13. A method comprising:receiving packets over one or more networks;
assigning the packets to packet queues;
based on the packet queues, determining when to process specific packets of the packets, the specific packets dequeued from the packet queues when processed;
tracking a delay associated with a particular packet queue of the packet queues, the delay based on a duration of time for which a designated marker packet has been in the particular packet queue, another packet being designated as the marker packet whenever the currently designated marker packet departs from the particular packet queue;
when the delay exceeds an expiration threshold, marking the particular packet queue as expired;
while the particular packet queue is marked as expired, dropping one or more packets assigned to the particular packet queue, the one or more packets including at least one packet other than the currently designated marker packet.