Short Message Service
Feature Summary and Revision History
Feature Description
How It Works
Configuring SMS Support
Monitoring and Troubleshooting
- Show Commands and/or Outputs
- Bulk Statistics
  - MME Schema
  - MME-SMS Schema

Short Message Service

Feature Summary and Revision History

Summary Data


Applicable Product(s) or Functional Area	MME
Applicable Platform(s)	ASR 5500 UGP VPC-DI VPC-SI
Feature Default	Disabled - Configuration Required
Related Changes in This Release	Not Applicable
Related Documentation	Command Line Interface Reference MME Administration Guide Statistics and Counters Reference

Revision History


Revision Details	Release
The SMS over SGd interface for EPS only Attach feature is first introduced in 21.20.19 and supported only in 21.24.	21.24
"New sub traffic type SMS added under traffic PS to configure Heuristic paging" was introduced in release 21.11. With this release, this feature is also applicable to release 21.8.9.	21.8.9
New sub traffic type SMS added under traffic PS to configure Heuristic paging.	21.11
First introduced.	21.8

Feature Description

The Short Message Service (SMS) is a means of sending messages of limited size to and from GSM/UMTS/EPS devices. SMS is a Store and Forward service, where messages are first sent to an entity called the Short Message Service Center (SMSC) and then forwarded to the recipient instead of transmitting directly to the destination.

If the recipient is not connected, the message is saved in the SMSC and when the receiver becomes available, the network will contact the SMSC and forward the SMS. Thus, a GSM/UMTS/EPS PLMN supports the transfer of short messages between service centers and UEs.

SMS is delivered over LTE through the following methods:

SMS over SGs: The LTE UE device sends and retrieves circuit switched (CS) based SMS messages through the SGs interface. This method is already supported by the MME.
SMS over IP: SIP based SMS messages are carried through IMS. The SMS to be transmitted is encapsulated in the SIP message. This method is not supported in this release.
SMS in MME: SMS in MME delivers SMS services over the SGd interface to the SMSC. This method is intended for networks that do not deploy GERAN or UTRAN. This method is supported in this release.
SMS over SGd: MME supports SMS over SGd for Combined EPS Attach and EPS only Attach.

For more information, see the Configuring MME Preference for SMS section.

How It Works

The SGd interface enables the transfer of short messages between the MME and the SMSC using Diameter protocol. SCTP is used as the transport protocol.

The Short Message Control Protocol (SM-CP) and Short Message Relay Protocol (SM-RP) are traditional SMS protocols between MSC/VLR and UE. The SMS will be sent by the MME bypassing the MSC/VLR.

SM-CP transmits the SMS and protects against loss caused by changing the dedicated channel. SM-RP manages the addressing and references.

With the new interface configuration towards SMSC, MME will setup an SCTP association with the peer SMSC and the Diameter capability exchange will be performed.

Limitations

This section lists the known limitations for the SMS feature:

MME will attempt to fallback to the SGs mode if SGd and SGs are enabled and if HSS rejects SMS in MME. This functionality is not supported in this release.
Multiple SMSC service association is not supported. Only one endpoint will be associated with an MME service. If multiple SMSC services are required, then the SMS router must be used.
The Serving Node Identity AVP is not supported in the Alert-Service-Centre-Request command. Hence SMSC needs to perform the "Send Routing Info for SM" procedure to retrieve the address of the new serving node from the HSS.
Sending or processing of the "Pending MT Short Message Indication" flag under Forward Relocation Request will not be supported.
Sending and processing of "MME number for MT SMS" and "MME Identifier for MT SMS" under Forward Relocation Request/Response are not supported.
SMS will not be processed when the MME common procedure is ongoing.
Notify Request to HSS for each UE due to removal of SMSC service is not supported.
Notify Request to HSS is not supported if UE does an IMSI Detach.
Delete Subscription Data Request from HSS is not supported for MO/MT SMS.
CDR generation is not supported.

Flows

This section describes the call flows related to the SMS feature.

Obtaining UE capability for SMS

Combined Attach: If the UE requests "SMS-only" in the Additional Update Type IE of combined attach and the network accepts the Attach Request for EPS services and "SMS-only", the network will indicate "SMS-only" in the Additional Update Result IE. If the SMS services are provided by SGd in the MME, the network will provide a TMSI and non-broadcast LAI in the Attach Accept message.

EPS Attach:To support the SMS-only handling option for NBIOT users, the MME must accept the Attach Request. The Attach Request must be associated with an Attach Type of "EPS Attach", or a "TAU Request" with an Update Type of "TA Updating" with an SMS-only indication in the Additional Update IE.

SMS Capability with HSS

A UE supporting SMS in MME needs to perform a registration with the HSS.

The following call flow illustrates the request for registration with the HSS.


Step	Description
1	The UE initiates combined Attach Update or combined TAU/LAU to an MME.
2	The MME sends an Update Location Request message to the HSS with the following data: SMS bit set in Feature-List in Supported-Features AVP. The Feature-List ID will be set to 2. "SMS-only" indication bit set in ULR-Flags AVP. MME address for MT-SMS routing in MME-Number-for-MT-SMS AVP. "SMS-only" indication set in SMS-Register-Request AVP.
3	HSS registers the UE for SMS support in MME.
4	If the HSS accepts to register the MME identity as an MSC identity for terminating SMS services, then the HSS cancels the MSC/VLR registration from the HSS.
5	For successful registrations, HSS sends a Location Update Answer (indication that the MME has registered for SMS) message to the MME. HSS sets the "MME Registered for SMS" bit in ULA-Flags AVP.

HSS-initiated Removal of Registration for SMS

The following procedure is applied when the HSS needs to indicate to the MME that it is no longer registered for SMS.

Figure 2. Removal of Registration for SMS


Step	Description
1	An event will trigger the cancellation of the MME being registered for SMS. For example, removal of the SMS subscription for the UE, CS location update, and so on.
2	The HSS sends an Insert Subscriber Data Request (Remove SMS registration) message to the MME to inform that it is no more registered for SMS in MME.
3	The MME sets the "MME Registered for SMS" parameter as not registered for SMS and the "SMS Subscription Data" is considered by the MME as invalid. It acknowledges with an Insert Subscriber Data Answer message to the HSS.

MO Forward Short Message Procedure

The MO Forward Short Message procedure is used between the serving MME and the SMSC to forward mobile originated short messages from a mobile user to a service center. MME checks the SMS related subscription data and forwards the short message.


Step	Description
1	The UE sends mobile originated SMS to MME in the Uplink NAS Transport message.
2	MME will encapsulate the SMS in CP-DATA+RP-DATA.
3	The message will be encoded into MO-Forward-Short-Message-Request (OFR) message and sent to SMSC.
4	MME acknowledges the received SMS by sending CP-ACK to UE in the Downlink NAS Transport message.
5	SMSC processes the received OFR message and responds backs with MO-Forward-Short-Message-Answer (OFA) message to MME.
6	MME forwards the acknowledgement from SMSC in CP-DATA+RP-ACK to UE.
7	UE acknowledges the SMS delivery by sending CP-ACK to MME in the Uplink NAS Transport message.

MT Forward Short Message Procedure

The MT Forward Short Message procedure is used between the SMSC and the serving MME to forward mobile terminated short messages.

When receiving the MT Forward Short Message Request, the MME checks if the user is known.

If it is an unknown user, an Experimental-Result-Code set to DIAMETER_ERROR_USER_UNKNOWN is returned.
The MME attempts to deliver the short message to the UE.

If the delivery of the short message to the UE is successful, the MME returns a Result-Code set to DIAMETER_SUCCESS.
If the UE is not reachable via the MME, the MME sets the MNRF flag and returns an Experimental-Result-Code set to DIAMETER_ERROR_ABSENT_USER.
If the delivery of the mobile terminated short message failed because the memory capacity exceeded, UE error, or UE not SM equipped, the MME returns an Experimental-Result-Code set to DIAMETER_ERROR_SM_DELIVERY_FAILURE with a SM Delivery Failure Cause indication.


Step	Description
1	The SMSC sends mobile terminated SMS to MME in the MT-Forward-Short-Message-Request (TFR) message.
2	If the UE is in IDLE mode then MME initiates paging and establishes an S1AP connection provided UE replies with paging response.
3	Once the UE is in CONNECTED mode, MME forwards the SMS in CP-DATA+RP-DATA to UE using the Downlink NAS Transport message.
4	The UE acknowledges the received message by sending CP-ACK in the Uplink NAS Transport message.
5	The UE processes the received SMS and sends CP-DATA+RP-ACK to MME.
6	The MME sends the MT-Forward-Short-Message-Answer (TFA) command to SMSC and forwards CP-ACK to the UE in the Downlink NAS Transport message.

MT Forward Short Message Procedure (UE Unreachable)

The MT Forward Short Message procedure is used between the SMSC and the serving MME to forward mobile terminated short messages for an UE that is unreachable.


Step	Description
1	The SMSC sends mobile terminated SMS to MME in the MT-Forward-Short-Message-Request (TFR) message.
2	If the UE is paged but is not reachable, MME sets the MNRF flag and sends the MT-Forward-Short-Message-Answer (TFA) message with Subscriber-absent cause to the SMSC.
3	When the UE becomes available and gets connected to the core network, MME clears the MNRF flag. MME sends the Alert-Service-Centre-Request (ALR) message to SMSC to inform that UE is reachable and that SMS delivery can be re-attempted. This is controlled by the mme sgd send message alr trigger mnrf CLI command and disabled by default.
4	The SMSC responds with the Alert-Service-Centre-Answer (ALA) command to the MME and then follows the route procedure of sending MT SMS to UE.
5	Also, the Notify Request to HSS will be sent with alert reason "user available". This is controlled by the mme s6a send message nor trigger mnrf CLI command and enabled by default.

MT Forward Short Message Procedure (UE Memory Unavailable)

This procedure is used between the SMSC and the serving MME to forward mobile terminated short messages for an UE that has unavailable memory.


Step	Description
1	The SMSC sends mobile terminated SMS to MME in the MT-Forward-Short-Message-Request (TFR) message, but UE memory is full and returns the RP Error with cause code "Memory capacity exceeded". MME sets the MNRF flag and sends the MT-Forward-Short-Message-Answer (TFA) message with cause code "SM Delivery Failure" and failure cause "Memory capacity exceeded" to SMSC.
2	Once the UE memory is available, it will send RP-SMMA message to MME. MME clears the MNRF flag and sends the Alert-Service-Centre-Request (ALR) message to SMSC to inform that UE memory is available and the SMS delivery can be re-attempted. This is controlled by the mme sgd send message alr trigger mnrf CLI command and disabled by default.
3	The SMSC responds with the Alert-Service-Centre-Answer (ALA) command to the MME and then follows the route procedure of sending MT SMS to UE.
4	The Notify Request to HSS will also be sent with alert reason "user memory available". This is controlled by the mme s6a send message nor trigger mnrf CLI command and enabled by default.

MT Forward Short Message Procedure (UE Moves due to HO)

This procedure is used between the SMSC and the serving MME to forward mobile terminated short messages for an UE that moves due to handover.


Step	Description
1	While the MNRF flag is set due to UE unreachable or UE memory unavailable, UE may do a handover (HO) and move to another MME or SGSN.
2	Since the MNRF flag was set, MME will send the Alert-Service-Centre-Request (ALR) message to SMSC to inform that UE has moved to another MME or SGSN. This is controlled by the mme sgd send message alr trigger mnrf CLI command and disabled by default.
3	The SMSC responds with the Alert-Service-Centre-Answer (ALA) command to the MME and then follows the route procedure of sending MT SMS to UE.
4	The Notify Request to HSS will also be sent with alert reason "user memory available". This is controlled by the mme s6a send message nor trigger mnrf CLI command and enabled by default.

Important

This procedure has the following limitations:

New Serving Node Identity AVP is not supported and SMSC needs to perform the "Send Routing Info for SM" procedure to retrieve the new serving node's address from the HSS.
Sending or processing of the "Pending MT Short Message Indication" flag under Forward Relocation Request will not be supported.

Standards Compliance

The SMS feature complies with the following standards:

3GPP TS 23.040 version 12.2.0: Digital cellular telecommunications system (Phase 2+); Universal Mobile Telecommunications System (UMTS); Technical realization of the Short Message Service (SMS)
3GPP TS 24.011 version 12.0.0: Digital cellular telecommunications system (Phase 2+); Universal Mobile Telecommunications System (UMTS); LTE; Point-to-Point (PP) Short Message Service (SMS) support on mobile radio interface
3GPP TS 24.301 version 13.12.0: Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3
3GPP TS 24.301 version 15.1.0: Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3
3GPP TS 29.272 version 12.11.0: Evolved Packet System (EPS); Mobility Management Entity (MME) and Serving GPRS Support Node (SGSN) related interfaces based on Diameter protocol
3GPP TS 29.272 version 15.2.0: Evolved Packet System (EPS); Mobility Management Entity (MME) and Serving GPRS Support Node (SGSN) related interfaces based on Diameter protocol
3GPP TS 29.338 version 13.4.0: Diameter based protocols to support Short Message Service (SMS) capable Mobile Management Entities (MMEs)
3GPP TS 29.338 version 14.3.0: Diameter based protocols to support Short Message Service (SMS) capable Mobile Management Entities (MMEs)

Configuring SMS Support

This section provides information on the CLI commands to configure the SMSC service for SMS support in MME.

Creating and Configuring SMSC Service

Use the following configuration to enable the SMSC service and configure the parameters in SMSC service to support MO/MT SMS delivery between SMSC, MME, and UE.

configure 
   context context_name 
      smsc-service smsc_svc_name 
         diameter { dictionary standard | endpoint endpoint_name } 
         mme-address mme_address 
         tmsi tmsi_value non-broadcast mcc mcc_value mnc mnc_value lac lac_value 
         default diameter dictionary 
         no { diameter endpoint | mme-address | tmsi } 
         end

NOTES:

context context_name : Creates or specifies an existing context and enters the Context Configuration mode. context_name specifies the name of a context entered as an alphanumeric string of 1 to 79 characters.
smsc-service smsc_svc_name : Creates and configures an SMSC Peer service to allow communication with SMSC peer. smsc_svc_name specifies the name of the SMSC service as an alphanumeric string of 1 to 63 characters.

Entering this command in the Context mode results in the following prompt:

[context_name]host_name(config-smsc-service)#
diameter { dictionary standard | endpoint endpoint_name } : Configures the Diameter interface to be associated with the SMSC service.
- dictionary standard : Configures the standard SGd dictionary.
- endpoint endpoint_name : Enables Diameter to be used for accounting and specifies which Diameter endpoint to use. endpoint_name must be an alphanumeric string of 1 to 63 characters.
mme-address mme_address : Configures the MME address to send SMS on the SGd interface. mme_address specifies the MME address (ISDN identity) as an integer from 1 to 15.
tmsi tmsi_value non-broadcast mcc mcc_value mnc mnc_value lac lac_value : Configures the TMSI to be sent to UE. tmsi_value specifies the 4-byte M-TMSI as an integer from 1 to 4294967295.
- non-broadcast : Configures the non-broadcast Location Area Identifier (LAI).
- mcc mcc_value : Configures the mobile country code (MCC) portion of non-broadcast LAI for the SMSC service as an integer from 100 through 999.
- mnc mnc_value : Configures the mobile network code (MNC) portion of non-broadcast LAI for the SMSC service as a 2- or 3-digit integer from 00 through 999.
- lac lac_value : Configures the location area code (LAC) value as an integer from 1 to 65535.
default : Configures the standard Diameter SGd dictionary by default.
no : Disables the specified configuration.

Verifying the Configuration

Use the following command to verify the configuration for all SMSC services or a specified SMSC service:

show smsc-service { all | name smsc_svc_name | statistics { all | name smsc_svc_name | summary } }

Configuring MME Preference for SMS

Use the following configuration to configure the MME preference for SMS and SMSC address.

configure 
   call-control-profile profile_name 
      sms-in-mme { preferred [ smsc-address smsc_address ] | smsc-address smsc_address | subscribe { eps-only-attach } [ notify ue ] } 
      no sms-in-mme { preferred [ smsc-address ] | smsc-address | subscribe { eps-only-attach } [ notify ue ] } 
      default sms-in-mme { subscribe { eps-only-attach } [ notify ue ] } 
      end

Note

When the sms-in-mme subscribe eps-only-attach command is enabled, the SC Address AVP between the MME and SMSC is handled as per 3gpp release 15.

NOTES:

call-control-profile profile_name : Creates an instance of a call control profile. profile_name specifies the name of a call control profile entered as an alphanumeric string of 1 to 64 characters.
sms-in-mme : Configures the SMS capability (SGd interface for SMS) in MME.
preferred : Configures the SMS preference in MME.
smsc-address smsc_address : Configures the SMSC address (ISDN identity) for the MME to send SMS on the SGd interface. smsc_address must be an integer from 1 to 15.
subscribe [ notify ue ] : Enables the Subscription Request for SMS services (via SGd) to HSS for all users.
- notify : Configures the notification to be sent to the users.
- ue : Sends SMS-Only indication to UE in Attach/TAU Accept message (only if HSS accepts SMS Registration for SGd).
default : Restores the default configuration, which is to enable the Subscription Request for SMS services (via SGd) to HSS for all users.
no : Deletes the specified configuration.
eps-only-attach: Configures support for SMS over SGd for Eps only Attach.

Associating SMSC Service with MME Service

Use the following configuration to associate an SMSC service with the MME service.

configure 
   context context_name 
      mme-service service_name 
         associate smsc-service smsc_svc_name [ context ctx_name ] 
         end

NOTES:

context context_name : Creates or specifies an existing context and enters the Context Configuration mode. context_name specifies the name of a context entered as an alphanumeric string of 1 to 79 characters.
mme-service service_name : Creates an MME service or configures an existing MME service in the current context. service_name specifies the name of the MME service as an alphanumeric string of 1 to 63 characters.
associate smsc-service smsc_svc_name : Associates an SMSC service with the MME service. smsc_svc_name specifies the name for a pre-configured SMSC service to associate with the MME service as an alphanumeric string of 1 to 63 characters.
context ctx_name : Identifies a specific context name where the named service is configured. If this keyword is omitted, the named service must exist in the same context as the MME service. ctx_name must be an alphanumeric string of 1 to 63 characters.

Configuring Alert SC Request on SGd interface

Use the following configuration to control sending the Alert SC Request (ALR) on SGd interface.

The user sends the Alert SC Request on SGd interface to SMSC in the event of user availability to received SMS (if user moved to active state from idle or user's memory is available). It is also sent if the user did a handover to the new MME/SGSN and any MT SMS was pending for the user.

configure 
   call-control-profile profile_name 
      [ no ] mme sgd send message alr trigger mnrf 
      end

NOTES:

call-control-profile profile_name : Creates an instance of a call control profile. profile_name specifies the name of a call control profile entered as an alphanumeric string of 1 to 64 characters.
mme : Configures MME capability.
sgd : Configures MME capability on SGd interface.
send : Configures MME capability to send on SGd interface.
message : Configures MME capability to send message on SGd interface.
alr : Configures MME capability to send Alert SC Request (ALR) on SGd interface.
trigger : Configures trigger to send the message.
mnrf : Sends message to trigger MNRF flag on SGd interface (SMS in MME).
no : Disables sending the ALR on SGd interface.
This command is disabled by default.

Verifying the Configuration

Use the following command to verify whether Alert SC Request (MME SGd Message Options) is enabled or disabled:

show call-control-profile full all

Configuring Notify Request on S6a Interface

Use the following configuration to control sending the Notify Request (NOR) on S6a interface.

The user sends the Notify Request on S6a interface to HSS in the event of user availability to received SMS (user moved to active state from idle or user's memory is available).

configure 
   call-control-profile profile_name 
      [ no ] mme s6a send message nor trigger mnrf 
      end

NOTES:

call-control-profile profile_name : Creates an instance of a call control profile. profile_name specifies the name of a call control profile entered as an alphanumeric string of 1 to 64 characters.
mme : Configures MME capability.
s6a : Configure MME capbility on S6a interface.
send : Configures MME capability to send on S6a interface.
message : Configures MME capability to send message on S6a interface.
nor : Configures MME capability to send Notify Request (NOR) on S6a interface.
trigger : Configures trigger to send the message.
mnrf : Sends message to trigger MNRF flag on S6a interface (SMS in MME).
no : Disables sending the NOR on S6a interface.
This command is enabled by default.

Verifying the Configuration

Use the following command to verify whether Notify Request (MME S6a Message Options) is enabled or disabled:

show call-control-profile full all

Configuring Queue Timers

Use the following configuration to configure the MT Queue, TC1N, TR1N, and TR2N timers.

configure 
   context context_name 
      mme-service mme_svc_name 
         emm { mt-queue-timeout mtq_timer | tc1n-timeout tc1n_timer | tr1n-timeout tr1n_timer | tr2n-timeout tr2n_timer } 
         default emm { mt-queue-timeout | tc1n-timeout | tr1n-timeout | tr2n-timeout }  
         end

NOTES:

context context_name : Creates or specifies an existing context and enters the Context Configuration mode. context_name specifies the name of a context entered as an alphanumeric string of 1 to 79 characters.
mme-service service_name : Creates an MME service or configures an existing MME service in the current context. service_name specifies the name of the MME service as an alphanumeric string of 1 to 63 characters.
mt-queue-timeout mtq_timer : Configures the timer to hold MT SMS in MT queue. MT SMS will be present in the queue while the previous SMS is being processed. The timer expiry will return error to SMSC for an absent subscriber. mtq_timer specifies the timeout in seconds, as an integer from 1 to 300.

Default: 30 seconds
tc1n-timeout tc1n_timer : Configures the retransmission timer to send CP SMS data to UE for MO/MT scenario. tc1n_timer specifies the timeout in seconds, as an integer from 1 to 20.

Default: 5 seconds
tr1n-timeout tr1n_timer : Configures the wait time to receive RP-Ack from UE for MT SMS, before sending error to SMSC. tr1n_timer specifies the timeout in seconds, as an integer from 1 to 300.

Default: 30 seconds
tr2n-timeout tr2n_timer : Configures the wait time to send RP-Ack to UE for MO SMS, before sending protocol error to UE. tr2n_timer specifies the timeout in seconds, as an integer from 1 to 300.

Default: 30 seconds
default : Resets the specified timer timeout to the default value.

Verifying the Configuration

Use the following command to verify the configuration for TC1N, TR1N, TR2N, and MT Queue timeout:

show mme-service [ all | name service_name ]

Configuring CP Data Retransmissions

Use the following configuration to configure the maximum number of retransmissions of CP data for MO or MT SMS scenario in MME.

configure 
   context context_name 
      mme-service service_name 
         [ default ] cp-data-max-retransmissions num_retrans 
         end

NOTES:

context context_name : Creates or specifies an existing context and enters the Context Configuration mode. context_name specifies the name of a context entered as an alphanumeric string of 1 to 79 characters.
mme-service service_name : Creates an MME service or configures an existing MME service in the current context. service_name specifies the name of the MME service as an alphanumeric string of 1 to 63 characters.
cp-data-max-retransmissions num_retrans : Configures the number of times CP Data for SMS is retransmitted. num_retrans must be an integer from 1 to 10.
default : Sets the default value to 2.

Verifying the Configuration

Use the following command to verify the count for maximum retransmissions of CP Data:

show mme-service [ all | name service_name ]

Configuring Heuristic paging for PS-SMS traffic via MME

Use the following configuration to configure Heuristic paging for PS-SMS traffic via MME.

configure 
   context context_name 
      lte-policy 
         paging-map  LTE_paging_map_name  
            precedence  map_precedence  traffic-type ps sms paging-profile LTE_paging_profile_name 
         end

NOTES:

sms : Configures paging profile for SMS via SGd.

Important

For more information on Heuristic paging see Heuristic and Intelligent Paging section of MME Administration Guide.

Monitoring and Troubleshooting

This section provides information on the show commands and bulk statistics available for the SMS Support feature.

Show Commands and/or Outputs

This section provides information regarding show commands and their outputs for the SMS Support feature.