Multiple RRAS Client Disconnects Cause Increased CPU Usage (193499)

SYMPTOMS

When you run the Routing and Remote Access Service on a system with clients who continuously connect and disconnect over a period of several hours, you notice a systematic slowdown on the server with a corresponding increase in CPU usage.

The slowdown can be characterized by using Performance Monitor to view the Processor object's % Processor Time counter, which indicates a maximum value of 100. Monitoring the Network Interface object's Bytes Sent and Bytes Received counters will also show consistent spikes during a client's connection period.

CAUSE

During a client's connection, the router will allocate memory on the server to perform a query against the interface table, allocating memory for the whole table. It does so by looking at the count of interfaces and allocates an amount equal to the number of connections multiplied by the number of bytes used by the router's interface table. Clients who dial in are counted as an interface by the router and are added to the table. However, when a client disconnects, the system does not decrement the connection count and subsequent connections continue to add to the size of the table. Repeated queries on the increasingly large amount of memory allocated to the router interface table results in the perceptible slowdown of the server.

RESOLUTION

To resolve this problem, obtain the latest service pack for Windows NT 4.0 or Windows NT Server 4.0, Terminal Server Edition. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

152734 How to Obtain the Latest Windows NT 4.0 Service Pack

STATUS

Microsoft has confirmed that this is a problem in Windows NT 4.0 and Windows NT Server 4.0, Terminal Server Edition. This problem was first corrected in Windows NT 4.0 Service Pack 4.0 and Windows NT Server 4.0, Terminal Server Edition Service Pack 4.