Description of the Internet Protocol Packet Size Setting


In Windows 98, it is possible to modify the default Maximum Transmission Unit (MTU) settings. This article describes these settings, and why it may be beneficial to alter them.

To view these settings, use the following steps:
  1. Click Start, point to Settings, click Control Panel, and then double-click Network.
  2. On the Configuration tab, click Dial-Up Adapter, and then click Properties.
  3. On the Advanced tab, click IP Packet Size. The following list shows the values you can select in the Values box:

    - Automatic Programmatic control, this is the default setting
    - Large 1500
    - Medium 1000
    - Small 576

    NOTE: When you use Automatic mode, all Point-to-Point Protocol (PPP) connections at speeds below 128kbps are made with an MTU of 576. At speeds above 128kbps, all connections are made with an MTU of 1500. Regardless of the MTU setting, the MTU will be further reduced to account for the network overhead if Virtual Private Networking (VPN) is used.

More Information

MTU is the Maximum Transmission Unit of a network. This is the greatest amount of data or "packet" size that can be transferred in one physical frame on a network. Fragmentation of packets occurs if a packet is sent across a network that has an MTU smaller than the packet's frame length. This leads to reduced performance levels as fragments need to be reassembled.

The Internet standard for MTU is 576. When you connect to an Internet resource, your data may have to go through a router that has an MTU of 576. This results in fragmentation if your MTU is greater than 576, which can result in a Web resource being loaded slowly.

Microsoft recommends using the default setting of Automatic for the Internet Protocol (IP) packet size.

NOTE: By default, the Windows 95 MTU is 1500. This setting can only be changed by editing the registry. For information about how to do this, see the following article in the Microsoft Knowledge Base:

ARTICLE-ID: 158474
TITLE : Windows TCP/IP Registry Entries