request, and subject to bandwidth management policy. RSVP provides the mechanisms to do
this, as a part of the IntServ architecture.
RSVP supports two different types of reservation:
: This comes as close as possible to emulating a dedicated virtual
'
(
)
*
)
+
,
-
-
.
circuit. It provides firm (mathematically provable) bounds on end to end queuing
delays by combining the parameters from the various network elements in a path, in
addition to ensuring bandwidth availability.
: This is equivalent to best effort service under unloaded
/
0
+
,
*
0
1
1
-
.
2
0
)
.
conditions. Hence, it is better than best effort, but cannot provide the strictly
bounded service that Guaranteed service promises.
2.2.3.2 Prioritization Based
Differentiated Services Framework (DiffServ): The Differentiated Services Framework
being defined by the IETF is intended to meet the need for relatively simple and coarse
methods of providing differentiated classes of service for Internet traffic, to support various
types of applications, and specific business requirements. The differentiated service
approach to providing quality of service in networks employs a small, well defined set of
building blocks from which a variety of services may be built. Network traffic is classified
and apportioned network resources according to bandwidth management policy criteria. To
enable QoS, classifications give preferential treatment to applications identified as having
more demanding requirements.
DiffServ currently has two standard per hop behaviors (PHBs) defined that effectively
represent two service levels (traffic classes):
(EF) EF minimises delay and jitter and provides the
3
4
5
6
7
8
9
6
7
:
;
<
=
>
<
7
8
?
@
highest level of aggregate quality of service. Any traffic that exceeds the traffic
profile (which is defined by local policy) is discarded.
(AF): Has four classes and three drop precedences
A
B
B
C
<
6
7
:
;
<
=
>
<
7
8
?
@
within each class. Excess AF traffic is not delivered with as high probability as the
traffic within profile, which means it may be demoted but not necessarily dropped.
&