An alternative form of CAM, known as Ternary CAM (T-CAM), extends the idea
of CAM to provide partial match searches. In essence, each bit in a slot can have three
values: zero, one, or ‘‘don’t care’’. Like a standard CAM, a T-CAM performs the
search operation in parallel by examining all slots simultaneously. Unlike a standard
CAM, however, a T-CAM only performs the match on bits that have the value zero or
one. Partial matching allows a T-CAM to be used in cases where two or more entries
in the CAM overlap — a T-CAM can find the best match (e.g., the longest prefix
match).