Paging Policy
Differentiation
This chapter describes
the Paging Policy Differentiation feature and explains how it is configured.
The product administration guides provide examples and procedures for
configuration of basic services on the system. It is recommended that you
select the configuration example that best meets your service model and
configure the required elements for that model, as described in the
P-GW
Administration Guide, the
S-GW
Administration Guide, or the
SAEGW
Administration Guide before using the procedures in this chapter.
This chapter includes
the following sections:
Feature
Description
S-GW/P-GW provide
configuration control to change the DSCP value of the user-datagram packet and
outer IP packet (GTP-U tunnel IP header). DSCP marking is done at various
levels depending on the configuration. When the Paging Policy Differentiation
(PPD) feature is enabled, however, the user-datagram packet DSCP (tunneled IP
packet) marking does not change.
Currently,
standards specify QCI to DSCP marking of outer GTP-U header only. All
configurations present at ECS, P-GW, and S-GW to change the user-datagram
packet DSCP value are non-standard. The standards-based PPD feature dictates
that P-CSCF or similar Gi entity marks the DSCP of user-datagram packet. This
user-datagram packet DSCP value is sent in DDN message by S-GW to MME/S4-SGSN.
MME/S4-SGSN uses this DSCP value to give paging priority.
Important:
P-GW and S-GW
should apply the PPD feature for both Default and Dedicated bearers. As per the
specifications, P-GW transparently passes the user-datagram packet towards
S-GW. This means, if PPD feature is enabled, operator can't apply different
behavior for Default and Dedicated bearers.
Relationships
Since P-GW/S-GW
support non-standard based DSCP marking, there is a conflict when both standard
based PPD feature and non-standard based user-datagram packet DSCP
configuration is enabled. To avoid this conflict:
-
APN and service
level configuration is ignored if PPD feature is enabled.
-
S-GW/P-GW can
alter the outer GTP-U header DSCP value, even if PPD feature is enabled.
-
User-datagram
packet DSCP value is unaltered by ECS, P-GW, and S-GW if PPD feature is
enabled.
-
At P-GW,
APN-level configuration is added to enable/disable the PPD feature.
-
At S-GW,
service-level configuration is added to enable/disable the PPD feature. This is
to send DSCP in Paging and Service Information IE of all the DDN messages
triggered by either IMS-PDN or Internet-PDN, etc.
Important:
It is up to
MME/S4-SGSN to use the Paging and Service Information IE of DDN message.
-
Separate Paging
feature and PPD feature co-exist in system. That means, if both features are
enabled, both Paging and Service Information IE and Separate-paging IE are sent
in DDN.
-
Currently on
P-GW, the DSCP configuration is getting applied at sub-session level during
call setup time. So, when the PPD CLI is enabled for P-GW, it is applicable for
new calls.
-
Currently on
S-GW, the DSCP configuration is getting applied at S-GW service level. So, when
PPD CLI is enabled in S-GW service, it is applicable for both new and existing
calls.
-
Once the PPD
CLI is enabled, it exists even after Session Recovery and ICSR switch over.
-
The Paging and
Service Information IE is used to carry per bearer paging and service
information.
License
PPD is a license
enabled feature. S-GW Paging Profile license key is required to enable PPD
functionality for P-GW, S-GW, and SAEGW.
Important:
Contact your Cisco
account representative for information on how to obtain a license.
How It Works
Architecture
S-GW
When S-GW supports
the PPD feature, it shall include new Paging and Service Information IE in the
Downlink Data Notification message triggered by the arrival of downlink data
packets at the S-GW. The Paging Policy Indication value within this IE will
contain the value of the DSCP in TOS (IPv4) or TC (IPv6) information received
in the IP payload of the GTP-U packet from the P-GW.
At S-GW,
service-level configuration enables/disables the PPD feature. Once the PPD is
configured, the feature is enabled and applicable for both existing and new
calls.
P-GW
User-datagram packet
DSCP value is unaltered by P-GW for downlink data. The PPD feature is supported
only for S5/S8 interface. For all Handoff scenarios from other interface to
S5/S8 interface, the PPD feature will get enabled if APN had it during its call
setup time at that interface.
At P-GW, APN-level
configuration enables/disables the PPD feature. If PPD feature is enabled for
the call and handoff happens from S5/S8 interface to any other interface, PPD
feature should get disabled. Now, if handoff happens and this call will come
back to S5/S8 interface, PPD feature should become enabled.
SAEGW
To support PPD
feature in SAEGW, both S-GW and P-GW configuration is required.
Relationships to
Other Features
-
The PPD feature
is license controlled under the license for S-GW Paging Profile. Once the
license is enabled, both features co-exist together and work independently.
That means, DDN message might carry both DSCP marking specified by PPD feature
and Priority DDN value specified by S-GW Paging Profile feature.
-
At S-GW, the
user-datagram packet DSCP value is used to send in DDN. S-GW can't change the
DSCP, as per the local configuration (APN profile or service level). At eNodeB,
the scheduling of the packet is based on the QCI instead of DSCP, however, any
EPC node should not change/modify the inner DSCP value.
-
If the PPD
feature is enabled, none of the EPS nodes should change the user-datagram
packet DSCP value. Therefore, ECS should avoid overwriting DSCP value of
user-datagram packet when PPD is enabled.
Standards
Compliance
The PPD functionality complies with
the following standards:
-
29.274, CR-1565, "Paging
Policy Indication in Downlink Data Notification Message"
-
23.401, CR-2731 "Paging policy differentiation for IMS voice"
Configuring Paging
Policy Differentiation Feature
For the PPD feature to work, it
must be enabled for P-GW and S-GW.
Both P-GW and S-GW services apply PPD configuration independently.
Therefore, for any downlink data packet from an APN, there could be a case
where P-GW does not have PPD configuration but S-GW has PPD configuration. To
avoid such a conflict, you must configure the PPD functionality on both P-GW
(APN level granularity) and S-GW (service level granularity).
Configuration
Enabling on
P-GW
The following CLI
commands are used to manage the functionality for the PPD feature.
The following
command enables the PPD feature on P-GW at APN level.
configure
context context_name
apn apn_name
paging-policy-differentiation
end
Enabling on
S-GW
The following
command enables the PPD feature on S-GW at service level.
configure
context context_name
sgw-service service_name
paging-policy-differentiation
end
Notes:
-
This is to send
DSCP in Paging and Service Information IE of all the DDN messages triggered by
either IMS-PDN or Internet-PDN, etc.
-
It is up to
MME/S4-SGSN to use the Paging and Service Information IE of DDN message.
-
If PPD feature
is enabled at S-GW service, it is applicable for all calls irrespective of the
APN profiles.
Disabling on
P-GW
The following
command disables the PPD feature on P-GW at APN level.
configure
context context_name
apn apn_name
no paging-policy-differentiation
end
Disabling on
S-GW
The following
command disables the PPD feature on S-GW at service level.
configure
context context_name
sgw-service service_name
no paging-policy-differentiation
end
Monitoring and
Troubleshooting Paging Policy Differentiation
This section includes show commands
in support of the PPD feature.
P-GW Show
Commands
This section provides information
regarding P-GW show commands and/or their outputs in support of the PPD
feature.
show apn name
<apn_name>
The following counter has been
added to display PPD functionality.
Paging Policy Differentiation : Enabled
show subscribers
pgw-only full all
The following counter has been added to display PPD functionality.
Paging Policy Differentiation : Enabled
SAEGW Show
Commands
This section provides information
regarding SAEGW show commands and/or their outputs in support of the PPD
feature.
show subscribers
saegw-only full all
The following counter has been added to display PPD functionality.
Paging Policy Differentiation : Enabled
S-GW Show
Commands
This section provides information
regarding S-GW show commands and/or their outputs in support of the PPD
feature.
show sgw-service
name <service_name>
The following counter has been added to display PPD functionality.
Paging Policy Differentiation : Enabled