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SIP connection is dropped on cluster failover Technical Level
Symptoms
  • SIP SBC (Session border controller) connection is disconnected when cluster failover occurs when SIP service with protocol inspection is being used in the rulebase. This is usually SIP TCP 5060 traffic.
  • TCP "First packet isn't syn" drops are seen for a few seconds after the failover.
  • Kernel debugs for SIP TCP as per (sk95369), shows:

    ;DATE TIME...;...;cpas_kbuf_get_ptr: glue_opq->size=184;
    ;DATE TIME...;...;sip_sync_conn_cpas_failover: calling cpas_sync_conn_state;
    ;DATE TIME...;...;cpas_sync_conn_state: syncing conn 0xd14530f8 (should_sync=0);
    ;DATE TIME...;...;cpas_is_queue_empty: side CPAS_CLIENT_SIDE, send queue is not empty;
    ;DATE TIME...;...;cpas_sync_conn: cannot sync conn ;
    ;DATE TIME...;...;sip_read_handler: total_len value at the end of the function 0;
    ;DATE TIME...;...;cpas_is_queue_empty: side CPAS_CLIENT_SIDE, send queue is not empty;
    ;DATE TIME...;...;cpas_sync_conn: cannot sync conn ;
Cause

When using the SIP service with sip_tcp protocol, traffic goes thru CPAS. CPAS fails to sync during failover because of founding data which is waiting for sending or waiting for processing.

This data may be heavy and transferring it between member would be a heavy process, hence by design the connection is not synced.


Solution
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