Network equipment and the way of Internet

Modem

Computer hardware, the digital signal can be transmitted through the modem to analog signal, through various types of broadband transmission, in the receiving end with another modem translated into the computer can read digital signals. The analog and digital signals here are electrical signals!

"The way of Surfing "
Narrow-band dial-up: Dial through 16900, the Internet when you can not call, when the telephone can not be online. (obsolete)
Broadband Internet access:
<1>ADSL Internet: Speed limit! ADSL is used for multiplexing of telephone lines (pair of twisted pair) although also through the telephone line to surf the internet, but the Internet calls do not affect each other.
<2>lan Internet (cell broadband): Unlimited speed! Fiber to the community, network cable to the household, the community LAN shared fiber-optic internet. The bandwidth is high but is greatly affected by other users.
<3> powerline: Improved power cord, plug-in power to the Internet.
<4> Cable TV Cable Internet: in development.
etc...
    
"Digital subscriber line DSL"
the DSL (Digital subscriber line) refers to the technology of digitized subscriber lines.
XDSL: All kinds of digital subscriber line, X can be a/h/s/c/i/v/ra and so on, representing different kinds of digital subscriber line technology. ADSL is one of the most common, the translation of non-symmetric digital subscriber line, that is, the uplink/downlink rate is different, downlink (switching to the user) faster, the uplink is slow, ADSL is commonly known as super-line pass.
the difference between different DSL technologies is different in transmission rate and distance, which can be broadly divided into two categories: symmetric and asymmetric.
symmetric DSL:HDSL, SDSL, MVL and other users replace the traditional t1/e1
most widely used: HDSL: Two pairs of twisted pair, more for switch, distance learning, video conferencing and so on.
asymmetric DSL:ADSL, RADSL, and VDSL are used for Internet or VOD (video-on-demand) systems.

"Differences in bandwidth allocation between switches and hubs"
Switches: Shared bandwidth, equal processing (each port is a separate conflict domain).
Hub: Shared bandwidth, first comes first (all ports of the hub belong to a conflict domain).

Assuming the current broadband 10M, if no other user access, switch and hub bandwidth can reach 10M, if there are other users access, the hub will be processed in order to send and receive data, may take 10 minutes, may occupy 9M bandwidth, this time other users can only wait for him to finish, There will be network congestion, and everyone in the switch is equal, everyone is 10M network, and the switch will not be processed according to the time, but the respective processing conflict, but this time we split the bandwidth, if there are 4 people, is the average 2.5M per person. will not produce 4 people at the same time online and everyone in a moment of bandwidth is 10M situation! The benefit of the switch is not to call bandwidth idle, which includes time idle and bandwidth idle.

Network equipment and the way of Internet