What is PoE

Power Over Ethernet

Power over Ethernet or PoE technology describes a system to transmit electrical power, along with data, to remote devices over standard twisted-pair cable in an Ethernet network. This technology is useful for powering IP telephones, wireless LAN access points, webcams, Ethernet hubs, computers, and other appliances where it would be inconvenient or infeasible to supply power separately. 

What is OFC

 Fibre Optic Cables

In 1954 a major breakthrough in technology occurred in the development of fibre optic cables. The principle of fibre optic cable was based on the total internal reflection of light. Light can be conducted along a curved glass rod due to multiple total internal reflections at the walls of the rod. Light would enter at one end of the fibre and emerge at the other end after numerous internal reflections with virtually all of its strength. 

Now a day there is two types of light cable available in market. 

1. Fiber Optic cable 

2. Liquid crystal Gel cable 

Optic cables 
These cables are made up of a bundle of optical fibres glass thread swaged at both ends. The fibre size used is usually between 10 to 25 mm in diameter. They have a very high quality of optical transmission, but are fragile. In fact, progressively as they are used, some optical fibres break. The loss of optical fibres may be seen when one end of the cable is viewed in daylight. The broken fibres are seen as black spots 

Gel cables 

These cables are made up of a sheath that is filled with a clear optical gel. (Liquid crystal). Theoretically they are capable of transmitting 30% more light than optic fibres. Swaged at both ends by quartz. Due to more light and better color temperature transmission this cable is recommended in those circumstances where documentation (movie, photography or TV) is performed. They pose three problems: 

· The quartz swaging at the ends is extremely fragile, especially when the cable is hot. The slightest shock, on a bench for example, can cause the quartz end to crack and thus cause a loss in the transmission of the light; 

· These cables transmit more heat than optical fibre cables. 

· These cables are made more rigid by a metal sheath, which makes them more difficult to maintain and to store. 

What is PING commend in networking

PING 

The ping command is used to see if a remote address is accessible. It is also used to see how long it takes to communicate over the network to the remote address. By pinging an address, you can tell if the network is down or if it is unusually slow. 

For example, to find out how long it takes for your computer to connect to www.google.com, you can type this in the command window: 
ping google.com 

And the response looks something like this
Pinging google.com [64.233.187.99] with 32 bytes of data: 

Reply from 64.233.187.99: bytes=32 time=42ms TTL=242 
Reply from 64.233.187.99: bytes=32 time=38ms TTL=242 
Reply from 64.233.187.99: bytes=32 time=36ms TTL=243 
Reply from 64.233.187.99: bytes=32 time=38ms TTL=243 

Ping statistics for 64.233.187.99: 
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), 
Approximate round trip times in milli-seconds: 
Minimum = 36ms, Maximum = 42ms, Average = 38ms

What is mean by ADSL

What is mean by ADSL 

 Asymmetric Digital Subscriber Line (ADSL) is one form of the Digital Subscriber Line technology, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voiceband modem can provide. It does this by utilizing frequencies that are not used by a voice telephone call.[1] A splitter, or DSL filter, allows a single telephone connection to be used for both ADSL service and voice calls at the same time. ADSL can generally only be distributed over short distances from the central office, typically less than 4 kilometres (2 mi),[2] but has been known to exceed 8 kilometres (5 mi) if the originally laid wire gauge allows for farther distribution. In 2005, the ability to transmit copper ADSL/DSL services over a fiber optic cable became possible by utilizing the RLH ADSL/DSL fiber optic link, providing distances from one point to the opposite end of the system of more than 30 miles.


What is mean by DSL

Digital subscriber line (DSL)
technology that exploits unused frequencies on copper telephone lines to transmit traffic typically at multi-megabit speeds. DSL can allow voice and high-speed data to be sent simultaneously over the same line. Because the service is 'always available,' end-users don't need to dial in or wait for call set-up. With DSL you are wired for speed.

Difference Between 32 bit and 64 bit processor.

32 bit and 64 bit Processor.

A 32 bit processor handles data in 32 bit chunks. A 64 bit processor handles data in 64 bit chunks. As a result, a 64 bit processor can handle twice as much data in one cycle as a 32 bit processor. 

Cores: Cores are the number of processors. A single core system has one CPU which has one core. 

A dual core system has one CPU with 2 cores in it. 

So a 64 bit processor with 2 cores can handle 4 times as much data in one cycle as a single core 32 bit processor. 

It used to be that in order to have multiple cores you had to have multiple physical CPUs. Most CPUs anymore actually have multiple cores on one physical CPU . This allowed for increased performance without having to increase the speed of the processors as the technology was running into physical limits of frequency (ghz) and processors could not be made to go much faster with current technology. 

You can use a 32 bit operating system on a 64 bit processor and many machines do. The primary reason to use a 64 bit operating system at this point is that a 32 bit operating system can only address about 3.5 gigs of RAM and a 64bit operating system can address TBs of RAM, far more than is currently available in personal computers.

What is TCP/IP in networking

TCP/IP(Transport Control Protocol / Internet Protocol)


TCP/IP stands for Transport Control Protocol / Internet Protocol suite. TCP/IP was created in 1983 to replace NCP, because TCP/IP can successfully switch packets from all shapes and sizes and varieties of networks. Therfore TCP/IP has become the backbone of the Internet and its composite LANs and WANs due to it's ability to switch packets from computer systems on any network to another network, regardless of network peculiarities, operating system differences and other packet differences. The TCP/IP protocol suite refers to several separate protocols that computers use to transfer data across the Internet, below are four of the most commonly used TCP/IP protocols, 
Components of TCP/IP 

IP - The Internet Protocol is a network layer protocol that moves data between host computers. 
TCP - The Transport Control Protocol is a transport layer protocol that moves multiple packet data between applications. 
UDP - The User Datagram Protocol is a transport layer protocol like TCP but is less complex and reliable than TCP. 
ICMP - The Internet Control Message Protocol carries network error messages and other network software requirements. 

Computer networks use a standard connection model which is called ISO/OSI. The ISO/OSI model has seven layer which the TCP/IP protocol suite has implemented, below is a list of the ISO/OSI layers and the TCP/IP counterpart layers, 
ISO/OSI Layer

Application 
Presentation 
Session 
Transport 
Network 
Data-Link 
Physical


Function 

file transfers, email, file servers,data formatting, encryption 
negotiation and establishment of a connection end to end data provision routing of packets transfer of addressable units of frames and error checking transmission of binary data over a communications network TCP/IP Protocols TFTP, BOOTP, SNMP, FTP, SMTP, MIME,TCP, UDP,IP, ICMP, RIP, OSPF, BGP, IGMP 
SLIP, CSLIP, PPP, ARP, RASP, MTU,ISO, 2110, IEEE, 802, IEEE 802.2 

Transport Communication Protocol / Internet Protocol 
TCP/IP is a "communications protocol" 

An agreement to speak a language 
The definition of the language 

Sample TCP/IP address 

200.210.220.5 

Classes of IP Address

 

CACHE MEMORY

Cache memory is random access memory (RAM).Which is a computer microprocessor can access more quickly than it can access regular RAM. As the microprocessor processes data, it looks first in the cache memory and if it finds the data there (from a previous reading of data), it does not have to do the more time-consuming reading of data from larger memory. 
Cache memory is sometimes described in levels of closeness and accessibility to the microprocessor. An L1 cache is on the same chip as the microprocessor. (For example, the PowerPC 601 processor has a 32 kilobyte level-1 cache built into its chip.) L2 is usually a separate static RAM (SRAM) chip. The main RAM is usually a dynamic RAM (DRAM) chip. 

In addition to cache memory, one can think of RAM itself as a cache of memory for hard disk storage since all of RAM's contents come from the hard disk initially when you turn your computer on and load the operating system (you are loading it into RAM) and later as you start new applications and access new data. RAM can also contain a special area called a disk cache that contains the data most recently read in from the hard disk

TYPES OF CACHE

1.Memory cache
2.Disk cache

The two main types of cache are: memory cache and disk cache. Memory cache is a portion on memory of high-speed static RAM (SRAM) and is effective because most programs access the same data or instructions over and over. By keeping as much of this information as possible in SRAM, the computer avoids accessing the slower DRAM.
Like memory caching, disk caching is used to access commonly accessed data. However, instead of using high-speed SRAM, a disk cache uses conventional main memory. The most recently accessed data from the disk is stored in a memory buffer. When a program needs to access data from the disk, it first checks the disk cache to see if the data is there. 

Another type of cache is known as "Internet browser cache" also known as "Temporary Internet Files". Internet cache is used to help improve how fast data is opened while browsing the Internet. In most cases, each time a web page is opened, it is sent to your browser's temporary cache on your hard disk drive. If that page is accessed again and has not been modified, the browser will open the page from your cache instead of downloading the page again. This saves users a lot of time, especially if that user is using a modem, and can also help save the web page owner on bandwidth. 

HARD DISK AND MEMORY

HARD DISK AND MEMORY - HOW IT WORKS

 

Memory is nothing but a Basic electronic part and stores some digital information in it. In Hard disk, the info are stored as magnetic field. Memory is simply what you are focusing on at the moment. It isn't as large as the hard drive, which can save much much more, but it is much faster which is why it is practical for only what you are currently using. You can almost think of them as short term and long term memory. Long term (hard drive) is the stuff that has been stored - archived if you will - for a time in the future, where as short term (memory) is for what you are doing right now. You can recall the information from long term and place it in your short term to use, but when you are finished, you push it right back to long term.

On a Hard Disk Drive, there is an index where the computer stores the location of saved files on the drive. When you try to access information, your processor sends a command where the HDD looks up the location of the information and then skips to that point on the disk. It then reads that information which is stored in the form of positive and negative charges, representing off and on or 0's and 1's. This code is called binary and is the language of computers.

The information it retrieves is then passed on to the memory (RAM) which is the information you are currently using. RAM is much faster than your HDD and thus is used for current tasks. While you are using the item it is stored in the RAM. When you save save something, it runs back to the HDD where it writes it on the disk and then registers where it was saved in the index. 

TYPES OF HARD DISK                                                   

Hard disks are generally accessed over one of a number of bus types, including 

ATA (IDE, EIDE) 

Serial ATA (SATA) 

SCSI

SAS

IEEE 1394

USB, and

and Fibre Channel.

  

 

NIC CARD- Network card

NIC CARD ( NETWORK INTERFACE CARD)















1. A Network Interface Card is what communicates with the computer uses to communicate over a network. Sometimes a NIC (said "nick") is integrated into your computer's motherboard or as a slot card. Most computers will come with a NIC. If not, they are easy to find at Staples or OfficeMax for purchase. 
2. 10/100 Mbps Ethernet Port are the speeds that your NIC is able to work at. A NIC with this configuration can work at 10 Mbps or 100 Mbps. 
3. An RJ-45 denotes the type of connector that is compatible with the NIC. An RJ-45 connector looks like a big phone connector. Go look at your phone connector. That is what is called an RJ-11 connector. Now look at the socket the phone cord plugs into either the phone or the wall. An RJ-45 connector is twice as big. So if the connector on the back of your NIC looks like a big phone plug could fit into it, that's what you need.