Avaya Configuring IP Multicasting and Multimedia Services Manuel d'utilisateur télécharger pdf (Page 143)

117355-C Rev 00

6-1

Chapter 6

Configuring QOSPF

QOSPF is an extension of OSPF that works in conjunction with RSVP to provide

quality of service for multicast dataflows.

For OSPF, the best path is the path with the least metric cost. OSPF does not

consider network resource information when it selects the best path to a

destination.

With QOSPF extensions added, OSPF/MOSPF calculates QoS routes that can

provide the best resources for a multicast flow even though the route may not be

the path with the least metric cost.

In Figure 6-1

, for example, host 3 (H3) on network 2 wants to send multicast data

at rate R to a group whose members (H1 and H2) reside on network 1. Without

QOSPF extensions, MOSPF in router 3 forwards the data to router 1 (using the

interface with lowest metric cost), whether or not router 1 has the resources to

transmit data at rate R.

Now assume that router 2 has the resources to transmit data at rate R and router 1

does not. With QOSPF enabled on all routers, OSPF forwards the data to router 2,

even though the interface has a higher metric cost.

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Avaya Configuring IP Multicasting and Multimedia Services Manuel d'utilisateur Page 143