G722 Wideband Codec settings in UCM 7.0

Dear Readers,

If you come from CCM 4.1 days and now studying for your Voice CCIE Lab Exam, you might be aware that there’s a new codec setting in UCM 7.0 and later, I’m talking about the G.722 Wideband codec, I wanted to talk about it today as it may cause some confusion when comparing it with G.711 negotiation and configuration.

G.722 is a wideband codec (within the family of ADPCM codecs) which first recommendation came out more than 15 years ago, it was developed as a necessity to create a new voice codec standard that provides a better voice telephony quality than the toll quality that G.711 offers. It basically doubles the audio content within the same bit rate of G.711 i.e. 64kps, meaning that a wider set of frequencies are encoded- decoded. Therefore for the G.711 recommendation the range is up to 3.44 Khz and for G.722 reaches the 8Khz of audio frequency, which translates into a higher voice quality.

If we talk about the UCM configuration of this codec, we see that in the regions settings, the codec G711 and G722 options are presented by separate, however, these two options basically means the same and tells that the codec negotiation between the two endpoints involved should occur at a desired maximum rate of 64kpbs.

When negotiating codec, the endpoints involved in the call advertise their codec capabilities to the UCM which then chooses the common codec between them.

Now, let’s suppose that we have two endpoints supporting and advertising the G.722, are involved in a call whose region relationship are set to G711 or G722 codec, what codec will be negotiated between them? (Assuming all the remaining parameters both in regions and phones are set to the default value), I’m sure you know this one!!, well, it will be G.722 because UCM will always give preference to the higher quality codec (unless the link loss type is set to lossy), which is G.722 over G.711 in this case.

We should also be aware that with default configurations G.722 codec will be advertised and negotiated for intraregion calls (again, if the endpoints support it) as the default intraregion codec is G.711 and link loss type is low loss, now the question is how to get rid of this codec advertising and negotiation, well, you can actually do it in several places. In CallManager Service parameters you can disable the G.722 negotiation for all devices in the cluster with the “G722 Codec Enabled” parameter; this will be enough if the requirement is to disable G.722 clusterwide. In addition you can also disable the G.722 advertising from the phones in Enterprise parameters and phone settings with the “Advertise G.722 Codec” setting, having as always the phone precedence over the general (Enteprise Parameter) configuration. Having this configured, phones supporting G.722 will negotiate G.711 codec as in the CCM 4.1 days.

Be also aware that Cisco is and will be supporting the G.722 codec in most of their newer voice products, so a basic knowledge of this codec is a must.

That’s all for now, play around with these settings in your lab and write your comments!!

Stay tuned for more!!

Otto Sanchez

CCIE #25592 (Voice)

Support Engineer – IPexpert, Inc

URL: http://www.IPexpert.com

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