Technical data

Configuring Codec Rules

The SIP ptime attribute is an optional part of the SIP Specification. It allows a SIP

media device to advertise, in milliseconds, the packetization rate of the RTP media

stream. For example, if ptime is set to the value “20” the SIP device sends 1 RTP

packet to the other party every 20 milliseconds. With this specification, the Meru

Meru Wireless LAN System can accurately reserve QoS bandwidth based on the Codec

and Packetization rate.

The following is a sample of the "ptime" attribute included as part of an SDP media

attribute:

m=audio 62986 RTP/AVP 0

a=rtpmap:0 PCMU/8000

a=ptime:20

If the ptime attribute is not present when the media is negotiated in SDP between

the SIP devices, the Meru Meru Wireless LAN System uses the default value of the

codec type specified with the qoscodec command.

To configure QoS Codec rules, you need to enter Codec configuration mode. To do

this, follow these steps:

Note:

The proper packetization rate must be configured to match the actual

media traffic or the QoS reservation will be inaccurate. A spreadsheet,

qoscodec_parameters.xls, is available from the Customer Support FTP site

that can help you to determine the correct values for the relevant parameters.

Please contact Customer Support for details and access.