Windows NT 4.0 DHCP Client Modified to be RFC 2131 Retransmission Compliant

ID: Q190552

The information in this article applies to:

SYMPTOMS

There will be occasional failures to lease an IP address during busy network or DHCP server times.


CAUSE

The DHCP client retry mechanism has been modified to be in compliance with RFC 2131.

The mechanism is described in RFC 2131, which states:

DHCP clients are responsible for all message retransmission. The client MUST adopt a retransmission strategy that incorporates a randomized exponential backoff algorithm to determine the delay between retransmissions. The delay between retransmissions SHOULD be chosen to allow sufficient time for replies from the server to be delivered based on the characteristics of the internetwork between the client and the server. For example, in a 10Mb/sec Ethernet internetwork, the delay before the first retransmission SHOULD be 4 seconds randomized by the value of a uniform random number chosen from the range -1 to +1. Clients with clocks that provide resolution granularity of less than one second may choose a non-integer randomization value. The delay before the next retransmission SHOULD be 8 seconds randomized by the value of a uniform number chosen from the range -1 to +1. The retransmission delay SHOULD be doubled with subsequent retransmissions up to a maximum of 64 seconds. The client MAY provide an indication of retransmission attempts to the user as an indication of the progress of the configuration process.
The new Windows NT DHCP client (Dhcpcsvc.dll) behaves as described in the RFC. It sends the first DHCP request plus up to three retries, if needed.


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, please see the following article in the Microsoft Knowledge Base:

Q152734 How to Obtain the Latest Windows NT 4.0 Service Pack


STATUS

Microsoft has confirmed this to be 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.


Keywords          : NT4SP4Fix kbbug4.00 kbfix4.00.sp4 
Version           : WinNT:4.0
Platform          : winnt 
Issue type        : kbbug

Last Reviewed: April 10, 1999