Unable to Activate Multiple DLS Connections Using the Same SAP
ID: Q180938
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The information in this article applies to:
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Microsoft SNA Server, versions 3.0 SP2, 4.0
SYMPTOMS
In a DLS (Distributed Link Service) environment where a "central" SNA
Server has distributed an 802.2 DLC (Data Link Control) link service
configured for MultiSap support, "remote" SNA Servers may have a problem
activating multiple connections through the distributed link service if
all of the connections are configured to use the same Local SAP.
CAUSE
An 802.2 Data Link Control (DLC) link services can support up to 128
connections over a particular Local SAP. The number of connections that
can be configured over using the same Local SAP will depend on the remote
MAC/SAP addresses the connections are configured to connect to.
When a DLC Link Service is initialized, DLC issues a DLC.OPEN.SAP command
to activate a SAP and reserve a number of link stations for that SAP. The
DLC Link Service is not designed to dynamically allocate additional link
stations after is SAP is opened, therefore it cannot allocate additional
link stations if the original allocation did not reserve enough to support
all of the configured connections for a particular SAP.
The problem described in the SYMPTOMS section can occur in a DLS
environment because the "Central" SNA Server that opens the SAPs for the
distributed 802.2 DLC link service does not know how many connections will
be using the link service. If the original allocation of link stations is
not sufficient to support the number of connections that will be using a
SAP, some of the configured connections using that SAP will not activate
and will stay in a "Pending" state.
STATUS
Microsoft has confirmed this to be a problem in Microsoft SNA Server
versions 3.0 SP2 and 4.0.
This problem was corrected in the latest SNA Server versions 3.0 and 4.0
U.S. Service Packs. For information on obtaining these Service Packs,
query on the following word in the Microsoft Knowledge Base (without the
spaces):
S E R V P A C K
MORE INFORMATION
The hotfix modified the DLC Link Service so that it uses the DLC_REALLOCATE
command to dynamically allocate more link stations after the DLC.OPEN.SAP
command has been issued if they are needed. Another enhancement was made to
the DLC Link Service so that it no longer allocates a SAP buffer pool for
every SAP that is opened. By default, Windows NT DLC does not use SAP
buffer pools. This change saves a maximum of 64 KB of memory per opened
SAP.
Note: The update DLC Link service has to be applied to the "Central" SNA
Server.
Steps to Reproduce This Problem:
- Have three SNA devices available to establish connections to (this can
be any combination of Hosts, AS/400 or SNA Servers).
- Set up a "Central" SNA Server site with one 802.2 DLC Link Service
configured with the "Allowed to be distributed" option selected and
the "Use Fixed SAP" option deselected.
- Set up a "Remote" SNA Server site with one Distributed Link Service
configured to use the link defined on the "Central" site in Step 2.
- On the "Remote" site configure three connections using the same
Local SAP on the same SnaRemX link service but to three different
SNA devices (MAC addresses).
- Activate the connections one at a time. The first two will go to an
Active
state and the last one will stay in a Pending state.
- Stop one of the Active connections, and the Pending connection
activate.
This can be reproduced the same way with two connections configured on
the "Remote" SNA Server and one local connection on the "Central" SNA
Server.
Note: There may be cases when more than two connections using the same
Local
SAP can be started before the next connection fails to activate. This will
depend on how the "Central" SNA Server is configured.
This problem does not occur if the distributed 802.2 link service is
configured with the "Use Fixed SAP" option enabled.
Additional query words:
Keywords : kbbug4.00 kbbug3.00.sp2 snadlc
Version : WINDOWS:3.0 SP2,4.0
Platform : WINDOWS
Issue type : kbbug