DOCUMENT:Q103880  30-JUL-2001  [crossnet]
TITLE   :Overview: Protocol Drivers
PRODUCT :Windows for Workgroups and Windows NT Networking Issues
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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

Reliable Connection Oriented--Session
-------------------------------------

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.

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