1. 1Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems Hierarchical Refresh Simple idea – for scaling of refreshes, use the same mechanism, but apply it to the Srefresh messages themselves Srefresh messages so refreshed are treated as if they had been newly received We’ll use the notation S 2 refresh for the second level refresh

2. 2Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems Sender Side Include a message ID in Srefresh messages with the Ack request bit set Time_Values object permitted in Srefresh When acked the message ID can be placed in a second level summary refresh (S 2 refresh) S 2 refresh need not carry message ID or be acked Note that it is not germane to this scheme that all Srefresh messages use the hierarchy

3. 3Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems Receiver Side Refresh Ack and save messagesAck and save Srefresh messages set timeout to according to time-values object Reset timers on retransmission of the Srefresh message or if Message ID listed in aReset timers on retransmission of the Srefresh message or if Message ID listed in a S 2 refresh Upon receipt of anUpon receipt of an S 2 refresh Nack any message Ids for which no message is found Reprocess each refreshed Srefresh as if it had just been received

4. 4Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems Dropping a Message ID When a message with ID ‘m’ has timed-out Locate Srefresh message containing the Message-ID ‘m’ Note the Srefresh’s own Message-ID ‘s’ Drop the Message ID ‘m’ from Srefresh ‘s’ Locate the S 2 refresh which contains ‘s’ Drop ‘s’ from this message Pick a new Message ID for the Srefresh ‘s*’

5. 5Traffic Eng. © 1999, Cisco Systems, Inc. Cisco Systems Dropping a Message ID(2) Pick a new Message ID for the Srefresh ‘s*’ Set the ack-request bit When acked, s* can be added to a S 2 refresh message