How to tweak your MTU and double your connection throughput?

Maximum Transmission Unit MTU is the default packet Windows uses to negotiate when a connection is opened between two computers, they must agree on an MTU by comparing MTU and selecting the smaller of the two.

How to double or triple
your Internet connection throughput?

Maximum Transmission Unit MTU is the default packet Windows uses to negotiate when a connection is opened between two computers, they must agree on an MTU by comparing MTU and selecting the smaller of the two.
 

How does it work?
If MTU is set too large for routers that are between the computers, these routers then fragment this information into packet size that it can handle.

This fragmentation can double the amount of time it takes to send a single packet. Windows has a built-in MTU Discovery that will adjust for this by sending out a packet that is marked as "Not Fragment".

Then the router sends back an error to the computer saying that the packet was too large, then Windows lowers the MTU until there are no more errors.

Most ISP uses an MTU of 576, then every time you start a connection, Windows must adjust down to this value. Even though Windows automatically adjusts the packet size, it still takes time to negotiate an acceptable MTU.

By setting this value manually, (see below MaxMTU setting) you greatly reduce the amount of work that Windows must do to negotiate with the ISP

Data shoots across the Internet and into your computer in "packets"--see bits.bytes for more info. These packets are sized for optimal transfer speed over the Internet back bone, routers and ethernet networks etc.

If you are connected through a modem and an ISP (Internet Service Provider), the default packet size is could be less than optimal. The result is a substantial performance degradation because the packets are fragmented and need to be re-assembled. See UART
 

How to tweak your MTU
and double your connection throughput?

1. Click START
2. Click RUN

3. Type this in the run box  REGEDIT [enter]
4. The registry editor box opens.... 

5. Click and highlight HKEY_LOCAL_MACHINE
6. Click edit, click find and at *find what* enter: maxmtu and hit [enter] key (it will takes a few minutes)

7. Click on MaxMTU to highlight it and right click to MODIFY, change data to 576 and close the registry, reboot the system and get ready to surf.

Other connection device that may require different MTU value? See bottom of page: Setting info for various connection device

Freeware to help speed-up your downloading?Prevent server time-out disconnection by you ISP

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Internet traffic travel in bursts governs by TCP and the speed a webpage single bit takes to get to your PCs is limited by...

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Setting serial port to the maximum can
optimize a PCs process data to the theoretical maximum data flow between serial port and the modem is governed by UART

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CGI: What the Heck Is That?
CGI or Common Gateway Interface
a method used to exchange data between the server...

If you are confused or can't find MaxMTU
below are some utilities that can help

1. PPP-Boost MTU freeware--(for Win 95,98,Me)
www.c3sys.demon.co.uk/ppp.htm 

2. TweakDUN shareware www.pattersondesigns.com/tweakdun  

3. MTU setting shareware
www.mjs.u-net.com/mtuspeed.htm 

Notes: TTL (Time To Live)
TTL is a field in the IP header which indicates how long a packet should be allowed to survive before it is discarded. TTL essentially determines the maximum number of hops permitted.

RWIN (TCP Receive Window)
RWIN determines how much data the receiving computer is prepared to receive. RWIN value that is set too high will result in greater data loss if the packet is lost or damaged in transit. RWIN value that is set too low will produce poor throughput.

MSS (Maximum Segment Size) is the largest segment of TCP data that Winsock is prepared to receive on a particular connection. When the TCP connection is initially established, both uses the minimum of each other's MSS value.

If the MSS is too low, the data/header ratio will be low. If the MSS is too high, will lead to large IP datagram and the packets will tend to fragment in transit where other networks may be having smaller MTU. Hence, performance can be increase by reducing MSS value.

Since packet headers are normally 40 bytes in length, your MSS value should always be set to MTUvalue minus 40 (i.e. if your MTU is 1500 the set MSS to 1460) at least 40 less than the value of the MTU.

Setting info for using various connection device

Using General Connection
MTU :1500
MSS :1460
RWIN :8192
TTL :64

Using Dial-up Modem Connections
MTU :576
MSS :1460
RWIN :2144 for 28.8/33.6 and 3216 for 56.6
TTL :64

Using Cable Modem or LAN Connections
MTU :1500
MSS :1460
RWIN :8192 or 29600
TTL :64

Windows 95/98/ME, using Cable Modem or DSL/ADSL
MTU :1500
MSS :1460
RWIN :372300
TTL :64

Windows 2000 using Cable Modem or DSL/ADSL
MTU : 1500
MSS : 1500
RWIN : 372300
TTL :128