d wa2el

Data NetworksSharing data through the use of floppy disks is not an efficient or cost-effective manner in which to operate businesses.

Sneakernet created multiple copies of the data.

Businesses needed a solution that would successfully address the following three problems: • How to avoid duplication of equipment and resources • How to communicate efficiently • How to set up and manage a network

Businesses realized that networking technology could increase productivity while saving money.

LANs, MANs, & WANsOne early solution was the creation of local-area network (LAN) standards which provided an open set of guidelines for creating network hardware and software, making equipment from different companies compatible.

What was needed was a way for information to move efficiently and quickly, not only within a company, but also from one business to another.

The solution was the creation of metropolitan-area networks (MANs) and wide-area networks (WANs).

WAN Network StructureWAN is a network of LANs

It consists of:• network edge:

applications and hosts connected by LANs

• network core: Switching nodes (e.g. routers, ATM

switches)network of networks

• access networks, physical media: Communication links to connect SN

LANs and WANs

Connection of LANs over a large geographical distance

The Internet is the biggest commercial WAN

Sprint US backbone network

Seattle

Atlanta

Chicago

Roachdale

Stockton

San Jose

Anaheim

Fort Worth

Orlando

Kansas City

CheyenneNew York

PennsaukenRelay

Wash. DC

Tacoma

DS3 (45 Mbps)OC3 (155 Mbps)OC12 (622 Mbps)OC48 (2.4 Gbps)

…

to/from customers

peering

to/from backbone

….

………POP: point-of-presence

Examples of Data Networks

Network History1940s large, unreliable electromechanical computers 1947 the invention of a semiconductor transistor

smaller, more reliable computers. 1950s mainframe computers; run by punched card programslate 1960-70s smaller minicomputers1977 Apple Computer Company introduced the microcomputer1981 IBM introduced its first personal computer. 1984 The user-friendly Macmid-1980s Users with started to share files using modems

This was “dial-up” or a “point-to-point” connection.mid-1980s Users would connect to the bulletin boards, leave and

pick up messages, as well as upload and download files.1960s-1990. Department of Defense (DoD) developed large, reliable,

WANs for military and scientific reasons. Instead of onlybeing able to communicate with one other computer manycomputers could be reached using the same connection. The DoDs WAN eventually became the Internet.

Networking Components

•Devices•Topology•Messages•Protocol•Media

1- Networking DevicesEquipment that connects directly to a network segment is referred to as a device.

These devices are broken up into two classifications. • end-user devices• network devices

End-user devices include computers, printers, scanners, and other devices that provide services directly to the user.

Network devices include all the devices that connect the end-user devices together to allow them to communicate.

Each individual NIC carries a unique code, called a Media Access Control (MAC) address.

Networking AddressesThe addresses are divided into:Physical addresses: is the machine address called Media Access Control (MAC) address. It is a 6 octet hexadecimal number. (ex: 2A:3E:14:23:1C:87)

Network addresses: is the LAN address called internet protocol (IP) address. It is a 4 dotted decimal number. (ex: 121.13.0.0). Application addresses: is the application address called port address. It is a decimal number.

Well Known Ports (0 to 1023): (ex: HTTP server port 80) Registered Ports (1024 to 49151): these are usually assigned to applications that a user has chosen to install Dynamic or Private Ports (49152 to 65535): these are

assigned dynamically to client applications

Networking Device Icons

RepeaterA repeater is a network device used to regenerate a signal. Repeaters regenerate analog or digital signals distorted by transmission loss due to attenuation. A repeater does not perform intelligent routing like a bridge or router.

HubHubs concentrate connections. In other words, they take a group of hosts and allow the network to see them as a single unit.

This is done passively, without any other effect on the data transmission.

Active hubs not only concentrate hosts, but they also regenerate signals.

BridgeBridges convert network transmission data formats as well as perform basic data transmission management. Bridges, as the name implies, provide connections between LANs. Not only do bridges connect LANs, but they also perform a check on the data to determine whether it should cross the bridge or not. This makes each part of the network more efficient.

Workgroup SwitchWorkgroup switches add more intelligence to data transfer management.

Not only can they determine whether data should remain on a LAN or not, but they can transfer the data only to the connection that needs that data.

Another difference between a bridge and switch is that a switch does not convert data transmission formats.

RouterRouters have all the capabilities of the previous devices. Routers can regenerate signals, concentrate multiple connections, convert data transmission formats, and manage data transfers. They can also connect to a WAN, which allows them to connect LANs that are separated by great distances. None of the other devices can provide this type of connection.

“The Cloud”The cloud is used in diagrams to represent where the connection to the internet is.

It also represents all of the devices on the internet.

2-Network TopologiesNetwork topology defines the structure of the network.

One part of the topology definition is the physical topology, which is the actual layout of the wire or media.

The other part is the logical topology, which defines how the media is accessed by the hosts for sending data.

Physical Topologies

Bus TopologyA bus topology uses a single backbone cable that is terminated at both ends.

All the hosts connect directly to this backbone.

Ring TopologyA ring topology connects one host to the next and the last host to the first.

This creates a physical ring of cable.

Star TopologyA star topology connects all cables to a central point of concentration.

Extended Star TopologyAn extended star topology links individual stars together by connecting the hubs and/or switches.

This topology can extend the scope and coverage of the network.

Hierarchical TopologyA hierarchical topology is similar to an extended star.

However, instead of linking the hubs and/or switches together, the system is linked to a computer that controls the traffic on the topology.

Mesh TopologyA mesh topology is implemented to provide as much protection as possible from interruption of service. Each host has its own connections to all other hosts. Although the Internet has multiple paths to any one location, it does not adopt the full mesh topology.

Logical TopologiesThe logical topology of a network is how the hosts communicate across the medium.

The most common types of logical topologies are:Broadcast UnicastMulticast Token passing.

Unicast

Multicast

Broadcast

Token Passing TopologyToken passing controls network access by passing an electronic token sequentially to each host.

When a host receives the token, that host can send data on the network. If the host has no data to send, it passes the token to the next host and the process repeats itself.

Two examples of networks that use token passing are Token Ring and Fiber Distributed Data Interface (FDDI).

3-Network ProtocolsProtocol suites are collections of protocols that enable network communication from one host through the network to another host.

A protocol is a formal description of a set of rules and conventions that govern a particular aspect of how devices on a network communicate.

4-MessagesData on the internet is transferred in ASCII code

4-MessagesA messsage “How are you” is transferred as?

4-Message Format

Data.....

AdAss

...

..L

Payload

5-MediaLAN media:

•Wired: copper cables (twisted pair, coaxial,…), optical cables.

•Wireless: wireless LAN (WLAN)

WAN media:•Wired: MPLS, Frame relay,….•Wireless: 3G, WiMax

Bandwidth

Measuring Bandwidth

LAN Media

WAN Media

ThroughputThroughput refers to actual measured bandwidth, at a specific time of day, using specific Internet routes, and while a specific set of data is transmitted on the network. Unfortunately throughput is often far less than the maximum possible digital bandwidth of the medium that is being used. The following are some of the factors that determine throughput:

• Internetworking devices • Type of data being transferred • Network topology • Number of users on the network • User computer • Server computer • Power conditions

Transfer Time Calculation

Why do we need the OSI Model?

To address the problem of networks increasing in size and in number, the International Organization for Standardization (ISO) researched many network schemes and recognized that there was a need to create a network model that would help network builders implement networks that could communicate and work together and therefore, released the OSI reference model in 1984.

Don’t Get Confused.

ISO - International Organization for Standardization

OSI - Open System Interconnection

IOS - Internetwork Operating System

The ISO created the OSI to make the IOS more efficient. The “ISO” acronym is correct as shown.

To avoid confusion, some people say “International Standard Organization.”

The OSI Reference Model

7 Application6 Presentation5 Session4 Transport3 Network2 Data Link1 Physical

The OSI Model will be used throughout your entire networking career!

Memorize it!

Layer 7 - The Application Layer


This layer deal with networking applications.

Examples: Email Web browsers

PDU – Protocol Data Unit (Application Data)

Layer 6 - The Presentation Layer


This layer is responsible for presenting the data in the required format which may include: Encryption Compression

PDU - Formatted Data

• Text• Data

ASCIIEBCDICEncrypted

• Sound• Video

MIDIMPEGQuickTime

• Graphics• Visual Images

TIFFJPEGGIF

Presentation Layer

Layer 5 - The Session Layer


This layer establishes, manages, and terminates sessions between two communicating hosts.

Example: Client Software

( Used for logging in)

PDU - Formatted Data

Vocabulary of two processes

Service Request

Service Reply

Session Layer

Layer 4 - The Transport Layer


This layer breaks up the data from the sending host and then reassembles it in the receiver.

It also is used to insure reliable data transport across the network.

PDU - Segments

Layer 3 - The Network Layer


Sometimes referred to as the “Cisco Layer”.

Makes “Best Path Determination” decisions based on logical addresses (usually IP addresses).

PDU - Packets

Network Layer

Path selection based on network addresses (e.g. IP addresses)

Multiplexing of network connectionsSegmentation and reassembly (block formation)

Error detection and possibly correction

Possibly flow control at network level

3

Provision of the “best“ route

Network Layer

Layer 2 - The Data Link Layer


This layer provides reliable transit of data across a physical link.

Makes decisions based on physical addresses (usually MAC addresses).

PDU - Frames

Layer 1 - The Physical Layer


This is the physical media through which the data, represented as electronic signals, is sent from the source host to the destination host.

Examples: CAT5 (what we have) Coaxial (like cable TV) Fiber optic

PDU - Bits

Host Layers


These layers only exist in the source and destination host computers.

Media Layers


These layers manage the information out in the LAN or WAN between the source and destination hosts.

Why Another Model?Although the OSI reference model is universally recognized, the historical and technical open standard of the Internet is Transmission Control Protocol / Internet Protocol (TCP/IP).

The TCP/IP reference model and the TCP/IP protocol stack make data communication possible between any two computers, anywhere in the world, at nearly the speed of light.

The U.S. Department of Defense (DoD) created the TCP/IP reference model because it wanted a network that could survive any conditions, even a nuclear war.

2 ModelsSide-By-Side

Application

TransportInternet

Network Access


TCP UDP

ARP IP ICMP

IEEE802.2

IEEE802.5

IEEE802.4

IEEE802.3 FDDI ATM Frame

Relay X.25 PPP

FTP

Teln

et

SMTP

DN

S

BO

OTP

/D

HC

P

TFTP

WW

W

SNM

P

POP3

IMA

P

RLO

GIN

LDA

P

RTP

Application

Presentation

Session

Transport

Network

Data LinkPhysical

77

66

55

44

33

22

11

Computer 1Computer 1Application

Presentation

Session

Transport

Network

Data Link

Physical

77

66

55

44

33

22

11

Computer 2Computer 2

Horizontal Communication

Ver

tical

C

omm

unic

atio

n

Concept of Encapsulation

Send Receive

Layer n+1

Layer n

nHeader n Data

n + 1Header n + 1 Data

nHeader n Data

n + 1Header n + 1 Data

Encapsulation through TCP/IP layers

Sending and Receiving Data in the Layer Model

Send Receive

1 2 3 4 5-7 Data 2

2 3 4 5-7 Data 2

3 4 5-7 Data

4 5-7 Data

5-7 Data

Data

1 2 3 4 5-7 Data 2

2 3 4 5-7 Data 2

3 4 5-7 Data

4 5-7 Data

5-7 Data

Data

Horizontal / Virtual Communication in the Layer Model

Send Receive

1 2 3 4 5-7 Data 2

2 3 4 5-7 Data 2

3 4 5-7 Data

1 2 3 4 5-7 Data 2

2 3 4 5-7 Daten 2

3 4 5-7 Data

Virtual Communication:

Layer 3 can communicate with Layer 3. The exchange of

information takes place in the respective header.

SANsA SAN is a dedicated, high-performance network used to move data between servers and storage resources.

Because it is a separate, dedicated network, it avoids any traffic conflict between clients and servers.

This method uses a separate network infrastructure that relieves any problems associated with existing network connectivity.

Virtual Private NetworkA VPN is a private network that is constructed within a public network infrastructure such as the global Internet. Using VPN, a telecommuter can access the network of the company headquarters through the Internet by building a secure tunnel between the telecommuter’s PC and a VPN router in the headquarters.

3 Types of VPNsAccess VPNs – Access VPNs provide remote access to a

mobile worker and small office/home office (SOHO) to the headquarters of the Intranet or Extranet over a shared infrastructure.

Intranet VPNs – Intranet VPNs link regional and remote offices to the headquarters of the internal network over a shared infrastructure. Intranet VPNs differ from Extranet VPNs in that they allow access only to the employees of the enterprise.

Extranet VPNs – Extranet VPNs link business partners to the headquarters of the network over a shared infrastructure using dedicated connections.

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