Gx Interface Support
Rel. 9 Gx Interface ▀
Cisco ASR 5x00 Packet Data Network Gateway Administration Guide ▄
325
Usage Monitoring at Session Level: PCRF subscribes to the session-level volume reporting over Gx by sending
the Usage-Monitoring-Information AVP with the usage threshold level set in Granted-Service-Unit AVP and
Usage-Monitoring-Level AVP set to SESSION_LEVEL(0). After the AVPs are parsed by DPCA, IMSA
updates the information to ECS. Once ECS is updated usage monitoring is started and constantly checked with
the usage threshold whenever the data traffic is present. In 11.0 and later releases, Monitoring Key at session
level is supported.
In 12.0 and later releases, enabling and disabling session usage in a single message from PCRF is supported.
This is supported only if the monitoring key is associated at session level.
In 12.0 and later releases, monitoring of usage based on input/output octet threshold levels is supported. Usage
is reported based on the enabled threshold level. If multiple levels are enabled, usage will be reported on all the
enabled levels even if only one of the levels is breached. Monitoring will be stopped on the missing threshold
levels in the response for the usage report from PCRF (expected to provide the complete set again if PCRF
wants to continue monitoring on the multiple levels enabled earlier).
Total threshold level along with UL/DL threshold level in the GSU AVP is treated as an error and only total
threshold level is accepted.
Usage Monitoring at Flow Level: PCRF subscribes to the flow-level volume reporting over Gx by sending the
Usage-Monitoring-Information AVP with the usage threshold level set in Granted-Service-Unit AVP and
Usage-Monitoring-Level AVP set to PCC_RULE_LEVEL(1). Monitoring Key is mandatory in case of a flow-
level monitoring since the rules are associated with the monitoring key and enabling/disabling of usage
monitoring at flow level can be controlled by PCRF using it. After the AVPs are parsed by DPCA, IMSA
updates the information to ECS. Once ECS is updated usage monitoring is started and constantly checked with
the usage threshold whenever the data traffic is present.
Usage monitoring is supported for static, predefined rules, and dynamic rule definitions.
Usage Monitoring for Static Rules: In the case of static rules, the usage reporting on last rule removal
associated with the monitoring key is not applicable. In this case only the usage monitoring
information is received from the PCRF.
Usage Monitoring for Predefined Rules: If the usage monitoring needs to be enabled for the predefined
rules, PCRF sends the rule and the usage monitoring information containing the monitoring key and
the usage threshold. The Monitoring key should be same as the one pre-configured in PCEF for that
predefined rule. There can be multiple rules associated with the same monitoring key. Hence enabling
a particular monitoring key would result in the data being tracked for multiple rules having the same
monitoring key. After DPCA parses the AVPs IMSA updates the information to ECS. Once ECS is
updated usage monitoring is started and constantly checked with the usage threshold whenever the
data traffic is present.
Usage Monitoring for Dynamic Rules: If the usage monitoring needs to be enabled for dynamic
ruledefs, PCRF provides the monitoring key along with a charging rule definition and the usage
monitoring information containing the monitoring key and the usage threshold. This would result in
the usage monitoring being done for all the rules associated with that monitoring key. After DPCA
parses the AVPs, IMSA updates the information to ECS. Once ECS is updated, the usage monitoring
is started and constantly checked with the usage threshold whenever the data traffic is present.
Monitoring key for dynamic ruledef is dynamically assigned by PCRF which is the only difference
with predefined rules in case of usage monitoring.
In releases prior to 15.0, when threshold breach happens for multiple monitoring keys at the same time, only one of the
monitoring key’s usage is reported and the rest of the monitoring keys’ usage is reported in CCR-T (threshold set to
infinity). On Tx expiry/TCP link error, unreported usage is stored at ECS and reported only on session termination.
In 15.0 and later releases, only one of the monitoring key’s usage is reported first. Upon receiving successful response
from PCRF, the rest of the monitoring keys’ usage is reported to PCRF. On Tx expiry/TCP link error, unreported usage
is stored at ECS. Any future successful interaction with PCRF for the session will send unreported UMI to PCRF.
