The main culprit of tracing the slow speed of the network

units began to purchase microcomputers into the information-based teaching era from the previous year. The first installation was ISDN first-line communication, and later changed to ADSL with PPPoE access mode with 512K bandwidth, with the increase of the number of microcomputers. Recently, the Internet has been upgraded to ADSL with fixed IP bandwidth of 1M. The network speed of the server can meet the access requirements twice, and the speed of the Windows 98 workstations brought by the server has not improved. Finally, the culprit was finally found. - MTU value setting. MTU is the abbreviation of English Maximum Transmission Unit, which means "maximum transmission unit". That is, the maximum number of bytes of data packets transmitted through the TCP/IP protocol.

First, the dual-channel ISDN is changed to 512K PPPoE ADSL, the workstation can not open some websites

The server adopts Windows XP, and uses the system's own connection sharing to let more than 30 Windows 98 workstations share the Internet. Because Windows XP comes with PPPOE dial-up software, third-party dial-up software is not used for stability and ease of use. Enable "New Connection Wizard" from the IE properties, select "Connect to the Internet", then select "Manually set up my connection", connect to the Internet by "Connect with broadband with username and password", enter the username and password. You can use the virtual dial-up method to access the Internet, and then enable "Internet Connection Sharing" in the connection properties, all workstations can access the Internet through the server.

It is very fast to open the webpage from the workstation to www.bdinfo.Net, but open www.163.com but only the title bar is displayed, but the content of the webpage is always open, and the Sohu is accessed from the server. There was no problem with the network. Later, many websites that could be opened from the Windows XP server could not be opened from the workstation. Since the server is a newly installed Windows XP operating system, the IP address of the workstation is set at 192.168.0.2~254, the gateway points to the IP address of the server 192.168.0.1, there is no problem in setting, and the workstation is originally connected via ISDN. It can also open the webpage normally, indicating that the network hardware connection is also normal. Through multi-party verification, we finally found the cause of the problem - the MTU value setting.

The ADSL MTU value of the PPPoE access mode is 1492, and the standard settings of the remaining various MTU values ​​are 1500. The default TCP/IP packet size in the Windows operating system is 1500, and the MTU value setting of some sites is greater than 1492, so the site cannot be accessed. Finally, this problem is solved by modifying the registry of the Windows 98 workstation and reducing the MTU value.

Click "Run" in the start menu, enter "regedit" and press Enter to enter the registry. Expand {HKEY_LOCAT_MacHINE\\

System\\CurrentControlSet\\Services\\Class\\NetTrans\\}, you will see a sub-item containing several 000X, look for the key name "DriverDesc", the key value is "TCP/IP "000X primary key, the key has the computer's network property settings, such as IP address 192.168.0.XX, gateway 192.168.0.1, subnet mask 255.255.255.0 and so on. Create a new "DWord value" under the key, name it "MaxMtu", and modify the key value to be 1450 in decimal, as shown in the figure. After setting up, restart the computer, the client can access the site that could not be accessed.

Second, PPPoE ADSL changed to fixed IP ADSL, network speed slowed

Since the unit added a computer room, the original 512K ADSL can not meet the teaching requirements, recently applied Modification of the original virtual dial-up 512K ADSL for fixed IP 1M bandwidth ADSL. First delete the original virtual dial-up connection, add the public network IP address, gateway, and DNS assigned by the ISP to the NIC properties, and download the data from the Internet through the server. It is obvious that the speed is increasing rapidly and connected to the “World Network” broadband speed measurement page. :http://www.linkwan.com/gb/broadmeter/SpeedAuto/
, the test connection to Beijing (China Host Network - Beijing Server) speed is about 80 kilobytes /sec, and the original use At 512K ADSL, it is only 40 kilobytes/second.

After two weeks of trials, workstation users responded to the 1M broadband opening, and felt that the network speed was not as fast as the original. Log in from the workstation to the "World Network" test page. The speed of connecting to Beijing is only 30~37 kilobytes/second. The software downloaded from "Huajun Software Park" is only about 20 kilobytes/second, and the same download is downloaded from the server. The file can reach 110 kilobytes/second. Reinstalling Windows XP on the server side, detecting the virus speed in the LAN can not be improved. Finally, reinstalling a workstation on Windows 98 and reconnecting to the network, the network speed is greatly improved, and the test connection to Beijing has reached or approached the server. At the end level, the speed of downloading the same file from the "Huajun Software Park" has also increased to 80 kilobytes per second.

Do you need to reinstall Windows 98 on more than 60 workstations? After careful thinking, I suddenly remembered that when using PPPoE virtual dial-up Internet access, I have modified the MTU value in the registry. Will this value affect the Internet speed? Open another workstation, find {HKEY_LOCAT_MacHINE\\System\\CurrentControlSet\\Services\\Class\\NetTrans\\}, delete the original MaxMtu key, restart the computer, and test the network again. The connection speed to Beijing has reached 70~80 thousand. Bytes/second, the speed of downloading the same file from the "Huajun Software Park" has also increased to about 80 kilobytes/second. The MTU key values ​​originally added in all Windows 98 workstations are deleted, and the entire network speed is restored.

It seems that the difference between the MTU value setting and the broadband access method will also affect the Internet speed.