This article was previously published under Q162594
You may want to use the NETBIOS interface made available in SNARAS toemploy Microsoft networking over your existing SNA network, which consistsmainly of 9600 SDLC multidrop links. This would allow you to use SystemsManagement Server remote control facilities and manage your computersrunning Windows NT Server through the Windows NT Administrative Utilitiesand the SNA Administrator UI.
However, implementing SNARAS over slow SDLC links on WAN networks canresult in the following errors. When the SNARAS connection is dialed usingthe remote access client phonebook, after 10 seconds or so the followingerror message appears:
Error 629 Port was disconnected by remote machine.
At this point, you have the option to cancel or retry. If you click Retry,after about 5 seconds the following error message may appear:
Error 651 Your modem or other connecting device has reported an error.
The very low network bandwidth being used is insufficient to host thecomplex protocols employed to achieve Microsoft networking. The lowbandwidth is further eroded as peer entities in all the protocol stacksbeing used time out request and initiate their retransmission routines.
The problem ultimately is the low bandwidth of the end-to-end connection,which can be as low as 120 KBps as a result of a mixture of low speed SDLClinks between FEPs and other SNA traffic over the same links. SNARASprovides a guaranteed delivery, but RAS "believes" that it is notguaranteed and this level of bandwidth is too low for RAS to use.
Upgrade slow links to links that can adequately handle NetBIOS/ServerMessage Block (SMB) traffic.
Within the SNARAS components connection timeouts can be seen by employingthe checked versions of Snaras.dll and Rassna.dll to produce internaltracing, as demonstrated below:
66:d5 ProcessAPPCWork - Outstanding verbs on conv 066:d5 RAS_LINE_CONNECTING66:d5 RECEIVEANDWAIT complete on AAR, rc1 0, rc2 066:d5 RAWComplete - connect error so terminate line66:d5 TermLine - start terminate on line AA66:d5 Client, Send TP id=03000000A03A170066:d5 IssueTPEnded - issue TP Ended type 1 on AAS
However, these failures occur as a result of an underlying network failurewhich can be seen if RAS PPP logging is enabled. The logs will show PPPpackets get received a very long time after they are sent, causing PPP LCPto come down and re-negotiate. So LCP goes up and down for a long timeuntil it disconnects. This is called a cross connection.Although there are Microsoft Knowledge Base articles that describe how totune timing parameters in the network protocols right up to SMB layer,Microsoft network architecture is not designed to work over networksoffering such low bandwidth.