для Cisco Cisco Packet Data Gateway (PDG)
Evolved Packet Data Gateway Overview
▀ Features and Functionality
▄ ePDG Administration Guide, StarOS Release 17
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In case of mismatch in the PDN type between UE requested and the one provided by AAA server the call shall be
released by ePDG with “invalid-pdn-type” as the disconnect reason.
released by ePDG with “invalid-pdn-type” as the disconnect reason.
ePDG and PGW support on the same chassis(with GTPv2)
ePDG and PGW services does work together in combo mode (both enabled on the same chassis) with common
component resources like IPsec being utilized in best effort manner. Session recovery including card migration is
supported for the combo mode
component resources like IPsec being utilized in best effort manner. Session recovery including card migration is
supported for the combo mode
ICSR-VoLTE Support
ePDG does supports VoLTE call marking when the dedicated bearer corresponding to the QCI configured as VoLTE is
created. The QCI-QOS-Mapping configuration is used for configuring QCI as VoLTE. The voLTE call does have
special handling of allowing data during the ICSR pending standby state and during the ICSR audit phase (at new
active) which helps in reducing the data outage for the VoLTE calls during planned ICSR switchover.
created. The QCI-QOS-Mapping configuration is used for configuring QCI as VoLTE. The voLTE call does have
special handling of allowing data during the ICSR pending standby state and during the ICSR audit phase (at new
active) which helps in reducing the data outage for the VoLTE calls during planned ICSR switchover.
Currently, when sessions are created on the ePDG, there is period of 60 seconds (configurable, explained below) lag
before the sessions are check-pointed to the standby chassis. If chassis failure occurs during this period, the sessions that
were not check-pointed are lost. Also, in some ICSR switchovers, a large number sessions that were not check-pointed
need to be flushed resulting in additional delay in the switchover. This causes significant issues for VoLTE service.
before the sessions are check-pointed to the standby chassis. If chassis failure occurs during this period, the sessions that
were not check-pointed are lost. Also, in some ICSR switchovers, a large number sessions that were not check-pointed
need to be flushed resulting in additional delay in the switchover. This causes significant issues for VoLTE service.
This is critical for IMS sessions. If an IMS session is not synchronized with the standby chassis and an ICSR switchover
event occurs, the newly active chassis does not have any information of this session and the ePDG is out of sync with
other network elements. This situation cannot be corrected until the UE registers again (max 2 hours) and VoLTE calls
cannot be delivered to the UE. Therefore, it is critical to minimize the interval in which the session is not synchronized
with the peer.
event occurs, the newly active chassis does not have any information of this session and the ePDG is out of sync with
other network elements. This situation cannot be corrected until the UE registers again (max 2 hours) and VoLTE calls
cannot be delivered to the UE. Therefore, it is critical to minimize the interval in which the session is not synchronized
with the peer.
In maintenance mode it's required that ePDG should automatically delete the voLTE calls when the voLTE bearer gets
teared down or subscriber becomes non-volte after deletion of all voLTE bearers.
teared down or subscriber becomes non-volte after deletion of all voLTE bearers.
In earlier release, "clear subs all non-volte" was implemented to clear non volte calls. Now "clear subs all non-volte
auto-del" shall be implemented to delete non volte calls and mark the volte calls for auto deletion when the volte bearer
is torn down. This helps in avoiding manual intervention from admin to cleanup calls again when volte bearer is torn
down and the call becomes non-voLTE. Once the call is marked for auto-deletion it cannot be reverted.
auto-del" shall be implemented to delete non volte calls and mark the volte calls for auto deletion when the volte bearer
is torn down. This helps in avoiding manual intervention from admin to cleanup calls again when volte bearer is torn
down and the call becomes non-voLTE. Once the call is marked for auto-deletion it cannot be reverted.
Local PGW Resolution Support
In the current implementation of PGW selection, ePDG uses PGW address provided by AAA or uses DNS resolution.
With local PGW resolution support, PGW address can be configured locally. If the above two methods (static and
dynamic) PGW selection fails, or if PGW address were available but not reachable, then only locally configured
addresses are referred and used. Also, if there is no PGW address received from AAA or, if no DNS setup is present,
then also locally configured PGW addresses are referred. This way the existing functionality of PGW selection is
retained, and added an additional backup-mode with local PGW address configuration resolution.
With local PGW resolution support, PGW address can be configured locally. If the above two methods (static and
dynamic) PGW selection fails, or if PGW address were available but not reachable, then only locally configured
addresses are referred and used. Also, if there is no PGW address received from AAA or, if no DNS setup is present,
then also locally configured PGW addresses are referred. This way the existing functionality of PGW selection is
retained, and added an additional backup-mode with local PGW address configuration resolution.
A new CLI is introduced in ePDG Service Config mode where epdg-service is associated with “subscriber-map”, which
is also an indication that “Local PGW Resolution Support” is enabled for epdg-service. The local PGW resolution will
take into effect only if the CLI is configured and none of the existing method of PGW resolution method results in
session creation.
is also an indication that “Local PGW Resolution Support” is enabled for epdg-service. The local PGW resolution will
take into effect only if the CLI is configured and none of the existing method of PGW resolution method results in
session creation.
Below are the Local PGW Resolution Support scenarios:
PGW address received from AAA, but unreachable