Alcatel-Lucent 7450 Manual page 160

Ingress Path Management for P2MP LSP Packets
associated with it. Two paths are enabled by default, a primary path and a secondary path, and
represent the high-priority and low-priority paths respectively. Each VPLS SAP, access interface,
and network interface will have a set of per forwarding class multicast and/or broadcast queues
which are defined in the ingress QoS policy associated with them. The expedited queues will be
attached to the primary path while the non-expedited queues will be attached to secondary path.
When IMPM is enabled and/or when a P2MP LSP ILM exists on the ingress IOM-3/IMM, the
remaining multicast paths are also enabled. 16 multicast paths are supported by default with 28 on
7950 XRS systems and 7750 SR12-e systems, with the latter having the tools perform system set-
fabric-speed fabric-speed-b. One path remains as a secondary path and the rest are primary
paths.
A separate pair of shared multicast queues is created on each of the primary paths, one for IMPM
managed packets and one for P2MP LPS packets not managed by IMPM. The secondary path does
not forward IMPM managed packets or P2MP LSP packets. These queues have default rate
(PIR=CIR) and CBS/MBS/Hi-Priority-Only thresholds but can be changed away from default
under the bandwidth policy.
A VPLS snooped packet, a PIM routed packet, or a P2MP LSP packet is managed by IMPM if it
matches a <*,G> or a <S,G> multicast record in the ingress forwarding table and IMPM is enabled
on the ingress MDA where the packet is received. The user enables IMPM on the ingress MDA
data path using the config>card>mda>ingress>mcast-path-management command.
A packet received on an IP interface and to be forwarded to a P2MP LSP NHLFE or a packet
received on a P2MP LSP ILM is not managed by IMPM when IMPM is disabled on the ingress
MDA where the packet is received or when IMPM is enabled but the packet does not match any
multicast record. A P2MP LSP packet duplicated at a branch LSR node is an example of a packet
not managed by IMPM even when IMPM is enabled on the ingress MDA where the P2MP LSP
ILM exists. A packet forwarded over a P2MP LSP at an ingress LER and which matches a <*,G>
or a <S<G> is an example of a packet which is not managed by IMPM if IMPM is disabled on the
ingress MDA where the packet is received.
When a P2MP LSP packet is not managed by IMPM, it is stored in the unmanaged P2MP shared
queue of one of the primary multicast paths.
By default, non-managed P2MP LSP traffic is distributed across the IMPM primary paths using
hash mechanisms. This can be optimized by enabling IMPM on any forwarding complex, which
allows the system to redistributed this traffic on all forwarding complexes across the IMPM paths
to achieve a more even capacity distribution. Be aware that enabling IMPM will cause routed and
VPLS (IGMP and PIM) snooped IP multicast groups to be managed by IMPM.
The above ingress data path procedures apply to packets of a P2MP LSP at ingress LER, LSR,
branch LSR, bud LSR, and egress LER. Note that in the presence of both IMPM managed traffic
and unmanaged P2MP LSP traffic on the same ingress forwarding plane, the user must account for
the presence of the unmanaged traffic on the same path when setting the rate limit for an IMPM
path in the bandwidth policy.
Page 160 7450 ESS MPLS Guide