Alcatel-Lucent ALE M3 - Page 58

ALE M3-M5-M7-M8 DeskPhones Administrator Guide
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simultaneously. When this feature is enabled on both phones, the type of encryption to use for the session is
negotiated between the IP phones. This negotiation process is compliant with RFC 4568.
When you place a call on the enabled SRTP phone, the IP 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 6000 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
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 6000 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 SIP-TLS/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.
The following table lists the parameters you can use to configure the SRTP.
Parameter
SIPGroup1SrtpWorkingMode
config.xml
Description
It configures whether to use voice encryption service.
Permitted
Values
0 - None
1 - Best effort
2 - Strict
3 - 0SRTP
Default
0