Troubleshooting delays in pcAnywhere connections over Wide Area Networks.

Article:TECH157421  |  Created: 2011-04-05  |  Updated: 2012-06-18  |  Article URL http://www.symantec.com/docs/TECH157421
Article Type
Technical Solution


Issue



You are experiencing an unusual delay in a connection between a Remote and a Host located on different subnets. You have eliminated Authentication as the cause of the delay, as you are using standard pcAnywhere authentication types.


Environment



Delays can be observed over large LAN and WAN environments.


Cause



When a pcAnywhere Remote attempts to connect to a Host, the Host will send an API call to Windows to resolve the hostname of the IP address that has just initiated the connection. There are two reasons for this:

  1. In order to notify the User of the name of the system that is connecting. This information is conveyed via a bubble notification in the Task tray.
  2. In order to record the hostname of the Remote system to the pcAnywhere or Windows Event logs if logging is enabled.

Name Resolution follows the sequence specified in the following registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\SERVICES\Tcpip\ServiceProvider

The system will try to resolve the hostname starting with the method with the lowest priority setting. The normal Windows XP priority order is as follows:

Entry

Priority

Method

LocalPriority

499

Local Names Cache

HostsPriority

500

Hosts File

DnsPriority

2000

DNS Lookup

NetbtPriority

2001

NetBT Name Resolution

In the above case, the Host system will first check its local DNS Resolver and NetBIOS caches, followed by its Hosts file to see if it already has an entry for the hostname of the Remote. If not, it will attempt to resolve the host name using a reverse DNS lookup on the IP address to its local DNS server. If a PTR record exists for the FQDN, the DNS server will return the hostname, pcAnywhere will extract the hostname from the FQDN and the connection will continue. However, if no such record exists, no valid forwarder is configured or if the DNS query times out with no response, the Host will send an NetBIOS name lookup directly to the Remote.

 


Solution



Adding the hostname and IP address of the Remote to the Hosts file of the Host machine can be used as a quick test to confirm that the delay is being caused by delays in Name Resolution.

Delays in name resolution can be be due to an incorrectly functioning DNS infrastructure. Ensure that nodes in the Hosts subnet are able to resolve the hostnames of machines in the Remotes subnet by a reverse DNS lookup. This can be tested by flushing the DNS ("ipconfig /flushdns") and NetBIOS ("nbtstat -c") caches, then running the command "nslookup <IP address>".

Unfortunately, there is no way to configure the pcAnywhere Host program to prevent this reverse DNS lookup of the remote computer.  If DNS resolution is not working, a review of DNS configuration may be necessary to ensure that Name Resolution services are optimized.




Article URL http://www.symantec.com/docs/TECH157421


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