SLh AVPs
SLh (application id: 16777291)
The SLh interface is a key reference point for supporting Location Services (LCS) within GSM, UMTS, and EPS networks. The SLh interface facilitates communication between the Gateway Mobile Location Center (GMLC) and the Home Subscriber Server (HSS). It primarily functions to enable the GMLC to obtain routing information necessary for locating a mobile subscriber (User Equipment, or UE) within the network.
In the context of Location Services, the SLh interface connects the GMLC to the HSS. The GMLC is responsible for handling location requests from external clients, such as emergency services or lawful interception authorities, and coordinating the retrieval of location information for a target UE. The HSS, on the other hand, stores and manages subscriber data, including information on the current serving node (e.g., MME, MSC, or SGSN) for each UE.
The SLh interface enables the GMLC to query the HSS for this routing information. This data is essential for the GMLC to accurately direct location requests to the correct network entity that can provide the UE's real-time location.
The primary purpose of the SLh interface is to allow the GMLC to retrieve routing information from the HSS. This routing information typically includes details such as the address of the Home GMLC (H-GMLC), the address of the visited MSC/MSC server, SGSN, or MME that is currently serving the UE. This information is crucial for the GMLC to effectively process and fulfill location requests.
SLh interface workflow:
- Location Request Initiation: An external Location Services client, such as emergency services, initiates a location request for a specific UE. This request is forwarded to the GMLC.
- Routing Information Query: Upon receiving the location request, the GMLC uses the SLh interface to send a "Send Routing Information for LCS" request to the HSS. The purpose of this request is to obtain the routing information required to locate the UE.
- Processing by HSS: The HSS processes the request and retrieves the relevant routing information, such as the address of the node (e.g., MME, MSC) currently serving the UE.
- Response to GMLC: The HSS returns the requested routing information to the GMLC via the SLh interface.
- Forwarding the Location Request: With the routing information now available, the GMLC forwards the location request to the appropriate serving node (e.g., MME, MSC) to retrieve the UE's location data.
- Location Data Delivery: The serving node processes the request and sends the UE’s location information back to the GMLC.
- Completion: The GMLC then forwards the obtained location data to the requesting LCS client, thereby completing the process.
For complete technical specification of SLg interface in Diameter protocol please refer to: [3GPP TS 29.173]
package com.mobius.software.telco.protocols.diameter.primitives.slh;
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Name |
AVP Code |
Data Type |
Vendor |
|
Additional-Serving-Node |
2406 |
Grouped |
3GPP |
|
Provides information about an additional network node serving the targeted user. This AVP is used in location-based services (LCS) and other scenarios where multiple network nodes may serve a single user. The AVP structure is defined as follows: SGSN-Number (Optional): The number of the SGSN (Serving GPRS Support Node) serving the user. MME-Name (Optional): The name of the MME (Mobility Management Entity) serving the user. SGSN-Name (Optional): The name of the SGSN serving the user. SGSN-Realm (Optional): The Diameter realm of the SGSN. MME-Realm (Optional): The Diameter realm of the MME. MSC-Number (Optional): The Mobile Switching Center (MSC) number serving the user. 3GPP-AAA-Server-Name (Optional): The name of the 3GPP AAA Server handling authentication and authorization. LCS-Capabilities-Sets (Optional): Identifies the LCS capabilities of the serving node. GMLC-Address (Optional): The Gateway Mobile Location Center (GMLC) address responsible for location-based services. Additional optional AVPs, as needed. |
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|
GMLC-Address |
2405 |
Address |
3GPP |
|
Contain the IPv4 or IPv6 address of H-GMLC or the V-GMLC associated with the serving node. |
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|
LCS-Capabilities-Sets |
2404 |
Unsigned32 (Bitmask) |
3GPP |
|
Used to indicate the Location Services (LCS) capabilities supported by a network node. It contains a bitmask where each bit represents support for a specific LCS capability set. The bit values and their meanings are defined in 3GPP TS 29.002. Bitmask Values: Bit 0: LCS Capability Set 1: Indicates support for LCS Release 98 or Release 99. If no bits are set, the sending node does not support LCS. An SGSN is not allowed to indicate support for this set. Bit 1: LCS Capability Set 2: Indicates support for LCS Release 4. Bit 2: LCS Capability Set 3: Indicates support for LCS Release 5. Bit 3: LCS Capability Set 4: Indicates support for LCS Release 6. Bit 4: LCS Capability Set 5: Indicates support for LCS Release 7 or later. Rules & Considerations: A node must set all bits corresponding to the LCS capability sets it supports. If the AVP is not included in a message from the VLR, the VLR is assumed to support at most LCS Capability Set 1. If the AVP is not included in a message from the SGSN, no LCS support is assumed. Any bits beyond bit 4 are considered reserved and must be ignored. |
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|
LMSI |
2400 |
OctetString |
3GPP |
|
Contain the Local Mobile Station Identity (LMSI) allocated by the VLR, as defined in 3GPP [TS 23.003]. For further details on the encoding of this AVP, see 3GPP [TS 23.003]. |
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|
MME-Name |
2402 |
DiameterIdentity |
3GPP |
|
Contain the Diameter identity of the serving MME. For further details on the encoding of this AVP, see IETF [RFC 6733]. |
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|
MME-Realm |
2408 |
DiameterIdentity |
3GPP |
|
Contain the Diameter Realm Identity of the serving MME. For further details on the encoding of this AVP, see IETF [RFC 6733]. |
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|
MSC-Number |
2403 |
OctetString |
3GPP |
|
The MSC-Number AVP is of type OctetString and it shall contain the ISDN number of the serving MSC or MSC server in international number format as described in [ITU-T Rec E.164] and shall be encoded as a TBCD-string. See 3GPP [TS 29.002] for encoding of TBCD-strings. |
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|
PPR-Address |
2407 |
Address |
3GPP |
|
Contains the IPv4 or IPv6 address of H-GMLC or the V-GMLC associated with the serving node. |
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|
RIA-Flags |
2411 |
Unsigned32 (Bitmask) |
3GPP |
|
Used to indicate specific capabilities or configurations of the serving node during Routing Information for LCS Answer (RIA) procedures. Bitmask Definition: 0: CombinedMME/SGSNSupportingOptimized-LCSProc: When set, this bit indicates that the UE is served by a combined MME/SGSN node which supports the optimized LCS procedure. Note: Bits not defined in this table shall be cleared by the sending HSS and discarded by the receiving GMLC. |
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|
Serving-Node |
2401 |
Grouped |
3GPP |
|
Contains identification and capability information about the network node currently serving the targeted user in location-based services (LCS) scenarios. The AVP structure is defined as follows: SGSN-Number (Optional): ISDN number of the serving SGSN in international format (TBCD-encoded). SGSN-Name (Optional): Diameter identity of the serving SGSN. SGSN-Realm (Optional): Diameter realm of the serving SGSN. MME-Name (Optional): Diameter identity of the serving MME. MME-Realm (Optional): Diameter realm of the serving MME. MSC-Number (Optional): ISDN number of the MSC or MSC Server (TBCD-encoded E.164). 3GPP-AAA-Server-Name (Optional): Diameter identity of the AAA server in WLAN or non-3GPP access. LCS-Capabilities-Sets (Optional): Bitmask representing the location capabilities supported by the serving node. GMLC-Address (Optional): IP address (IPv4 or IPv6) of the associated GMLC node. Additional optional AVPs may be present. |
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|
SGSN-Name |
2409 |
DiameterIdentity |
3GPP |
|
Contains the Diameter identity of the serving SGSN. For further details on the encoding of this AVP, see IETF [RFC 6733]. |
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|
SGSN-Realm |
2410 |
DiameterIdentity |
3GPP |
|
Contain the Diameter Realm Identity of the serving SGSN. For further details on the encoding of this AVP, see IETF [RFC 6733]. |
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