Session Setup Failure - Cisco ASR 5000 Administration Manual

▀ How it Works
If eWAG finds a matching session using the session identification parameters then the older session is replaced
with the newer session on receipt of the Accounting-Start message under the following conditions:
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Important:
spread across all WLANs are expected to be unique.
Note that at any time, only one APN is supported for a subscriber. This is because APN selection is tied with WLAN
attach. UE can be connected to only one WLAN (SSID) at a time. So, during session establishment with eWAG only
one APN can be supplied in Accounting-Start. If a new request comes with same Username+MSISDN but a different
APN, it would mean that the UE lost connection with the WLAN and then re-attached.
Also, note that the IMSI and MSISDN should have one-to-one relationship. So, eWAG uses only MSISDN for session-
identification. In case where different IMSI arrives for same MSISDN call, the older call gets replaced as explained
above.

Session Setup Failure

This section presents call flows for setup failure scenarios.
A call setup request via Accounting-Start can fail due to any of the following reasons:

Mandatory AVP Missing No Resource

GTP Tunnel Setup Failure
▄ Cisco ASR 5000 Enhanced Wireless Access Gateway Administration Guide
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Matching session found at eWAG with same Username+MSISDN and Wi-Fi IP address received in the
new Accounting-Start message but containing different APN. This is the scenario where the same
subscriber is trying to connect through different APN.
Matching session found at eWAG with same Username+MSISDN and Wi-Fi IP address received in the
new Accounting-Start message but containing different Accounting-Session-ID. This is the scenario
where the same subscriber is trying to connect again after loosing the previous session for some
reason (for example, got detached from the WLAN, UE restart, and so on).
Matching session found at eWAG with same Username+MSISDN and Wi-Fi IP address received in the
new Accounting-Start message but containing different NAS-IP-Address. This is the scenario where
the same subscriber is trying to connect again due to loosing the previous session for some reason (for
example, got detached from the WLAN, UE restart, and so on) and when the subscriber is trying to re-
connect it is coming through different WLC/ISG.
Matching session found at eWAG with same Username+MSISDN and Wi-Fi IP address received in the
new Accounting-Start message but containing different Source IP address. This is the scenario where
the same subscriber is trying to re-connect due to loosing the previous session for some reason (for
example, getting detached from the WLAN, UE restart, and so on) and when the subscriber tries to re-
connect it is coming through different Wi-Fi AAA.
Matching session found at eWAG with same Username+MSISDN and Wi-Fi IP address received in the
new Accounting-Start message but containing different IMSI. This negative scenario should not occur
as MSISDN and IMSI will have one-to-one mapping. However, the session will be replaced if this
scenario does happen and IMSI is handled in similar way as all the other parameters explained earlier.
In this release, eWAG does not support overlapping IP addresses. The IP addresses for all UEs
Enhanced Wireless Access Gateway Overview
OL-28188-02