Architectures
Discuss E-Mail
Discuss HTTP and HTML
Discuss E-Commerce
Discuss Software as a Service (SAS)
Definition/Overview:
Network applications: Network applications are simply the things networks are used for.
Key Points:
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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?
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)
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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
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
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SOAP response message brings the reply
SOAP messages are written in XML
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