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Media settings

The media settings determine how audio is sent between the devices. The devices negotiate via SIP before a call is connected. All devices must support the same media types, codecs, and security settings.

Codec

Codecs are used to convert an analog voice signal to a digitally encoded version and vice versa. Codecs vary in the sound quality they deliver and the bandwidth required. The Avaya B179 supports the most common codecs and each codec can be given a precedence depending on your requirements for high quality audio or low bandwidth use. Ensure that you configure IP Office to use the same codec and codec priority. Refer to Codec selection for more information.

Procedure
  1. On the phone, press MENU > SETTINGS > ADVANCED > enter your PIN > MEDIA > CODEC (or press 6,2,4,1 from the main menu—you will be asked to enter the PIN).

  2. Set the codec priority and press OK when you are satisfied.

    The priority can be set from 4 (high) to 1 (low) or 0 (disabled), and must match that of IP Office.

Security

The media in VoIP calls is usually sent using the RTP protocol (Real-time Transport Protocol). RTP is a standardized packet format for delivering audio and video over the Internet.

SRTP (Secure Real-time Transport Protocol) is an extension of RTP to provide encryption, message authentication and integrity for the audio and video streams.

All devices must support SRTP to establish a connection. It is therefore possible to set SRTP as disabled, optional or mandatory.

  1. On the phone, press MENU > SETTINGS > ADVANCED > enter your PIN > MEDIA > SECURITY (or press 6,2,4,4 from the main menu—you will be asked to enter the PIN).

  2. Configure SRTP and secure signalling and press OK. Refer to the table below for a brief description of each option.

SRTP If set to disabled, the media is sent using RTP. Note that despite this setting, the Avaya B179 will still use a secure channel if the opposite device demands it.

If set to optional or mandatory, a padlock will be shown in the bottom right-hand corner of the screen. If the other devices support SRTP, the padlock will be locked. Otherwise, an open padlock will be displayed.

If set to mandatory, the call will not be connected if the other devices do not support SRTP.

Secure signalling The SIP messages (signalling) and the SRTP cipher key are sent on a different channel than the media and are not affected by the RTP/SRTP setting. To ensure a secure connection, the signalling must be secured using TLS or SIPS. Note that the SIP transport setting must be set accordingly.

VAD

Voice Activity Detection (speech detection) is a technique used in speech processing to detect the presence or absence of human speech in regions of audio. In VoIP applications, VAD is mainly used to avoid unnecessary coding and transmission of silence packets, saving on computation and network bandwidth.

  1. On the phone, press MENU > SETTINGS > ADVANCED > enter your PIN > MEDIA > VAD (or press 6,2,4,2 from the main menu—you will be asked to enter the PIN).

  2. Configure speech detection and press OK when you are satisfied.

DTMF

DTMF (Dual-tone Multi-Frequency) signalling is used for telephone signalling over the line to the phone switch or PBX.

If the device itself generates the tones and they are sent in the voice-frequency band, the method is called Inband. This is not the best method when using VoIP. Low bit rate codecs may corrupt the signalling tones and make it difficult for the switch to identify them.

RFC 2833 is a method of carrying DTMF signals in RTP packets using a separate RTP payload format. With this method a PSTN gateway reproduces the DTMF tones sent from the end device.

With SIP Info, the DTMF signals are sent as SIP requests. The SIP switch creates the tones if the call is transferred to the PSTN.

Use RFC 2833 or SIP Info as preferred methods. Switch to inband only if you encounter problems using DTMF signalling with your PBX/SIP switch.

Ensure that the DTMF configuration on the phone matches the DTMF configuration in IP Office. Otherwise, you will be unable to access voicemail in IP Office via the B179 as a result of incompatible signalling tones. Refer to B179 extension settings for IP Office configuration.

Procedure
  1. On the phone, press MENU > SETTINGS > ADVANCED > enter your PIN > MEDIA > DTMF SIGNALLING (or press 6,2,4,3 from the main menu—you will be asked to enter the PIN).

  2. Configure the desired signalling settings and press OK when you are satisfied.

Advanced

First RTP port— If the RTP packets must be directed to a specific port series, the first port number is set here.