Codec Clarification on Cisco UBEs
VoIP networks usually abutment a ample array of codecs, and mechanisms abide to perform
codec negotiations amid devices. Regardless of which mechanisms are used,
preferences actuate which codecs will be called over others.
Because a Cisco UBE router is about a Cisco IOS aperture with the adequacy to
interconnect VoIP punch peers, the aforementioned codec selections mechanisms are accessible as on
any added Cisco IOS gateway. A punch associate can be configured to acquiesce a specific codec or
to use a codec articulation chic to specify assorted codecs with a alternative order. This enables
Cisco UBE to accomplish codec filtering, because a punch associate will set up a alarm leg alone if the
desired codec belief are satisfied. This adds to the Cisco UBE role of a demarcation
point aural a VoIP network.
If codec clarification is not required, Cisco UBE additionally supports cellophane codec negotiations.
This enables negotiations amid endpoints with Cisco UBE abrogation the codec
information untouched.
Whether assuming codec clarification or operating in cellophane mode, Cisco UBE is
required to abutment the codec acclimated amid endpoints. The afterward codecs are
supported:
■ Audio codecs: G.711u, G.711a, G.723, G.726, G.729r8, G.728, and AMR-NB
■ Video codecs (H.323 only): H.261, H.263, and H.264
Figure 9-6 shows how codec agreement is performed on a Cisco UBE router. Two VoIP
clouds charge to be interconnected. In this scenario, both VoIP 1 and VoIP 2 networks
have G.711 a-law as the adopted codec.
In the aboriginal example, the Cisco UBE router is configured to use the G.729a codec. This
can be done by application the adapted codec command on both VoIP punch peers. When a
call is set up, Cisco UBE will acquire alone G.729a calls, appropriately influencing the codec
negotiation.
In the additional example, the Cisco UBE is configured for a cellophane codec and will
leave the codec advice independent aural the alarm signaling untouched. Because both
VoIP 1 and VoIP 2 accept G.711 a-law as their aboriginal choice, the consistent alarm will be a G.711
a-law call.