Page 176 - CISSO_Prep_ Guide

provide more consistent levels of performance. When this path
or circuit was permanently set up, this was called a permanent
virtual circuit (PVC). When the circuit was established as best
available at the time of communication, it would be called a
virtual switch circuit (SVC).

Many organizations chose to pay a premium to be guaranteed a
certain amount of bandwidth for their communications. This is
called Quality of Service (QoS).

Other developments in communications have included the
development of Multi-Protocol Label Switching (MPLS). MPLS
runs over frame relay or ATM. It allows engineering of the
traffic, including defining the route the information will travel,
QoS, and CoS (class of service) where different types of packets
can receive priority handling - voice getting priority over data,
for example.

Physical Media

There are many ways to connect devices today - wireless to
wired, fiber to copper. Each type has advantages and
disadvantages.

Wired technologies
Twisted Pair - twisted pair is the cheapest and possibly the
easiest type of media to work with. Over the years, we have seen
the development of higher grades of cable - both shielded (STP)
and unshielded twisted pair (UTP) that can handle higher-speed
traffic. UTP is connected to devices using simple RJ45
connectors. Every cable will be affected by attenuation - the loss