User's Manual 202 Document #: LTRT-10466
Mediant 500L MSBR
17.6 Configuring Analog Settings
The Analog Settings page allows you to configure various analog parameters. For a
detailed description of the parameters appearing on this page, see ''Configuration
Parameters Reference'' on page 779.
This page also selects the type (USA or Europe) of FXS and/or FXO coefficient
information. The FXS coefficient contains the analog telephony interface characteristics
such as DC and AC impedance, feeding current, and ringing voltage.
To configure the analog parameters:
1. Open the Analog Settings page (Configuration tab > VoIP menu > Media > Analog
Settings).
Figure 17-8: Analog Settings Page
2. Configure the parameters as required.
3. Click Submit.
4. To save the changes to flash memory, see ''Saving Configuration'' on page 606.
17.7 Configuring Media (SRTP) Security
The device supports Secured RTP (SRTP) according to RFC 3711. SRTP is used to
encrypt RTP and RTCP transport for protecting VoIP traffic. SRTP requires a key
exchange mechanism that is performed according to RFC 4568 – “Session Description
Protocol (SDP) Security Descriptions for Media Streams”. The key exchange is done by
adding a 'crypto' attribute to the SDP. This attribute is used (by both sides) to declare the
various supported cipher suites and to attach the encryption key. If negotiation of the
encryption data is successful, the call is established.
SRTP supports the following cipher suites (all other suites are ignored):
AES_CM_128_HMAC_SHA1_32
AES_CM_128_HMAC_SHA1_80
ARIA_CM_128_HMAC_SHA1_80
ARIA_CM_192_HMAC_SHA1_80
When the device is the offering side, it generates an MKI of a size configured by the
'Master Key Identifier (MKI) Size' parameter. The length of the MKI is limited to four bytes.
If the remote side sends a longer MKI, the key is ignored. The key lifetime field is not
supported. However, if it is included in the key it is ignored and the call does not fail.
The device supports the following session parameters (as defined in RFC 4568, SDP
Security Descriptions for Media Streams):
UNENCRYPTED_SRTP
UNENCRYPTED_SRTCP
UNAUTHENTICATED_SRTP
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