Forwarding table incorporating hash table and content addressable memory
US6735670B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | May 12, 2000 |
| Grant date | May 11, 2004 |
| Priority date | — |
| Expiry date | May 12, 2020 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L69/22
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
A forwarding table comprising a combination of a hash table and a content addressable memory (CAM). The forwarding table combines a one way hash table and a small CAM to perform the forwarding information retrieval function. The CAM is used when an address cannot be found in the hash table. When MAC addresses are being added to the forwarding table, they are first tried in the hash table. The address is applied to the hash function and a resulting index input to the hash table. If a hit occurs, it indicates that an entry at that index already exists and a location in the CAM is then allocated for that address. As long as the CAM does not become full, a 100% hit rate is guaranteed. During retrieval, the hash table or the CAM forms the forwarding information output to the next processing stage. If an entry is not found in the hash table, it will typically be found in the CAM. If no entry is found in either, the received frame is flooded to all the ports of the network device.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.