MME restoration is a
3GPP specification-based feature designed to gracefully handle the sessions
at S-GW once S-GW detects that the MME has failed or restarted.
If the S-GW detects an MME failure based on a different restart
counter in the Recovery IE in any GTP Signaling message or Echo Request / Response,
it will terminate sessions and not maintain any PDN connections.
As a part of this
feature, if a S-GW detects that a MME or S4-SGSN has restarted,
instead of removing all the resources associated with the peer node,
the S-GW shall maintain the PDN connection table data and
MM bearer contexts for some specific S5/S8
bearer contexts eligible for network initiated service restoration,
and initiate the deletion of the resources associated with all the
other S5/S8 bearers.
bearers eligible for network initiated service restoration are determined
by the S-GW based on operator's policy, for example, based on the
QCI and/or ARP and/or APN.
The benefit of this
feature is that it provides support for the geo-redundant pool feature
on the S4-SGSN/MME. In order to restore session when the
MME receives a DDN, the S-GW triggers restoration when the serving
MME is unavailable, by selecting another MME and sending DDN. This
helps in faster service restoration/continuity in case
of MME/S4-SGSN failures.
This mode is
used to configure a pool of IP addresses associated with a pool
ID and pool type (either MME or S4-SGSN) for Network Triggered Service
Exec > Global Configuration
> NTSR Pool Configuration
configure > ntsr pool
pool-id id > pool-type type
Entering the above command
sequence results in the following prompt:
The commands or keywords/variables
that are available are dependent on platform type, product version,
and installed license(s).