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Most PSTN carriers only offer support of the for G.711ulaw, G.711alaw, and the G.729 codecs.
For inbound PSTN calls to the customer, by default, the Peeredge Switch will only forward forwards the PSTN vendor-supported codecs to the customer’s SBC/PBX. The The Peeredge Switch can be configured to filter out codecs offered by the upstream carrier and/or add additional codecs in the SIP Invite w/SDP offer to the customer SBC/PBX.
For outbound PSTN calls, by default, the Peeredge Switch will always select selects the first codec in the list of codecs offered in the customer’s SIP Invite w/SDP message that the upstream carrier supports. If If there is are no upstream carrier-supported codecs in the list of codecs offered in the SIP Invite w/SDP message, then transcoding can be enabled on the Peeredge Switch.
Recommendations
Since Since most PSTN carriers only support the G.711ulaw, G.711alaw, and the G.729 codecs, 46Labs 46 Labs STRONGLY RECOMMENDS only including these codecs in the SIP Invite w/SDP. Our Our testing with several enterprise SBC/PBX systems has shown shows there are often “hidden” hidden design challenges in complex call flows when using codecs not supported by upstream carriers.
When voice quality is the primary design consideration, 46Labs 46 Labs recommends using the G.711 codec.
When minimizing network bandwidth usage is the primary design consideration, the G.729 codec can be configured as the preferred codec.
The Peeredge Switches do not support video codecs. Video Video codecs should not be included in the SDP of any SIP messages sent to the Peeredge Switches.