Boosting Your Internet Connection Speed With XMark 7.0

You can use XMark 7.0 to optimize, among other things, your Internet connection. This article outlines the steps required to do this, and what each of the adjustable parameters means.

Before You Begin

Start up XMark and go to the Tune Up tab page. From the tree view, select Internet and Network, under the System category. You're now ready to tweak.

Tweaking

Each of the parameters that can be tweaked is explained below.

MTU (Maximum Transmission Unit)

This setting determines the maximum packet size, in bytes, that TCP/IP will use when sending information over the network. If you are using Internet Connection Sharing (ICS) or PPPoE (Point-to-Point Protocol over Ethernet) for your broadband connection, you must have an MTU size of 1492 or less. On all other Ethernet connections (such as cable modem), you can use an MTU size of up to 1500. An MTU that is set too high or too low can limit the Internet's bandwidth. Sometimes, with an MTU of 1492, you may experience a slow connection. In such a case, use an MTU of around 1454. If you're using a dial-up connection, you should use an MTU of 576 for 56K modems or 288 for 28.8K or 33.6K modems.

You can find out the maximum MTU size for your network by following these steps:

1. Go to the Home tab page.
2. Click Diagnostic Testing from the task pane.
3. Browse to Internet -> Optimal MTU.
4. Click Run Test.

The lowest possible MTU value is 68, though you'll probably never have to set it that low. You should accept 1500 as the absolute maximum value for MTU. If you wish to use the Windows default settings, just set the value to 0.

Path MTU Discovery

The MTU you set up in the last step is valid only for your system. Other systems with which you may interact on the Internet also have their own MTUs. If you enable Path MTU Discovery, TCP/IP will try to detect the optimal MTU for each node along the path to the destination server. This will keep the MTU from being too high, avoiding packet fragmentation. It is therefore strongly recommended that you enable Path MTU Discovery, unless you are having problems reaching some servers.

Path MTU Black Hole Detection

If you're having problems reaching some servers, the problem may be due to a black hole router. A black hole router, in layman's terms, is a node along a network that does not support Path MTU Discovery. Normally, with this setting disabled, TCP/IP skips over black hole routers, assuming that they use the same MTU as your own system. If you enable this setting, it tells TCP/IP to locate the black hole routers and lower the MTU. Because locating black hole routers takes a lot of time and bandwidth, it is recommended that you disable black hole detection.

Time To Live Hops

Time To Live (TTL) is a counter that keeps track of the number of seconds left until a connection attempt times out. The TTL counter starts with a predetermined value, usually 64 or 128, and gets decreased by one every time a server is reached along a path (a 'hop' is made) or every time a second has passed trying to reach a server along a path. If the path is too long (too many hops) or too much time has been spent trying to reach a server, the packet expires. The recommended value for TTL is 128. You should never set this above 256.

Receive Window Size (RWIN)

The TCP window size is the amount of data that can be transmitted over the network before an acknowledgement is needed from the destination server. If you set this too low, you will incur a lot of overhead. If you set it too high, too much data will have to be retransmitted if the destination server does not acknowledge the packets. This is a setting that leaves a lot of room for experimenting. However, there is one constraint: the value of the RWIN should be a multiple of the MSS (maximum segment size). The MSS is the maximum effective size of a packet, which is usually equal to 40 bytes less than your MTU size. For a dial-up connection, your data transmission is not very reliable, so it is recommended that the RWIN be set to a lower value, such as 2144 or 4288 (with an MTU of 576). For a cable connection, the transmission is also not very reliable, but you can afford to increase the RWIN because of the greater bandwidth, so the RWIN for a cable connection should be between 23360 and 93440. Make sure that you enable selective acknowledgements and window scaling if you set an RWIN of more than 65535. For PPPoE connections such as DSL, since the connection is more reliable than cable, you should set the RWIN value to somewhere between 92928 and 371712. For faster dedicated connections, such as T1 or OC3, you can go as high as 747520.

Maximum Duplicate Acknowledgements

Optimizing this value allows for faster retransmission when a packet loss is encountered. Set this to 2 for best performance.

Selective Acknowledgements

This improves throughput for unreliable connections. You must enable this for RWIN values of more than 65535.

RFC 1323 Options

The RFC 1323 revision to TCP/IP introduces two new features: window scaling, and time stamps. It is strongly recommended that you enable both of these features for best performance. They must be enabled with RWIN sizes of more than 65535.

Conclusion

This article has given you a guide to boosting your Internet connection speed using XMark's tune-up feature, and an explanation of what each tweak does. If you would like further clarification or are experiencing difficulties, contact us and we will revise this article to include your suggestions.