The invention describes a method of performing re-synchronizations on a DSL line to optimize the synchronization rate of the line. The line is monitored over a period of time, and a stable SNR margin is determined, below which the line is observed to lose synchronization. Historical synchronization rates and associated SNR margins for the line are recorded, and the highest stable synchronization rate is determined as the historical synchronization rate that does not have any associated SNR margins below the stable SNR margin. The method attempts to optimize the synchronization rate of the line towards this highest stable synchronization rate. To do this, the current target SNR margin imposed by DLM is identified, for example, by interrogating the DLM system or by noting the SNR margin on the line immediately after the most recent synchronizations. Assuming the current synchronization rate on the line is less than the highest stable rate, then the synchronization rate is optimized by triggering a synchronization of the line when the SNR margin is greater than the target SNR margin plus an additional predetermined amount. The result should be an increase in the synchronization rate, and can be repeated until the synchronization rate reaches the highest stable synchronization rate.