[TABS_R id=10143]
You issue the show running-config command on a CME router and receive the following partial output:
Examine the output, and use the information you gather to answer the question.
Based on the configuration, which of the following codecs should be displayed in the call statistics when a user presses the ? key twice on an IP phone? (Select the best answer.)
- G.711 alaw
- G.711 µlaw
- G.726
- G.729
- iLBC
Explanation:
Given the configuration commands in this scenario, the G.729 codec should be displayed in the call statistics when a user presses the question mark (?) key twice on the IP phone. The G.729 codec is a high-complexity compressed codec that consumes bandwidth at a rate of 8 Kbps. Cisco IOS uses the G.729 codec by default unless you specify a codec by issuing the codec command in dial peer configuration mode. For example, the codec g729br8 command configures a dial peer to use the G.729 Annex B codec, which adds Internet Engineering Task Force (IETF)standard voice activity detection (VAD) and comfort noise generation features to the G.729 codec.
There are two ways that you can verify the codec that is being used on a call from a Cisco IP phone: by pressing the ? key twice while a call is in progress and by pressing settings> Status > Call Statistics after a call has been disconnected. Both methods of accessing call statistics display the same information, including the codec being used by the caller, the codec being used by the receiver, the size of voice packets being transmitted, the size of voice packets being received, the average amount of jitter on the call, the maximum amount of jitter on the call, and the number of packets that were discarded by the receiver.
Neither the G.711 a-law codec nor the G.711 µ-law (mulaw) codec will be used by the dial peer. The G.711 codec is an uncompressed, 64Kbps audio codec common to all Voice over IP (VoIP) devices. Two variations of G.711 encoding exist: µlaw and a-law. Only the United States, Canada, and Japan use the G.711 µlaw codec to encode audio data; the rest of the world uses G.711 a-law. To configure a dial peer to use the G.711 a-law codec, you should issue the codec g711alaw command in dial peer configuration mode. To configure a dial peer to use the G.711 µlaw codec, you should issue the codec g711ulaw command in dial peer configuration mode.
The G.726 codec will not be used by the dial peer. The G.726 codec is a medium complexity compression codec. To configure a dial peer to use the G.726 codec at a bit rate of 32 Kbps, you should issue the codec g726r32 command in dial peer configuration mode.
The Internet Low Bitrate Codec (iLBC) will not be used by the dial peer. The iLBC codec is a nonproprietary, high- complexity compression codec that consumes bandwidth at a rate of up to 15.2 Kbps. To configure a dial peer to use the iLBC codec, you should issue the codec ilbc command in dial peer configuration mode.
[TABS_R id=10143]