Chapter 9 Voice
P-2812HNU-51c User’s Guide
207
SRTP Support When you make a VoIP call using SIP, the Real-time Transport Protocol
(RTP) is used to handle voice data transfer. The Secure Real-time
Transport Protocol (SRTP) is a security profile of RTP. It is designed to
provide encryption and authentication for the RTP data in both unicast
and multicast applications.
SRTP uses the Advanced Encryption Standard (AES) cipher for data
encryption. The P-2812HNU-51c supports encryption using AES with a
128-bit key. To protect data integrity, SRTP uses a Hash-based Message
Authentication Code (HMAC) calculation with Secure Hash Algorithm
(SHA)-1 to authenticate data. HMAC SHA-1 produces a 80 or 32-bit
authentication tag that is appended to the packet.
Both the caller and callee should use the same algorithms to establish
an SRTP session.
SRTP Support Select this option to enable SRTP on the P-2812HNU-51c.
Crypto Suite Select the encryption and authentication algorithm set used by the P-
2812HNU-51c to set up an SRTP media session with the peer device.
Select AES_CM_128_HMAC_SHA1_80 or
AES_CM_128_HMAC_SHA1_32 to enable both data encryption and
authentication for voice data.
Select AES_CM_128_NULL to use 128-bit data encryption but disable
data authentication.
Select NULL_CIPHER_HMAC_SHA1_80 to disable encryption but
require authentication using the default 80-bit tag.
DTMF Mode
DTMF Mode
Control how the P-2812HNU-51c handles the tones that your telephone
makes when you push its buttons. You should use the same mode your
VoIP service provider uses.
RFC2833 - send the DTMF tones in RTP packets.
InBand - send the DTMF tones in the voice data stream. This method
works best when you are using a codec that does not use compression
(like G.711). Codecs that use compression (like G.729 and G.726) can
distort the tones.
SIPInfo - send the DTMF tones in SIP messages.
Transport Type
Transport Type Select the transport layer protocol (TCP, UDP or TLS) used for SIP.
AUTO is available when you select the Support Locating SIP Server
option. If you select AUTO here, the P-2812HNU-51c sends a DNS
Name Authority Pointer (NAPTR) query to locate the SIP server and get
the supported transport layer protocol(s).
FAX Option This field controls how the P-2812HNU-51c handles fax messages.
G.711 Fax
Passthrough
Select this if the P-2812HNU-51c should use G.711 to send fax
messages. The peer devices must also use G.711.
Table 58 VoIP > SIP > SIP Service Provider (continued)
LABEL DESCRIPTION
