Paradyne BitStorm 2400, User Manual

Page: 20 / 90

1. BitStorm 2400 Overview
1-10
December 2002 2400-A2-GB20-10
Multicast Group Membership Management
Multicast group membership management operations include:
!
Joining a Multicast Group
!
Multicast Group Membership Query
!
Multicast Group Membership Report
!
Leaving a Multicast Group
!
Summarizing IGMP reports to minimize duplicate information being forwarded
to the router interface
!
Generating proxy Queries Messages in the event there is no local multicast
enabled router
Multicast Traffic Routing
To properly and efficiently implement multicast traffic routing in the access
network, the following situations are handled:
!
First Member Joining the Multicast Group
!
Multicast packet forwarding and replication at Layer 2 elements
!
Detecting the presence of IGMP Version 1 or IGMP Version 2 hosts on
subscriber segments.
!
Determining when the last active member leaves a multicast group
Multicast IP Address and MAC Address Mapping
IP Multicast addresses are 32-bits long with the four high order bits set to “1110,”
which leaves 28 bits for multicast groups. When IP Multicast traffic is routed across
a Layer 2 network, the lower 23 bits of the 28-bit Multicast Group Address are
mapped into the lower 24 bits of the corresponding MAC multicast address and the
most significant bit is set to 0. The higher 24 bits of the MAC multicast address are
fixed to 01.00.5E.
Because only 23 bits of the 28 bits of the IP multicast address are mapped into the
MAC multicast address, this leaves 32 IP multicast addresses mapped into a
single MAC multicast address. The CO and the BitStorm 2400 both need to
inspect the IP header in the multicast frame to determine the actual IP multicast
group for forwarding traffic on the right port.