LM Server Fails to Report Errors During Timeout Anomaly

ID: Q97817

The information in this article applies to:

Microsoft LAN Manager, version 2.1

SUMMARY

In Microsoft LAN Manager 2.1, a problem with a slow link most likely causes the NetBIOS STO (Send Timeout) to expire. The workstation defaults to 45 seconds (per SESSTIMEOUT) on its side of the session, but the server defaults to only 34 seconds (per SRVHEURISTIC 15) on its side and times out, breaking the session.

Associated with this problem in a way not fully understood is a secondary condition: the server service does not report an error in the log. The client side gets a NetBIOS "Session ended abnormally" error (18) and, if using an MS-DOS command line, normally reports a NET805. In one reported instance of this problem, a token ring multiplexer (hardware) problem disrupted access to the file server to such a degree that finally no LAN users could log-on, but none of the expected network control block timeouts or VC errors were logged in the server's error log. The network was using LM 2.1 on client and server.

Physical unit connected workstations, running on the same cabling system (and segments), did not experience any problems. The problem was solved by replacing a card in one of the Fibronics Unimux FM 892 token ring hubs. This component was already slated for replacement because of other problems with the Fibronix Unimux equipment (see below).

SYMPTOMS

Users unable to log on (logon script inaccessible); apparently all LANusers affected at same time.

Bypassing log-on script: Messages from Windows: Group xxx is damaged, and Windows groups loaded from the network were not shown.

TYPEin all files on the server from a workstation shows that 20 percent of all files on production server 1 are inaccessible. Messages:

Invalid file handle <filename>
NET805 Network drive no longer exists reading drive W:

Files could be RENAMED or DELETEd but not COPYed.

After an error occurred, the session with the SERVER was severed (status: DISCONNECTED).

Files were accessible and OK on the file server itself, or when accessed from production server 2 (as a workstation).

Set of files giving problems was consistent across all connected PC workstations.

An attempt to examine file permissions for these files via the NET ADMIN command issued at an OS/2 workstation with ADMIN privilege failed. Error message: Network path does not exist.

No entries were found in PC error logs, server or NET AUDit file.

Network Management System (for LAN cabling) showed increased error rate on one of the rings.

Physical unit (data link control) connected workstations on same cabling system experienced no problems.

Symptoms were identified on Dell, and IBM PS/2, with MS-DOS and OS2, running Madge, IBM, and Microsoft protocol stacks.

CAUSE

The problems are caused by an intermittent error on a fiber optic repeater. After repeater interface board was replaced, the symptoms ceased.

RESOLUTION

Spider network trace findings:

Increased rate of lost frames and CRC errors on one of the "user" rings.

Request to server (for file access) is completed.

Server sends Data Ack.

Server sends response to redirector (giving file status info: HPFS386).

Server sends Data Ack.

Server sends file contents (Data Only or Last).

Client sends a response, which is repeated 7 times - LLC frame: DSAP=F0 SSAP=F0 S_Format PDU Response=RR N(R)=78 F=1.

Client sends command EFh (command not recognized by Spider).
LLC: Response=UA F=1
NET: Command=EF Opt1=22 Opt2=0 TrxCorrellator=0600 RespCorr=0174
DestName=< 1>z< 4><ff>SMB-

Client sends same frame again.

Client sends: NAME QUERY.

Server sends: NAME RECOGNIZED.

Client sends: Session Initialize.

Server sends: Session Confirm.

Additional query words: 2.00 2.10 2.10a 2.20 unimux FM 892

Keywords :
Version : :2.1
Platform :
Issue type :