Nsapi Allocation; Ue Identity And Location Information Support - Cisco ASR 5000 Administration Manual
Enhanced wireless access gateway
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DHCP-based Enhanced Wireless Access Gateway Overview
NSAPI Allocation
D-eWAG is responsible for allocating NSAPI values before sending the Create-PDP-Context-Request message to the
GGSN. Although the D-eWAG acts as an SGSN in terms of GTP tunnel establishment, it also manages NSAPI
allocation as WLAN UEs do not send NSAPI in this case. The default NSAPI allocated by D-eWAG is 15.
UE Identity and Location Information Support
The D-eWAG supports sending UE identity and location information to the GGSN, which the GGSN can use for
Lawful Intercept support.
RAI
The RAI IE in CPC Request sent to GGSN is encoded using the MCC MNC or PLMN ID configured at D-eWAG.
ULI
The User Location Information (ULI) IE in CPC Request sent to GGSN is encoded using the "Called-Station-ID" AVP
received in Authentication-Request message at D-eWAG. The "Called-Station-ID" AVP contains the Access Point
Identifier (AP Identifier), which is composed of the Location Area Code Cell Identity (LAC_CI) — that is, Location
Area Code (LAC) and Cell Id (CI) separated by an underscore. For example, if the access point is assigned LAC = 123
and CI = 56789, then the "Called-Station-ID" AVP will contain 123_56789. As per 3GPP TS 23.003, the LAC and CI
are each 2 bytes in length.
Note that the "Called-Station-ID" AVP is optional in RADIUS Auth/Accounting Requests. WLC supports different
format of "Called-Station-ID". However, for ULI functionality to work, "Called-Station-ID" AVP should be received in
AP Identifier format. If Called-Station-ID is received in AP Identifier format then it is sent to GGSN in ULI IE of CPC
request.
The "User Location Information" IE is encoded in Cell Global Identifier (CGI) format to indicate WLAN AP location
information where the UE is currently located.
The "Geographic Location Type" field is used to convey what type of location information is present in the
"Geographic Location" field. To indicate Cell Global Identity format, it should be set to 0.
The "Geographic Location" field is used to convey the actual geographic information as indicated in the "Geographic
Location Type" field. The MCC MNC octets should be set to PLMN ID of the PLMN where D-eWAG is located. The
LAC and CI octets should be set to Called-Station-ID AP-Identifier LAC and CI components.
After the UE moves to a different access point, WLC sends a RADIUS Accounting Interim with the new Access Point
location in "Called-Station-ID" AVP. D-eWAG checks the older ULI and if it is different, it will send UPC Request
with ULI with the new Access Point location.
UE MAC to IMEI Mapping Support
The UE MAC to IMEI Mapping Support feature allows user identity information to be provided to the GGSN. This
support can be enabled/disabled from the CLI. When enabled, the UE MAC received in "Calling-Station-Id" RADIUS
attribute is mapped to IMEIsV and sent in GTP CPC message to the GGSN.
Cisco ASR 5000 Enhanced Wireless Access Gateway Administration Guide ▄
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