Configuring Codec Rules
Codec rules are configurable and can be specified with the commands in this section.
If your SIP phones support “ptime” then you will not need to configure any codec rules. Otherwise, you should configure QoS rules and ensure the rule you set is based on the packetization/sample rate that the phone uses.
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 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 Wireless LAN System uses the default value of the codec type specified with the qoscodec command.
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.
To configure QoS Codec rules, you need to enter Codec configuration mode. To do this, follow these steps:
Configuring Codec Rules
| Command | Purpose |
| configure terminal | Enter global configuration mode. |
| qoscodec rule-id codec <codec-type> qosprotocol {H323v1|sip} tokenbucketrate tbr maxdatagramsize maxdg minpolicedunit minpol samplerate sr | Enter QoS Codec configuration for the specified rule ID. Use show qoscodec to obtain a list of rule IDs. The following are the required parameters:
codec. Enter the Codec type after at the Codec keyword. The acceptable Codec types are given below. qosprotocol. The QoS protocol. This can be one of the following: H323 (H.323); sip (SIP – Session Initiation Protocol) tokenbucketrate. Token bucket rate, from 0 to 1000 Kbps or 164 Mbps, depending on the box checked. maxdatagramsize. Maximum datagram size. From 0 to 1,500 bytes. minpolicedunit. Minimum policed unit. From 0 to 1,500 bytes. samplerate. Sample rate. From 0 to 200 packets per second. |
| … commands … | Enter the QoS CODEC configuration commands here. |
| end | Return to privileged EXEC mode. |
| copy running-config startup-config | This is an optional step to save your entries in the configuration file. |
The Codec type can be one of the following
TABLE 28: QoS Codec Type
| Type | Description |
| 1016 | 1016 Audio: Payload Type 1, Bit Rate 16 Kbps |
| default | Contains the default TSpec/ RSpec for unknown codecs or codecs for which there is no entry in the codec translation table |
| dv14 | DV14 Audio: Payload Type 5, Bit Rate 32 Kbps |
| dv14.2 | DV14.2 Audio: Payload Type 6, Bit Rate 64Kbps |
| g711a | G711 Audio: Payload Type 8, G.711, A-law, Bit Rate 64 Kbps |
Configuring Codec Rules
TABLE 28: QoS Codec Type
| Type | Description |
| g711u | G711 Audio: Payload Type 0, G.711, U-law, Bit Rate 64 Kbps |
| g721 | G721 Audio: Payload Type 2, Bit Rate 32 Kbps |
| g722 | Audio: Payload Type 9, Bit Rate 64 Kbps, 7KHz |
| g7221 | G7221 Audio: Payload Type *, Bit-Rate 24 Kbps, 16KHz |
| g7221-32 | G7221 Audio: Payload Type *, Bit-Rate 32 Kbps, 16KHz |
| g723.1 | G7231 Audio: Payload Type 4, G.723.1, Bit Rate 6.3Kbps |
| g728 | G728 Audio: Payload Type 15, Bit Rate 16Kbps |
| g729 | G729 Audio: Payload Type 16, Bit Rate 8Kbps |
| g7red | Proprietary MSN Codec Audio: Payload Type * |
| gsm | GSM Audio: Payload Type 3, Bit Rate 13Kbps |
| h261 | H.261 Video |
| h263 | H.263 Video |
| lpc | IPC Audio: Payload Type 7, Bit Rate 2.4 Kbps |
| mpa | MPA Audio: Payload Type 14, Bit Rate 32 Kbps |
| siren | Proprietary MSN Audio: Payload Type *, Bit Rate 16Kbps, 16KHz |
The following commands are used in the QoS Codec configuration mode:
TABLE 29: QoS CODEC Configuration Mode Commands
| Command | Purpose |
| tokenbucketsize size | Token bucket size in bytes. From 0 to 16,000 bytes. Defaults to 8. |
| peakrate rate | Traffic spec peak rate. From 0 to 1,000,000 bytes/second. Defaults to 0. |
| rspecrate rate | Reservation spec rate. From 0 to 1,000,000 bytes/second. Defaults to 0. |
| rspecslack slack | Reservation spec slack. From 0 to 1,000,000 microseconds. Defaults to 0. |
Configuring Codec Rules