Dsp Pattern Detector; Qsig Tunneling - AudioCodes Mediant 500 E-SBC User Manual

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21.5.1.1 DSP Pattern Detector

For TDM tunneling applications, you can use the DSP pattern detector feature to initiate
the echo canceller at call start. The device can be configured to support detection of a
specific one-byte idle data pattern transmitted over digital E1/T1 timeslots. The device can
be configured to detect up to four different one-byte data patterns. When the defined idle
data pattern is detected, the channel resets its echo canceller.

To configure DSP pattern detector:
1. In the IPMedia Settings page (Configuration tab > VoIP menu > Media > IPMedia
Settings), do the following:
a. Set the 'IPMedia Detectors' parameter (EnableDSPIPMDetectors) to Enable.
b. Set the 'Enable Pattern Detector' parameter (EnablePatternDetector) to Enable.
2. Configure the number (e.g., 5) of consecutive patterns to trigger the pattern detection
event, using the ini file parameter, PDThreshold.
3. Configure the patterns that can be detected by the Pattern Detector, using the ini file
parameter, PDPattern. For example:
PDPattern = 84, 85, 212, 213 ; for idle patterns 54, 55, D4
and D5

21.5.2 QSIG Tunneling

The device supports QSIG tunneling over SIP, according to IETF Internet-Draft draft-elwell-
sipping-qsig-tunnel-03 ("Tunnelling of QSIG over SIP") and ECMA-355/ISO/IEC 22535.
This is applicable to all ISDN variants. QSIG tunneling can be applied to all calls or to
specific calls using IP Profiles.
QSIG tunneling sends all QSIG messages as raw data in corresponding SIP messages
using a dedicated message body. This is used, for example, to enable two QSIG
subscribers connected to the same or different QSIG PBX to communicate with each other
over an IP network. Tunneling is supported in both directions (Tel-to-IP and IP-to-Tel).
The term tunneling means that messages are transferred 'as is' to the remote side without
being converted (QSIG > SIP > QSIG). The advantage of tunneling over QSIG-to-SIP
interworking is that by using interworking, QSIG functionality can only be partially achieved.
When tunneling is used, all QSIG capabilities are supported and the tunneling medium (the
SIP network) does not need to process these messages.
QSIG messages are transferred in SIP messages in a separate Multipurpose Internet Mail
Extensions (MIME) body. Therefore, if a message contains more than one body (e.g., SDP
and QSIG), multipart MIME must be used. The Content-Type of the QSIG tunneled
message is 'application/QSIG'. The device also adds a Content-Disposition header in the
following format:
Content-Disposition: signal; handling=required.
QSIG tunneling is done as follows:

Call setup (originating device): The QSIG Setup request is encapsulated in the SIP
INVITE message without being altered. After the SIP INVITE request is sent, the
device does not encapsulate the subsequent QSIG message until a SIP 200 OK
response is received. If the originating device receives a 4xx, 5xx, or 6xx response, it
disconnects the QSIG call with a 'no route to destination' cause.

Call setup (terminating device): After the terminating device receives a SIP INVITE
request with a 'Content-Type: application/QSIG', it sends the encapsulated QSIG
Setup message to the Tel side and sends a 200 OK response (no 1xx response is
sent) to IP. The 200 OK response includes an encapsulated QSIG Call Proceeding
User's Manual 340
Mediant 500 E-SBC
Document #: LTRT-10427