The origin of ADSL

the origin of p>ADSL

in p>1989, at&; Bellcore, a subsidiary of T, hopes to develop a transmission technology that can use traditional telephone lines to transmit images, animations and pictures at the same time, and can calculate at Mbps, so ADSL has been developed. ADSL (Asymmetric Digital Subscriber Line Asymmetric Digital Subscriber Line) is a new Modem technology. Its architecture is based on the existing two-core copper wire telephone network system. As long as the existing telephone line is converted into a high-speed digital line, the analog transmission method will be changed to a digital one. In this way, you can upload bandwidth at high speed. Unlike ISDN, ADSL does not need to replace most of the equipment in the telephone building, but only needs to install an ADSL Modem ATU-C in the telephone building and an ADSL Modem ATU-R at the user end, which has already completed the ADSL architecture. ADSL divides the line into three channels within its bandwidth:

1. downstream (receiving channel; Download): it is a one-way high-speed channel, which is transmitted from the computer room of the telecommunications company to the direction of the client, and its rate is 1.536 Mbps to 6.144 Mbps.

Second, upstream (transmission channel; Upload): it is a two-way full-duplex channel, and some products are designed to be unidirectional, and the upload rate is 16 Kbps to 64 Kbps.

Third, POTS channel: that is, using the basic 4 KHz bandwidth, Provide POTS service (Plain Old Telephone Service), that is, the channel currently used for talking on the phone.

ADSL Modem uses a larger bandwidth than voice to transmit data, so the speed can be improved. At the same time, it adopts advanced arithmetic, A telephone line can be divided into three different frequency spectrums: the higher frequency spectrum is used for downloading, while the lower frequency spectrum is used for uploading. As for the -4KHz channel, it is generally used for voice (POTS). Unlike ISDN, ADSL will not be disturbed by voice channels. Therefore, you can still make calls on the same line at the same time when using ADSL Modem

Introduction to ADSL technology

At present, there is basically only one way for home computers to access the Internet by telephone line. Although the speed of MODEM has been continuously improved to reach 33.6Kbps, and 56Kbps products have been introduced one after another, its physical limit is 64Kbps, and its potential is limited. This rate can't meet the needs of more and more network multimedia applications. With the interactive multimedia application becoming a reality, the throughput of the network is increasing. Now, it has become a reality to use ADSL (Asymmetric Digital Subscriber Line) technology to browse the Internet through a telephone line, and to enjoy advanced data services such as video conferencing, video on demand, online music, online TV and online MTV through online learning, entertainment and shopping.

so what is ADSL technology? ADSL is a technology that provides broadband data transmission services for homes and offices through existing ordinary telephone lines. ADSL is asymmetric digital signal transmission, which can provide high-speed downlink rate up to 8Mbit/s on the existing copper twisted pair, that is, ordinary telephone lines. {Because ADSL is very sensitive to distance and line conditions, the rate will be affected with the increase of distance and the deterioration of lines} It is much higher than ISDN rate; The uplink rate is 1Mbit/s and the transmission distance is 3 km-5 km. The main feature of ADSL technology is that it can make full use of the existing copper cable network (telephone line network) and provide users with high broadband services by installing ADSL equipment at both ends of the line. Another advantage of ADSL is that it can be stored on a telephone line with ordinary telephones, and ADSL transmission can be carried out while answering and making calls on an ordinary telephone line without affecting each other. Users can access the broadband multimedia information network and the Internet through ADSL, at the same time, they can watch movies and TV programs, hold a video conference, and download data files at a high speed. That's not all. You can also use the telephone on this same telephone line without affecting other activities mentioned above. It is also very convenient and fast to install ADSL. When installing ADSL on the existing telephone line, there is no need to make any changes to the existing line except installing ADSL communication terminal at the user end.

how many different types of p>XDSL are there?

at present, there are many different DSL technologies that provide broadband by telephone lines, which are generally referred to as XDSL, including:

ADSL, G.Lite, CDSL, EtherLoop, HDSL, IDSL, RADSL, SDSL and vdsl.

ADSL (asymmetric digital subscriber line) :

ADSL technology is the most commonly used XDSL technology at present. Just from the word asynchronous, we know that its download speed is different.

G.Lite:

G.Lite is developed by Mircosoft, Intel, UAWG (Universal ADSL Working Group) composed of Compaq is developed based on ADSL. The advantage is that it is not necessary to install Splitter on the user side. However, its bandwidth will be relatively reduced.

CDSL (consumer digital subscriber line):

CDSL is a non-splitter XDSL technology developed by Rockwell.

Ethernet LOACL loop. :

EtherLoop is a broadband technology developed by Nortel Networks, which is based on Ethernet's packets processing mode and XDSL modulation mode. However, because it uses "half-duplex" transmission mode, Therefore, you can't upload and download at the same time.

IDSL:

IDSN, that is, ISDN, is an encoding method using 2B1Q. Up to 128kbps.

radsl (rate adaptive digital subscriber line):

radsl adopts carrier less amplification and phase modulation (cap). The modulation mode of. The download speed on it is limited by the ratio of line prime number and Signal to Noise. As long as the upload speed is faster, the download speed will be faster.

SDSL (symmetric digital subscriber line). :

the characteristic of p>SDSL is that the download speed is consistent.

vdsl (very high bit-rate digital subscriber line). :

The speed of p>VDSL is the fastest among various XDSL technologies, and it can reach 53Mbps or above.

PPPoA and PPPoE dispel doubts

PPPoA (point-to-point protocol over ATM)

PPPoA is developed based on PPP technology. And connect the client through ATM Card.

PPPoE (point-to-point protocol over Ethernet)

The full name of PPPoE is Point-to-point protocol over Ethernet (RFC 2516). It is one of the most commonly used transmission modes of broadband ISP in the world at present. This technology is developed by Redback Networks Inc, RouterWare Inc and UUNET Technologies Inc are based on PPP (Point-to-Point) and Ethernet.

The biggest advantage of p>PPPoE is that it enables ISP to provide broadband services (including XDSL, Cable and Wireless), which can reduce a lot of costs for ISP. And RASPPPoE, PPPoE surfing software such as NTS EnterNet and WinPoET can be used on any PPPoE broadband. < P > PPPoE software is used to authenticate users and record the connection time of users on xDSL/Cable/LMDS and other network architectures. And get the dynamic/static IP.

Introduction to PPPoE

The full name of PPPoE is Point-to-Point Protocol Over Ethernet (RFC 2516), which is one of the most commonly used transmission methods for broadband service providers in the world. This technology is developed by Redback Networks Inc, RouterWare Inc and UUNET Technologies Inc are based on PPP (Point-to-Point) and Ethernet. But so far, PPPoE has not become a standard

The biggest advantage of PPPoE is that it enables ISP to provide broadband services (including XDSL, Cable and Wireless), which can reduce a lot of costs for ISP.

In terms of users, it can be said that there are good and bad. In terms of benefits:

1) PPPoE uses Microsoft Dial-Up Networking (DUN) to establish PPP connection just like general 56k dial-up Internet access. But because Windows itself has no PPPoE driver (Windows xp is built in), Therefore, it is necessary to install EnterNet 3 or WinPoET.

2) You can share the bandwidth with general * * * Internet access software.

3) More operating systems support it (but it is impossible to compare it with DHCP).

4) If you want to cancel the service, the Ethernet Card can be used for Lan or other broadband services.

5) Driver update speed is much faster than ATM Card.

6) There is little chance to rush to other devices and IRQ.

On the downside:

1) About 5-1% bandwidth will be used to process PPPoE signals at speed.

2) ping time will increase.

3) MTU (Maxium Transmission Unit) must be smaller than 1492.

4) There are many problems in the software itself, such as slow connection speed, Time-out connection.

Installation method of PPPoE broadband:

Hardware:

Users only need to install a 1 Base-T/ 1 Base-TX Lan Card is installed in the PCI slot of the computer. Then connect the ADSL Modem with Standard or Cross-Over UTP cable (depending on which ADSL modem is used).

Software:

The first thing is to install the driver of Lan Card, and then install the PPPoE connection program provided by ISP. When the installation is completed, you can use this program to create a User Profile.