802.17c Protected Inter-Ring Connection Rafi Ram - Corrigent Systems July 2007

PIRC Suggestion Highlights Stations A & B are members of a protection group (PG) for interconnect between two rings Station A and station B are protection group members (PGM) One of the interconnected rings shall be provisioned as the “primary” ring and the other as “secondary” ring The station on the secondary ring with the lower MAC address is designated as the “0” member, and the other as the “1” member

Network Diagram Stations A & C are “peer” stations Stations B & D are “peer” stations Stations A & B are “mate” stations Stations C & D are “mate” stations Stations A & B are protection group members on the primary ring Station A is the “0” member and station B is the “1” member Stations C & D are protection group members on the secondary ring Station C is the “0” member and station D is the “1” member

Station-OK State Variable Station-OK = (adminStatus==UP) AND (mateVisable==TRUE) AND

Peer Stations Communication Peer stations exchange messages which are also used as “keep-alive” The messages consist the following information (per protection group): Station-OK state variable Peer keep-alive timer expired The peer messages are sent : periodically after a protection event after change of admin-status after peer keep-alive timer expires

Self-OK State Variable Self-OK = (my_Station-OK==TRUE) AND (my_KA_Timer_Expired==FALSE) AND (peer_Station-OK==TRUE) AND (peer_KA_Timer_Expired==FALSE)

Mate Stations Communication Mate stations exchange messages which are also used as “keep-alive” Mate stations exchange the value of the Self-OK state variable (per protection group) : The mate messages are sent : periodically after a protection event after change Self-OK state variable value The messages could be new control type or new OAM type

PIRC Stations Communication

Mate-OK State Variable Mate-OK = (mateVisable==TRUE) AND (mate_Self-OK==TRUE) AND (mate_KA_Timer_Expired==FALSE)

PGM State Machine

MAC Table Flush 802.17b – When an interconnecting station no longer appears in the topology, the MAC entries associated with that stations are deleted When a PIRC station it sends SAS_Group_Notify message when : it changes PG state to “FWD-None” it changes PG state from “FWD-All” to “FWD-mine”

myFlow(frame) Function The function could be used to implementation of the load-balancing functionality On of the possible implementations of the myFlow function could be : myFlow(frame) = (hashing(frame) modulo 2) == member-type The hashing could be on the service class and/or VLAN “member-type” equals to 0 if the station is the 0 member, and equals to 1 if the station is the 1 member

PIRC Sublayer Logic on the Path Client  MAC as State Table Row Condition Action 1 MAC is on primary ring Forward 2 PG state is “fwd-none” Discard 3 PG state is “fwd-all” 4 myFlow(frame) 5 -

PIRC Sublayer Logic on the Path Client  MAC as Pseudo-Code if (MAC is on primary ring) forward frame else if (((PG state is “fwd-mine”) and myFlow(frame)) or (PG state is “fwd-all”)) then discard frame

PIRC Sublayer Logic on the Path MAC  Client as State Table Row Condition Action 1 (MAC is on primary ring) and (RPR SA is the mate MAC address) and (PG state is “fwd-all”) Discard 2 MAC is on primary ring Forward 3 RPR SA is the mate MAC address 4 PG state is “fwd-none” 5 PG state is “fwd-all” 6 myFlow(frame) 7 -

PIRC Sublayer Logic on the Path MAC  Client as Pseudo-Code if (MAC is on primary ring) if ((PG state is “fwd-all”) and (RPR SA is the mate MAC address)) discard frame else forward frame if (RPR SA is the mate MAC address) if (((PG state is “fwd-mine”) and myFlow(frame)) or (PG state is “fwd-all”)) then

Local Tributaries at PIRC Stations According to the suggested algorithm, if the PIRC station are isolated on the primary ring, then their local tributaries are also disconnected Complicating the algorithm to allow forwarding through the secondary ring is not critical because : isolation on the primary ring is a DUAL failure if the primary ring has isolation, the local tributaries at the PIRC stations are usually not the biggest problem