How does TCAM differs from CAM

[nuggetinu]

Hi,

I've searched and read about both, and CAM is easily understandable. TCAM is somewhat complex and not that straight forward. Can someone outline the differences or make a side by side comparison to how TCAM differs from CAM, to make the differences easily understandable?

Thanks in advance.

[Reza Sharifi]

Hi,

Have a look at this link:

https://supportforums.cisco.com/t5/network-infrastructure-documents/cam-content-addressable-memory-vs-tcam-ternary-content/ta-p/3107938

HTH

[Joseph W. Doherty]

Are you familiar with wildcard matching?

If so, CAM support something like find "ABC" while TCAM supports something like find "A?C". The former will only match "ABC", the latter will match where the first letter is "A" and the third letter is "C" and the second letter doesn't matter.

[nuggetinu]

To what part of the process is parallel searching present? I cannot understand where does the parallel searching occur in the process.

[gs.skills]

Hello,

when the data enter the hardware for a match, this data is compared with all entries in the TCAM in one shot. It's about electronic (so it's not really parallel search, it's more a simultaneous match), you should look for an electronic diagram of a TCAM: the wire for each bit run all along the TCAM memory.

Regards,

Guillaume

[nuggetinu]

Thanks all. One last thing. If the adjacency table corresponds the MAC address to the IP address from the FIB, where is the corresponding egress port that the packet will be forwarded to? As as a last stage of the process it suddenly stops at the adjacency table. Does this also has the corresponding port to that MAC address, like in CAM?