Networking: 2010

UTP implementation

EIA/TIA specifies an RJ-45 conector for UTP cble. The letters RJ stand for registered jack and the number 45 refers to a specific wiring sequence. The RJ-45 transparant and connector show eight colored wires. Four of the wires, T1 through T4, carry the voltage and are called tip. The other four wires, R1 through R4 are grounded and are called rinf. Tip and ring are terms that originated in the early day of the telephone. Today, these terms refer to the positive and the negative wirein a pair. The wires in the first pair in the cable or a connector aredesignated as T1 and R1. The second pair is T2 and R2, the third is T3 and T3, and the fourth is T4 and T4.

The RJ-45 connector is the male component, which is crimped on the end of the cable. When a male connector is viewedfrom the front, the pin location are numbered on the left to 1 on the right as seen in figure.

The jack is the female component in a network device, wall outlet, or patch panel as seen in figure follow :

Figure follow show the punch-down connection at the back of the jack where the Ethernet UTP cable connects.

For electricity to run between the connector and the jack, the order of the wires Must follow T 568A or T 568B color code found in the EIA/TIA-568-B.1 stadard..

To determine the EIA/TIA category of cable that should be used to connect a device, refer to the documentation for that device or look for a label on the device near the jack. If there are no labels or documentation available, use category 5E or greater as higher categories can be used in place of lower ones. Then determine whether to use straight-through cable or a crossover cable.

Next to article oneday again….

Networking Terminology

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Businesses needed a solution that would successfully address the following three problem :

How to avoid duplication of equipment anf resources
How to communicate efficiently
How to set upand manage a network.

One early solution was creation of local-area network (LAN) standard. LAN standard provided an open set of guidelines that companies used to create network hardware and software. As a result, the equipment from different companies besame compatible. Thie allowed for stability in LAN implementations.

In a LAN system, each departement of the company is a kind of electronic island. As the use of computer in bussinesses grew, LANs become insufficient.

A new tecnology was necessary to share information efficiently and quickly within a company and between businesses. The solution was the creation of metropolitan-area networks (MANs) and Wide-area Networks (WANs).

Figure summarizes the relative size of LANs and WANs.

TCP/IP Models

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The US Departement of Defense (DoD) created the TCP/IP reference model, because it wanted to design a network that could service any conditions, including a nuclear war. In a world connected bydifferent type of communication media such as copper wire, microwapes, optical fibers and satellite links, the DoD wanted transmission of packet every time and under any condition. This very difficult design problem brought about the creation of the TCP/IP model.

Unlike the proprietary networking technilogies mentioned earlier, TCP/IP was developed as an open standard. This meant that anyone was free to use TCP/IP. This helped speed up the development of TCP/IP as a standard.

The TCP/IP model has the following four layers : Aplications layer, Transport layer, internet layer, and network access layer.

Although some of the layers in the TCP/IP model have the same name as layer in the OSI model, the layers of the two models do not correspond exactly. Most notably, the application layer has different functions in each model.The designers of TCp/IP flet that the application layer should include the OSI session and presentation layer details. They created an application layer that handles issues of presentation, encoding, and dialog control.

The transport layer deals with the quality of service issues of reliability, flow control, and error correction. One of its protocols, the transmission control protocol (TCP), provides excellent and flexible way to create reliable, well-flowing, low-error network communications.

TCP is a connection-oriented protocol. It maintains a dialogue between source and destination while packaging application layer information into units called segment. Connection-oriented does notmean that a circuit exists between the communicatingcomputers. It does mean that eyer 4 segments travel back and foth between two host to acknowledge the connection exists logically for some period.

The purpose of the internet layer is to divide TCP segment into packets and send them from any network. The packets arrive at the destination network independent of the path they took to get there. The specific protocol that governs this layer is called the internet protocol (IP). Best path determination and packet switching occur at this layer.

The relationship between IP and TCP is an important one. IP can be thought to point the way for the packets, while TCP provides a reliable transport.

The name of the network access layer is very broad and somewhat confusing. It is also known as the host-to-network layer. This layer is concerned with all of the components, both physical and logical, that are required to make physiical link. It includes the networking technology details, including all the details in the OSI physical and data link layer.

Follow the illustrates some of the common protocols specified by the TCP/IP reference model layer. Some of the most commonly used application layer protocols include the follow :

File transfer Protocol (FTP)
Hypertext transfer protocol (HTTP)• Domain Name System (DNS)
Trivial File Transfer Protocol (TFTP)

The common transfort layer protocols include :

Transport Control Protocol (TCP)
User Datagram Protocol (UDP)

The primary protocol of the internet layer is :

Internet Protocol (IP)

The network access layer lefers to any particular technology used on a specific network.

A comparison of the OSI model and the TCP/IP model will point out some similarities and differences.
OSI Model TCP/IP Model

Smilarities include :

Both have layers
Both have application layers, though they include very different service
Both have comparable transport nd network layers
Both models need to be know by networking professionals.
Both assume packets are switched. This mean individual packets may take different paths to rech the same destination. This is contrasted with circuit-switched networks where all the packets take the same path.

Differences include :

TCP/IP combines the presentation and session layer issues into it s applications layer.
TCP/IP combines the OSI data link and physical layers into the network access layer.• TCP/IP appears simpler because it has fewer layers.
TCP/IP protocol are the standards around which th internet developed, so the TCP/IP model gains credibility just because of its protocols. In contrast, networks are not usually built on the OSI protocol, even though the Osi model is used as a guide.

Although TCP/IP protocols are the standards around which the internet has grown, this curriculum will used the OSI model for the following reasons :

It is geberic, protocol-independent standard.
It has more detils, wich make it more helpful for teaching and learning.
It has more detils, wich can be helpful when troubleshooting.

Networking profesionals differ in their opinions on which model to use. Due to the nature of the industry it is necessary to become familiar with both. Both the OSI and TCP/IP models will be referred to throughout the curiculum. The focus will be on yhe followoing :

TCP as an TCP layer 4 protocol
IP as an OSI layer 3 protocol
Ethernet as a layer 2 and layer 1technology

Remember that there is a difference between a model and an actual protocol the is used in networking. The OSI model will be used to describe TCP/IP protocols.

Networking OSI models

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The erly development of nerworks was disorganized in may ways. The early 1980s saw tremendous increases in the number and size of networks. As compaies realized the advantages of using networking technology, networks were added or expanded almost as rapidly as new network technologies were introduced.

By the mid-1980s, these companies began to experience problems from the rapid expansion. Just as people who do not speak the same language have difficulty communicating with eachother, it was difficult for networks that used different spesifications and implementations to exchange information. The same problem occurred with the companies that developed private or proprietary networking technologies. Propietary means that one or a small group of companies controls all usage of the technology. Networking technologies strictly following proprietary rules could not comunicate with tecnologies that followed different propietary rules.

To address the problem of network incompatibility, the international organization for standardization ( ISO ) researched networking models like Digital Equipment Corporation net ( DECnet ), system Network Architecture ( SNA ), and TCP/IP in order to find a generally applicable set of rules for all networks. Using this reserch, the ISO created a network model that helps vendors create networks that are compatible with other networks.

The open system interconnection ( OSI ) reference model released in 1984 was the descriptive network model that the ISO created. It provided vendors with a set of standards thet ensured greater compatibility and interoperability among various network technologies produced by companies around the world.

The OSI model has become the primary for network communications. Although there are other models in existence, most network vendors relate their products to the Osi reference model. This is specially true when they want to educate users on the use of their products. It is cinsidered the best tool available for teaching people about sending and receiving data on a network.

Networking Topology

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Network 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 hoe the hosts access the media to send data. The physical topologies that are commonly used are as follows :

A bus topology uses a single backbome cable that is terminated at both ends. All the hosts connect directly to this backbone.
A ring topology connects one host to the next and the last host to the first. This creates a physical ring of cable.
A star topology connects all cable to a central point.
An extended star topology links individual star together by connecting the hubs or switches.
A hierarchical topology is similar to an extended star. How ever, instead of linking the hubs or switch together, the system is linked to a computer that control the traffic on the topology.
A mesh topology is implemented to provide as much protection as possible from interruption of service. For example, a nuclear power plant might use a mesh topology in the networked control systems. As seen in the graphic, 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.

The logical topology of a network determines how the hosts communicate across the medium. The two most common types of logical topologies are broadcat and token passing.

The use of a broadcast topology indicates that each host sends its data to all other hosts on the network medium. There is no order that the stations must follow to use the network. It is first come, first serve. Ethernet works this wy as will be explained later in the course.

The second topology is token passing. In this type of topology, an electronic token is passed sequentially to each host. When a host receives the tokn, 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 example of networks that use token passing are token ring and fiber distributed data interface ( FDDI ). A variation of token ring anf FDDI is Arcnet. Arcnet is token passing on a bus topology.

Testing connectivity with ping

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Ping is a basic program that verifies a particular IP address exists and accept requests. The computer acronym ping stands for packet internet or inter-Network Groper. The name was contrived to match the submariners’ term for the sound of a returned sonar pulse from an underwater object.

The ping command works by sending special Internet protocol ( IP ) packets, called internet control massage protocol ( ICMP ) Echo Request datagrams, to a specified destination. Each packet sent is a request for a reply. The output response for a ping contains the success ratio and round-trip time to the destination.

The ping command is used to test the NIC transmit and receive function, The TCP/IP configuration, and network connectivity. The following types of ping commands can be issued :

Ping 127.0.0.1 – This is a unique ping and is called an internal loopback test. It is used to verify the TCP/IP network configuration.
Ping IP address of host computer – A ping to a host PC verifies the TCP/IP address configuration for the local host and connectivityto the host.
Ping default-gateway IP address- A ping to the default gateway indicates if the router that connects local network to other networks can be reched.
Ping remote destination IP address- A ping to remote destination verifies connectivity to a remote host.

what is the network??

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To anderstand the role that computers play in a networking system, consider the internet. Internet connections are essential for businesses and education. Careful planning is required to build a network that will connect tothe internet. Even for an individual personal computer (PC ) to connect to the internet, some planning and decisions are required. Computer resources must be considered foe internet conection. This includes the type of device that connects the PC to the internet, such as a network interface card ( NIC ) or modem. Protocols, or rules, must be configured before a computer can connect to the internet. Proper selection of a web browser is also imortant.

Requirements for internet connection.

The internet is the largest data network on eart. The internet consists of many large and small networks that are interconnected. Individual computers are the sources and destinations of information through the internet. Connection to the internet can be broken down into the physical connection, the logical connection, and applications.

A physical connection is made by conneting an adapter card, sach as a modem or a NIC, from a PC to a network. The physical connection is used to transfer signals between PCs wihin the local area network ( LAN ) and to remote devices on the internet.
Many networking divices are spescal purpose computers, with many of the same components as general purpose PCs.

A computer must work properly before it can be used to access information such as Web-based content. This will require you to troubleshoot basic hardware and software problems. Therfore, you must be familiar with the follow small, discreet PC component. You sould also be pamiliar with the following PC subsystems :

1. Translator
2. Integrated circuit
3. Resistor
4. Capacitor
5. Connector
6. Light emitting diode ( LED )
7. Printed circuit board ( PCB )
8. CD-ROM drive
9. Central processing unit ( CPU )
10. Hard disk drive
11. Microprocessor
12. Motherboard
13. Bus
14. Random-access memory ( RAM )
15. Read-only Memory ( ROM )
16. Expansion slot
17. Power supply
18. Backplane
19. Network interface card ( NIC )
20. Video card
21. Audio Card
22. Parallel port
23. Serial port
24. Mouse port
25. USB port
26. Firewire
27. Power card

Think of the internal components of a PC as a network of devices that are all attached to the system bus.