9Nis
MS08-020 : How predictable is the DNS transaction ID?
Today we released MS08-020 to address a weakness in the Transaction ID (TXID) generation algorithm in the DNS client resolver. The TXID is a 16-bit entity that is primarily used as a synchronization mechanism between DNS servers/clients; in fact, you can think of it as an Initial Sequence Number (ISN) for DNS query/response exchanges.