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How to Change T7 Timer in the SS7 ISDN User Part

Introduction:

This article describes how to modify the ISUP timer T7 on the Dialogic® Integrated Media Gateways, including the Dialogic® IMG 2020 Integrated Media Gateway (IMG 2020), formerly referred to as Dialogic® BorderNet™ 2020 Session Border Controller.

T7 timer in the SS7 ISDN User Part (ISUP) is defined in Section 2.1.1.1.e), ITU-T Recommendation Q.764 (1997), Signalling System No. 7 – ISDN user part signalling procedures:
When the originating exchange has sent the Initial Address Message the awaiting address complete timer (T7) is started. If timer (T7) expires, the connection is released and an indication is returned to the calling subscriber.

ITU Q.764 Table A.1 (Timers in the ISDN User Part) recommends T7 range from 20 to 30 seconds. By default the IMG Gateway sets T7 timer to 20 seconds.

This article describes a way to change the T7 timer on an IMG Gateway by using a raw API.


Procedure:

In the IMG, the ISUP T7 timer is PPL Timer ID 4 in the PPL Component ISUP CPC (Call Processing Control - PPL id 0x0012). 

A Raw API file can be created and applied to the IMG configuration to change the value of this timer. A Raw API file is a plain text file containing hexadecimal API command bytes.

The attached example changes the ISUP T7 timer to 30 seconds on ISUP CICs:

00 17 00 cf 00 01 01 01 02 0d 03 ss ss cc 0d 03 ee ee dd 00 12 01 04 0b b8

API Length: 0x0017
API 0x00CF - PPL Timer Configure
Reserved: 0x00
Sequence Number: 0x01
Node id: 0x01
AIB Address Method: 0x01 - Range
Number of AEs to follow - 0x02
Address Element 1 (0x0D), Length 0x03, defines the Starting Logical Channel - ss ss cc (ss ss is starting logical span, cc is starting logical channel)
Address Element 1 (0x0D), Length 0x03, defines the Ending Logical Channel - ee ee dd (ee ee is ending logical span, dd is ending logical channel)
PPL id: 0x0012 ISUP CPC (Call Processing Control)
PPL Timer Type: 1
PPL Timer ID: 4 - ISUP T7
PPL Timer Value (10ms unit): 0xbb8 (3000)

Steps to find the logical span of SS7 CICs (physical span) to be configured:
- Telnet to Dialogic® IMG 1010
- Type d to Advanced Menu
- Type k to display assigned span
Advanced Debug> k
Assigned Spans
 

PhyID LogID Profile State Timing
(comp.if.grp) def/act host/act
------------ ------------- ------- -------- ------
(00.01.00) 0x003d( 61) E1 / E1 INS/INS REF2*
(01.00.00) 0x0020( 32) E1 / E1 INS/INS
(01.01.00) 0x0021( 33) E1 / E1 INS/INS
(01.02.00) 0x0022( 34) E1 / E1 INS/INS
(01.03.00) 0x0023( 35) E1 / E1 INS/INS
(01.04.00) 0x0024( 36) E1 / E1 INS/INS
(01.05.00) 0x0025( 37) E1 / E1 INS/INS
(01.06.00) 0x0026( 38) E1 / E1 INS/INS
(01.07.00) 0x0027( 39) E1 / E1 INS/INS
(01.08.00) 0x0028( 40) E1 / E1 INS/INS
(01.10.00) 0x002a( 42) E1 / E1 INS/AIS
(01.14.00) 0x002e( 46) E1 / E1 INS/LOS

comp '0' : the E1 span is configured on Signaling Interface Span
comp '1' : the E1 span is configured on Bearer Interface Span
if : offset of E1 span on Signaling/Bearer interface

Note:
The second API command in the attached example is used to tag the SS7 component after the PPL ISUP CPC PPL timer change, this is essential:
 

00 0c 00 d0 00 01 00 00 01 01 01 00 00 01

API Length: 0x000C
API 0x00d0 - Tag Configuration
Reserved: 0x00
Sequence Number: 0x01
Node id: 0x00
AIB Address Method 0x00 - Individual AEs
Number of AEs to follow - 0x01
Address Element: 0x01
Data Length: 0x01
Data[0] Slot Number: 0x00 - SS7
Tag (MSB, LSB): 0x0001

For more information on component tagging please see the following article:

Tagging Software Module After Configuration changes by Raw API

Please refer to the IMG Gateway documentation for instructions on how to apply the Raw API file.

IMG 1010 and IMG 1004:

http://www.dialogic.com/webhelp/IMG1010/10.5.3/WebHelp/img.htm#procedures/general/down_raw_file.htm

IMG 2020:

http://www.dialogic.com/webhelp/BorderNet2020/2.2.0/WebHelp/default.htm#rawapimessage.htm

Product List

Dialogic® IMG 1010 Integrated Media Gateway
Dialogic® IMG 1004 Integrated Media Gateway
Dialogic® IMG 2020 Integrated Media Gateway (IMG 2020), formerly referred to as Dialogic® BorderNet™ 2020 Session Border Controller

Glossary of Acronyms / Terms

ISUP - ISDN User Part
ISUP CIC - Circuit Identification Code

Related Documentation

ITU-T Recommendation Q.763 (1997), Signalling System No. 7 – ISDN User Part formats and codes.
ITU-T Recommendation Q.764 (1997), Signalling System No. 7 – ISDN user part signalling procedures