Cisco Unified Border Element (SP Edition) Configuration Guide: Unified Model
IMS Rx and Diameter
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IMS Rx, Diameter, and IMS Rf

Table Of Contents

IMS Rx, Diameter, and IMS Rf

Contents

Information About IMS Rx Interfaces

Configuring IMS Rx

Configuring an IMS Rx Interface

Configuring Media Service for IMS Rx

Disabling Preliminary AAR Messages

Configuration Examples for IMS Rx

Configuration Example for IMS Rx Interface

Configuration Example for IMS Rx Media Service

Configuration Example for Disabling Preliminary AAR Messages

Information About the Diameter Protocol in the SBC

Configuring SBC Diameter Routing

Configuring Diameter Host-Based Routing

Configuring Diameter Realm-Based Routing

Configuration Examples for Diameter Routing

Configuration Example for Diameter Host-Based Routing

Configuration Example for Diameter Realm-Based Routing

Information About IMS Rf Billing Interfaces

Offline Charging Events

Rf Billing Error Handling

Restrictions for IMS Rf Billing Interfaces

Configuring an IMS Rf Billing Interface

Configuration Example for IMS Rf Billing Interface


IMS Rx, Diameter, and IMS Rf


The Cisco Unified Border Element (SP Edition) supports IP Multimedia Subsystem (IMS) Rx interfaces, Diameter protocol, and IMS Rf interfaces.

An IMS Rx is a Third Generation Partnership Project (3GPP) interface that runs between an application function and a Policy Charging and Rules Function (PCRF) in a 3GPP architecture.

The Diameter is an Authentication Authorization Accounting (AAA) protocol and is an enhanced version of the RADIUS (Remote Authentication Dial-In User Service) protocol.

An IMS Rf is an interface that runs between Charging Trigger Function (CTF) and Charging Data Function (CDF) in a 3GPP architecture.

Feature History for IMS Rx, Diameter, and IMS Rf

Release
Modification

Cisco IOS XE Release 3.1S

The IMS Rx Interfaces feature was introduced.

The Diameter feature was introduced.

Cisco IOS XE Release 3.7S

The IMS Rf Billing Interface feature was introduced.


Contents

Information About IMS Rx Interfaces

Configuring IMS Rx

Configuration Examples for IMS Rx

Information About the Diameter Protocol in the SBC

Configuring SBC Diameter Routing

Configuration Examples for Diameter Routing

Information About IMS Rf Billing Interfaces

Configuring an IMS Rf Billing Interface

Configuration Example for IMS Rf Billing Interface

Information About IMS Rx Interfaces

An IMS Rx interface is a 3GPP interface that runs between an application function and a Policy Charging and Rules Function (PCRF) in a 3GPP architecture. In this case, SBC is the application function.

SBC uses the Rx interface to communicate with the PCRF during call initiation and renegotiation to ensure that a call conforms to policy. SBC uses the Rx interface during registration to learn access network information.

The PCRF performs the following functions for SBC via an IMS Rx interface:

Confirms that call media requests conform to the appropriate policy.

Opens gates or pinholes in the media route, and specifies the appropriate QoS.

Requests per-flow charging information when needed.

Informs SBC of media-plane events.

An IMS Rx interface can be configured as a pure Rx environment or as a mixed Rx and media resource environment in unified SBC.

Features Supported

SBC can be deployed as the application function connecting to a PCRF via an Rx interface, in a mobile network, under an IMS or non-IMS environment. SBC supports the following requirements for these environments:

Support for precondition call flows with Rx

Support for late-INVITE and PRACK with Rx

SIP late and early interworking in combination with Rx

SIP PRACK and non-PRACK interworking in combination with Rx

Support for session binding on registration

SBC does not add any IMS-specific SIP headers to requests or responses in non-IMS environment, and does not add P-Charging-Vector or P-Access-Network-Info information

SBC can also use an Rx interface to query a policy server to perform admission control for requests from subscribers on an access network in non-IMS environments.

Restrictions

SBC does not provide preferred or alternate routes for SIP or DNS interfaces.

SBC does not support use of Rx in combination with local call transfers.

Lawful Intercept of media for calls using Rx is not possible.

SBC does not support Packet Cable billing on Rx interfaces.

Call Failures

If the PCRF fails to respond to a request from SBC, SBC treats only the individual request as failed.

Only fully established calls are maintained during redundant switchovers. Calls in the process of being set up are dropped.

Configuration

See the "Configuring IMS Rx" section for the procedure for configuring an IMS Rx Interface.

See the "Configuration Examples for Diameter Routing" section for configuration examples of IMS Rx.

Configuring IMS Rx

This section describes the following procedures:

Configuring an IMS Rx Interface

Configuring Media Service for IMS Rx

Disabling Preliminary AAR Messages

Configuring an IMS Rx Interface

Use the following procedure to configure an IMS Rx interface.

SUMMARY STEPS

1. configure terminal

2. sbc sbc-name

3. sbe

4. adjacency sip adjacency-name

5. ims realm realm-name

6. ims rx

7. ims pani

8. end

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 2 

sbc sbc-name

Example:

Router(config)# sbc MySBC

Creates the SBC service on Cisco Unified Border Element (SP Edition) and enters into SBC configuration mode.

Step 3 

sbe

Example:

Router(config-sbc)# sbe

Enters the mode of the signaling border element (SBE) function of the SBC.

Step 4 

adjacency sip adjacency-name 
Example:
Router(config-sbc-sbe) adjacency sip A_1 

Enters the mode of an SBE SIP adjacency.

Step 5 

ims realm realm-name

Example:

Router(config-sbc-sbe-adj-sip)# ims realm Realm_1

Configures an IMS realm for use by an IMS Rx interface.

Step 6 

ims rx

Example:

Router(config-sbc-sbe-adj-sip)# ims rx

Configures an IMS Rx interface for access adjacency

Step 7 

ims pani

Example:

Router(config-sbc-sbe-adj-sip)# ims pani

(Optional) Configures the P-Access-Network-Info (PANI) header process preference for the adjacency.

Step 8 

end

Example:

Router(config-sbc-sbe-enum-entry)# end

Exits configuration mode and returns to privileged EXEC mode.

Configuring Media Service for IMS Rx

Use the following procedure to configure media service for IMS Rx.

SUMMARY STEPS

1. configure terminal

2. sbc sbc-name

3. sbe

4. cac-policy-set policy-set-id

5. cac-table table-name

6. table-type policy-set

7. entry entry-id

8. ims media-service

9. end

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 2 

sbc sbc-name

Example:

Router(config)# sbc SBC1

Creates the SBC service on Cisco Unified Border Element (SP Edition) and enters into SBC configuration mode.

Step 3 

sbe

Example:

Router(config-sbc)# sbe

Enters the mode of the signaling border element (SBE) function of the SBC.

Step 4 

cac-policy-set policy-set-id

Example:

Router(config-sbc-sbe)# cac-policy-set 1

Enters the mode of CAC policy set configuration within an SBE entity, creating a new policy set if necessary.

policy-set-id—Integer chosen by the user to identify the policy set. The range is 1 to 2147483647.

Step 5 

cac-table table-name

Example:

Router(config-sbc-sbe-cacpolicy)# cac-table testSecure

Enters the mode for configuration of an admission control table (creating one if necessary) within the context of an SBE policy set.

table-name—Name of the admission control table.

Step 6 

table-type policy-set

Example:

Router(config-sbc-sbe-cacpolicy-cactable)# table-type policy-set

Configures a CAC table to allow the use of media resources and 3rd party transcoding resources as well as Rx resources the table type of a CAC table within the context of an SBE policy set.

Step 7 

entry entry-id

Example:

Router(config-sbc-sbe-cacpolicy-cactable)# entry 1

Enters the mode to modify an entry in an admission control table.

entry-id—Specifies the table entry.

Step 8 

ims media-service 
Example:

Router(config-sbc-sbe-cacpolicy-cactable-entry) # ims media-service

(Optional) Configures a CAC table to allow the use of media resources and third party transcoding resources as well as Rx resources.

Step 9 

end

Example:

Router(config-sbc-sbe-enum-entry)# end

Exits configuration mode and returns to privileged EXEC mode.

Disabling Preliminary AAR Messages

Use the following procedure optionally to prevent preliminary AAR messages from being sent during an IMS Rx session.

SUMMARY STEPS

1. configure terminal

2. sbc sbc-name

3. sbe

4. cac-policy-set policy-set-id

5. cac-table table-name

6. table-type policy-set

7. entry entry-id

8. ims rx preliminary-aar-forbid

9. end

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 2 

sbc sbc-name

Example:

Router(config)# sbc SBC1

Creates the SBC service on Cisco Unified Border Element (SP Edition) and enters into SBC configuration mode.

Step 3 

sbe

Example:

Router(config-sbc)# sbe

Enters the mode of the signaling border element (SBE) function of the SBC.

Step 4 

cac-policy-set policy-set-id

Example:

Router(config-sbc-sbe)# cac-policy-set 1

Enters the mode of CAC policy set configuration within an SBE entity, creating a new policy set if necessary.

policy-set-id—Integer chosen by the user to identify the policy set. The range is 1 to 2147483647.

Step 5 

cac-table table-name

Example:

Router(config-sbc-sbe-cacpolicy)# cac-table testSecure

Enters the mode for configuration of an admission control table (creating one if necessary) within the context of an SBE policy set.

table-name—Name of the admission control table.

Step 6 

table-type policy-set

Example:

Router(config-sbc-sbe-cacpolicy-cactable)# table-type policy-set

Configures a CAC table to allow the use of media resources and third party transcoding resources as well as Rx resources the table type of a CAC table within the context of an SBE policy set.

Step 7 

entry entry-id

Example:

Router(config-sbc-sbe-cacpolicy-cactable)# entry 1

Enters the mode to modify an entry in an admission control table.

entry-id—Specifies the table entry.

Step 8 

ims rx preliminary-aar-forbid

Example:

Router(config-sbc-sbe-cacpolicy-cactable-entry) # ims rx preliminary-aar-forbid

Prevents preliminary AAR messages from being sent during an IMS Rx session.

Step 9 

end

Example:

Router(config-sbc-sbe-enum-entry)# end

Exits configuration mode and returns to privileged EXEC mode.

Configuration Examples for IMS Rx

This section provides the following examples:

Configuration Example for IMS Rx Interface

Configuration Example for IMS Rx Media Service

Configuration Example for Disabling Preliminary AAR Messages

Configuration Example for IMS Rx Interface

The following example shows how to configure an IMS Rx interface:

Router# configure terminal 
Router(config)# sbc mySBC 
Router(config-sbc)# sbe 
Router(config-sbc-sbe)# adjacency sip A_1 
Router(config-sbc-sbe-adj-sip)# ims realm Realm_1 
Router(config-sbc-sbe-adj-sip)# ims rx 
Router(config-sbc-sbe-adj-sip)# ims pani 
Router(config-sbc-sbe-adj-sip)# end 

Configuration Example for IMS Rx Media Service

The following example shows how to configure media service for IMS Rx:

Router# configure terminal 
Router(config)# sbc MySBC 
Router(config-sbc)# sbe
Router(config-sbc-sbe)# cac-policy-set 1
Router(config-sbc-sbe-cacpolicy)# cac-table my_table
Router(config-sbc-sbe-cacpolicy-cactable)# table-type policy-set
Router(config-sbc-sbe-cacpolicy-cactable)# entry 1
Router(config-sbc-sbe-cacpolicy-cactable-entry)# ims media-service 
Router(config-sbc-sbe-cacpolicy-cactable-entry)# end 

Configuration Example for Disabling Preliminary AAR Messages

The following example shows how to prevent preliminary AAR messages from being sent during an IMS Rx session (optional):

Router# configure terminal
Router(config)# sbc MySBC 
Router(config-sbc)# sbe
Router(config-sbc-sbe)# cac-policy-set 1
Router(config-sbc-sbe-cacpolicy)# cac-table my_table
Router(config-sbc-sbe-cacpolicy-cactable)# table-type policy-set
Router(config-sbc-sbe-cacpolicy-cactable)# entry 1
Router(config-sbc-sbe-cacpolicy-cactable-entry)# ims rx preliminary-aar-forbid 
Router(config-sbc-sbe-cacpolicy-cactable-entry)# end 

Information About the Diameter Protocol in the SBC

Diameter is an Authentication Authorization Accounting (AAA) protocol and is an enhanced version of the RADIUS (Remote Authentication Dial-In User Service) protocol. Diameter is the protocol of choice for the next generation IMS network developed by 3GPP.

When the Diameter protocol is implemented on a network, the Policy Charging and Rules Function (PCRF) acts as the Diameter server and the Application Function (AF), in our case SBC, acts as the Diameter client. SBC performs the functions of an IMS Rx Diameter client application and handles policy information and media reservations at the border of an access network.

SBC Diameter provides users with the option of configuring of either of two types of routing:

Host-based routing

Realm-based routing where multiple peers can be configured

Interfaces are referred as reference points in IMS. Reference points are named using unique acronyms, such as Rx (receiving reference point).

Features Supported

The following features are supported by SBC Diameter:

SBC Diameter runs over TCP.

SBC Diameter uses IPv4 addressing only.

SBC Diameter supports IP Security Protocol (IPSEC).

SBC Diameter supports multiple peers per realm.

SBC Diameter supports redundancy switchover of Diameter peers as follows:

All Diameter messages are sent to the primary peer of the realm by default.

If the primary peer fails, Diameter switches to a secondary peer and retransmits all pending messages

Restrictions

SBC Diameter has the following restrictions:

SBC Diameter does not replicate states or outstanding requests during redundancy switchovers. All states and outstanding requests are lost after a switchover from a failed active connection to a backup connection.

SBC Diameter does not support IPv6 addressing.

IPv6 is not supported.

Configuration

See the "Configuring SBC Diameter Routing" section for the procedure for configuring the Diameter protocol in SBC.

See the "Configuration Examples for Diameter Routing" section for configuration examples of the Diameter protocol in SBC.

Configuring SBC Diameter Routing

This section provides two routing configurations:

Configuring Diameter Host-Based Routing

Configuring Diameter Realm-Based Routing

Configuring Diameter Host-Based Routing

Use the following procedure to configure Diameter host-based routing. This procedure sets up an Rx adjacency first and then the Diameter host-based routing.

SUMMARY STEPS

1. configure terminal

2. sbc sbc-name

3. sbe

4. adjacency sip adjacency-name

5. ims realm realm-name

6. ims rx pcrf pcrf-name

7. ims pani [received | rx | received rx | rx received]

8. exit

9. diameter

10. origin-realm realm-name

11. origin-host host-name

12. activate

13. end

14. show sbc sbc-name sbe diameter

15. show sbc sbc-name sbe diameter peers peer-name

16. show sbc sbc-name sbe diameter stats

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 2 

sbc sbc-name

Example:

Router(config)# sbc MySBC

Creates the SBC service on Cisco Unified Border Element (SP Edition) and enters into SBC configuration mode.

Step 3 

sbe

Example:

Router(config-sbc)# sbe

Enters the mode of the signaling border element (SBE) function of the SBC.

Step 4 

adjacency sip adjacency-name 
Example:
Router(config-sbc-sbe) adjacency sip Adj_1 

Enters the mode of an SBE SIP adjacency.

Step 5 

ims realm realm-name

Example:

Router(config-sbc-sbe-adj-sip)#ims realm Rx_Realm_1

Creates an IMS realm for the Rx.

Step 6 

ims rx pcrf pcrf-name

Example:

Router(config-sbc-sbe-adj-sip)# ims rx pcrf cisco.com

Configures an IMS Rx reference point on this SIP adjacency and specifies the PCRF host where the Rx messages are routed.

Step 7 

ims pani [ received | rx | received rx | rx received ]

Example:

Router(config-sbc-sbe-adj-sip)# ims pani rx received

(Optional) Configures the P-Access-Network-Info (PANI) header process preference for the adjacency.

Step 8 

exit

Example:

Router(config-sbc-sbe-enum)# exit

Exits to the previous mode.

Step 9 

diameter

Example:

Router(config-sbc-sbe)# diameter

Enters the Diameter configuration mode.

Step 10 

origin-realm realm-name

Example:

Router(config-sbc-sbe-diameter)# origin-realm cisco.com

Configures the name of SBC's local realm for diameter messages.

Step 11 

origin-host host-name

Example:

Router(config-sbc-sbe-diameter)# origin-host sbc.cisco.com

Configures the name of SBC's local host for diameter messages.

Step 12 

activate

Example:

Router(config-sbc-sbe-enum)# activate

Activates Diameter host-based routing.

Step 13 

end

Example:

Router(config-sbc-sbe-enum-entry)# end

Exits configuration mode and returns to privileged EXEC mode.

Step 14 

show sbc sbc-name sbe diameter

Example:

Router# show sbc MySBC sbe diameter

Displays the local configuration information for Diameter.

Step 15 

show sbc sbc-name sbe diameter peers peer-name

Example:

Router# show sbc MySBC sbe diameter peers Peer1

Displays the configuration information for IMS peers.

Step 16 

show sbc sbc-name sbe diameter stats

Example:

Router# show sbc MySBC sbe diameter stats

Displays the transport statistics for an IMS peer.

Configuring Diameter Realm-Based Routing

Use the following procedure to configure Diameter realm-based routing.

SUMMARY STEPS

1. configure terminal

2. sbc sbc-name

3. sbe

4. adjacency sip adjacency-name

5. ims realm realm-name

6. ims rx

7. exit

8. diameter

9. origin-realm realm-name

10. origin-host host-name

11. peer peer-name ipv4 ipv4-address

12. peer peer-name ipv4 ipv4-address

13. realm realm-name [app rx] peer peer-name [priority priority]

14. realm realm-name [app rx] peer peer-name [priority priority]

15. activate

16. end

17. show sbc sbc-name sbe diameter peers

18. show sbc sbc-name sbe diameter peers peer-name

19. show sbc sbc-name sbe diameter peers peer-name

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 2 

sbc sbc-name

Example:

Router(config)# sbc MySBC

Creates the SBC service on Cisco Unified Border Element (SP Edition) and enters into SBC configuration mode.

Step 3 

sbe

Example:

Router(config-sbc)# sbe

Enters the mode of the signaling border element (SBE) function of the SBC.

Step 4 

adjacency sip adjacency-name 
Example:
Router(config-sbc-sbe) adjacency sip Adj_1 

Enters the mode of an SBE SIP adjacency.

Step 5 

ims realm realm-name

Example:

Router(config-sbc-sbe-adj-sip)#ims realm Rx_Realm_1

Creates an IMS realm for the Rx.

Step 6 

ims rx

Example:

Router(config-sbc-sbe-adj-sip)# ims rx pcrf cisco.com

Configures an IMS Rx reference point on this SIP adjacency.

Step 7 

exit

Example:

Router(config-sbc-sbe-enum)# exit

Exits to the previous mode.

Step 8 

diameter

Example:

Router(config-sbc-sbe)# diameter

Enters the Diameter configuration mode.

Step 9 

origin-realm realm-name

Example:

Router(config-sbc-sbe-diameter)# origin-realm cisco.com

Configures the domain name of an IMS local realm.

Step 10 

origin-host host-name

Example:

Router(config-sbc-sbe-diameter)# origin-host sbc.cisco.com

Configures the domain name of the local IMS host.

Step 11 

peer peer-name ipv4 ipv4-address

Example:

Router(config-sbc-sbe-diameter)# peer peerA address ipv4 1.2.3.4

Configures the name and IPv4 address of peerA.

Step 12 

peer peer-name ipv4 ipv4-address

Example:

Router(config-sbc-sbe-diameter)# peer peerB address ipv4 1.2.3.5

Configures the name and IPv4 address of peerB.

Step 13 

realm realm-name [app rx] peer peer-name [priority priority]

Example:

Router(config-sbc-sbe-diameter)# realm test.com app rx peer peerA

Configures a peer and assign the peer to the realm.

Step 14 

realm realm-name [app rx] peer peer-name [priority priority]

Example:

Router(config-sbc-sbe-diameter)# realm test.com app rx peer peerB priority 10

Configures another peer and assign the peer to the realm.

Step 15 

activate

Example:

Router(config-sbc-sbe-enum)# activate

Activates Diameter realm-based routing.

Step 16 

end

Example:

Router(config-sbc-sbe-enum-entry)# end

Exits configuration mode and returns to privileged EXEC mode.

Step 17 

show sbc sbc-name sbe diameter peers

Example:

Router# show sbc MySBC sbe diameter peers

Displays the configuration information for all IMS peers.

Step 18 

show sbc sbc-name sbe diameter peers peer-name

Example:

Router# show sbc MySBC sbe diameter peers peerA

Displays the configuration information for peerA.

Step 19 

show sbc sbc-name sbe diameter peers peer-name

Example:

Router# show sbc MySBC sbe diameter peers peerB

Displays the configuration information for peerB.

Configuration Examples for Diameter Routing

This section provides the following examples:

Configuration Example for Diameter Host-Based Routing

Configuration Example for Diameter Realm-Based Routing

Configuration Example for Diameter Host-Based Routing

The following example shows how to configure Diameter host-based routing:

Router# configure terminal 
Router(config)# sbc MySBC 
Router(config-sbc)# sbe 
Router(config-sbc-sbe) adjacency sip Adj_1 
Router(config-sbc-sbe-adj-sip)# ims realm Rx_Realm_1 
Router(config-sbc-sbe-adj-sip)# ims rx pcrf cisco.com 
Router(config-sbc-sbe-adj-sip)# ims pani 
Router(config-sbc-sbe-enum)# exit 
Router(config-sbc-sbe)# diameter 
Router(config-sbc-sbe-diameter)# origin-realm cisco.com 
Router(config-sbc-sbe-diameter)# origin-host sbc.cisco.com 
Router(config-sbc-sbe-enum)# activate 
Router(config-sbc-sbe-enum-entry)# end 
Router# show sbc MySBC sbe diameter 

Router# show sbc MySBC sbe diameter peers Peer1

Router# show sbc MySBC sbe diameter stats

Configuration Example for Diameter Realm-Based Routing

The following example shows how to configure Diameter realm-based routing:

Router# configure terminal
Router(config)# sbc MySBC 
Router(config-sbc)# sbe 
Router(config-sbc-sbe) adjacency sip Adj_1 
Router(config-sbc-sbe-adj-sip)# ims realm Rx_Realm_1 
Router(config-sbc-sbe-adj-sip)# ims rx 
Router(config-sbc-sbe-enum)# exit 
Router(config-sbc-sbe)# diameter 
Router(config-sbc-sbe-diameter)# origin-realm cisco.com 
Router(config-sbc-sbe-diameter)# origin-host sbc.cisco.com 

Router(config-sbc-sbe-diameter)# peer peerA address ipv4 1.2.3.4

Router(config-sbc-sbe-diameter)# peer peerB address ipv4 1.2.3.5

Router(config-sbc-sbe-diameter)# realm test.com app rx peer peerA

Router(config-sbc-sbe-diameter)# realm test.com app rx peer peerB priority 10

Router(config-sbc-sbe-enum)# activate 
Router(config-sbc-sbe-enum-entry)# end 
Router# show sbc MySBC sbe diameter peers 
Router# show sbc MySBC sbe diameter peers peerA 
Router# show sbc MySBC sbe diameter peers peerB 

Note You can use the following, existing ASR1000 IPSEC functionality to provide secure Diameter protocol transport:


 
   
crypto isakmp policy 1
     encr aes
     authentication pre-share
     group 2
 
   
crypto isakmp key cisco123 address 0.0.0.0 0.0.0.0
crypto ipsec transform-set testcpoc esp-des esp-md5-hmac
 
   
crypto map diamap 10 ipsec-isakmp
     set peer 192.68.9.1
     set security-association lifetime kilobytes 536870912
     set transform-set testcpoc
     match address 199
 
   
access-list 199 permit ip 192.169.0.0 0.0.255.255 193.169.0.0 0.0.255.255
 
   
interface SBC01
 ip address 192.68.9.2 255.255.255.0
 crypto map diamap

Information About IMS Rf Billing Interfaces

The SBC supports Rf billing interfaces for SIP-to-SIP calls when operating as a Proxy Call Session Control Function (P-CSCF) and as an Interconnection Border Control Function (IBCF). The Charging Trigger Function (CTF) in the SBC uses an Rf billing interface to provide offline charging information to the billing domain in an IMS network. The Rf billing interface uses the Diameter protocol for sending billing information to the Charging Data Function (CDF). Offline charging is used for network services that are paid periodically, for example, a user may have a subscription for voice calls that is paid for on a monthly basis.

In IMS, billing information originates from the CTF. The CTF sends Accounting Request (ACR) messages containing billing information to the CDF, which collates this information into event-based and session-based Call Detail Record (CDR) files. The CDF then passes the files to the Charging Gateway Function (CGF), which is responsible for nonvolatile storage of the CDRs and for other functions such as, duplicate detection, error correction, and filtering. The CGF transfers the files to the billing domain for eventual account reconciliation. This final transfer is not time sensitive and can occur in batch mode. The billing domain uses the CDR to charge for the services used.

Offline Charging Events

For both event-based charging and session-based charging, the CTF supports the accounting state machine. The task of reporting offline charging events to the CDF is managed through a Diameter Accounting Request (ACR) message. The IMS Rf interface supports the ACR event types described in Table 66.

Table 66 IMS Rf ACR Event Types

Event Type
Description

START

Starts an accounting session.

INTERIM

Updates an accounting session.

STOP

Stops an accounting session.

EVENT

Indicates a one-time accounting event.


The START, INTERIM, and STOP event types are used for session-based charging. The EVENT type is used either for event-based charging or to indicate a failed attempt at establishing a session.

Rf Billing Error Handling

This section describes how the SBC handles the various types of Rf billing errors.

CDF Connection Failure

If the connection to the primary CDF is broken, the SBC sends the corresponding charging information to the secondary CDF (if present). If statically configured CDFs are used, the secondary CDF is the redundant peer of the next highest priority. If the dynamic CDF discovery task is performed, the secondary CDF is the address in the next ccf parameter in the P-Charging-Function-Address header. This process continues until a CDF responds, or there are no more CDFs. In the latter scenario, if an appropriate file system is available, the charging messages are stored in the nonvolatile memory until the CDF connection is restored. The connection to any of the available CDFs has no impact on the call setup.

No Reply from CDF

Because DIAMETER messages are transmitted over TCP or Stream Control Transmission Protocol (SCTP), a missing Accounting Answer response to an ACR must indicate that a connection is going down. In such a scenario, the procedure described in CDF Connection Failure section is followed.

Failure Response from CDF

The CDF can return any failure encountered while collecting billing information from the SBC, in the ACA message, even though the connection to the peer is active.

If the failure return code is DIAMETER_UNABLE_TO_DELIVER, this message is cached in nonvolatile memory and follows the procedure described in CDF Connection Failure section.

If the failure return code is any other value, a PD log is created to convey this information to the user, but no other action is taken.

Duplicate Detection

The SBC does not retransmit DIAMETER requests because the underlying TCP transport handles such requests. The CDF does not handle duplicate requests from the SBC.

CDF Detected Failure

If the SBC fails over, some Rf sessions may not be closed correctly, for example, when a call is set up during failover. The CDF must close CDRs pertaining to a particular session if it detects that ACRs are not received within a certain period.

Restrictions for IMS Rf Billing Interfaces

The IMS Rf Billing Interfaces feature has the following restrictions:

The SBC does not support Rf billing for SIP-to-H.323 calls and H.323-to-H.323 calls.

The SBC does not support Rf billing in a non-IMS network.

The SBC does not supply the PS-Information attribute-value pairs (AVP) on its messages. Therefore, the SBC does not send the Cisco Gateway GPRS Support Node (GGSN)-Address AVP.

The SBC does not supply the Third Generation Partnership Project (3GPP)-Charging-ID AVP.

Configuring an IMS Rf Billing Interface

Use the following procedure to configure an IMS Rf billing interface.

SUMMARY STEPS

1. configure terminal

2. sbc sbc-name

3. sbe

4. adjacency sip adjacency-name

5. ims rf

6. ims realm realm-name

7. exit

8. billing

9. method 3gpp-rf

10. rf index

11. origin-host host-name

12. origin-realm realm-name

13. realm realm-name [usePCFAHeader | cdf cdf-name {FQDN FQDN-name | ipv4 ipv4-address | vpn vpn-name} [port port-number] [priority priority-number]]

14. attach

15. activate

16. end

17. show sbc sbc-name sbe adjacencies adjacency-name [authentication-realms | detail | peers]

18. show sbc sbc-name sbe billing instance [instance-index] [rf {realms [realm-name current5mins]} | {cdfs [cdf-name]}]

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

configure terminal

Example:

Router# configure terminal

Enters the global configuration mode.

Step 2 

sbc sbc-name

Example:

Router(config)# sbc MySBC

Creates the SBC service on the Cisco Unified Border Element (SP Edition) and enters the SBC configuration mode.

Step 3 

sbe

Example:

Router(config-sbc)# sbe

Enters the mode of the signaling border element (SBE) function of the SBC.

Step 4 

adjacency sip adjacency-name 
Example:
Router(config-sbc-sbe) adjacency sip A_1

Enters the SBE SIP adjacency mode.

Step 5 

ims rf

Example:

Router(config-sbc-sbe-adj-sip)# ims rf

Configures an IMS Rf interface for access adjacency.

Step 6 

ims realm realm-name

Example:

Router(config-sbc-sbe-adj-sip)# ims realm Realm_1

Configures an IMS realm for use by an IMS Rf interface.

Step 7 

exit

Example:

Router(config-sbc-sbe-adj-sip)# exit

Exits the SBE SIP adjacency mode.

Step 8 

billing

Example:

Router(config-sbc-sbe)# billing

Configures the IMS Rf billing method.

Step 9 

method 3gpp-rf

Example:

Router(config-sbc-sbe-billing)# method 3gpp-rf

Enables the 3GPP Rf billing method on the SBC.

Step 10 

rf index

Example:

Router(config-sbc-sbe-billing)# rf 0

Creates a new Rf billing instance.

Step 11 

origin-host host-name

Example:

Router(config-sbc-sbe-billing-rf)# origin-host sbc.com

Configures the domain name of an IMS local host. This value is displayed in the diameter Origin-Host AVP.

Step 12 

origin-realm realm-name

Example:

Router(config-sbc-sbe-billing-rf)# origin-realm cisco.com

Configures the domain name of an IMS local realm. This value is displayed in the diameter Origin-Realm AVP.

Step 13 

realm realm-name [usePCFAHeader | cdf cdf-name {FQDN FQDN-name | ipv4 ipv4-address | vpn vpn-name} [port port-number] [priority priority-number]]

Example:

Router(config-sbc-sbe-billing-rf)# realm cisco.com cdf cdf1 ipv4 192.0.2.1 port 3688

Enables dynamic CDF detection.

Step 14 

attach

Example:

Router(config-sbc-sbe-billing-rf)# attach

Attaches an adjacency to an account on the SBE.

Step 15 

activate

Example:

Router(config-sbc-sbe-billing-rf)# activate

Activates billing after it is configured.

Step 16 

end

Example:

Router(config-sbc-sbe-billing-rf)# end

Exits the configuration mode and returns to the privileged EXEC mode.

Step 17 

show sbc sbc-name sbe adjacencies adjacency-name [authentication-realms | detail | peers]

Example:

Router# show sbc asr sbe adjacencies adj1 detail

Displays whether IMS Rf is enabled or not.

Step 18 

show sbc sbc-name sbe billing instance [instance-index] [rf {realms [realm-name current5mins]} | {cdfs [cdf-name]}]

Example:

Router# show sbc asr sbe billing instance 6 rf realms realm1 current5mins

Displays the configuration of the Rf billing interface.

Configuration Example for IMS Rf Billing Interface

The following example shows how to configure the IMS Rf Billing Interface feature:

configure terminal
sbc MySBC
sbe
adjacency sip test
ims rf 
ims realm cisco.com
billing
method 3GPP-RF
rf 0
orig-host sbc.com
orig-realm cisco.com
rf 0 realm cisco.com cdf cdf1 ipv4 1.2.3.4 port 3688
rf 0 realm cisco.com cdf cdf2 cdf.cisco.com priority 2
attach
activate
end
 
   

The following is a sample output of the show sbc sbe billing instance command:

Router# show sbc asr sbe billing instance 1 
 
   
Billing Manager Information:
Local IP address:            3.3.3.3
LDR check time:              0:0
Method                       rf
Admin Status:                UP
Operation Status:            UP
 
   
Billing Methods
Instance:                    1
Type:                        3GPP-RF
Transport Mechanism Status:  FAILED
Active Calls Billed:         0
Deact-mode:                  abort
Admin Status:                UP
Operation Status:            UP
LDR check time:              24:0
Origin Host:                 yfasr.open-ims.test
Origin Realm:                open-ims.test