The keep-alive mechanism for Microsoft SQL Server 2000 allows remote attackers to cause a denial of service (bandwidth consumption) via a "ping" style packet to the Resolution Service (UDP port 1434) with a spoofed IP address of another SQL Server system, which causes the two servers to exchange packets in an infinite loop.
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2002/ms02-039
http://www.securityfocus.com/bid/5312
http://www.iss.net/security_center/static/9662.php