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NETWORK BASICS

Network A system of interconnected computers and computerized peripherals such as printers is called computer network. This interconnection among computers facilitates information sharing among them. Computers may connect to each other by either wired or wireless media. A computer network consists of a collection of computers, printers and other equipment that is connected together so that they can communicate with each other.  


Network application
A Network application is any application running on one host and provides a communication to another application running on a different host, the application may use an existing application layer protocols such as: HTTP(e.g. the Browser and web server), SMTP(e.g. the email-client). And may be the application does not use any existing protocols and depends on the socket programming to communicate to another application. So the web application is a type of the network applications. 
There are lots of advantages from build up a network, but the th…

CABLE & CONNECTORS


CABLE & CONNECTORS
In order for the communication to take place, cables play important role. Cable is the medium through which information usually moves from one network device to another. There are several types of cable which are commonly used with LANs. The type of cable chosen for a network is related to the network's topology, protocol, and size. 






  • Unshielded Twisted Pair (UTP) Cable  
  • Shielded Twisted Pair (STP) Cable  
  • Coaxial Cable  
  • Fiber Optic Cable  

Twisted pair cabling is a type of wiring in which two conductors of a single circuit are twisted together for the purposes of canceling out electromagnetic interference (EMI) from external sources; for instance, electromagnetic radiation from unshielded twisted pair (UTP) cables, and cross-talk between neighboring pairs. In balanced pair operation, the two wires carry equal and opposite signals and the destination detects the difference between the two. This is known as differential mode transmission. Noise sources introduce signals into the wires by coupling of electric or magnetic fields and tend to couple to both wires equally. The noise thus produces a common-mode signal which is cancelled at the receiver when the difference signal is taken. 


Unshielded twisted-pair (UTP) cable is the most common networking media. Unshielded twisted-pair (UTP) consists of four pairs of thin, copper wires covered in color-coded plastic insulation that are twisted together. The wire pairs are then covered with a plastic outer jacket. UTP cables are of small diameter and it doesn’t need grounding.  Since there is no shielding for UTP cabling, it relies only on the cancellation to avoid noise.  Colors used for Twisted Pair wires are Orange, Orange-White, Blue, Blue-White, Green, Green-White, Brown and Brown-White. The connector used on a UTP cable is called as RJ-45 (Registered Jack 45) connector. Below picture shows an RJ45 jack, attached to UTP cable. Eight color-coded wires inside Twisted-Pair cable is attached to eight pins in a RJ45 jack as shown below. Each wire in the Twisted Pair cable is crimped into 8 pins in the RJ45 jack. 

One end of the Unshielded Twisted Pair cable with RJ45 jacks attached is plugged in to computer's Ethernet NIC card port and other end is plugged to the wall mount plate with female RJ45 port (receptacle), as shown below. From the wall mount RJ45 female receptacle, Unshielded Twisted Pair cable is wired to the Local Area Network (LAN) switches.  
UTP cabling has different categories. Each category of UTP cabling was designed for a specific type of communication or transfer rate. The most popular categories in use today is 5e and 6, which can reach transfer rates of over 1000 Mbps (1 Gbps). Unshielded Twisted Pair cables support a maximum distance of 100 Meters (from NIC Card to Switch Port), without signal distortion. 



Category 1
Voice Only

Category 2
Data
4 Mbps
Category 3
Data
10 Mbps
Category 4
Data
16 Mbps
Category 5
Data
100 Mbps
Category 5e
Data
1 Gbps
Category 6
Data
1/10 Gbps
Category 7
Data
1000 Mbps

 
It has been categorized into three categories based on the equipment that are being connected through these wires.  
i. Straight Through Cable  
ii. Cross Over Cable  
iii. Roll Over Cable  
Explanation:  


Straight through cables are used to connect different devices like Switch to PC. Switch to Router. Router to Switch etc. Straight-through cables are used when each end of the communication transmits and receives on different pairs.  

  
Pin 1: white/orange (pair 2) TX Data + 
Pin 2: orange (pair 2) TX Data - 
Pin 3: white/green (pair 3) RecvData+ 
Pin 4: blue (pair 1
Pin 5: white/blue (pair 1) 
Pin 6: green (pair 3) RecvData- 
Pin 7: white/brown (pair 4
Pin 8: brown (pair 4) 


The term “crossover cable” is a bit generic, but in general it refers to copper-based, twisted-pair Ethernet cables. So this would include Category-5, Category-5E and Category-6 cabling. The “normal” version is a straight-through cable, but a crossover makes the change from input to output. In a cross over the cable, the send and receive wires are "crossed over", meaning the wires are opposite on each end. This allows two PCs to talk to each other, has it connects the send of one computer to the receiver of the other. Hence, the cross over cables are used to connect similar devices like PC to PC Router to Router, Switch to Switch, Hub to Hub etc. A crossover cable directly connects two network devices of the same type to each other over Ethernet. Ethernet crossover cables are commonly used when temporarily networking two devices in situations where a network router, switch or hub is not present. 

Compared to standard Ethernet cables, the internal wiring of Ethernet crossover cables reverses the transmit and receive signals. The reversed color-coded wires can be seen through the RJ-45 connectors at each end of the cable: 
  • Standard cables have an identical sequence of colored wires on each end  
  • Crossover cables have the 1st and 3rd wires (counting from left to right) crossed, and the 2nd and 6th wires crossed  
An Ethernet crossover cable will also feature the name "crossover" stamped on its packaging and wire casing. Ethernet crossover cables should only be used for direct network connections. 

A crossover cable takes the output of one end of the cable and connects it to the input of the other. If you were using an Ethernet switch or hub, the crossing over would happen within that device. However, if you don’t want to bother with introducing that external device, with its power requirements, you can use a crossover cable. Another use for the cable would be to connect two hubs together. 


A rollover cable is a network cable that connects a computer terminal to a network router’s console port. It is also referred to as a Cisco console cable and is normally flat and light blue so as to distinguish it from other network cable types. The pin-outs on one end of the cable are reversed from the opposite end, which is how the cable derived its name. Rollover cables are also known as Yost cables or Yost Serial Device Wiring Standard connectors. Roll over cables are used to connect to the console port of the device. It gets the name rollover because the pin outs on one end are reversed from the other, as if the wire had been rolled over and you were viewing it from the other side. A rollover cable is identified by comparing each end of the cable while they are beside each other. The wire that connects the pin on the outside of the plug on the left-hand side is the same  color as the wire connecting the pin on the outside of the plug on the right-hand side. If Cisco Systems produced the rollover cable, the first pin will be white on one of the two connectors and pin number 8 will be white on the other. 

White-Orange
1
Equal
8
Brown
Orange
2
Equal
7
White Brown
White Green
3
Equal
4
Blue
Green
6
Equal
5
White-Blue
White-Blue
5
Equal
6
Green
Blue
4
Equal
3
White-Green
White-Brown
7
Equal
2
Orange
Brown
8
Equal
1
White-Orange


Fiber optic connectors are unique. Fiber cables transmit pulses of light instead of electrical signals, so the terminations must be much more precise. Instead of merely allowing pins to make metal-to-metal contact, fiber optic connectors must align microscopic glass fibers perfectly in order to allow for communication. While there are many different types of fiber connectors, they share similar design characteristics. Simplex vs. duplex: Simplex means 1 connector per end while duplex means 2 connectors per end. There are three major components of a fiber connector: the ferrule, the connector body, and the coupling mechanism.  
                        


Simplex is one direction. A good example would be your keyboard to your CPU. The CPU never needs to send characters to the keyboard but the keyboard always sends characters to the CPU. In many cases, Computers almost always send characters to printers, but printers usually never send characters to computers Simplex requires only one lane . 


Half-Duplex is like the dreaded "one lane" road you may have run into at construction sites. Only one direction will be allowed through at a time. Railroads have to deal with this scenario more often since it's cheaper to lay a single track. A dispatcher will hold a train up at one end of the single track until a train going the other direction goes through. The only example I could think of for Half-Duplex is actually a Parallel interface. Even though parallel is eight lanes, data travels through the lanes in the same direction at the same time but never in both directions at the same time. The IEEE-1284 allows printers to send messages to the computer. The printer cannot send these messages while the computer is sending characters but when the computer stops sending characters, then the printer can send messages back. It's kind of like some roads that head into downtown. In the morning, they're one way roads, allowing traffic to go into downtown. In the evening their one way roads, allowing traffic to head out of downtown. The only advantage that Half-Duplex would have is the single lane or single track is cheaper than the double lane or double track. 


Full-Duplex is like the ordinary two-lane highway. In some cases, where traffic is heavy enough, a railroad will decide to lay a double track to allow trains to pass in both directions. In communications, this is most common with networking. Our fiber optic hubs have two connectors on each port, one for each lane of a two-lane roadway. Full-Duplex fiber is two cables bundled or tied together to form the two-lane roadway. In 100Base-TX, the two lanes are housed in the same jacket. RS232 was also designed to handle Full-duplex but some of our short haul modems and converters give the user the option to go Half-Duplex or Simplex to reduce the number of conductors needed to connect between them.  


Coaxial cable, referred to as coax, contains a center conductor made of copper that’s surrounded by a plastic jacket, with a braided shield over it. A plastic such as polyvinyl chloride (PVC) or fluoroethylenepropylene (FEP, commonly known as Teflon) covers this metal shield. The Teflon-type covering is frequently referred to as a plenum-rated coating, and it’s definitely expensive but often mandated by local or municipal fire code when cable is hidden in walls and ceilings. Plenum rating applies to all types of cabling and is an approved replacement for all other compositions of cable sheathing and insulation like PVC-based assemblies.


Determine which type of cable you need. Newer networking hardware, adapters, switches and routers are connected with what's called a straight through cable. This is the type of Ethernet cable that generally ships with today's networking devices. In some cases you'll need a cross-over cable for , connecting older devices by their switches or connecting two hubs (a technique called daisy-chaining), or connecting two older laptops to each other (for file transferring, for example. Cross-over cables are rarely needed for networking hardware that's only about three or four years old, thanks to a technology known as Auto-MDIX, which can automatically sense on network ports if a straight through or cross-over connection is needed and will make the appropriate connection. However, if you want to link older equipment, check your device's documentation to see if the connection requires a cross-over cable. 


Get the right tools. You will need a spool of Cat5 (Cat5e is now the standard) or Cat6 (if your network is Gigabit Ethernet) cable. Cat5 or Cat6 cable can have plenum or PVC jackets. PVC cable is cheaper, but it also releases a toxic smoke if it catches on fire, so some building codes prohibit it. Plenum, on the other hand, does not release these toxic fumes. If you have no prohibitions preventing the use of PVC and are new to making Ethernet cables, your best bet is to start with PVC coated cable. It's cheaper and easier to work with because the wiring is not as soft as a Plenum cable's. You'll also need RJ-45 plugs or "heads" plastic modular plugs that terminate both ends of the cable, a wire cutter (or a good, sharp pair of scissors), a wire stripper and an RJ-45 crimper. The crimper is used to secure the heads at each end of the wire. You can purchase crimpers, cable and plugs from a slew of online stores or Radio Shack.  


Cut the wire to the desired length and strip about an inch of the jacket off, exposing the four twisted pairs of inner wiring. When stripping the cable, be careful not to nick the wires. This can cause problems with the connection. Do this at both ends of the cable. 


Prepare your wire for termination or "crimping". Untwist the wire. Arrange your wires based on whether you need a straight through or crossover cable. For a straight through, arrange the wires, on both ends as you are holding and looking at the cable, from left to right: white-orange, orange, white-green, blue, white-blue, green, white-brown, brown. For a cross-over cable, the wire arrangement is different at both ends. At one end, arrange as follows: white-green, green, white-orange, blue, white-blue, orange, and white-brown, brown. At the other end, arrange as you would for a straight-through cable: white-orange, orange, white-green, blue, white-blue, green, white-brown, brown.  


Terminate the cable at both ends. Straighten the wires out as much as possible; it will make them easier to place inside of the RJ-45 plug. Get the wires as close to one another as possible, holding them between your thumbs, index, and middle fingers. Trim the wires down evenly to about a quarter of an inch. Here's the tricky part that may take some practice: slip the wires inside of the RJ-45 plug with the clip-side down. Don't try to jam the wires in, they should slip inside the clip and fit snug. You don't want to see any wires between the plug and the jacket; you want just a bit of the jacket going into the plug. You also want to make sure each wire is making contact with the gold leads in the plug. Take the crimper and crimp down on the plug, pressing the crimper firmly, but not too hard.  


Take the crimper and crimp down on the plug, pressing the crimper firmly, but not too hard.  


Test the cable. Connect a networking device with an LED indicating network activity to your network using the cable you created. Ensure you are getting a strong signal.  


A registered jack (RJ) is a standardized physical network interface for connecting telecommunications or data equipment. The physical connectors that registered jacks use are mainly of the modular connector and 50-pin miniature ribbon connector types. The most common twisted-pair connector is an 8-position, 8-contact (8P8C) modular plug and jack commonly referred to as an RJ45 connector. 
  • An 8-pin/8-position plug or jack is commonly used to connect computers onto Ethernet-based local area networks (LAN). 
  • Two wiring schemes–T568A and T568B–are used to terminate the twisted-pair cable onto the connector interface. 

More commonly known as a modem port, phone connector, phone jack or phone line, the Registered Jack11 (RJ-11) is a four or six wire connection for telephone and Modem connectors in the US. The picture is an example image of what the RJ-11 phone cable and connection.  


Bay-net Neill Concelman connector, (sometimes erroneously called a British Naval Connector or Bayonet  Nut Connector, a type of connector used with coaxial cables such as the RG-58 A/U cable used with the 10Base-2 Ethernet system. The basic BNC connector is a male type mounted at each end of a cable. This connector has a center pin connected to the center cable conductor and a metal tube connected to the outer cable shield. A rotating ring outside the tube locks the cable to any female connector. BNC T-connectors (used with the 10Base-2 system) are female devices for connecting two cables to a network interface card (NIC). A BNC barrel connector allows connecting two cables together. 


An optical fiber connector terminates the end of an optical fiber, and enables quicker connection and disconnection than splicing. The connectors mechanically couple and align the cores of fibers so light can pass. Better connectors lose very little light due to reflection or misalignment of the fibers. In all, about 100 fiber optic connectors have been introduced to the market.  


A patch panel is a mounted hardware unit containing an assembly of port locations in a communications or other electronic or electrical system. In a network, a patch panel serves as a sort of static switchboard, using cables to interconnect computers within the area of a local area network (LAN) and to the outside for connection to the Internet or other wide area network (WAN). A patch panel uses a sort of jumper cable called a patch cord to create each interconnection. 
Patch panels are most commonly found in Ethernet networks, making Cat5 patch panels and Cat6 patch panels the most common, but patch panels can be used in many other applications. A patch panel, sometimes referred to as a patch bay or a jack field, is a panel designed for the management of cable connections.


1) Identify the color codes of straight through & cross over cable.  
2) Cut the CAT 5 or CAT 6 cable using crimper & plugged in to RJ-45 connector. 
3) Ping two computer after using straight through cable.  
4) Ping tow computer using cross over cable.  



a) Equal resistance  
b) The same diameter  
c) Both A & B  
d) A common axis  

  
a) Inner conductor  
b) Outer conductor  
c) Diameter of cable  
d) Insulating Material  


a) Pure Ethernet  
b) Ethernet Over SDH  
c) Ethernet over MPLS  
d) All of the mentioned  


a) Coaxial Cable  
b) Twisted pair Cable 
 c) Optical fiber  
d) None of the Above  


a) Coaxial Cable 
b) Twisted pair Cable  
c) Optical fiber  
d) None of the Above 

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