DNS, codecs, and the default voice · Visual
A one-way-audio rumor
SRV
DNS SRV is the preferred
lookup.
PDF
Codec
G.711 is the default.
PDF
Ptime
20 ms is written as a
practitioner note,
Gateway
DTMF
RFC 4733 is named if
digits must survive.
Design
Signaling
RFC 3261 is the
signaling reference.
Design
Split
The two columns stay
split in the ticket.
Admin
Keep practitioner numbers in their own column.
Sources and go deeper
Technical requirements PDF
.
vendor
. last checked 2026-10. Fetched for this lab in October 2026. Re-read before you buy hardware or open a firewall.
SIP trunk options chapter
.
vendor
. last checked 2026-10.
RFC 3261
.
rfc
. last checked 2026-10.
RFC 4733
.
rfc
. last checked 2026-10.
RFC 3550, RTP
.
rfc
. last checked 2026-10.
RFC 3551, RTP profile for audio and video
.
rfc
. last checked 2026-10.
ITU-T G.711
.
standard
. last checked 2026-10.
RFC 1035, domain names
.
rfc
. last checked 2026-10.
RFC 2782, DNS SRV
.
rfc
. last checked 2026-10.
confirm
. A 20 ms packet time is a practitioner note about Cisco gateways, not a figure quoted from the Five9 technical requirements in this lab. last checked 2026-10.