ProCurve 8200zl Uživatelská příručka stáhnout pdf (Strana 109)

PIM-SM (Sparse Mode)

PIM-SM Operation and Router Types

Unlike PIM-DM, PIM-SM assumes that most hosts do not want to receive

multicast traffic, and uses a non-flooding multicast model to direct traffic for

a particular multicast group from the source to the VLAN(s) where there are

multicast receivers that have joined the group. As a result, this model sends

traffic only to the routers that specifically request it.

PIM-SM Operation

In a given PIM-SM domain, routers identified as Designated Routers (DRs),

Rendezvous Points (RPs), and a Bootstrap Router (BSR) participate in deliv-

ering multicast traffic to the IP multicast receivers that request it. This

approach avoids the flooding method of distributing multicast traffic

(employed by PIM-DM) and is best suited for lower bandwidth situations.

The software supports the following operation to enable multicast traffic

delivery within a PIM-SM domain:

■ From a pool of eligible DR candidates in each VLAN, one Designated

Router (DR) is elected for each VLAN interface having at least one PIM-

SM router. In a multinetted domain, this DR supports multicast traffic

from a source on any subnet in the VLAN.

■ From a pool of eligible Bootstrap Router (BSR) candidates in the domain,

one BSR is elected for the entire domain.

■ From a pool of eligible Candidate Rendezvous Points (C-RPs), one is

elected to support each multicast group or range of groups allowed in the

domain, excluding any group supported only by static-RPs. The multicast

groups allowed in the domain are determined by the aggregation of the

groups allowed by the individually configured RPs and any static-RPs.

(Note that RP-Cs and static RP’s can be configured with overlapping

support for a given set of multicast groups.)

Rendezvous-Point Tree (RPT)

When a DR in a VLAN receives traffic for a particular multicast group from a

source on that VLAN, the DR encapsulates the traffic and forwards it to the

RP elected to support that multicast group. The RP decapsulates the traffic

and forwards it on toward the multicast receiver(s) requesting that group. This

forms a Rendezvous Point Tree (RPT) extending from the DR through any

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ProCurve 8200zl Uživatelská příručka Strana 109