System information

Dialogic
®
HMP Software Release 3.0WIN Release Guide — December 2010 25
Dialogic Corporation
Features
while the RTP resource provides one RTP channel for the audio stream and one RTP
channel for the video stream.
• The RTP channel for a video stream cannot be used for an audio stream.
• The programming libraries that provide multimedia-related enhancements and
additions are identified in the following outline of multimedia functionality:
– The Dialogic® Multimedia API Library records and plays the multimedia data
using a multimedia device.
– The Dialogic® Device Management API Library is used to connect the multimedia
device with an IP media device.
– Multimedia record and playback between Dialogic
®
HMP Software and remote IP
endpoints is accomplished by using both the multimedia and IP media devices.
– The Dialogic® IP Media Library API Library provides the IP multimedia session
control.
– The Dialogic® Global Call API Library must be used in third party call control
(3PCC) mode. The Global Call API library provides multimedia support through
SIP third party call control. A convenience API is available to process the Session
Description Protocol (SDP).
See the Dialogic
®
Multimedia API Library Reference and the Dialogic
®
Multimedia
API Programming Guide for details about the Dialogic
®
Multimedia API. See the
Dialogic
®
Host Media Processing Software Release 3.0WIN Administration Guide for
Licensing information.
3.2 Secure Real-time Transport Protocol (SRTP)
Real-time Transport Protocol (RTP) is commonly used for the transmission of real-time
audio or video streams in Internet telephony applications. Secure RTP (SRTP) is an
enhancement to RTP that provides confidentiality, message authentication, and replay
protection for RTP and the companion Real Time Control Protocol (RTCP). “Replay
protection” is protection against the interception of an RTP packet and later reintroduction
into the packet stream.
SRTP can be thought of as residing between an RTP application and the transport layer.
On the sending side, SRTP intercepts an RTP packet and forwards an equivalent SRTP
packet. At the receiving side, SRTP receives an SRTP packet and the equivalent RTP
packet is passed up the protocol stack.
In SRTP, the payload (and padding) of RTP and RTCP packets may be authenticated or
encrypted. RTCP packets are always authenticated, but encryption on RTP and RTCP
packets and authentication on RTP packets is optional.
Many different encryption and message authentication algorithms exist, but RFC 3711
specifies the following default pre-defined algorithms:
• For encryption, the pre-defined cipher is the Advanced Encryption Standard (AES)
operating in Segmented Integer Counter Mode.
Note: Currently, only Segmented Integer Counter Mode is supported.