Analyzing a successful call setup between extensions within 3CX

Introduction

This chapter gives you an overview of how a call is established within 3CX and how you can trace through these steps by reading the server activity log. The Server activity log can be accessed by clicking on the Server Activity Log node in the 3CX Management Console.

This server status log lists all important events that 3CX Phone System is processing, and is the most important tool when troubleshooting an issue.

In this chapter, we step through the events being logged for a simple extension to extension call.

Call setup between two internal extensions

Table – Logs generated for an internal-to-internal call (logging level = verbose)

Step 1 – Incoming call detected

When an incoming call is detected, a number of messages are reported to the server status log:

Log message 1 [CM503001] (all logging levels)

Call(3): Incoming call from Ext.100 to <sip:101@172.18.130.28>

This allows us to understand a number of things.

  1. Every call request is assigned a Call ID. Most log messages directly related to the call will quote this Call ID, to allow us to distinguish log messages by call. In this case the Call ID is 3.
  2. The call request was made by Extension 100.
  3. The number dialed by Extension 100 was “101”.
  4. The IP address of the PBX Server is 172.18.130.28.

Log message 2 [CM505001] (logging levels medium or verbose)

Ext.100: Device info: Device Identified: [Man: GrandStream;Mod: GXP-2000;Rev: General] Capabilities:[reinvite, no-replaces, unable-no-sdp, recvonly] UserAgent: [Grandstream GXP2000 1.0.1.9] Transport: [sip:172.18.130.28:5060]

3CX Phone System analyses requests from “Extension”-type devices, and attempts to identify the Make and Model. This allows the PBX to improve interaction with Extension devices by working around shortcomings in the device’s design.

Log message 3 [XXyyyy] and Log message 4 [MS210000] (logging level verbose)

Remote SDP is set for legC:3.1

C:3.1:Offer received

3CX Phone System has received media delivery parameters for Ext.100: the IP address, the Port number for media sending and receiving, and the list of codecs which Ext.100 will support for this call. This will later on become a basis with which to connect to the intended destination.

Log message 5 [XXyyyy] (logging levels medium or verbose)

Making route(s) to <sip:101@172.18.130.28>

3CX Phone System is calculating the destination that “101”, as dialled by the caller, represents according to the PBX settings and configured devices.

Step 2 – Contacting Destination

Log messages 6 [CM503004] (all logging levels) and 7 [MS210006] (logging level verbose)

Call(3): Calling: Ext:101@[Dev:sip:101@172.18.130.27:53920;rinstance=31fd69a11933ab52]

C:3.2:Offer provided. Connection(direct): 172.18.130.102:5004(5005)

3CX Phone System has resolved the dialled number “101” as Ext.101, and is calling this extension, using the set of media delivery parameters retrieved earlier from Ext.100.

For this call, Ext.100 will be expecting to send/receive media (to/from Ext.101) on its port 5004.

Since both extensions participating in this call reside inside the same subnet (Ext.100:172.18.130.102 and Ext.101:172.18.130.27), the media connection will be established directly between the two extensions, rather than using the PBX Server as a Media Proxy.

Step 3 – Destination responds

Log messages 8 [CM503002] and 9 [CM505001] (logging levels medium and verbose)

Call(3): Alerting sip:101@172.18.130.27:53920;rinstance=31fd69a11933ab52

Ext.101: Device info: Device Identified: [Man: Counterpath;Mod: X-Lite;Rev: General] Capabilities:[reinvite, no-replaces, unable-no-sdp, recvonly] UserAgent: [X-Lite release 1011s stamp 41150] Transport: [sip:172.18.130.28:5060]

3CX Phone System has received the first communication from the destination (for this call) – typically notifying the PBX that Ext.101 is ringing. This response also allows the PBX to attempt auto-recognition of Make and Model for Ext.101.

Log messages 10 [XXyyyyyy], 11 [MS210001], and 12 [MS210007] (logging level verbose)

Remote SDP is set for legC:3.2

C:3.2:Answer received. RTP connection: 172.18.130.27:20556(20557)

C:3.1:Answer provided. Connection(direct): 172.18.130.27:20556(20557)

3CX Phone System has received media delivery parameters for Ext.101: the IP address, the Port number for media sending and receiving, and the list of codecs which Ext.101 will support for this call (this will be a subset of the codecs list generated by Ext.100). These parameters are sent back to Ext.100, completing the circuit so both Ext.100 and Ext.101 know what each others’ media parameters will be for this call.

For this call, Ext.101 will be expecting to send/receive media (to/from Ext.100) on its port 20556.

Step 4 – Destination picks up the call

Log messages 13 [CM503007] and 14 [CM503007] (all logging levels)

Call(3): Device joined: sip:100@172.18.130.102:5062

Call(3): Device joined: sip:101@172.18.130.27:53920;rinstance=31fd69a11933ab52

3CX Phone System joins Ext.100 and Ext.101 to the call.

Log message 15 [XXyyyyyy] (logging level verbose)

Session 58 of leg C:3.1 is confirmed

3CX Phone System confirms that the Session is in progress.

Step 5 – Call Termination

Log messages 16 [CM503008] and 17 [CM503008] (all logging levels)

Call(3): Device sip:100@172.18.130.102:5062 was disconnected – Call Terminated Call(3): Device sip:101@172.18.130.102:53920 was disconnected – Call Terminated

3CX Phone System has notices that one of the parties has hung up, and proceeds to disconnect all participants to this call.

Call setup between an external extension and an internal extension.

Table – Logs generated for an external-to-internal call (logging level = verbose)

In this scenario, the 3CX Phone System Server Status page will generate the same messages, but with some small differences due to the fact that one of the entities is external to the PBX Server’s local LAN.

Step 1 – Incoming call detected

Log message 1 [CM503001] (all logging levels)

Call(1): Incoming call from Ext.144 to “100”<sip:100@82.102.83.161>

  1. Ext.144 is an external extension, because it is referencing the PBX with its public IP address
  2. The PBX Server’s IP address is 82.102.83.161

Log message 2 [CM505001] (logging levels medium or verbose)

Ext.144: Device info: Device Identified: [Man: Counterpath;Mod: eyeBeam;Rev: General] Capabilities:[reinvite, no-replaces, unable-no-sdp, recvonly] UserAgent: [eyeBeam release 1013t stamp 43070] Transport: [sip:82.102.83.161:5060]

3CX Phone System analyses requests from “Extension”-type devices, and attempts to identify the Make and Model.

Log message 3 [XXyyyy] and Log message 4 [MS210000] (logging level verbose)

Remote SDP is set for legC:1.1

C:1.1:Offer received. RTP connection: 82.102.77.26:13882(13883)

3CX Phone System has received media delivery parameters for Ext.144: the IP address, the Port number for media sending and receiving, and the list of codecs which Ext.144 will support for this call.

For this call, Ext.144 will be expecting to send/receive media (to/from the PBX Server) on its port 13882.

This will later on become a basis with which to connect to the intended destination.

Log message 5 [XXyyyy] (logging levels medium or verbose)

Making route(s) to “100”<sip:100@82.102.83.161>

3CX Phone System is calculating the destination that “100”, as dialled by the caller, represents according to the PBX settings and configured devices.

Step 2 – Contacting Destination

Log messages 6 [CM503004] (all logging levels) and 7 [MS210006] (logging level verbose)

Call(1): Calling: Ext:100@[Dev:sip:100@10.172.0.110:2051;line=nvl8wvm9]

C:1.2:Offer provided. Connection(proxy mode): 10.172.0.5:7036(7037)

3CX Phone System has resolved the dialled number “100” as Ext.100, and is calling this extension, using the set of media delivery parameters retrieved earlier from Ext.144.

For this call, the PBX Server will be expecting to send/receive media (to/from Ext.100) on its port 7036.

Since the extensions participating in this call reside inside different subnets (Ext.144:82.102.77.26 and Ext.100:10.172.0.110), the media connection will be established using the PBX Server as a blind proxy. This is also often referred to as “Pass-Thru” mode.

Step 3 – Destination responds

Log messages 8 [CM503002] and 9 [CM505001] (logging levels medium and verbose)

Call(1): Alerting sip:100@10.172.0.110:2051;line=nvl8wvm9

Ext.100: Device info: Device Identified: [Man: Snom;Mod: 320;Rev: General] Capabilities:[reinvite, replaces, able-no-sdp, recvonly] UserAgent: [snom320/6.5.12] Transport: [sip:10.172.0.5:5060]

3CX Phone System has received the first communication from the destination (for this call) – typically notifying the PBX that Ext.100 is ringing. This response also allows the PBX to attempt auto-recognition of Make and Model for Ext.100.

Log messages 10 [XXyyyyyy], 11 [MS210001], and 12 [MS210007] (logging level verbose)

Remote SDP is set for legC:1.2

C:1.2:Answer received. RTP connection: 10.172.0.110:64050(64051)

C:1.1:Answer provided. Connection(proxy mode):82.102.83.161:9012(9013)

3CX Phone System has received media delivery parameters for Ext.100: the IP address, the Port number for media sending and receiving, and the list of codecs which Ext.100 will support for this call (this will be a subset of the codecs list generated by Ext.144). These parameters are sent back to Ext.144, completing the circuit so both Ext.144 and Ext.100 know what each others’ media parameters will be for this call.

For this call, the PBX Server will be expecting to send/receive media (to/from Ext.144) on its port 9012.

For this call, Ext.100 will be expecting to send/receive media (to/from the PBX Server) on its port 64050.

Step 4 – Destination picks up the call

Log messages 13 [CM503007] and 14 [CM503007] (all logging levels)

Call(3): Device joined: sip:100@172.18.130.102:5062

Call(3): Device joined: sip:101@172.18.130.27:53920;rinstance=31fd69a11933ab52

3CX Phone System joins Ext.100 and Ext.101 to the call.

Log message 15 [XXyyyyyy] (logging level verbose)

Session 58 of leg C:3.1 is confirmed

3CX Phone System confirms that the Session is in progress.

Step 5 – Call Termination

Log messages 16 [CM503008] and 17 [CM503008] (all logging levels)

Call(3): Device sip:100@172.18.130.102:5062 was disconnected – Call Terminated Call(3): Device sip:101@172.18.130.102:53920 was disconnected – Call Terminated

3CX Phone System has notices that one of the parties has hung up, and proceeds to disconnect all participants to this call.

Liked this article?


Get notified of new articles
or share
You might also be interested in: