# &adminguide;

## Overview

This module contains all method related to the IMS policy and charging control functions performed by an Application Function (e.g. P-CSCF) over the Rx interface. This module is dependent on the CDP (C Diameter Peer) modules for communicating with PCRF as specified in 3GPP specification TS 29.214.

## Dependencies

### &kamailio; Modules

The Following modules must be loaded before this module:

- IMS Dialog

- Usrloc PCSCF

- TM - Transaction Manager

- CDP - C Diameter Peer

- CDP_AVP - CDP AVP Applications

### External Libraries or Applications

This module requires the internal IMS library.

## Parameters

### `rx_dest_realm` (string)

This is the name of the Diameter realm of the Diameter server (typically a PCRF).

Default value is 'ims.smilecoms.com'.

#### `rx_dest_realm` parameter usage

    ...
    modparam("ims_qos", "rx_dest_realm", "ims.smilecoms.com")
    ...

### `rx_forced_peer` (string)

FQDN of the Diameter server (typically a PCRF) to communicate with. If not set then realm routing is used. If you use this, the routing defined in your diameter xml configuration file (CDP) will be ignored and as a result you will lose the benefits of load balancing and failover.

Default value is ''.

#### `rx_forced_peer` parameter usage

    ...
    modparam("ims_qos", "rx_forced_peer", "pcrf.ims.smilecoms.com")
    ...

### `rx_auth_expiry` (integer)

This is the expiry length in seconds of the initiated Diameter sessions.

Default value is 7200.

#### `rx_auth_expiry` parameter usage

    ...
    modparam("ims_qos", "rx_auth_expiry", 14400)
    ...

### `cdp_event_latency` (integer)

This is a flag to determine whether or slow CDP responses should be reported in the log file. 1 is enabled and 0 is disabled.

Default value is 1.

#### `cdp_event_latency` parameter usage

    ...
    modparam("ims_qos", "cdp_event_latency", 1)
    ...

### `cdp_event_threshold` (integer)

This time in milliseconds is the limit we should report a CDP response as slow. i.e. if a CDP response exceeds this limit it will be reported in the log file. This is only relevant is cdp_event_latency is enabled (set to 0).

Default value is 500.

#### `cdp_event_threshold` parameter usage

    ...
    modparam("ims_qos", "cdp_event_threshold", 500)
    ...

### `cdp_event_latency_log` (integer)

This time log level at which we should report slow CDP responses. 0 is ERROR, 1 is WARN, 2 is INFO and 3 is DEBUG. This is only relevant is cdp_event_latency is enabled (set to 0)

Default value is 0.

#### `cdp_event_latency_log` parameter usage

    ...
    modparam("ims_qos", "cdp_event_latency_log", 1)
    ...

### `authorize_video_flow` (integer)

This is a flag that specifies whether or not to authorize video flows. 1 means video flows will be authorized over Rx and 0 means video flows will not be authorized over Rx

Default value is 1.

#### `authorize_video_flow` parameter usage

    ...
    modparam("ims_qos", "authorize_video_flow", 0)
    ...

### `cdp_event_list_size_threshold` (integer)

This is a threshold on the size of the cdp event list. Once the queue exceeds this length a warning is logged. 0 disables this feature

Default value is 0.

#### `cdp_event_list_size_threshold` parameter usage

    ...
    modparam("ims_qos", "cdp_event_list_size_threshold", 10)
    ...

### `audio_default_bandwidth` (integer)

This parameters defines the default bandwidth for Audio, if no "b=AS"-Parameter is found in the SDP.

Default value is 64 (64 kBit)

#### `audio_default_bandwidth` parameter usage

    ...
    modparam("ims_qos", "audio_default_bandwidth", 32)
    ...

### `video_default_bandwidth` (integer)

This parameters defines the default bandwidth for Video, if no "b=AS"-Parameter is found in the SDP.

Default value is 128 (128 kBit)

#### `video_default_bandwidth` parameter usage

    ...
    modparam("ims_qos", "video_default_bandwidth", 256)
    ...

### `early_qosrelease_reason` (String)

This sets the default Reason, when a call is terminated in early stage due to QoS-failure.

Default value is "QoS released", a call in early stage would be released with "488 QoS released".

#### `early_qosrelease_reason` parameter usage

    ...
    modparam("ims_qos", "early_qosrelease_reason", "Sorry - QoS failed")
    ...

### `confirmed_qosrelease_headers` (String)

These headers are added to the BYE-Message, when a confirmed call is terminated due to a QoS failure.

Default value is "", no Extra-Headers

The headers must end with CRLF.

#### `confirmed_qosrelease_headers` parameter usage

    ...
    modparam("ims_qos", "confirmed_qosrelease_headers", "X-Reason: QoS failed\r\n")
    ...

### `regex_sdp_ip_prefix_to_maintain_in_fd` (String)

The flow-description AVP is typically populated using IP:port information present in the SDP. Certain (buggy) UEs can change ports midway during calls which causes the flow-description to no longer match the traffic. This parameter allows the flow-description AVP to use to the any keyword instead of certain IP:port combinations in the SDP. The parameter is a regex that if set adds an extra filter for all IPs that do not match the regex with the any keyword in the flow-description AVP

Default value is "", no extra filters added

#### `regex_sdp_ip_prefix_to_maintain_in_fd` parameter usage

    ...
    modparam("ims_qos", "regex_sdp_ip_prefix_to_maintain_in_fd", "10.21.0.1")
    ...

### `terminate_dialog_on_rx_failure` integer

If set then active dialogs associated with an Rx session are torn down in the Rx session fails

Default value is 1, dialogs are torn down

#### `terminate_dialog_on_rx_failure` parameter usage

    ...
    modparam("ims_qos", "terminate_dialog_on_rx_failure", 0)
    ...

### `delete_contact_on_rx_failure` integer

If set then contacts associated with signalling Rx sessions are deleted if the Rx session fails

Default value is 1, contacts are deleted

#### `delete_contact_on_rx_failure` parameter usage

    ...
    modparam("ims_qos", "delete_contact_on_rx_failure", 0)
    ...

### `include_rtcp_fd` integer

If set then a flow description is added for media flows - next available odd port is used as the default for RTCP traffic

Default value is 0, RTCP flow description not added

#### `include_rtcp_fd` parameter usage

    ...
    modparam("ims_qos", "include_rtcp_fd", 1)
    ...

### `af_signaling_ip` (String)

Set P-CSCF IPv4 address to generate the flows for the UE - PCSCF signaling path. Used only for AAR register, Flow-Description AVP (507)

Default value is 127.0.0.1

#### `af_signaling_ip` parameter usage

    ...
    modparam("ims_qos", "af_signaling_ip", "127.0.0.1")
    ...

### `af_signaling_ip6` (String)

Set P-CSCF IPv6 address to generate the flows for the UE - PCSCF signaling path. Used only for AAR register, Flow-Description AVP (507)

Default value is ""

#### `af_signaling_ip6` parameter usage

    ...
    modparam("ims_qos", "af_signaling_ip6", "fd16::205:2dee:ce4a:ab22")
    ...

### `media_type` (String)

Describe Media Type AVP(520) for AAR register

Default value is 'control'

#### `media_type` parameter usage

    ...
    modparam("ims_qos", "media_type", "audio")
    ...

### `flow_protocol` (String)

Describe Flow protocol for Flow-Description AVP (507). Used only for AAR register

Default value is 'IP'

#### `flow_protocol` parameter usage

    ...
    modparam("ims_qos", "flow_protocol", "UDP")
    ...

### `omit_flow_ports` integer

If set to 1 ommit ports for Flow-Description AVP (507). Used only for AAR register

Default value is 0, Add ports to Flow-Description AVP (507)

#### `omit_flow_ports` parameter usage

    ...
    modparam("ims_qos", "omit_flow_ports", 1)
    ...

### `rs_default_bandwidth` integer

Describe default RS-Bandwidth AVP(522) for AAR

Default value is 0

#### `rs_default_bandwidth` parameter usage

    ...
    modparam("ims_qos", "rs_default_bandwidth", 600)
    ...

### `rr_default_bandwidth` integer

Describe default RR-Bandwidth AVP(521) for AAR

Default value is 0

#### `rr_default_bandwidth` parameter usage

    ...
    modparam("ims_qos", "rr_default_bandwidth", 2000)
    ...

### `suspend_transaction` integer

If enabled, suspends the tm transaction while doing the AAR.

Default value is 1 (enabled)

#### `suspend_transaction` parameter usage

    ...
    modparam("ims_qos", "suspend_transaction", 0)
    ...

### `recv_mode` integer

If set to 0, rx_aar_register() takes the received-from address values (IP, port, proto) from the IP frame. If set to 1, it takes them from Via header.

Default value is 0

#### `recv_mode` parameter usage

    ...
    modparam("ims_qos", "recv_mode", 1)
    ...

### `dialog_direction` integer

If set to 1, DLG_MOBILE_ORIGINATING is set to rx_add_media_component_description_avp() instead of DLG_MOBILE_REGISTER (which corresponds to value 3).

Default value is 3

#### `dialog_direction` parameter usage

    ...
    modparam("ims_qos", "dialog_direction", 1)
    ...

### `trust_bottom_via` (int)

If set to 1 it will trust the bottom Via as the UE IP/port/transport when doing client identification.

Normally, the UE identification should be done on IPsec SPIs and source IP/port of the packets. In some cases the ims_* modules trust the top Via on requests and the bottom Via on responses. In some (better) cases this trusts the received-from IP (or the alias in the Contact header).

This parameter allows for an external-to-Kamailio IPsec functionality to be used. That will be in charge of guaranteeing that the bottom Via header is always correct (on requests; on responses the P-CSCF itself should guarantee unmodified Via headers stack). Then the code here will always use the bottom Via as the source of truth for IMS UE identification.

Note: this will prefer the standard received and rport values, if present, over the actual Via sent-by host and port.

Note: !! trusting the Via header has security drawbacks, as it might be easily spoofed by an attacker. Hence, without extra security, the P-CSCF shouldn't trust the Via header for client identification on requests and the ims_registrar_pcscf module would require a fix or extension for that. !!

See also the same parameter in the ims_registrar_pcscf module.

Default value is 0 (trust received-from IP and alias in Contact, and, unfortunately somewhat wrongly top/bottom Via on requests/responses).

#### `trust_bottom_via` parameter usage

    ...
    modparam("ims_qos", "trust_bottom_via", 1)
    ...

## Functions

### `Rx_AAR_Register(route_block, domain)`

Perform an AAR on Diameter RX interface to subscribe to signalling status. This purpose of this is tell a Diameter server (typically a PCRF) to inform the requesting Diameter client on changes to the status of signalling bearer for the same framed IP address. For more details see 3GGP TS 29.214.

Meaning of the parameters is as follows:

- Route block to resume after async UAR Diameter reply.

- domain that usrloc_pcscf uses to store user information.

Return codes:

- -1 - error: There was an error, so we must either ignore it (no subscription) or send 403 (depends on behaviour you want)

  0 - Success: AAR-Request sent, reply is processed asynchronously.

  1 - Success: No need to send AAR-Request, as a subscription still exists (continue as normal)

This function can be used from REQUEST_ROUTE.

p.s. this is executed asynchronously. See example on how to retrieve return value

#### Rx_AAR_Register

    ...
    if(Rx_AAR_Register("REG_AAR_REPLY","location")==0){
        exit;
    }
    ...
    route[REG_AAR_REPLY]
    {
        switch ($avp(s:aar_return_code)) {
            case 1:
                xlog("L_DBG", "Diameter: AAR success on subscription to signalling\n");
                break;
            default:
                xlog("L_ERR", "Diameter: AAR failed on subscription to signalling\n");
                t_reply("403", "Can't register to QoS for signalling");
                exit;
        }
    ...

### `Rx_AAR(route_block, direction, subscription_id, subscription_id_type)`

Perform an AAR on Diameter RX interface to request resource authorisation from a Diameter server (typically a PCRF). For more details see 3GGP TS 29.214.

Meaning of the parameters is as follows:

- Route block to resume after async UAR Diameter reply.

- direction of this message - orig, term, etc.

- subscription_id to hard code subscription ID for AAR. Used for some broken PCRFs. Leave blank to use default

- subscription_id_type to hard code subscription ID type for AAR. Only applicable if subscription_id is set. Set to -1 to use default. This is as per RFC 4006: END_USER_E164 0, END_USER_IMSI 1, END_USER_SIP_URI 2, END_USER_NAI 3, END_USER_PRIVATE 4

This function can be used only from ONREPLY_ROUTE, only for replies to INVITE, UPDATE, PRACK. The reply and request must have SDP, for this function to work properly.

p.s. this is executed asynchronously. See example on how to retrieve return value

#### Rx_AAR

    ...
    if(Rx_AAR("ORIG_SESSION_AAR_REPLY","orig","",-1)==0){
        exit;
    }
    ...
    route[ORIGN_SESSION_AAR_REPLY]
    {
        if ($avp(s:aar_return_code) != 1) {
            xlog("L_ERR", "IMS: AAR failed Orig\n");
            dlg_terminate("all", "Sorry no QoS available");
        } else {
            xlog("L_DBG", "Diameter: Orig AAR success on media authorization\n");
        }
    }
    ...

## Statistics

### AAR Timeouts (aar_timeouts)

The number of timeouts on sending an AAR. i.e. no response to AAR.

### Average AAR Response Time (aar_avg_response_time)

The average response time in milliseconds for AAR-AAA transaction.