MVID 20h - Request Initialization
Destination Address: C0-00-00-00-00-02 (Ring Parameter Server)
Destination Class: 5 (Ring Parameter Server)
Source Class: 0 (ring station)
Subvectors: SVID 23h - Adapter Software Level
SVID 22h - Product Instance ID
This frame is transmitted in phase 4 of the insertion process to request operational parameters from the ring parameter server (RPS).
First of all, a token-ring adapter starts operation with default parameter values. Then it send a 'request initialization' MAC frame the the ring parameter server's functional address. If there is no reply, the adapter will further use the default parameter values; if there is a reply, it will change its paramter values accordingly.
Bridges are often used as ring parameter server (RPS).