Troubleshooting External PSTN calls with No-way audio/dead Air Issue

Muthurani Lavanya Paneerselvam · ‎01-17-2013

Introduction
Problem Description
Resolution
Related Information

Introduction

This document discusses how to Troubleshoot No-way audio/ dead Air Issue for the PSTN Outbound and Inbound Calls.

Problem Description

Outbound and inbound calls are not working - no-way audio. The PSTN Outbound and Inbound Calls are going through and getting connected fine but after that there is nothing heard, No-way audio/dead air issue for the PSTN calls outbound.

Network Scenario

Mobile phone->PSTN -T1 PRI--> MGCP Gateway -->CUCM -- IP Phone

Components

CUCM 8.5.1

MGCP Gateway IOS version 12.1

Resolution

Troubleshooting Procedure

1) The CUCM traces revealed that the call was connected fine and there was no issue found in the sdi/sdl traces.

CUCM only plays role in the call setup /tear-down of connection but not during conversation.

The Inbound and outbound calls have symptoms of dead air.
CUCM traces reveal that the call connects all fine and there seems to be loss of audio packets.
While testing the call customer didn't notice any change in TX count. It was showing zero while RX count was increasing gradually.
Installed the Wireshark tool.

2) The Gateway isdn debugs below also didn't reveal the root cause. MGCP Gateway Debugs

MGCP Gateway Debug for Troubleshooting

Transfer Capability = Speech

Transfer Mode = Circuit

Transfer Rate = 64 kbit/s

Channel ID i = 0xA98381

Exclusive, Channel 1

Facility i = 0x9F8B0100A10F02014A06072A8648CE1500040A0100

Protocol Profile = Networking Extensions

0xA10F02014A06072A8648CE1500040A0100

Component = Invoke component

Invoke Id = 74

Operation = InformationFollowing (calling_name)

Name information in subsequent FACILITY message

Calling Party Number i = 0x2183, '9186255864'

Plan:ISDN, Type:National

Called Party Number i = 0x80, '43000'

Plan:Unknown, Type:Unknown

000365: *Jan 12 02:58:18.271: ISDN Se0/0/0:23 Q931: TX -> CALL_PROC pd = 8 callref = 0x9FC1

Channel ID i = 0xA98381

Exclusive, Channel 1

000366: *Jan 12 02:58:18.367: ISDN Se0/0/0:23 Q931: TX -> ALERTING pd = 8 callref = 0x9FC1

Progress Ind i = 0x8088 - In-band info or appropriate now available

000367: *Jan 12 02:58:18.543: ISDN Se0/0/0:23 Q931: RX <- FACILITY pd = 8 callref = 0x1FC1

Facility i = 0x9F8B0100A11702014B020100800F4E4F5244414D203630323030202020

Protocol Profile = Networking Extensions

0xA11702014B020100800F4E4F5244414D203630323030202020

Component = Invoke component

Invoke Id = 75

Operation = CallingName

Name Presentation Allowed Extended

Name = NORDAM 60200

000368: *Jan 12 02:58:21.255: ISDN Se0/0/0:23 Q931: TX -> CONNECT pd = 8 callref = 0x9FC1

000369: *Jan 12 02:58:21.287: ISDN Se0/0/0:23 Q931: RX <- CONNECT_ACK pd = 8 callref = 0x1FC1

[Connection to 10.17.2.9 closed by foreign host]

D6506#telnet 10.17.2.9

d3825voice#debug isdn q931

debug isdn q931 is ON.

d3825voice#term mon

d3825voice#

000405: *Jan 12 03:08:43.303: ISDN Se0/0/0:23 Q931: TX -> DISCONNECT pd = 8 callref = 0x0007

Cause i = 0x8090 - Normal call clearing

000406: *Jan 12 03:08:43.583: ISDN Se0/0/0:23 Q931: RX <- RELEASE pd = 8 callref = 0x8007

000407: *Jan 12 03:08:43.603: ISDN Se0/0/0:23 Q931: TX -> RELEASE_COMP pd = 8 callref = 0x0007

000408: *Jan 12 03:08:48.355: ISDN Se0/0/0:23 Q931: TX -> SETUP pd = 8 callref = 0x0008

Bearer Capability i = 0x8090A2

Standard = CCITT

Transfer Capability = Speech

Transfer Mode = Circuit

Transfer Rate = 64 kbit/s

Channel ID i = 0xA98397

Exclusive, Channel 23

Facility i = 0x9F8B0100A116020101020100800E4E574420546573742050686F6E65

Protocol Profile = Networking Extensions

0xA116020101020100800E4E574420546573742050686F6E65

Component = Invoke component

Invoke Id = 1

Operation = CallingName

Name Presentation Allowed Extended

Name = NWD Test Phone

Calling Party Number i = 0x0181, '3165543998'

Plan:ISDN, Type:Unknown

Called Party Number i = 0xA0, '6341600'

Plan:Unknown, Type:National

000409: *Jan 12 03:08:48.583: ISDN Se0/0/0:23 Q931: RX <- CALL_PROC pd = 8 callref = 0x8008

Channel ID i = 0xA98397

Exclusive, Channel 23

000410: *Jan 12 03:08:49.683: ISDN Se0/0/0:23 Q931: RX <- ALERTING pd = 8 callref = 0x8008

Progress Ind i = 0x8088 - In-band info or appropriate now available

000411: *Jan 12 03:08:53.031: ISDN Se0/0/0:23 Q931: RX <- CONNECT pd = 8 callref = 0x8008

000412: *Jan 12 03:08:53.403: ISDN Se0/0/0:23 Q931: TX -> CONNECT_ACK pd = 8 callref = 0x0008

000413: *Jan 12 03:11:26.731: ISDN Se0/0/0:23 Q931: RX <- DISCONNECT pd = 8 callref = 0x8008

Cause i = 0x8090 - Normal call clearing

000414: *Jan 12 03:11:26.967: ISDN Se0/0/0:23 Q931: TX -> RELEASE pd = 8 callref = 0x0008

000415: *Jan 12 03:11:27.031: ISDN Se0/0/0:23 Q931: RX <- RELEASE_COMP pd = 8 callref = 0x8008

called number: 316 -6341600

calling party: 316 554 3998

Then the packet capture was taken on interface of the MGCP Gateway.

3). Ping from the Subnet the IP Phone

Ping from the subnet of the ip phone to GW's interface and vice versa wasn't working fine.

Root cause

The MGCP GW was having two interfaces GIG 0/0 and Ethernet GIG 0/1 both in same subnet.
The signaling and media for mgcp was binded to gig 0/0..
It was found that no routing exists between gig 0/0 and the device IP subnet.
The wire-shark trace/packet capture was taken for the outbound calls at BOTH the interfaces of the GWs i.e. Ethernet GIG 0/0 and 0/1.

Solution

All the traffic and signaling was happening through the second interface 0/1 and the below change were made and router was reloaded to get things back to normal:-

MGCP bind media source-interface (interface Ethenet Gig 0/1)

So that binded the MGCP media streaming to the Ethernet GIG interface 0/1

MGCP Interface was wrongly configured and that is the cause for the issue. Binding the correct source interface ensured that the media streaming got through for the inbound/outbound calls.

Make test calls and ensure the calls are all going through fine and media got through for the inbound/outbound calls.

Related Information

Cisco Unified Communications Manager Troubleshooting TechNotes