The settings on this screen determine how your data is packaged for transmission. If you can imagine shipping a shirt in a furniture box, you can see that some ways of packaging are more efficient than others. The most efficiency occurs when the package fits the item, or holds a whole number multiple of those items. We will use this analogy to explain the settings below.

Maximum Transmission Unit (MTU) and Maximum Segment Size (MSS)

Your item to be shipped is a unit whose size is set by the Maximum Transmission Unit (MTU) value. Just as a parcel service may not accept boxes over a certain size, so your Internet Service Provider (ISP) will accept packets of information only up to a certain size. If your MTU value is different than that preferred by your ISP, Windows begins an electronic negotiation until your computer and your ISP settle on the smallest of the two values.It is best for you to use the largest MTU allowed by your ISP. A larger MTU would be sent in pieces to fit the smaller allowed MTU. This negotiation and piecemeal transmission take more time than does an exact fit.

Windows 95 default MTU is 1500. Windows 98 default MTU is 576. 576 is the appropriate size for most modems. Local area networks generally use 1500.

Time to Live

Undeliverable packages eventually end up in a warehouse with no more attempt to deliver them. So also undeliverable electronic messages are not allowed to roam the Internet forever. If not delivered within the Time to Live (TTL), the message dies. Windows 95 default is 32. Windows 98 default is 128. As the Internet grows it has been desirable to allow more time for a message to find its way.

Receive window (RWIN)

Your Receive Window buffers (holds temporarily) all the incoming message segments until it is full. It then passes the messages on to other devices in your system.

To continue the package analogy, imagine that you are receiving many packages. You unwrap each one, discarding the wrappings, and place the item in a bag beside you. Each item corresponds to a message segment (MSS) which in size is 40 bytes less than the MTU value. The 40 bytes were for routing information and are no longer needed.

After a few items your bag is full and you must empty your bag before you can continue. The point at which you must pause to empty the bag depends on the size of your bag. Your Receive Window corresponds to the bag. You may make it the size you like, but the most efficient size is a whole number multiple of your MSS. Remember, MSS = MTU - 40.

Return to Network Settings.