The IEEE 802.17 working group
created the RPR standard to address these service provider requirements.
RPR and Multiservice Support As mentioned in point C above and discussed in
greater detail later in this chapter, RPR provides 4 classes of service. It also contains a
ring wide protocol that makes each switch aware of the state of every link on the ring.
The practical result of these two mechanisms is that delay and delay variation on the
RPR become irrelevant even for voice and video applications. Hence, RPR networks
support any data or circuit application with whatever performance is required for the
application.
RPR and Quality of Service These same mechanisms ensure quality of service (see
Table 12.1). An RPR ring is deterministic. The performance of services put on a ring is
Resilient Packet Ring (RPR) 331
guaranteed. Along with classes of service and ring-wide awareness of the bandwidth
state of each inter-switch link there is a transit buffer, described in greater detail later
in the chapter, which passes any traffic through the switch without queuing. This
eliminates delay variation from the RPR network. Ethernet switches, having no network-
wide information about link-states on the network may require packets to queue
at each node.
Pages:
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765