AMBR value [QOS] Missed in RAR for the Sy Trigger to Change the Policy Counter

Introduction

This document describes how to troubleshoot the issue of AMBR value [QOS] miss in RAR for the Sy trigger to change the policy counter.

Prerequisites

Requirements

Cisco recommends that you have knowledge of these topics:

• PCRF/CPS
• Diameter Protocol

Components Used

The information in this document is based on Cisco Policy Suit for PCRF solution.

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, ensure that you understand the potential impact of any command.

Abbreviations

Problem

When you apply throttle (new Policy-Counter-Status) after a new session is created the AMBR values are not applied in RAR sent to PGW, only the QCI value was being sent.

        QoS-Information:
        Default-EPS-Bearer-QoS:
                QoS-Class-Identifier: 8
        Revalidation-Time: -486962116

Issue Analysis

When you look at the PCRF trace, it is seen that the OCS sends an SNR immediately after the SLR/SLA exchange.

This SNR has the same Policy-Counter-Status (NoThrottle) value as the SLA.

As the SNR is processed, you can see the PCRF loads the Unlimited_AMBR table properly, until this everything works fine.

A few minutes later, a new SNR is sent to the PCRF with a Policy-Counter-Status change (apply Throttle1). When you process this, PCRF does not load the Unlimited_AMBR table, so the AMBR values for Throttle1 are not attained, so are not passed to the PGW in the RAR.

These are some snips from the debug log to understand the above behavior in detail.

CRD Table Loaded during CCR-I Properly

-------- Debugging Messages --------------------------------
INFO core Tagging message with ID: GX_TGPP
INFO diameter Adding extracted AVP to policy: DiameterMessageAvp [code=QoS-Class-Identifier, value=8]
INFO core Start session triggered
INFO TGPP [Rel9] features supported on session 0001-diamproxy.mod-ggsae01-gx.epc.mnc099.mcc530.3gppnetwork.org;405022273;510802;5f4efc9a-5202
INFO gx Creating new diameter session 0001-diamproxy.mod-ggsae01-gx.epc.mnc099.mcc530.3gppnetwork.org;405022273;510802;5f4efc9a-5202
INFO custrefdata Adding AVP [APN_TABLE/LOGICAL_APN], value: DATA
INFO custrefdata Adding AVP [LOCATION_TABLE/LOCATION_REF], value: HOME
INFO custrefdata Adding AVP [PROFILE_TABLE/PROFILE_ID], value: PROFILE_DATA
INFO custrefdata Adding AVP [QCIREF/QCI], value: 8
INFO custrefdata Adding AVP [Unlimited_AMBR/Throttle3_AMBR_DOWN], value: 20000000
INFO custrefdata Adding AVP [Unlimited_AMBR/Throttle2_AMBR_UP], value: 5000000
INFO custrefdata Adding AVP [Unlimited_AMBR/Throttle6_AMBR_UP], value: 600000000
INFO custrefdata Adding AVP [Unlimited_AMBR/Throttle3_AMBR_UP], value: 20000000
INFO custrefdata Adding AVP [Unlimited_AMBR/Throttle4_AMBR_DOWN], value: 50000000
INFO custrefdata Adding AVP [Unlimited_AMBR/Throttle1_AMBR_DOWN], value: 1200000
INFO custrefdata Adding AVP [Unlimited_AMBR/Throttle2_AMBR_DOWN], value: 5000000
INFO custrefdata Adding AVP [Unlimited_AMBR/Throttle5_AMBR_UP], value: 100000000
INFO custrefdata Adding AVP [Unlimited_AMBR/Throttle6_AMBR_DOWN], value: 600000000
INFO custrefdata Adding AVP [Unlimited_AMBR/Throttle1_AMBR_UP], value: 1200000
INFO custrefdata Adding AVP [Unlimited_AMBR/Throttle5_AMBR_DOWN], value: 100000000
INFO custrefdata Adding AVP [Unlimited_AMBR/Throttle4_AMBR_UP], value: 50000000
INFO auth Success ALLOW_ALL authorization
INFO core Switching credential id to 53099204XXXXXX for session
INFO core domain: mobile
INFO sy Created new Sy diameter session
INFO sy Triggering synchronous SLR Message on sessioniMOD-PCRF01-qns01-1.cluster-MOD1.-Model;1597873954;1029;6862816375560209413
INFO debug-code The Sy Policy Counter Status is : NoThrottle

Immediate SNR after the CCR

Here also the CRD table loading was proper and selected desired QOS based on the policy counter received from SNR.

-------- Debugging Messages --------------------------------
INFO core Tagging message with ID: SY_V11
INFO core Successful load by key: diameterSessionKey:iMOD-PCRF01-qns01-1.cluster-MOD1.-Model%3B1597873954%3B1029%3B6862816375560209413
INFO custrefdata Adding AVP [APN_TABLE/LOGICAL_APN], value: DATA
INFO custrefdata Adding AVP [LOCATION_TABLE/LOCATION_REF], value: HOME
INFO custrefdata Adding AVP [PROFILE_TABLE/PROFILE_ID], value: PROFILE_DATA
INFO custrefdata Adding AVP [QCIREF/QCI], value: 8
INFO custrefdata Adding AVP [Unlimited_AMBR/Throttle3_AMBR_DOWN], value: 20000000
INFO custrefdata Adding AVP [Unlimited_AMBR/Throttle2_AMBR_UP], value: 5000000
INFO custrefdata Adding AVP [Unlimited_AMBR/Throttle6_AMBR_UP], value: 600000000
INFO custrefdata Adding AVP [Unlimited_AMBR/Throttle3_AMBR_UP], value: 20000000
INFO custrefdata Adding AVP [Unlimited_AMBR/Throttle4_AMBR_DOWN], value: 50000000
INFO custrefdata Adding AVP [Unlimited_AMBR/Throttle1_AMBR_DOWN], value: 1200000
INFO custrefdata Adding AVP [Unlimited_AMBR/Throttle2_AMBR_DOWN], value: 5000000
INFO custrefdata Adding AVP [Unlimited_AMBR/Throttle5_AMBR_UP], value: 100000000
INFO custrefdata Adding AVP [Unlimited_AMBR/Throttle6_AMBR_DOWN], value: 600000000
INFO custrefdata Adding AVP [Unlimited_AMBR/Throttle1_AMBR_UP], value: 1200000
INFO custrefdata Adding AVP [Unlimited_AMBR/Throttle5_AMBR_DOWN], value: 100000000
INFO custrefdata Adding AVP [Unlimited_AMBR/Throttle4_AMBR_UP], value: 50000000
INFO core domain: mobile
INFO Sy client Sending SNA Message on session iMOD-PCRF01-qns01-1.cluster-MOD1.-Model;1597873954;1029;6862816375560209413
INFO debug-code The Sy Policy Counter Status is : NoThrottle
INFO debug-code The Sy Policy Counter Status is : NoThrottle

RAR sent to PGW with Proper QOS info

Message: com.broadhop.diameter2.messages.DiameterRequestMessage
Application Id: Gx (16777238)
Command Code: Gx_RAR (258)
Dest host: 0001-diamproxy.mod-ggsae01-gx.epc.mnc099.mcc530.3gppnetwork.org
Dest realm: epc.mnc099.mcc530.3gppnetwork.org
Device protocol: GX_TGPP
End to end id: 0 (0x00000000)
Hop by hop id: 0 (0x00000000)
Origin state: 0
Stack name: null
Session-Id: 0001-diamproxy.mod-ggsae01-gx.epc.mnc099.mcc530.3gppnetwork.org;405022273;510802;5f4efc9a-5202
Auth-Application-Id: 16777238
Re-Auth-Request-Type: 0
QoS-Information:
APN-Aggregate-Max-Bitrate-UL: 600000000
APN-Aggregate-Max-Bitrate-DL: 600000000
Default-EPS-Bearer-QoS:
QoS-Class-Identifier: 8
Revalidation-Time: -486962716
============================================================

Consecutive SNR Received

Here the CRD table is not loaded for Unlimited_AMBR.

-------- Debugging Messages --------------------------------
INFO core Tagging message with ID: SY_V11
INFO core Successful load by key: diameterSessionKey:iMOD-PCRF01-qns02-1.cluster-MOD1.-Model%3B1597874000%3B1089%3B6862816573128705089
INFO custrefdata Adding AVP [APN_TABLE/LOGICAL_APN], value: DATA
INFO custrefdata Adding AVP [LOCATION_TABLE/LOCATION_REF], value: HOME
INFO custrefdata Adding AVP [PROFILE_TABLE/PROFILE_ID], value: PROFILE_DATA
INFO custrefdata Adding AVP [QCIREF/QCI], value: 8
INFO core domain: mobile
INFO Sy client Sending SNA Message on session iMOD-PCRF01-qns02-1.cluster-MOD1.Spark-Model;1597874000;1089;6862816573128705089
INFO debug-code The Sy Policy Counter Status is : Throttle1
INFO debug-code The Sy Policy Counter Status is : Throttle1
INFO debug-code ECGI : 530992xxxxxx
INFO debug-code IMSI : 530992041xxxxxxx
INFO debug-code CGI :
INFO debug-code Next Eval Time: 2020-09-02T10:03:05Z
INFO core domain: mobile
INFO rt Added revalidation time Wed Sep 02 03:13:00 UTC 2020
INFO gx Sending RAR Message on session 0001-diamproxy.mod-ggsae01-gx.epc.mnc099.mcc530.3gppnetwork.org;405022275;511314;5f4efd58-5202

RAR Sent without AMBR in QOS info

Expected to sent with reduced QOS value.

Message: com.broadhop.diameter2.messages.DiameterRequestMessage
Application Id: Gx (16777238)
Command Code: Gx_RAR (258)
Dest host: 0001-diamproxy.mod-ggsae01-gx.epc.mnc099.mcc530.3gppnetwork.org
Dest realm: epc.mnc099.mcc530.3gppnetwork.org
Device protocol: GX_TGPP
End to end id: 0 (0x00000000)
Hop by hop id: 0 (0x00000000)
Origin state: 0
Stack name: null
Session-Id: 0001-diamproxy.mod-ggsae01-gx.epc.mnc099.mcc530.3gppnetwork.org;405022275;511314;5f4efd58-5202
Auth-Application-Id: 16777238
Re-Auth-Request-Type: 0
QoS-Information:
Default-EPS-Bearer-QoS:
QoS-Class-Identifier: 8
Revalidation-Time: -486962116
============================================================

Further, the debug qns logs were looked into, and it was seen that the table was skipped due to condition is false CCR

MOD-PCRF01-qns02 MOD-PCRF01-qns02 2020-09-02 02:13:00,740 [pool-108-thread-1] DEBUG c.b.policy.impl.RulesPolicyService - Policy event: Message: com.broadhop.diameter2.messages.DiameterRequestMessage
Application Id: Sy (16777302)
Command Code: Sy_SNR (8388636)
Dest host: mod-pcrf01-lb
Dest realm: epc.mnc099.mcc530.3gppnetwork.org
Device protocol: SY_V11
End to end id: 1874920025 (0x6fc10259)
Hop by hop id: 30806209 (0x01d610c1)
Origin state: 0
Stack name: null
Origin host: sy01.mod02.bumblebee.co.nz
Origin realm: mod02.bumblebee.co.nz
Session-Id: iMOD-PCRF01-qns01-1.cluster-MOD1.Spark-Model;1597873954;1029;6862816375560209413
Auth-Application-Id: 16777238
Policy-Counter-Status-Report:
Policy-Counter-Identifier: THROTTLE
Policy-Counter-Status: Throttle1
Route-Record: sy01.mod02.bumblebee.co.nz
QPS-Internal-Route-Record-Host: mod-dsc02.epc.mnc099.mcc530.3gppnetwork.org
QPS-Internal-Route-Record-Realm: epc.mnc099.mcc530.3gppnetwork.org, no return address
<SNIP>
.
.
.
.
</SNIP>
MOD-PCRF01-qns01 MOD-PCRF01-qns01 2020-09-02 02:13:00,742 [pool-109-thread-1] DEBUG c.b.c.i.CustomerReferenceDataManager - Skipping table Unlimited_AMBR since condition is false CCR

Further, the PB is investigated to understand the behavior of CRD table load.

Once you walk through the provided SVN dump, It is found for this configuration for this table: Unlimited_AMBR

The activation condition for this table is based on CCR Trigger.

So, if you see the content of this CCR trigger, the condition is, a Gx diameter session exists with a Command code 272. Ie. CCRs.

Because of this, the tables do not load without a corresponding to CCR. Ie. SNR doesn’t have a right to load CRD without an initial CCR [I or U]

Solution

Add the CRD activation trigger for SY session, and perform a publish of the new configuration.

Post publish of this new change, did multiple attempts of data calls, and all were successful. All the consecutive SNRs were able to load the CRD table and proper QOS being sent in RAR based on the incoming policy counter change from Sy.