Configuring global call settings

Identifies the greatest video size that the IP gateway will send and receive when connected to a video endpoint.

Note that this setting only applies when the IP gateway is processing the media (that is, the call is transcoded). In a non-transcoded call, the size of the video is determined by the endpoints. For more information about non-transcoded mode, refer to the information for the Allow non-transcoded calls setting, below.

Choose the unit-wide setting for motion/sharpness trade off. The options are:

• Favor motion: the IP gateway will try and use a high frame rate. That is, the IP gateway will strongly favor a resolution of at least 25 frames per second
• Favor sharpness: the IP gateway will use the highest resolution that is appropriate for what is being viewed
• Balanced: the IP gateway will select settings that balance resolution and frame rate (where the frame rate will not be less than 12 frames per second)

The settings for motion (frames per second) and sharpness (frame size or resolution) are negotiated between the endpoint and the IP gateway. This setting controls how the IP gateway will negotiate the settings to be used with an endpoint.

Identifies the network capacity (measured in bits per second) used by the media channels established by the IP gateway to a single caller.

When the IP gateway makes a call to an endpoint, the IP gateway chooses the maximum bandwidth that is allowed to be used for the media channels which comprise that call. This field sets that maximum bandwidth, and is the total bandwidth of the audio channel and video channel combined.

Before setting the value for the default bandwidth to and from the IP gateway, consider the amount of bandwidth available on your network. As a general rule, you should set the default bandwidth to be less than the available bandwidth.

Where you have connected the IP gateway to the internet via an ADSL connection, we recommend that you set the default bandwidth from the IP gateway to half of your upstream ADSL bandwidth (that is the connection from your network to your Internet Service Provider). Bear in mind that this setting affects traffic on both ports of the IP gateway.

Sets the bandwidth that the IP gateway will advertise to the endpoint when it calls it.

<same as transmit> will set the default bandwidth to the IP gateway to the same value as the default bandwidth from the IP gateway. Under most circumstances, <same as transmit> is the appropriate setting. However, in the case of an ADSL connection, you can set the default bandwidth to the IP gateway to be higher than the default bandwidth from the IP gateway; but bear in mind that this setting affects traffic on both ports of the IP gateway.

Sets the length of time for which the IP gateway will attempt to make a connection to an endpoint. After this time has elapsed and if there is no response from the endpoint, the IP gateway will stop attempting to connect and will proceed to the failed call action.

The default setting is 30 seconds.

The failed call action is dependant on how the call was placed. For more information, refer to Configuring failed call settings.

Note that if you set it to 0, it will never stop attempting to connect to an endpoint that is not responding.

Selecting this option allows non-transcoded calls on the IP gateway.

If you want to allow high definition (HD) calls to take place (or any calls of above 4CIF resolution) through the IP gateway, you must select this option.

This option is only available if you have the High Definition (HD) video feature key installed. For more information about installing feature keys, refer to Upgrading the firmware.

When you enable non-transcoded calls, the IP gateway will prefer to use non-transcoded mode for any call where that is possible. For example, for H.323 to H.323 calls where the endpoints have common codecs and resolutions available, non-transcoded mode will be used. This is likely to be the case for most H.323 to H.323 calls.

If you have the encryption feature key installed, you can configure the IP gateway to encrypt calls and to accept encrypted calls. Choose from:

• Optional: Encryption will be used if one of the endpoints in the call requires it. Where both endpoints are also set to encryption optional, whether or not encryption will be used is decided by the endpoints. In transcoded calls, it is possible for one part of the call to be encrypted and the other part not to be encrypted; in a non-transcoded call, encryption is either used for both parts of the call or not at all
• Required: Encryption must be used by both parts of the call (that is, by both endpoints in the calls)
• Disabled: Encryption will not be used by any call

For information about installing feature keys, refer to Upgrading the firmware.

AES encryption is used for H.323 calls.

SRTP encryption is used for SIP calls.

Note that non-transcoded calls will only take place where you have the HD video feature key installed and the Allow non-transcoded calls option selected.

For more information refer to Using encryption with the IP gateway .

Restricts the IP gateway's choice of audio codecs to be used for transmitting audio to endpoints.

When communicating with an endpoint, the IP gateway receives a list of supported audio codecs from the endpoint. The IP gateway chooses an audio codec from those available, and sends audio data to the endpoint in that format.

Determines which audio codecs the IP gateway advertises to remote endpoints, restricting the endpoints' choice of channels available for sending audio data to the IP gateway.

Restricts the IP gateway's choice of video codecs to be used for transmitting video to endpoints.

When communicating with an endpoint, the IP gateway receives a list of supported video codecs from the endpoint. The IP gateway chooses a video codec from those available, and sends video data to the endpoint in that format.

Determines which video codecs the IP gateway advertises to remote endpoints, restricting the endpoints' choice of channels available for sending video data to the IP gateway.

Sets the format for video transmitted by the IP gateway.

• NTSC
  The IP gateway will transmit video at 30 frames per second (or a fraction of 30, for example: 15fps)
• PAL
  The IP gateway will transmit video at 25 frames per second (or a fraction of 25, for example: 12.5fps)

This option should be set to match your endpoints' video configuration. If you set this incorrectly, the smoothness of the video both to and from the endpoints might suffer.

NTSC is typically used in North America, while PAL is typically used in the UK and Europe.

Sets the maximum payload size (in bytes) of the packets sent by the IP gateway for outgoing video streams (from the IP gateway to connected video endpoints).

Typically, you only need to set this value to lower than the default (1400 bytes) if there was a known packet size restriction in the path between the IP gateway and potential connected endpoints.

Video streams generally contain packets of different lengths. This parameter only sets the maximum size of a transmitted network datagram. The IP gateway optimally splits the video stream into packets of this size or smaller. Thus, most transmitted packets will not reach this maximum size.

Enables the IP gateway to request that the endpoint send lower speed video if it fails to receive all the packets which comprise the far end's video stream.

The IP gateway can send these messages to endpoints requesting that the bandwidth of the video that they are sending be decreased based on the quality of video received by the IP gateway.

If there is a bandwidth limitation in the path between the endpoint and the IP gateway, it is better for the IP gateway to receive every packet of a lower rate stream than to miss some packets of a higher rate stream.

When enabled, when the IP gateway connects to an endpoint, the caller ID that the endpoint will see is the name of the calling endpoint.

Without this option selected, the caller ID that the called party will see is the model name of the IP gateway. For example: Codian IP GW 3520.

When the IP gateway receives a call from an audio-only device, if that call is to be connected to a device that can receive video, then the IP gateway can send a display. This display reads "Audio only call".

When enabled, the IP gateway will send this display to the destination of audio-only calls.

For video endpoints receiving an audio-only call, it can be reassuring to see a display that confirms that no part of the call is missing.

However, for audio-only calls placed through the IP gateway to an MCU, a video port will be used unnecessarily; where video ports are at a premium, uncheck this option.

You can choose to enable or disable content channel video.

With this option unselected, content will not be available to any endpoint. If you check this option, H.239 content can be used in both transcoded and non-transcoded calls.

Select this option to have the IP gateway convert any out-of-band DTMF tones that it receives into in-band DTMF.

Both H.323 and SIP can send DTMF tones in-band (within the audio stream) and out-of-band. Out-of-band DTMF has the advantage that the tones do not sound over any voice, but will not be compatible with analogue telephones.  For example, if you are calling out from an IP phone system through an IP gateway to a traditional call center with an automated audio menu, you will need to be using in-band DTMF tones to select an option, so this option may be required.

Note that IP phones can interpret in-band DTMF and will continue to work as expected with this option enabled.

Select the setting for media encryption for SIP calls:

• All transports: If encryption is used for a call, the media will be encrypted using SRTP regardless of transport mechanism used for call control messages.
• Secure transports (TLS) only: If encryption is used for a call, the media will only be encrypted in calls that are set up using TLS.
• Disabled: SRTP will not be used for any calls. The IP gateway will not encrypt media for SIP calls.

For more information refer to Using encryption with SIP.

When disabled, the IP gateway will not advertise that it is able to encrypt using SRTP. It is only necessary to disable SRTP if it is causing problems.