Cisco Cisco Packet Data Interworking Function (PDIF)
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MME Changes in Release 17
MME Enhancements for 17.0 ▀
Release Change Reference, StarOS Release 17 ▄
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With this feature the MME can now support a maximum of 64,000 eNodeB connections on the ASR 5500 platform with
a fully loaded system (chassis). The maximum number of MME Managers has been increased to 16 in order to support
this increase in eNodeB connections.
a fully loaded system (chassis). The maximum number of MME Managers has been increased to 16 in order to support
this increase in eNodeB connections.
On the ASR 5000, the number of supported eNodeBs and MME Managers has not changed (32,000 and 8 respectively).
Operators can potentially reduce operating expenditures as a greater number of eNodeBs can be connected to the same
MME.
MME.
CSCum35668 - Node Restoration: MME handling of PGW restart
Feature Changes
MME handling of PGW Restart
This feature requires that a valid MME Resiliency license key be installed. Contact your Cisco Account or Support
representative for information on how to obtain a license.
representative for information on how to obtain a license.
P-GW Restart Notification Procedure is a standards-based procedure supported on the S-GW to notify detection of P-
GW failure to the MME/S4-SGSN. P-GW failure detection is performed by the S-GW when it detects that the P-GW
has restarted (based on restart counter received from the restarted P-GW) or when it detects that P-GW has failed but
not restarted (based on path failure detection). When an S-GW detects that a peer P-GW has restarted, it deletes all PDN
connection table data and bearer contexts associated with the failed P-GW and notifies the MME via P-GW Restart
Notification. The S-GW indicates in the echo request/response on S11/S4 interface that the P-GW Restart Notification
procedure is supported.
GW failure to the MME/S4-SGSN. P-GW failure detection is performed by the S-GW when it detects that the P-GW
has restarted (based on restart counter received from the restarted P-GW) or when it detects that P-GW has failed but
not restarted (based on path failure detection). When an S-GW detects that a peer P-GW has restarted, it deletes all PDN
connection table data and bearer contexts associated with the failed P-GW and notifies the MME via P-GW Restart
Notification. The S-GW indicates in the echo request/response on S11/S4 interface that the P-GW Restart Notification
procedure is supported.
P-GW Restart Notification Procedure is an optional procedure and is invoked only if both the peers, MME/S4-SGSN
and S-GW, support it.
and S-GW, support it.
In the absence of this procedure, the S-GW will initiate the Delete procedure to clear all the PDNs anchored at that
failed P-GW, which can lead to flooding of GTP messages on S11/S4 interface if there are multiple PDNs using that S-
GW and P-GW.
failed P-GW, which can lead to flooding of GTP messages on S11/S4 interface if there are multiple PDNs using that S-
GW and P-GW.
In this release, the MME adds support for the P-GW restart handling procedures as specified in 3GPP TS 23.007
v11.6.0. An S-GW will send the “PGW Restart Notification” message only to the SGSNs / MMEs that indicated their
support of this feature through the Echo Request -> Node Features IE -> PRN bit.
v11.6.0. An S-GW will send the “PGW Restart Notification” message only to the SGSNs / MMEs that indicated their
support of this feature through the Echo Request -> Node Features IE -> PRN bit.
This feature reduces the S11 signaling load between the S-GW and MME in case of a P-GW restart.
PDN Deactivation Behavior
If a PDN is impacted and needs to be restored:
If all PDNs of a UE are impacted, a UE in ECM-Connected state will be explicitly detached with cause “reattach
required” and a UE in ECM-IDLE state will be paged. If Paging is successful, then the UE will be explicitly
detached with cause “reattach required”. Otherwise, the UE will be implicitly detached.
detached with cause “reattach required”. Otherwise, the UE will be implicitly detached.
If some PDNs of a UE are impacted, a UE in ECM-Connected will be sent NAS Deactivate Bearer Request with
cause “reactivation requested” and a UE in ECM-IDLE state will be paged. If Paging is successful, then the UE
will be sent a NAS Deactivate Bearer Request with cause “reactivation requested”. Otherwise, the PDN will be
locally deactivated.
will be sent a NAS Deactivate Bearer Request with cause “reactivation requested”. Otherwise, the PDN will be
locally deactivated.
If a PDN is impacted but does not need to be restored:
If all PDNs of a UE are impacted, a UE in ECM-Connected state will be explicitly detached with cause “reattach
required” and a UE in ECM-IDLE state will be paged. If Paging is successful, then the UE will be explicitly
detached with cause “reattach required”. Otherwise, the UE will be implicitly detached.
detached with cause “reattach required”. Otherwise, the UE will be implicitly detached.