ogy that can also consider the application used (for example, Telnet or FTP).
Layer 4 switching provides additional routing above layer 3 by using the port
numbers found in the Transport layer header to make routing decisions.
These port numbers are found in Request for Comments (RFC) 1700 and
reference the upper-layer protocol, program, or application.
layer 4 port numbers. Another example is accounting information gathered
by NetFlow switching in Cisco's higher-end routers.
means a QoS can be defined for each user. For example, a number of users
can be defined as a Video group and be assigned more priority, or band-
width, based on the need for videoconferencing.
response time would suffer. This filter table must be much larger than any
layer 2 or 3 switch. A layer 2 switch might have a filter table only as large as
the number of users connected to the network, maybe even less if some hubs
are used within the switched fabric. However, a layer 4 switch might have
five or six entries for each and every device connected to the network! If the
layer 4 switch does not have a filter table that includes all the information,
the switch will not be able to produce wire-speed results.
provides high-speed scalability with low latency. It accomplishes this high