Cisco Cisco ASR 5000
SGSN Support for Peer-Server Blocking
How it Works ▀
SGSN Administration Guide, StarOS Release 18 ▄
How it Works
The SCTP associations are between PSPs and ASPs. The control to bring down a SCTP association is added at the PSP
level. The option for
level. The option for
shutdown/no shutdown
is added under each PSP configuration. This information is stored in
SCT and is forwarded to the Session Controller.The Session Controller sends this configuration request to the Master
Link Manager via a messenger call. The Link Manager receives the configuration from the Master Manager. Based on
the current association state and the CLI (
Link Manager via a messenger call. The Link Manager receives the configuration from the Master Manager. Based on
the current association state and the CLI (
shutdown/no shutdown
) issued the following actions are taken:
1. If the CLI
shutdown
is issued, the shutdown flag is set. When the association is in an ESTABLISHED state, the
Link Manager initiates a SCTP SHUTDOWN towards the peer and moves to the LOCKED state after
shutdown procedure is completed.
shutdown procedure is completed.
2. If the CLI
no shutdown
is issued, the shutdown flag is not set and this serves as a trigger to INIT towards the
peer, provided the PSP is already in LOCKED state and SGSN is configured as client. A SCTP INIT is
triggered towards the peer. If the association is in any state other than LOCKED state, the configuration is
ignored.
triggered towards the peer. If the association is in any state other than LOCKED state, the configuration is
ignored.
The following table provides information on various Peer Server blocking scenarios based on the CLI configuration:
CLI
configuration
configuration
Current
Association State
Association State
SGSN Action
Result Association
State
State
shutdown
LOCKED
1. No action taken.
2. Association remains in LOCKED state.
2. Association remains in LOCKED state.
shutdown
CLOSED
1. Association is marked as LOCKED.
2. SCTP Abort is sent on receiving Init from peer, and the
2. SCTP Abort is sent on receiving Init from peer, and the
Init is dropped.
LOCKED
shutdown
COOKIE-WAIT
1. Association is marked as LOCKED.
2. SCTP Abort is sent for every subsequent Init from peer.
2. SCTP Abort is sent for every subsequent Init from peer.
LOCKED
shutdown
COOKIE-
ECHOED
ECHOED
1. Association is marked as LOCKED.
2. SCTP Abort is sent on receiving Init from peer and the
2. SCTP Abort is sent on receiving Init from peer and the
Init is dropped.
LOCKED
shutdown
ESTABLISHED
1. SCTP SHUTDOWN is initiated
2. The association is moved to the LOCKED state after
2. The association is moved to the LOCKED state after
SCTP shutdown procedure is complete
LOCKED
shutdown
SHUTDOWN-
PENDING
SHUTDOWN-
SENT
SHUTDOWN-
RECEIVED
SHUTDOWN-
ACK SENT
PENDING
SHUTDOWN-
SENT
SHUTDOWN-
RECEIVED
SHUTDOWN-
ACK SENT
Once the SCTP shutdown procedure is completed the association
is moved to the LOCKED state.
is moved to the LOCKED state.
LOCKED
no shutdown
LOCKED
If SGSN is the client, an INIT is initiated and the association is
moved to COOKIE-WAIT state. If SGSN is the server the
association is moved to CLOSED state
moved to COOKIE-WAIT state. If SGSN is the server the
association is moved to CLOSED state
COOKIE-WAIT (on
triggering
INIT)/CLOSED
triggering
INIT)/CLOSED