Abstract: A packet switched network tester for testing a network using a packet delay variation test profile that has a plurality of different delays for applying to timestamps of packets received at the tester, the tester being configured to: detect a packet; determine whether a test profile delay when applied to the packet would result in a packet delayed to a time after any preceding packet; if not, repeat the steps of detecting and determining with subsequent packets; if yes, apply the delay to the timestamp of the packet and identify the next test profile delay; and repeat for the next test profile delay the steps of detecting and determining.

Abstract: An in-line tester (10) for testing a telecommunications network. The tester (10) is connectable in line in a communications channel in the network, between network elements or nodes (12), so that all packets within that channel have to flow through it.