Yealink SIP-T41S Administrator's Guide

Security Features
114
When you place a call on the enabled SRTP phone, the phone sends an INVITE message with the RTP/RTCP
encryption algorithm to the destination phone. As described in RFC 3711, RTP/RTCP streams may be encrypted
using an AES (Advanced Encryption Standard) algorithm.
Example of the RTP encryption algorithm carried in the SDP of the INVITE message:
m=audio 11780 RTP/SAVP 0 8 18 9 101
a=crypto:1 AES_CM_128_HMAC_SHA1_80 > inline:NzFlNTUwZDk2OGVlOTc3YzNkYTkwZWVkMTM1YWFj
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 respond-
ing 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
When SRTP is enabled on both phones, RTP streams will be encrypted, and a lock icon appears on the LCD
screen of each IP phone after a successful negotiation.
Note: If you enable SRTP, then you should also enable TLS. This ensures the security of SRTP encryption. For more inform-
ation on TLS, refer to Transport Layer Security (TLS). You can configure the IP phone to include unencrypted RTP/RTCP
streams in SDP offers by “account.X.srtp.unencrypted_rtp.enable”/”account.X.srtp.unencrypted_rtcp.enable”.
Topic
SRTP Configuration
SRTP Configuration
The following table lists the parameters you can use to configure the SRTP.
Parameter
account.X.srtp_encryption
[1]
<MAC>.cfg

Yealink SIP-T41S Specifications

General

Mounting	Desk/Wall
Handset type	Wired handset
Product type	IP Phone
Product color	Black
Keypad illumination	Yes
Wi-Fi	No
Networking standards	IEEE 802.3af
Ethernet LAN data rates	10, 100 Mbit/s
Ethernet LAN interface type	Fast Ethernet
Supported network protocols	SIP v1, SIP v2, LLDP/CDP/DHCP, OpenVPN, IEEE802.1X, IPv6, FTP/TFTP/HTTP/HTTPS
Volume control	Digital
Number of programmable keys	6
Lines quantity	6 lines
Phonebook capacity	1000 entries
Dual-Tone Multi-Frequency (DTMF) modes	In-band, Out-of band, SIP info
Input frequency	50/60 Hz
AC adapter input voltage	100 - 240 V
AC adapter output current	1.2 A
AC adapter output voltage	5 V
Display diagonal	2.7 \
Display resolution	192 x 64 pixels
Operating temperature (T-T)	-10 - 50 °C
Operating relative humidity (H-H)	10 - 95 %
Voice codecs	CNG, G.711Mu, G.711a, G.723.1, G.726, G.729ab, VAD, iLBC
Certification	CE
Cables included	LAN (RJ-45)
Number of handles included	1 pc(s)
Harmonized System (HS) code	85171800

Weight and Dimensions

Depth	189 mm
Width	212 mm
Height	175 mm
Package depth	223 mm
Package width	246 mm
Package height	120 mm