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| 1.2 |  | Key Characteristics of Various Switching Technologies |
| 1.2.5 |  | Mulilayer switching |

MLS combines Layer 2 switching, Layer 3 routing functionality, and the caching of Layer 4 port information. Multilayer switching provides wire-speed (hardware-based) switching enabled by Application-Specific Integrated Circuits (ASICs) within a switch, which share the duties normally assumed by the CPU.

With multilayer switching, the switch caches information about a given flow of data through the switch, inspecting the PDU header information of the first frame in the flow and switching the remaining data at wire speed based on the information from the first frame. This explains the phrase used in multilayer switching, route once, switch many.

> Note: The term flow loosely describes a stream of data between two endpoints across a network. The flow can be based on Layer 2 and 3 information or a combination of Layer 2, 3, and 4 information.