Nine access methods

 

The Internet seems to be the only "network" that allows everyone to invest in their own networks ". The way everyone goes online is different. To sum up, this article mainly analyzes nine access methods: PSTN, ISDN, DDN, LAN, ADSL, VDSL, Cable-Modem, PON, and LMDS. Which one is more comfortable to access the Internet?

 

I. dial-up access

 

 

 

 

 

PSTN (PublishedSwitchedTelephoneNetwork, public telephone exchange network) refers to "dial-up access", that is, accessing the Internet through a common telephone line. You cannot receive phone calls when surfing the Internet. At present, the maximum speed is 56 kbps, which has reached the channel capacity limit determined by Xiannong's theorem. Although the speed is far from meeting the needs of broadband multimedia information transmission, but the biggest benefit is convenience, popularity, and low cost. There is a telephone line, plus a hundred dozen small "MODEM" (MODEM, MODEM? That's all.

 

 

 

Currently, fees are mainly pre-paid, such as 163, 169, 165, and 167 of China Unicom. You can go to the business office of the company to apply for a private account and password, and use these accounts to access the Internet. The fee is charged based on the network fee + call fee. Generally, an hour is between 2 yuan and 5 yuan. Discounts are available for holidays and daily promotions. If you do not apply for an account, there are also many direct dial-up Internet accounts. For example, if the password is 263, the user name is "263" and the password is "263 ". Direct access to the Internet is relatively less favorable, this method is more suitable for those users who have not been online for a long time. The fee is also charged based on the network fee + call fee. In addition, you can purchase an Internet connection card with an account and password, such as China Telecom's 2901 card and China Unicom's 163 card, the Internet access fee is generally 4 yuan/hour. This method helps to control the Internet cost and is especially suitable for users who often travel online. It can be purchased from street stalls where IC phone cards are even sold in many places.

 

 

 

2. No mistakes made by ISDN

 

 

 

Integrated Service Digital Network (ISDN) is commonly known as one-line communication. Its main feature is that users can receive calls at will while surfing the Internet, and its speed is faster, the normal Modem can be accessed after dialing for 1-5 minutes. The actual speed is 20-50 kbps. The ISDN can be accessed within 1-3 seconds. The actual speed can reach-kbps. Test data shows that the dual-line Internet access speed cannot double, and narrowband ISDN cannot meet the needs of high-quality broadband applications such as VOD.

 

 

 

However, the cost is higher than that for telephone access. A user uses a dedicated terminal device for ISDN, which consists of a network terminal NT1 and an ISDN adapter. The ISDN adapter and Modem are also divided into two types: Internal and External. the built-in ones are generally called ISDN built-in cards or ISDN adapter cards. The external ISDN adapter is called TA. The price of the ISDN built-in card is 300 ~ It is about 400 yuan, while TA is about 1000 yuan. In addition, its monthly rental fee is 1.5 times of the monthly rental fee of ordinary telephone, that is, 32.4 yuan. The fee is charged based on the network fee + call fee. When the hourly Internet access fee is high, it can be twice the normal dial-up Internet access fee.

 

 

 

3. ADSL individual broadband

 

 

 

ADSL (asyuncricaldigitalsubscriberline), asymmetric digital user loop? It is a technology that provides broadband data services through common telephone lines. ADSL supports the uplink speed of 640kbps-1Mbps and the downlink speed of 1Mbps-8Mbps. The valid transmission distance is within 3-5 km. In the ADSL access scheme, each user has a separate line connected to the ADSL local terminal, and the data transmission bandwidth is exclusive to each user. Compared with the first two access methods, ADSL does not require dialing and is always online. The actual speed can reach-kbps, which is much faster.

 

 

 

It costs a lot in the early stage and requires a nic. Generally, the initial installation fee is about 300 yuan, but the cost for accessing the Internet is relatively small. Currently, the subscription is generally used, and the duration ranges from 49 yuan to 380 yuan. You can open an account in each business office, and professional technicians will install and debug the account.

 

 

 

4. DDN mainly targets organizations

 

 

 

DDN is short for DigitalDataNetwork. What is the communication rate of DDN at N × 64 Kbps? N = 1-32? Of course, the higher the speed, the higher the rental fee. You need to apply for an account to rent a DDN business. DDN charges can generally be based on monthly subscription and traffic calculation, which is different from the pay-as-you-go billing method for dial-up Internet access. DDN is expensive for leasing, mainly for group companies and other units that need comprehensive use. DDN charges vary according to different bandwidth rates. For example, if China Telecom applies for a 1000 kbps ddnleased line in the region, the monthly rental fee is about yuan.

 

 

 

V. faster bandwidth of VDSL

 

 

 

VDSL is faster than ADSL. With VDSL, the maximum downloading rate within a short distance can reach 55 Mbps, And the upload speed can reach 2.3 Mbps. VDSL uses a pair of copper wires, with a valid transmission distance of more than 1000 meters. However, the VDSL technology is still in its infancy, long-distance applications still need to be tested, and the popularization of endpoint devices also takes time.

 

 

 

6. Cable-modem depends on wired

 

 

 

Cable-Modem is an ultra-high-speed Modem that has been used for trial in the past two years? CATV? Network for data transmission, is a relatively mature technology. With the development of cable TV networks and the continuous improvement of people's quality of life, using CableModem to access the Internet through cable TV networks has become a high-speed access method that attracts more and more industry attention.

 

 

 

Cable-Modem connections can be divided into two types: symmetric rate type and asymmetric rate type. The data upload speed is the same as the data download speed, both between kbps-2mbps; the latter data upload speed is between kbps-10mbps, and the data download speed is 2 mbps-40mbps.

 

 

 

Because of the use of the shared structure, as users increase, the access rate of individuals will decrease, and the security and confidentiality will also be poor. The most important thing is that the radio and television systems do not have their own internet outlets, and the networks in various regions are self-contained and not connected to the whole. All the internet outlets of China Telecom, China Netcom, and China Unicom are rented.

 

 

 

VII. PON Optical Fiber entry

 

 

 

PON (Passive Optical Network) is a point-to-multiple-point Optical Fiber Transmission and access technology. downlink broadcast and uplink time-division multiplexing are used. PON includes ATM-PON (APON) and Ethernet-PON (EPON. The bandwidth used by each PON user can be flexibly divided from 64 Kbps to 155Mbps. The user connected to an OLT shares the bandwidth of 155Mbps.

 

 

 

8. LMDS Wireless Communication

 

 

 

This is currently a wireless access technology that can be used for community broadband access. The bandwidth of each end user can reach 25 Mbps. However, the total bandwidth is 600 Mbps, and users under each base station share the bandwidth. Therefore, if a base station has a large number of users, the bandwidth allocated to each user is very small.

 

 

 

China Netcom's "MOBILEOFFICE" is a wireless broadband access method, which meets the needs of mobile office, but is the same as that of mobile phones, base station receiving equipment must be provided within a certain distance around the user's Internet access equipment. It is obviously unrealistic to lay a large number of base stations. China Netcom has only made some attempts in public gathering places such as hotels and airports.

 

 

 

9. LAN community broadband

 

 

 

LAN access uses Ethernet technology and optical fiber cables and twisted pair wires to perform integrated wiring for the community. So it is called residential broadband because this method is the most widely used in all residential areas connected to broadband. The user's home computer can access the Internet through the five modules on the wall through the five jumpers.

 

 

 

The LAN can provide a shared bandwidth of more than 10 MB, and can be upgraded to more than MB as needed. At present, carriers engaged in this method on the market mainly include Great Wall broadband and blue wave wanwei, China Telecom and radio and television.

 

 

 

The disadvantage is that the leased line speed is often very low, which restricts the development of the LAN method, and the security problem of users in the same switch is also worth considering.