MTU stands for maximum (or minimum) transmission unit.
Comcast is the largest cable and Internet service provider in the United States. When a recipient computer is too busy to process incoming data, it usually returns an MTU error messages, which Comcast passes on to the sender. Xbox Live users get these messages frequently.
Internet Communications
Data sent over the Internet is broken down into units called packets. The packets are transmitted on a first-available-route basis and reassembled in the correct order by the receiving computer. The size of the packets allowed affects network speed. Between high-speed computers, bigger is better. But sending large packets is problematic when low speed modems are also attached to the network. Too large a packet sent to a 14.4K modem can jam up the network for all of the 54K modems.
MTU Parameters
A number of factors can determine the allowable size of an MTU. On the computer side, the type of network interface being used (NIC card, USB and Ethernet) is a factor. On the network side, the MTU is determined by the ISP's transmission protocols. A third factor is the recipient computer. When a modem is occupied, it will return an MTU message which is essentially a digital busy signal. The computer is telling the sender, "This is too big for me to process at this time."
Protocols
In telecommunications, protocols are the rules and formats that govern exchanges of data between computers. Protocols are assembled in layers and the MTU of a protocol is the maximum (or minimum) amount of data that can be passed from one protocol layer to another. Protocols handle such aspects of communications as signaling, error detection and authentication.
