RTP, RTCP and T.38 Parameters

The RTP, RTCP and T.38 parameters are described in the table below.

RTP/RTCP and T.38 Parameters

Parameter

Description

'Dynamic Jitter Buffer Minimum Delay'

configure voip > media rtp-rtcp > jitter-buffer-minimum-delay

[DJBufMinDelay]

Global parameter defining the minimum delay (in msec) of the device's dynamic Jitter Buffer.

You can also configure the feature per specific calls, using IP Profiles ('Dynamic Jitter Buffer Minimum Delay' parameter). For a detailed description of the parameter and for configuring the feature, see Configuring IP Profiles.

Note: If the feature is configured for a specific profile, the settings of the global parameter is ignored for calls associated with the profile.

'Dynamic Jitter Buffer Optimization Factor'

configure voip > media rtp-rtcp > jitter-buffer-optimization-factor

[DJBufOptFactor]

Global parameter defining the Dynamic Jitter Buffer frame error/delay optimization factor.

You can also configure the feature per specific calls, using IP Profiles ('Dynamic Jitter Buffer Optimization Factor' parameter) . For a detailed description of the parameter and for configuring the feature, see Configuring IP Profiles .

Note: If the feature is configured for a specific profile, the settings of the global parameter is ignored for calls associated with the profile.

'RTP Redundancy Depth'

configure voip > media rtp-rtcp > RTP-redundancy-depth

[RTPRedundancyDepth]

Global parameter that enables the device to generate RFC 2198 redundant packets. You can also configure this feature per specific calls, using IP Profiles ('RTP Redundancy Depth' parameter). For a detailed description of the parameter and for configuring this feature in the IP Profiles table, see Configuring IP Profiles.

Note: If you configure this feature for a specific IP Profile, the device ignores this global parameter for calls associated with the IP Profile.

'Enable RTP Redundancy Negotiation'

configure voip > sip-definition settings > rtp-rdcy-nego-enbl

[EnableRTPRedundancyNegotiation]

Enables the device to include the RTP redundancy dynamic payload type in the SDP (according to RFC 2198).

[0] Disable (default)
[1] Enable = The device includes in the SDP message the RTP payload type "red" and the payload type configured by the [RFC2198PayloadType] parameter.

a=rtpmap:<PT> red/8000

Where <PT> is the payload type as defined by the [RFC2198PayloadType] parameter. The device sends the SIP INVITE message with "a=rtpmap:<PT> red/8000" and responds with a 18x/200 OK containing "a=rtpmap:<PT> red/8000" in the SDP.

Note:

The parameter is applicable only to the Gateway application.
For this feature to work, configure the [RTPRedundancyDepth] parameter to 1 (i.e., enabled).
Currently, negotiation of the "red" payload type is not supported and therefore, should be configured to the same PT value for both parties.

'RFC 2198 Payload Type'

configure voip > media rtp-rtcp > RTP-redundancy-payload-type

[RFC2198PayloadType]

Defines the RTP redundancy packet payload type (according to RFC 2198).

The valid value is 96 to 127. The default is 104.

Note:

The parameter is applicable only if you configure the [RTPRedundancyDepth] parameter to 1.
The device ignores this parameter for Rx payload types and uses the payload type determined during SDP negotiation. For using this configured payload type, see the [BackwardPTBehavior] parameter.

'Packing Factor'

[RTPPackingFactor]

N/A (controlled internally by the device according to the selected coder).

'RFC 2833 TX Payload Type'

configure voip > media rtp-rtcp > telephony-events-payload-type-tx

[RFC2833TxPayloadType]

Defines the Tx RFC 2833 DTMF relay dynamic payload type for outbound calls.

The valid range is 96 to 127. The default is 96.

Note: When RFC 2833 payload type negotiation is used (i.e., the parameter FirstTxDTMFOption is set to 4), this payload type is used for the received DTMF packets. If negotiation isn't used, this payload type is used for receive and for transmit.

'RFC 2833 RX Payload Type'

configure voip > media rtp-rtcp > telephony-events-payload-type-rx

[RFC2833RxPayloadType]

Defines the Rx RFC 2833 DTMF relay dynamic payload type for inbound calls.

The valid range is 96 to 127. The default is 96.

Note:

The device ignores this parameter for Rx payload types and uses the payload type determined during SDP negotiation. For using this configured payload type, see the [BackwardPTBehavior] parameter.
When RFC 2833 payload type negotiation is used (i.e., the parameter [FirstTxDTMFOption] is set to 4), this payload type is used for the received DTMF packets. If negotiation isn't used, this payload type is used for receive and transmit.

[EnableDetectRemoteMACChange]

Determines whether the device changes the RTP packets according to the MAC address of received RTP packets and according to Gratuitous Address Resolution Protocol (GARP) messages.

[0] = Nothing is changed.
[1] = If the device receives RTP packets with a different source MAC address (than the MAC address of the transmitted RTP packets), then it sends RTP packets to this MAC address and removes this IP entry from the device's ARP cache table.
[2] = (Default) The device uses the received GARP packets to change the MAC address of the transmitted RTP packets.
[3] = Options 1 and 2 are used.

Note:

For the parameter to take effect, a device restart is required.
If the device is located in a network subnet which is connected to other gateways using a router that uses Virtual Router Redundancy Protocol (VRRP) for redundancy, then set the parameter to 0 or 2.

'Forward Invalid RTP Packets'

[RTPFWInvalidPacketHandling]

Defines the device's handling of invalid RTP and RTCP packets.

[0] Forward Packets = Forwards the invalid packets as is.
[1] Forward Packets and Issue Warnings = (Default) Forwards the invalid packets and issues warnings (sent to the syslog) to notify of the invalid packets.
[2] Drop Packets and Issue Warnings = Drops the invalid packets and issues warnings to notify of the invalid packets.

Note:

The parameter is applicable only if the IP Profile parameter 'Mediation Mode' is configured to RTP Forwarding.

'RTP Base UDP Port'

configure voip > media rtp-rtcp > base-udp-port

[BaseUDPport]

Global parameter that defines the lower boundary of the UDP port used for RTP, RTCP (RTP port + 1) and T.38 (RTP port + 2). For more information on configuring the UDP port range, see Configuring RTP Base UDP Port.

The range of possible UDP ports is 6,000 to 65,535. The default base UDP port is 6000.

Note: For the parameter to take effect, a device restart is required.

configure voip > media rtp-rtcp > udp-port-spacing

[UdpPortSpacing]

Defines the port spacing ("jumps") of local UDP ports allocated by the device to media channels (legs) within the configured port range.

[2] = The device allocates ports in "jumps" of 2 ports.

Note: For UDP port spacing of 2, you must configure the device to use the same port for RTP and T.38, by configuring the [T38UseRTPPort] ini file parameter to 1.

[4] = (Default) The device allocates ports in "jumps" of 4 ports.
[5] = The device allocates ports in "jumps" of 5 ports.
[10] = The device allocates ports in "jumps" of 10 ports.

For more information on configuring the UDP port range, port allocation and spacing, see Configuring RTP Base UDP Port.

Note: A device restart is required for the parameter to take effect.

configure voip > gateway digital settings > rtcp-act-mode

[RTCPActivationMode]

Disables RTCP traffic when there is no RTP traffic. This feature is useful, for example, to stop RTCP traffic that is typically sent when calls are put on hold (by an INVITE with 'a=inactive' in the SDP).

[0] = (Default) Active Always - RTCP is active even during inactive RTP periods, i.e., when the media is in 'recvonly' or 'inactive' mode.
[1] = Inactive only If RTP inactive - No RTCP is sent when RTP is inactive.

Note: The parameter is applicable only to the Gateway application.

'T.38 Fax Session'

configure voip > sip-definition settings > t38-sess-imm-strt

[T38FaxSessionImmediateStart]

Enables fax transmission of T.38 "no-signal" packets to the terminating fax machine.

[0] Disable (default)
[1] Immediate Start on Fax = Device activates T.38 fax relay upon receipt of a re-INVITE with T.38 only in the SDP.
[2] Immediate Start on Fax & Voice = Device activates T.38 fax relay upon receipt of a re-INVITE with T.38 and audio media in the SDP.

The parameter is used for transmission from fax machines connected to the device and located inside a NAT. Generally, the firewall blocks T.38 (and other) packets received from the WAN, unless the device behind NAT sends at least one IP packet from the LAN to the WAN through the firewall. If the firewall blocks T.38 packets sent from the termination IP fax, the fax fails.

To overcome this, the device sends No-Op (“no-signal”) packets to open a pinhole in the NAT for the answering fax machine. The originating fax doesn't wait for an answer, but immediately starts sending T.38 packets to the terminating fax machine.

Note: To enable No-Op packet transmission, use the [NoOpEnable] and [NoOpInterval] parameters.

configure voip > sip-definition settings > t38-use-rtp-port

[T38UseRTPPort]

Defines the port (with relation to RTP port) for sending and receiving T.38 packets.

[0] = (Default) Use the RTP port +2 to send/receive T.38 packets.
[1] = Use the same port as the RTP port to send/receive T.38 packets.

Note:

For the parameter to take effect, a device restart is required.
When the device is configured to use V.152 to negotiate audio and T.38 coders, the UDP port published in SDP for RTP and for T38 must be different. Therefore, set the T38UseRTPPort parameter to 0.

'T38 Fax Max Buffer'

configure voip > sip-definition settings > t38-fax-mx-buff

[T38FaxMaxBufferSize]

Defines the maximum size (in bytes) of the device's T.38 buffer. This value is included in the outgoing SDP when T.38 is used for fax relay over IP.

The valid range is 500 to 3000. The default is 3,000.

QoE Parameters

[QoEMediaStatisticTimer]

Defines the interval (in msec) for QoE collection and report generation.

The valid value range is 0 to 65,535. The default is 30,000 (i.e., 30 seconds).

For more information, see Configuring Interval for QoE Report Collection and Generation.

Note:

For the parameter to take effect, a device restart is required.

No-Op Packets Parameters

no-operation-enable

[NoOpEnable]

Enables the device to send RTP or T.38 No-Op packets during RTP or T.38 silence periods. This mechanism ensures that the NAT binding remains open.

[0] = Disable (default)
[1] = Enable

Note: You can also enable the feature per IP Profile (for SBC calls only) , using the 'Generate No-Op Packets' IP Profile parameter.

[NoOpInterval]

Defines the interval (msec) between each RTP or T.38 No-Op packet sent by the device during the silence period (i.e., no RTP/T.38 traffic).

The valid range is 20 to 600,000. The default is 1,000.

Note: To enable No-Op packet transmission, use the [NoOpEnable] parameter.

no-operation-interval

[RTPNoOpPayloadType]

Defines the payload type of No-Op packets.

The valid range is 96 to 127. For the range of Dynamic RTP Payload Type for all types of non hard-coded RTP Payload types, refer to RFC 3551. The default is 120.

Note:

The parameter is applicable only if the IP Profile parameter 'Generate No-Op Packets' is enabled, or the [BackwardPTBehavior] parameter is enabled.
When configuring the parameter, make sure that its settings don't cause collisions with other payload types.
The device ignores this parameter for Rx payload types and uses it only for Tx payload types.

RTP Control Protocol Extended Reports (RTCP XR) Parameters

For more information on RTCP XR, see Configuring RTCP XR.

'Enable RTCP XR'

configure voip > media rtp-rtcp > voice-quality-monitoring-enable

[VQMonEnable]

Enables voice quality monitoring and RTCP XR, according to RFC 3611.

[0] Disable (default)
[1] Enable Fully = Calculates voice quality metrics, uses them for QoE calculations, reports them to OVOC (if configured), and sends them to remote side using RTCP XR.
[2] Enable Calculation Only = Calculates voice quality metrics, uses them for QoE calculations, reports them to OVOC (if configured), but doesn't send them to remote side using RTCP XR.

'Minimum Gap Size'

[VQMonGMin]

Defines the voice quality monitoring - minimum gap size (number of frames).

The default is 16.

'Burst Threshold'

[VQMonBurstHR]

Defines the voice quality monitoring - excessive burst alert threshold.

The default is -1 (i.e., no alerts are issued).

'Delay Threshold'

[VQMonDelayTHR]

Defines the voice quality monitoring - excessive delay alert threshold.

The default is -1 (i.e., no alerts are issued).

'R-Value Delay Threshold'

[VQMonEOCRValTHR]

Defines the voice quality monitoring - end of call low quality alert threshold.

The default is -1 (i.e., no alerts are issued).

'Tx RTCP Packets Interval'

configure voip > media rtp-rtcp > rtcp-interval

[RTCPInterval]

Defines the time interval (in msec) between adjacent RTCP XR reports. This interval starts from call establishment. Thus, the device can send RTCP XR reports during the call, in addition to at the end of the call. If the duration of the call is shorter than this interval, RTCP XR is sent only at the end of the call.

The valid value range is 0 to 65,535. The default is 5,000.

'Disable RTCP XR Interval Randomization'

configure voip > media rtp-rtcp > disable-RTCP-randomization

[DisableRTCPRandomize]

Determines whether RTCP report intervals are randomized or whether each report interval accords exactly to the parameter RTCPInterval.

[0] Disable = (Default) Randomize
[1] Enable = No Randomize

'Gateway RTCP XR Report Mode'

configure voip > sip-definition settings > rtcp-xr-rep-mode

[RTCPXRReportMode]

Enables the device to send RTCP XR in SIP PUBLISH messages and defines the interval at which they are sent.

[0] Disable = (Default) RTCP XR is not sent.
[1] End Call = RTCP XR is sent at the end of the call.
[2] End Call & Periodic = RTCP XR is sent at the end of the call and periodically according to the RTCPInterval parameter.
[3] End Call & End Segment = RTCP XR is sent at the end of the call and at the end of each media segment of the call. A media segment is a change in media, for example, when the coder is changed or when the caller toggles between two called parties (using call hold/retrieve). The RTCP XR sent at the end of a media segment contains information only of that segment. If the segment doesn't contain RTP/RTCP content, the RTCP XR is not sent. For call hold, the device sends an RTCP XR each time the call is placed on hold and each time it is retrieved. In addition, the Start timestamp in the RTCP XR indicates the start of the media segment; the End timestamp indicates the time of the last sent periodic RTCP XR (typically, up to 5 seconds before reported segment ends).

Note: The parameter is applicable only to the Gateway application.

'Publication IP Group ID'

publication-ip-group-id

[PublicationIPGroupID]

Defines the IP Group to where the device sends RTCP XR reports.

By default, no value is defined.

'SBC RTCP XR Report Mode'

configure voip > sip-definition settings > sbc-rtcpxr-report-mode

[SBCRtcpXrReportMode]

Enables the sending of RTCP XR reports of QoE metrics at the end of each call session (i.e., after a SIP BYE). The RTCP XR is sent in the SIP PUBLISH message.

[0] Disable (default)
[1] End of Call

Note: The parameter is applicable only to the SBC application.