Configuring RAS Callback Time Parameters (111068)
The information in this article applies to:
- Microsoft Remote Access Service 1.0, when used with:
- Microsoft LAN Manager 1.x
- Microsoft Remote Access Service 1.1, when used with:
- Microsoft LAN Manager 1.x
- Microsoft Remote Access Service 1.1a, when used with:
- Microsoft LAN Manager 1.x
- Microsoft Windows NT Server 3.1
- Microsoft Windows NT Server 3.5
- Microsoft Windows NT Workstation 3.1
- Microsoft Windows NT Workstation 3.5
- Microsoft Windows NT Advanced Server 3.1
- Microsoft Windows for Workgroups 3.11
This article was previously published under Q111068 SUMMARY
Callback Time is the time interval that a Remote Access Service (RAS)
server waits before it calls back a client when the Callback feature is
enabled. This article describes how Callback Time works and when to use the
"CALLBACKTIME=" and "CallBackTime:" parameters in various RAS versions.
This information supplements the "Administrator's Guide for Microsoft LAN
Manager Remote Access" version 1.0 and 1.1 regarding the CALLBACK feature
and supplements page 57 of the Windows NT version 3.1 "Remote Access
Service" manual regarding the CallBackTime parameter.
MORE INFORMATIONLAN Manager RAS 1.0 and 1.1 Server
LAN Manager RAS 1.x servers use the parameter, CALLBACKTIME= to define
Callback Time. Callback Time is dictated by the server regardless of any
parameter that may be defined at the client.
LAN Manager RAS 1.0 and 1.1 Client
RAS 1.x clients do not have an individual Callback Time parameter and do
not provide the server with a Callback Time. Thus, they depend on the
server to define Callback Time.
Windows NT version 3.1 and 3.5 RAS Server
Windows NT servers use the CallBackTime: registry parameter to define the
default Callback Time for any RAS client that does not provide an
individual Callback Time to the server (RAS 1.x clients must use this
default).
Windows RAS Client and Windows for Workgroups 3.11 RAS Client
Windows for Workgroups 3.11 RAS clients and Windows NT 3.1 and 3.5 RAS
clients have a CALLBACKTIME= entry in the MODEM.INF file that determines
the individual client's Callback Time. The client communicates this to the
Windows NT RAS server during initial authentication. The Windows NT RAS
server CallBackTime: registry value is ignored when the RAS client supplies
a callback time. Clients connecting to RAS 1.x servers are not able to
communicate their individual Callback Times and must accept the server's
default. NOTE: On a Windows NT RAS client there are two Callback Time parameters;
the CALLBACKTIME= entry in MODEM.INF, which applies to the client function
of RAS and the CallBackTime: registry parameter, which applies to the
server function of RAS. Therefore, when a Windows NT RAS client connects to
Windows NT RAS server, it is the client's CALLBACKTIME= entry in MODEM.INF
that determines the Callback Time, not the CallBackTime: registry entry.
How Windows for Workgroups 3.11 and Windows NT Callback Time Works
After the RAS client hangs up the line, it sends an AutoAnswer command to
the modem within approximately one half of the specified Callback Time. To
allow the client modem sufficient time to switch to AutoAnswer mode and
receive the call, the Windows NT RAS server waits for the full Callback
Time before it attempts to call back.
Do Not Set Windows For Workgroups 3.11 CALLBACKTIME= Value Larger Than 170
Windows for Workgroups 3.11 RAS clients with Callback Time values greater
than 170 seconds do not wait long enough for the server to call back. The
client times out with the following error message:
Error 638: The request has timed out.
However, this is an unusually long Callback Time and there should not be
any need to set the value that high.
The Windows for Workgroups 3.11 RAS client times out because its callback
algorithm sets the modem to AutoAnswer mode after approximately one half
Callback Time and then only waits for about another 85 seconds for the
server to call back. So, when the Callback Time is set very large, for
example, 200 seconds, the client waits for 100 + 85 seconds before it times
out, but the server won't call until 200 seconds have past.
Modification Type: | Major | Last Reviewed: | 12/1/2003 |
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Keywords: | KB111068 |
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