1. A system comprising:buffer memory banks configured to temporarily buffer data units received over a plurality of network interfaces;
a traffic manager configured to select particular entries in particular buffer memory banks in which to store particular portions of the data units, the traffic manager further configured to write linking data that defines chains of entries within the buffer memory banks, each chain linking all of the entries in a single buffer memory bank that store data belonging to a same data unit;
a garbage collector configured to free previously utilized entries in the buffer memory banks for use in storing data for newly received data units;
one or more memories storing garbage collection lists for the buffer memory banks, each of the buffer memory banks having a different garbage collection list;
wherein the garbage collector is configured to free previously utilized entries in part by gradually traversing particular chains of entries and freeing traversed entries, the garbage collection lists indicating to the garbage collector starting addresses of the particular chains;
wherein the traffic manager is further configured to, in response to a determination to dispose of a given data unit, for each given buffer memory bank in at least a set of the buffer memory banks, write, to the given buffer memory bank's garbage collection list, data indicating a starting address of a chain of entries that store data for the given data unit in the given buffer memory bank.