Unable to Transfer Files Across DEC 250 and DEC 500 Routers
Article ID: 128797
Article Last Modified on 11/1/2006
APPLIES TO
- Microsoft Windows NT Workstation 3.5
- Microsoft Windows NT Workstation 4.0 Developer Edition
- Microsoft Windows NT Server 3.5
- Microsoft Windows NT Server 4.0 Standard Edition
This article was previously published under Q128797
SYMPTOMS
When you attempt to copy large files across Digital Equipment Corporation
(DEC) 250 and DEC 500 routers using the TCP/IP protocol, the file transfer
fails.
CAUSE
DEC 250 and DEC 500 are IP/DECNet Routers. For wide area networks (WAN)
with DECNet as the primary protocol, the MTU size may be set to 512 bytes.
These routers may not send ICMP Destination Unreachable messages with
Fragmentation Needed in its code field if the datagram requires
fragmentation. Instead the frame is dropped. When the Windows NT
EnablePMTUDiscovery parameter is turned on (set by default), the "Don't
Fragment" bit is set in the IP datagram indicating to the router that it
should not fragment this packet. At this time the router should respond
with a destination unreachable ICMP message.
RESOLUTION
To correct this problem, you must modify the Registry.
WARNING: Using Registry Editor incorrectly can cause serious, system-wide
problems that may require you to reinstall Windows NT to correct them.
Microsoft cannot guarantee that any problems resulting from the use of
Registry Editor can be solved. Use this tool at your own risk.
- Run Registry Editor (REGEDT32.EXE).
- From the HKEY_LOCAL_MACHINE subtree, go to the following key:
\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
- From the Edit menu choose Add Value.
- Add the following:
Value Name: EnablePMTUDiscovery
Data Type: REG_DWORD
Data: 0
Radix: Hex
- Quit Registry Editor.
- Shutdown and restart Windows NT.
The products included here are manufactured by Digital Equipment
Corporation, a vendor independent of Microsoft; we make no warranty,
implied or otherwise, regarding these products' performance or reliability.
Additional query words: prodnt
Keywords: kb3rdparty kbnetwork KB128797