Yealink SIP-T2XP Administrator's Manual page 234

Administrator's Guide for SIP-T2xP and SIP-T19P IP Phones
a=crypto:2 AES_CM_128_HMAC_SHA1_32
inline:NzkyM2FjNzQ2ZDgxYjg0MzQwMGVmMGUxMzdmNWFm
a=crypto:3 F8_128_HMAC_SHA1_80 inline:NDliMWIzZGE1ZTAwZjA5ZGFhNjQ5YmEANTMzYzA0
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:18 G729/8000
a=fmtp:18 annexb=no
a=rtpmap:9 G722/8000
a=fmtp:101 0-15
a=rtpmap:101 telephone-event/8000
a=ptime:20
a=sendrecv
The callee receives the INVITE message with the RTP encryption algorithm, and then
answers the call by responding with a 200 OK message which carries the negotiated
RTP encryption algorithm.
Example of the RTP encryption algorithm carried in the SDP of the 200 OK message:
m=audio 11780 RTP/SAVP 0 101
a=rtpmap:0 PCMU/8000
a=rtpmap:101 telephone-event/8000
a=crypto:1 AES_CM_128_HMAC_SHA1_80
inline:NGY4OGViMDYzZjQzYTNiOTNkOWRiYzRlMjM0Yzcz
a=sendrecv
a=ptime:20
a=fmtp:101 0-15
SRTP is configurable on a per-line basis. When SRTP is enabled on both IP phones, RTP
streams will be encrypted, and a lock icon appears on the LCD screen of each IP
phone after successful negotiation.
Note
If you enable SRTP , then you should also enable TLS. This ensures the security of SRTP
encryption. For more information on TLS, refer to
Procedure
SRTP can be configured using the configuration files or locally.
Configuration File
218
Transport Layer Security
<MAC>.cfg
on page 211.
Configure SRTP feature on a
per-line basis.
For more information, refer to
SRTP on page 387.