Overview: Protocol Drivers

THE PROTOCOL DRIVER

The redirector uses the services of a protocol driver (such as NetBEUI or TCP/IP) to communicate with the network. Generally speaking, the redirector formats a server message block (SMB) request and submits it to the protocol driver to be transmitted on the network.

Microsoft network system protocol drivers provide two data transfer service types required by the redirector for communication with remote stations:

• Reliable connection oriented, also called session
• Unreliable connectionless, also called datagram

In this transfer service, the protocol driver assumes responsibility for transferring the entire message (that has been passed down from the redirector) from source to destination, with full acknowledgment from the destination station, and within an acceptable time period. If, for any reason, the protocol driver cannot transfer the message within the time specified, it returns an explanatory error code to the redirector.

The redirector uses this service for remote file reads and writes, and all other operations that require guaranteed reliable data transfer.

Unreliable Connectionless--Datagram

In this transfer service, the protocol transmits the message once or a specified number of times, assuring only that the message was properly transmitted on the network medium. No acknowledgment from destination stations is required.

The redirector uses this service for operations that do not require guaranteed message delivery, such as "broadcasting" a message to multiple users.

MULTIPLE PROTOCOL DRIVERS

Two stations must run the same protocols in order to communicate.

An important feature of Microsoft network systems is that you can install and concurrently use a variety of protocol drivers, so that you can simultaneously communicate with remote stations running different protocols.