Dial-up Internet

Telephone dialing, the Internet data is modulated in the voice band, the local side is the access server. That is, the equivalent of a computer to dial a phone to the access server, if the network has been connected, the phone can not hang up. Due to the limitation of voice bandwidth, this way the maximum rate of Internet access is about 56kbps, (this number is how to come, interested in the Shannon theorem can be studied). In fact, there is a benefit of the network access location, as long as the phone can get through on the line, you can call the U.S. telecommunications service provider's number to access foreign networks, of course, the premise is to pay international long-distance charges.

ASDL is a DSL (Digital Subscribe line) technology, there are VSDL/HDSL and so on. The local access device is located at the nearest telephone office of the user, only using the "last kilometer" phone line closest to the user. Using Frequency Division multiplexing technology the frequency band and voice frequency bands used in the Internet are different, so you can use the Internet while calling. But the bandwidth of the Internet is closely related to the length of the telephone line and the line quality of the user access network.

Dial-up Internet needs to use a modem, called modulation and demodulation of a network device, it can translate the computer digital signal can be transmitted along the ordinary telephone line pulse signal, and these pulse signal can be received by another modem on the other end of the line, and translated into computer-readable language. Modulation is the conversion of a digital signal into an analog signal transmitted over a telephone line, and a demodulation that converts an analog signal into a digital signal. Collectively referred to as modems. "Dial-up Internet" is a form of operator's use of account authentication for its Internet users. The commonly used PPPoE is a dial-up Internet format. There is no difference between the two, to say the difference can only say one is the network hardware is software. But the two coexist, like using a telephone line to connect to the modem, and dial-up Internet is the way to use the connection network on the user terminal.

For most dial-up users, due to the time and space of the Internet, it is very undesirable to assign a fixed IP address (static IP) to each user, which will result in a great waste of IP address resources. As a result, these users will usually automatically get a dynamic IP address after each dial-up of the ISP's host, which is certainly not arbitrary, but rather an address in the legal interval of the network ID and host ID requested by the ISP. The IP address of the dial-up user at any two connections is likely to be different, but the IP address does not change during each connection time.

ADSL virtual dialing is in the ADSL Digital line dial, different from the analog telephone line with the modem dial, and the use of special protocol PPP over Ethernet (PPPoE), after dialing directly by the authentication server to verify, the user needs to enter the user name and password, After the test is passed, a high-speed user number is established and the corresponding dynamic IP is assigned. Virtual dial-up users need to pass a user account and password to verify the identity, the user account and 163 account number, the user is the application of their own choice, and this account is limited, can only be used for ADSL virtual dialing, can not be used for ordinary modem dialing. ADSL Virtual Dial Broadband access is currently the mainstream way of broadband operators in China, the need to adopt broadband router ADSL virtual dial-up access is mainly Ethernet interface without the built-in routing function of the ADSL MODEM.