This article was previously published under Q152719
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This article describes a new feature that is included in Windows NT 3.51Service Pack 5. This feature is designed to allow you to reduce networktraffic related to Windows NT trust relationship polling over a wide areanetwork (WAN) using perhaps a leased line (for example, an ISDN or X.25line) where the leased line provider charges by the amount of networktraffic. Trust relationship polling occurs between domain controllers (DCs)to establish a secure channel.
In Windows NT 3.51 without this new feature, if the secure channel cannotbe established, it is retried every 15 minutes. With this new featureinstalled you can control the intervals between which a DC sends discoverypackets in search of a DC of a trusted domain.
Microsoft has made a fix in Netlogon.dll so that you can increase the timebetween retries and you can increase the time in which NETLOGON assumes aDC is reachable (ScavengeInterval and ExpectedDialupDelay).
When Windows NT Uses Polling Between Domain Controllers
In Windows NT 3.51, once a secure channel to a trusted domain has beenestablished (that is, after the DC in domain_A found a DC in the trusteddomain_B), Windows NT does not continue to poll the secure channel to makesure the secure channel is still available.
If, however, the DC is contacted for some other reason, for example, if auser logs on and a pass-through authentication to the other domain isrequired, the first DC needs to contact the second DC again and networkpolling of the secure channel starts for this reason once again and stopsafter the the pass-through authentication is completed.
Regular network traffic packets are not caused by trust relationshippolling of the secure channel, so if you frequently observe frames relatedto trust relationship traffic on your WAN router, it is probably caused byan unreliable WAN in which case this new feature helps you reduce this typeof network traffic.
NETLOGON Debug Output Samples
The following sections numbered 1, 2, 3, and 4 are about the NETLOGON debugoutputthat appears when trusts are involved:
The following NETLOGON debug-output is from a primary domain controller(PDC) ofthe trusting domain that cannot find a DC in the trusted domain (thenetwork cableis disconnected):
The above frames show that the PDC tries to find the DC by callingNlDcDiscoveryMachine three times and waits five seconds between each retry.
After these three retries the Scavenger Timer causes NETLOGON to look forthe trusted domain again every 15 minutes. Here are some of the frames thatappear (sent by the PDC of the trusting domain):
*BROADCAST NBT NS: Query req. for MASTERDOM <1C>: check to find a trusted domain DC
Because the PDC cannot find a DC by broadcasting the PDC starts using WINS:
*BROADCAST ARP_RARP ARP: Request, Target IP: 22.214.171.124: find the router to get to WINS
The PDC of the trusting domain can find a DC in the trusted domain:
NETLOGON debug output:
00:00:00 NlInitTrustList: domainname in LSA 00:00:00 NlUpdateTrustListBySid: domainname: Added to local trust list 00:00:00 NlDcDiscoveryMachine: domainname: Start Discovery 00:00:00 NlDcDiscoveryMachine: MASTERDOM: Found DC \\D-SPOCK on transport \Device\NetBT_Lance1 00:00:00 NlDcDiscoveryMachine: MASTERDOM: DC \\D-KIRK ignored. DC previously found. 00:00:00 NlDcDiscoveryMachine: MASTERDOM: DC \\NTD-UHURA ignored. DC previously found. 00:00:00 NlDcDiscoveryMachine: MASTERDOM: DC \\D-MCKOY ignored. DC previously found.
Here are some of the frames that appear (sent by the PDC of the trustingdomain to the DC of the trusted domain):
NETLOGON SAM LOGON request from client RESCTL1 D-KIRK NETLOGON SAM LOGON request from client RESCTL1 D-SPOCK NETLOGON SAM LOGON request from client RESCTL1 NETLOGON SAM LOGON request from client RESCTL1 D-MCKOY NETLOGON SAM Response to SAM LOGON request D-SPOCK RESCTL1 NETLOGON SAM LOGON request from client RESCTL1 126.96.36.199 NETLOGON SAM Response to SAM LOGON request D-KIRK RESCTL1 NETLOGON SAM LOGON request from client RESCTL1 NTD-UHURA NETLOGON SAM Response to SAM LOGON request NTD-UHURA RESCTL1 NETLOGON SAM Response to SAM LOGON request D-MCKOY RESCTL1
After the trust setup fails once because the cable is purposelydisconnected, the following NETLOGON debug-output occurs with the cablereconnected. The PDC tries to log on to the trusted domain:
00:00 NlSessionSetup: MASTERDOM Try Session setup 00:00 NlStartApiClientSession: MASTERDOM: Bind to server \\D-SPOCK. 00:00 NlSetStatusClientSession: MASTERDOM: Set connection status to 0 00:00 NlSessionSetup: MASTERDOM Session setup Succeeded
Here are some of the frames sent between trusting PDC and trusted DC:
R_LOGON RPC Client call logon:NetrServerReqChallenge(..) R_LOGON RPC Server response logon:NetrServerReqChallenge(..) R_LOGON RPC Client call logon:NetrServerAuthenticate2(..) R_LOGON RPC Server response logon:NetrServerAuthenticate2(..) R_LOGON RPC Client call logon:NetrLogonSamLogon(..) R_LOGON RPC Server response logon:NetrLogonSamLogon(..) R_LOGON RPC Client call logon:NetrLogonSamLogoff(..) R_LOGON RPC Server response logon:NetrLogonSamLogoff(..) NETLOGON SAM LOGON request from client RESCTL1 D-MCKOY NETLOGON SAM LOGON request from client RESCTL1 D-KIRK NETLOGON SAM LOGON request from client RESCTL1 NTHANSJUS
After the trust is established, the connection to the trusted domain istimed out (internally in NETLOGON):
00:00:00 NlTimeoutApiClientSession Called 00:00:45 NlTimeoutApiClientSession Called 00:01:30 NlTimeoutApiClientSession Called 00:02:15 NlTimeoutApiClientSession Called 00:02:15 NlTimeoutApiClientSession: MASTERDOM: Unbind from server \\D- SPOCK. 00:03:00 NlTimeoutApiClientSession CalledThis causes only the following frames to appear on the network: SMB C close file, FID = 0x805 RESCTL1 D-SPOCK IP SMB R close file D-SPOCK RESCTL1 IP RESCTL1 D-SPOCK TCP .A...., len: 0, seq: 7004192, ack: 422155081, win: 7883, src RESCTL1 D-SPOCK IP
The DC calls NlTimeoutApiClientSession every 45 seconds.
And finally the PDC drops the connection to the trusted DC by closing thenamed pipe.
NOTE: The PDC does not drop the secure channel and therefore does not haveto rediscover the DC in the trusted domain. This saves the PDC scavengerfrom having to look for the DC every 15 minutes.
Microsoft has confirmed this to be a problem in SNA Server for Windows NTversion 3.51.
This problem was corrected in the latest Windows NT 3.51 U.S. ServicePack. For information on obtaining the Service Pack, query on thefollowing word in the Microsoft Knowledge Base (without the spaces):