R3303-HP HSR6800 Routers High Availability Configuration Guide

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Broadcast, multicast, and unknown unicast transmission
Figure 13 Broadcast, multicast, and unknown unicast transmission on an RPR ring
Figure 13 shows how a broadcast, multicast, or unknown unicast frame is transmitted on an RPR ringlet:
1. The source station inserts the frame into the data stream on Ringlet 0 or Ringlet 1.
2. Transit and destination stations copy and transit the frame if the TTL of the frame has not expired.
3. The frame is stripped when it returns to the source station or when its TTL expires.
Topology discovery
RPR performs automatic topology discovery to collect such information as the number of stations, ring
state, and order of the stations on the ring to build a topology database. This database does not change
after the ring topology becomes stable.
Topology database
Each RPR station maintains a topology database that describes the topology of the entire RPR ring. Based
on this database, the station creates its ringlet selection table.
A topology database contains three categories of information:
• Ringlet topology information, such as the number of stations, ring state, and available bandwidth.
• Local station topology information, such as the MAC address, protection mode, protection state,
station name, and topology checksum of the local station and the neighbor stations.
• Topology information of other stations, such as the MAC address, validity state, reachability,
protection mode, station ID, station name, and reserved bandwidth.
Topology discovery process
During the topology discovery process, RPR uses the following three types of control frames to transmit
topology data: topology protection (TP), attribute discovery (ATD), and topology checksum (TC).
• TP frames convey configuration and status information of stations. The stations on an RPR ring
broadcast TP frames to advertise their configuration and status information, and update their own
topology databases after receiving TP frames from other stations. Finally, all the stations reach an
agreement on the topology of the ring.
• ATD frames convey attributes of the local station such as the MAC address and station name. These
attributes will be included in the topology database.