Glossary
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subnetwork
1) Any network that is part of a larger IP network and is
identified by a subnet address. A network administrator segments a network
into subnetworks in order to provide a hierarchical, multilevel routing struc-
ture, and at the same time protect the subnetwork from the addressing com-
plexity of networks that are attached. Also known as a subnet. See also: IP
address, subnet mask, and subnet address. 2) In OSI networks, the term spe-
cifically refers to a collection of ESs and ISs controlled by only one adminis-
trative domain, using a solitary network connection protocol.
SVC
switched virtual circuit: A dynamically established virtual circuit, cre-
ated on demand and dissolved as soon as transmission is over and the circuit
is no longer needed. In ATM terminology, it is referred to as a switched vir-
tual connection. See also: PVC.
switch
1) In networking, a device responsible for multiple functions such
as filtering, flooding, and sending frames. It works using the destination
address of individual frames. Switches operate at the data link layer of the
OSI model. 2) Broadly, any electronic/mechanical device allowing connec-
tions to be established as needed and terminated if no longer necessary.
switch block
The switch block is a combination of layer 3 switches and
layer 3 routers. The layer 2 switches connect users in the wiring closet into
the access layer and provide 10 or 100Mbps dedicated connections. 1900/2820
and 2900 Catalyst switches can be used in the switch block.
switched Ethernet
Device that switches Ethernet frames between seg-
ments by filtering on hardware addresses.
switched LAN
Any LAN implemented using LAN switches. See also:
LAN switch.
switch-fabric
The central functional block of any switch design; respon-
sible for buffering and routing the incoming data to the appropriate output
ports.
synchronous transmission
Signals transmitted digitally with precision
clocking. These signals have identical frequencies and contain individual
characters encapsulated in control bits (called start/stop bits) that designate
the beginning and ending of each character. See also: asynchronous trans-
mission and isochronous transmission.
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