RCA THOMSON SpeedTouchTM (Wireless) Business DSL Router - Manual (Page 16)

Chapter 2
Introduction
E-NIT-CTC-20041213-0013 v0.5
14
2.2 Relative versus Guaranteed QoS
Types of QoS There are two different approaches to achieve QoS:
 Guaranteed QoS
:
Measurable connection parameters are specified for certain data or for a
connection, for example a guaranteed amount of bandwidth or delay across the
network. This allows for an exact specification and measurement of the Quality
of Service of data or a connection.
Examples of “guaranteed QoS” are Integrated Services (IntServ) and ATM QoS
like VBR and CBR connections.
 Relative QoS
(also referred to as differentiated QoS):
A priority indication is given as connection parameter to certain data or to a
connection, so that this data or connection will be handled with precedence
over data or connections with less priority. Obviously this approach guarantees
no specified bandwidth or latency, but it is the easiest approach to achieve
some level of QoS for high priority data.
Examples of “relative QoS” are Differentiated Services (DiffServ, DS) and
Ethernet VLAN user priority indication.
The guaranteed QoS approach is slightly more complicated than Relative
QoS because the connection parameters have to be specified and may be
verified throughout the entire network.
In case of relative QoS, data is often specified to belong to a certain Class of
Service (CoS) instead of QoS. Treatment and priority of data throughout the
network is configured for each supported CoS.