Hubs vs. Switches vs. Routers - Router Alley

Multilayer Switching
Hubs vs. Switches vs. Routers v1.31 – Aaron Balchunas 12
Multilayer switching is a generic term, referring to any switch that
forwards traffic at layers higher than Layer-2. Thus, a Layer-3 switch is
considered a multilayer switch, as it forwards frames at Layer-2 and packets
at Layer-3.
A Layer-4 switch provides the same functionality as a Layer-3 switch, but
will additionally examine and cache Transport-layer application flow
information, such as the TCP or UDP port.
By caching application flows, QoS (Quality of Service) functions can be
applied to preferred applications.
Consider the following example:
Network and application traffic flows from ComputerA to the Webserver
and Fileserver will be cached. If the traffic to the Webserver is preferred,
then a higher QoS priority can be assigned to that application flow.
Some advanced multilayer switches can provide load balancing, content
management, and other application-level services. These switches are
sometimes referred to as Layer-7 switches.
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