How to analyze an SS7 ISUP Trace
Introduction:
The Dialogic® IMG 1010 Integrated Media Gateway, the Dialogic® IMG 1004 Integrated Media Gateway and the Dialogic® IMG 2020 Integrated Media Gateway (IMG 2020), formerly referred to as Dialogic® BorderNet™ 2020 Session Border Controller support Call Tracing, which allows a user to view various items of information on a per call basis. With the IMG 1010 and IMG 1004, the call trace is saved to a log file in the following directory in the Dialogic® Gate Control Element Management System (GCEMS) server: opt/dialogic/common/calltracing (Software 10.5.1+). With the IMG 2020, the call trace is saved to a file at the location specified in the Call Trace object in the WebUI.
Call Trace log files have the following naming convention: syslog_<ChassisSerialNumber>_<YYMMDD>_.log
A Call Trace log includes information such as:
- Call Leg Information
- Call ID Information
- Call Duration
- RTCP Stats
- Codec Information
- Routing Information
This article describes how to analyze an SS7 ISUP trace in an IMG call tracing log.
For information on how to convert a call trace file to a pcap file that can be viewed in Wireshark please refer to the following article:
Sample Call Flow:
This example uses
this sample IMG call tracing log.
This is a call from SIP to SS7; the call flow is as follows:
Click on the following image to view it full-size: 
Analyzing the SS7 ISUP (ITU) traces : Note: Detailed ISUP message decoding is available in
this Wireshark file.
1. IMG sent ISUP Initial Address Message (IAM) to PSTN
11:42:38.284 CALL(SS7) (01:00002:01)
SENT: STK: 2 PRI: 00
DPC: 0-34-1 OPC: 0-35-1
SLS: 0x3d CIC: 00061 (0x003d)
IAM [0048000a03020907031047172653000a070310058826030000]
11:42:38.284 CALL(SS7) (01:00002:01) SENT IAM to (0x119:0x111:61)
This IAM message was sent on SS7 Stack id (2) to DPC: 0-34-1 (0x111) CIC: 61 (0x3d), IMG's OPC is 0-35-1 (0x119).
The ISUP parameters, including the mandatory fixed part, the mandatory variable part and the optional part, are listed between square brackets.
The IAM ISUP parameters are decoded as follows:
Click on the following image to view it full-size: 
Note: More IAM ISUP parameters decoding are included in the Wireshark file
isup-itu.pcap.
2. IMG received an ISUP Address Complete Message (ACM) from PSTN
11:42:38.644 CALL(SS7) (01:00002:01)
RCVD: STK: 2 PRI: 00
DPC: 0-35-1 OPC: 0-34-1
SLS: 0x0d CIC: 00061 (0x003d)
ACM [000400]
11:42:38.644 CALL(SS7) (01:00002:01) RCVD ACM from (0x111:0x119:61)
This ACM was received on SS7 Stack id (2) from the PSTN, which has OPC: 0-34-1 (0x111), CIC: 61 (0x3d), IMG is its DPC 0-35-1 (0x119)
The ACM parameter is decoded as follows:
Click on the following image to display it full-size: 
3. IMG received an ISUP Answer Message (ANM) from PSTN
11:42:39.874 CALL(SS7) (01:00002:01)
RCVD: STK: 2 PRI: 00
DPC: 0-35-1 OPC: 0-34-1
SLS: 0x0d CIC: 00061 (0x003d)
ANM [00]
11:42:39.874 CALL(SS7) (01:00002:01) RCVD ANM from (0x111:0x119:61)
This ANM was received on SS7 Stack id (2) from PSTN, which has OPC: 0-34-1 (0x111), CIC: 61 (0x3d), IMG is its DPC 0-35-1 (0x119)
There are no ISUP parameters in this ANM message.
4. IMG sent an ISUP Release Message (REL) to PSTN
11:42:58.514 CALL(SS7) (01:00002:01)
SENT: STK: 2 PRI: 00
DPC: 0-34-1 OPC: 0-35-1
SLS: 0x3d CIC: 00061 (0x003d)
REL [0200028090]
11:42:58.514 CALL(SS7) (01:00002:01) SENT REL cause 16 to (0x119:0x111:61)
This REL message was sent on SS7 Stack id (2) to DPC: 0-34-1 (0x111) CIC: 61 (0x3d), IMG's OPC 0-35-1 (0x119).
The REL parameter is decoded as follows:
Click on the following image to display it full-size: 
5. IMG received an ISUP Release Complete Message (RLC) from PSTN
11:42:58.574 CALL(SS7) (01:00002:01)
RCVD: STK: 2 PRI: 00
DPC: 0-35-1 OPC: 0-34-1
SLS: 0x0d CIC: 00061 (0x003d)
RLC [00]
11:42:58.574 CALL(SS7) (01:00002:01) RCVD RLC from (0x111:0x119:61)
This RLC was received on SS7 Stack id (2) from PSTN, which has OPC: 0-34-1 (0x111), CIC: 61 (0x3d), IMG is its DPC 0-35-1 (0x119)
There are no ISUP parameters in this RLC message.
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
IAM - Initial Address Message
ACM - Address Complete Message
ANM - Answer Message
REL - Release Message
RLC - Release Complete
Related Documentation
First published: 15-Jun-2010
Last published: 17-Jun-2010
Open access: Product rule: ; Page rule: Auto
