Version

SGmb AVPs

SGmb (application id: 16777292)

The SGmb interface in the Diameter protocol is used for communication between the Multimedia Broadcast Multicast Service Gateway (MBMS-GW) and the Broadcast Multicast Service Center (BM-SC). This interface is crucial for managing and controlling MBMS sessions in E-UTRAN/UTRAN networks.

The primary purpose of the SGmb interface is to facilitate the following key functions:

  • Session Management: It manages the start, update, and stop of MBMS sessions. When the BM-SC decides to initiate an MBMS session, it uses the SGmb interface to signal the MBMS-GW, which then sets up the necessary resources across the network to deliver the service. Similarly, the BM-SC uses the SGmb interface to update ongoing sessions (e.g., adjusting service areas or attributes) or terminate sessions once the service is no longer needed.
  • Path Failure Detection: The interface allows the BM-SC and MBMS-GW to monitor the integrity of the MBMS data paths. If a failure is detected on the SGmb path, such as a loss of connection between the BM-SC and MBMS-GW, the SGmb interface enables the detection and appropriate response to restore service continuity.
  • M1 Interface Information Transfer: The SGmb interface is also used for transferring local MBMS information related to the M1 interface, which is crucial for synchronizing and managing MBMS services across the network.

SGmb interface workflow:

Session Initiation:

  • When the BM-SC decides to start an MBMS session, it sends a message over the SGmb interface to the MBMS-GW, indicating the session parameters such as QoS requirements, service area, and control nodes involved (e.g., MME, SGSN).
  • The MBMS-GW receives this message and proceeds to allocate the necessary network resources to support the session.

Session Update:

  • During an active MBMS session, if there is a need to update session parameters (e.g., extending the service area or modifying QoS), the BM-SC sends an update message over the SGmb interface to the MBMS-GW.
  • The MBMS-GW updates the session according to the new parameters and ensures that all relevant network elements are informed of the changes.

Session Termination:

  • When the MBMS service is no longer required, the BM-SC sends a session stop message over the SGmb interface to the MBMS-GW.
  • The MBMS-GW then deallocates the resources and informs all involved nodes to terminate the session.

Heartbeat Procedure:

  • The SGmb interface supports a heartbeat mechanism that enables the BM-SC and MBMS-GW to detect any failures in the communication path between them.
  • This procedure involves the periodic exchange of heartbeat messages, allowing the detection of path failures or restarts of the MBMS nodes.

For complete technical specification of SGmb interface in Diameter protocol please refer to: [3GPP TS 29.061]

package com.mobius.software.telco.protocols.diameter.primitives.sgmb;

Name

AVP Code

Data Type

Vendor

Diagnostic-Info

933

Unsigned32 (Bitmask)

3GPP

Used to convey diagnostic information in MBMS (Multimedia Broadcast Multicast Service) signaling. This AVP contains a bitmask, where each bit represents a specific diagnostic condition.

Bit 0 (UPFAIL): When set, this bit indicates that a User Plane Failure has been detected by the MBMS Gateway. This failure detection is in accordance with the specifications detailed in subclause 20.3.2.1 of 3GPP [TS 23.007].

Bits not defined in the table should be cleared by the sending MBMS GW and ignored by the receiving BM-SC.

MBMS-Access-Indicator

923

Enumerated

3GPP

Specifies the network coverage areas where the MBMS (Multimedia Broadcast Multicast Service) bearer service will be delivered. It indicates whether the service is restricted to UTRAN (3G), E-UTRAN (4G/LTE), or both.

Enumerated Values:

0 UTRAN: MBMS bearer service is delivered only in UTRAN (3G) coverage areas.

1 E-UTRAN: MBMS bearer service is delivered only in E-UTRAN (4G/LTE) coverage areas.

2 UTRAN-AND-E-UTRAN: MBMS bearer service is available in both UTRAN (3G) and E-UTRAN (4G/LTE) coverage areas.

MBMS-BMSC-SSM-UDP-Port

926

OctetString

3GPP

Specifies the source UDP port number at the BM-SC (Broadcast/Multicast Service Center) for IP multicast encapsulation of IP multicast datagrams on the Sgi-mb (transport) plane.

MBMS-Cell-List

934

OctetString

3GPP

Provides a list of MBMS cells that the E-UTRAN (Evolved Universal Terrestrial Radio Access Network) uses to determine a set of radio resources for broadcasting MBMS services. This AVP helps define the actual transmission area by specifying a subset of Evolved Cell Global Identifiers (E-CGIs) from the full MBMS service area.

AVP Format:

First 2 octets: Number (N) of E-CGI codes (1 to 4096).

Next (56*N) bits: N ECGI codes, each encoded per 3GPP [TS 29.274], subclause 8.21.5.

The E-CGI format and semantics follow 3GPP [TS 23.003], subclause 19.6.

MBMS-Data-Transfer-Start

929

Unsigned64

3GPP

Indicates the time at which the radio resources for MBMS data transfer are set up. It is measured in seconds relative to 00:00:00 UTC on 1 January 1900.

The time value is encoded as:

First 32 bits (integer part): Number of whole seconds since 1 January 1900.

Last 32 bits (fractional part): Fraction of a second with a granularity of 1 /2^32 seconds.

This AVP is only valid for E-UTRAN (LTE) access types.

MBMS-Data-Transfer-Stop

930

Unsigned64

3GPP

Specifies the time at which the radio resources for MBMS data transfer are released. It is measured in seconds relative to 00:00:00 UTC on 1 January 1900.

The time value is encoded as:

First 32 bits (integer part): Number of whole seconds since 1 January 1900.

Last 32 bits (fractional part): Fraction of a second with a granularity of 1 /2^32 seconds.

This AVP is only valid for E-UTRAN (LTE) access types.

MBMS-Flags

931

Unsigned32 (Bitmask)

3GPP

Provides control indications for MBMS (Multimedia Broadcast/Multicast Service) sessions. It is a bitmask AVP where specific bits define different behaviors related to MBMS session management.

Bitmask Definition:

0: MSRI (MBMS Session Re-establishment Indication): When set, it indicates that the MBMS Session Start Request message is being used to re-establish an MBMS session.

1: LMBCRI (Local MBMS Bearer Context Release Indication): When set, it indicates that the MBMS Session Stop Request message is used to locally release the MBMS bearer context in the MBMS-GW and associated MME/SGSNs.

Bits that are not defined in this table must be cleared by the sender and ignored by the receiver.

MBMS-GW-SSM-IP-Address

924

IPv4 Address (OctetString)

3GPP

Represents the IPv4 destination multicast address used on the Sgi-mb transport plane for IP multicast encapsulation of application IP multicast datagrams by the BM-SC (Broadcast Multicast Service Center).

MBMS-GW-SSM-IPv6-Address

925

IPv6 Address (OctetString)

3GPP

Represents the IPv6 destination multicast address prefix used on the Sgi-mb transport plane for IP multicast encapsulation of application IP multicast datagrams by the BM-SC (Broadcast Multicast Service Center).

MBMS-GW-UDP-Port

927

OctetString

3GPP

Specifies the UDP port on the MBMS-GW that is used to receive user plane data. This AVP is critical in the MBMS (Multimedia Broadcast Multicast Service) architecture, ensuring proper data forwarding and reception within the multicast transport plane.

MBMS-GW-UDP-Port-Indicator

928

Enumerated

3GPP

Specifies whether the MBMS user plane data must be delivered on a UDP port assigned by the MBMS-GW. This ensures correct routing of MBMS traffic over the Sgi-mb (multicast transport) interface.

Enumerated Values:

1: UDP-PORT-REQUIRED: The MBMS user plane data must be delivered on the UDP Port assigned by the MBMS-GW.

Restart-Counter

932

Unsigned32

3GPP

Monotonically increasing value used to track the restart events of an MBMS entity. Whenever an MBMS node restarts and loses its previous state, this counter is incremented to indicate a fresh system state. It is primarily included in Diameter messages over the SGmb reference point, such as: Capabilities Exchange Request (CER) / Answer (CEA), Session Establishment, Modification, or Termination messages.


 

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