Tracking H.323 Calls in CUCM SDI Traces

Tracking H.323 Calls in CUCM SDI Traces Disclaimer: This document is written with CUCM 5+ in mind, but will be applicable to all CUCM versions with small amounts of tweaking. Disclaimer 2: This is a first draft and I'm extremely open to input and user contributed edits. If you see something wrong, or that could be better, comment on the doc and I can make you a contributor.

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Enable Traces on page 1 Recreate Issue / Place Test Calls on page 1 Download Relevant Traces on page 1 Download Advanced Analytical Application on page 2 Dissect Traces on page 2 • Locate the problem call on page 2 • Locate the calling party on page 4 • Find the Process ID for this call and Process ID for the called party on page 4 • Track the called process to the correct node on page 5 • Find the Outbound H.225 Setup on page 6 • Find the Negotiated H.245 Port on page 9 • Locate the H.245 TTPid based on H.245 Port on page 10 • Find the Capabilities in the Terminal Capability Set on page 12 • Find the Codec, IP addresses, and UDP Ports used on page 13

Enable Traces Follow this excellent document for turning on CUCM traces. Pay particular attention to the H.225 and H.245 check boxes.

Recreate Issue / Place Test Calls Get the calling party number, called party number, and time of the call.

Download Relevant Traces Follow these instructions to download CallManager traces from all nodes in the cluster during the time of the call.

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Tracking H.323 Calls in CUCM SDI Traces

Download Advanced Analytical Application I prefer Notepad++, but any text editor with highlighting or searching will work. If you want to run unix2dos on the trace files beforehand you could even use the standard Windows Notepad. Downloading a tool like TripleComboTool or TranslatorX is basically cheating, but can be useful.

Dissect Traces This is where all of the fun comes in. We now have folders full of trace files. You can download the traces I used for this example in the attached file H323Trace.zip. Somewhere in the potentially Gigabytes of files we collected is our call. Here's how to find it then track it.

Locate the problem call I like to use a tool like WinGrep, or even Linux grep to just get an idea of which trace files to look at.

My example call has the following details:

Calling Party - 7021004 Called Party - 8011000 Calling Time (Taken from Placed Calls phone menu) - 11:45

The seach queries would be things like cn="7021004 dd="8011000

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Tracking H.323 Calls in CUCM SDI Traces

These two strings will find the Digit Analysis line in CUCM. cn stands for Calling Number. dd stands for Dialed Digits. Let's take a look at using grep to find the trace file we're interested in. jasburns@jasburns-gentoo ~/trace/H323Trace $ grep -REi --include "ccm*.txt" "dd=\"8011000" * cucm7-sub1/2010-06-24_11-47-16/cm/trace/ccm/sdi/ccm00000002.txt:06/24/2010 11:45:32.095 CCM|Digit analysis: match(pi="2", fqcn="7021004", cn="7021004",plv="5", pss="", TodFilteredPss="", dd="8011000",dac="0")

The grep command used the flags

-R recursive -E extended regular expressions (in case we want to get fancy with regex) -i case insensitive search (in case we want to get lazy) --include to search through only files that had names like ccm*.txt

If we only knew the calling number we could change our search string accordingly. If we received no resutls we could remove the cn or dd portion and just search for the number. If searching for the 7 digit number didn't work we could search for just the last 4 digits until we found our call.

Based on the search we see that our file is located in cucm7-sub1/2010-06-24_11-47-16/cm/trace/ccm/sdi/ccm00000002.txt

We also see some interesting things about the digit analysis line:

pss="" and TodFilteredPss="" means that the calling phone has a Calling Search Space set to . This value is usually the ordered list of partition inside the calling party's CSS.

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Tracking H.323 Calls in CUCM SDI Traces

Let's open the trace file ccm*02.txt in our text editor and look at this line above.

Locate the calling party If we track back up just a few lines we can see the SCCP phone that made the call 06/24/2010 11:45:32.089 CCM|StationInit: (0000003) SoftKeyEvent softKeyEvent=1(Redial)

The TCP Handle of that particular IP Phone is 0000003. That indicates this phone was the 3rd one to register since starting the CCM process on this node. We could do a grep for that particular TCP handle to get all SCCP messages sent to and from the phone.

StationInit - The phone sent this message to CUCM StationD - The CUCM sent this message to the phone

Let's use Notepad++ to highlight this in the trace. Highlight the handle, right click, select "Using 1st Style". Now this will be light blue anywhere in the trace file.

Find the Process ID for this call and Process ID for the called party Each call leg has a CallID. This is a unique identifier for that leg of the call. It's commonly referred to as a CI. Each call also has a cdcc process. This is primary call control process for the call. Each called party has a process associated with it. This is where CUCM is going to send the call.

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Tracking H.323 Calls in CUCM SDI Traces

We can learn all of these in the few lines after the Digit Analysis Block 06/24/2010 11:45:32.095 CCM|Digit analysis: insert daResEntry to daResCache. KeyCi=42514739 ,PID:Cdcc(2,174,4)

Here we learn the Ci for the call 42514739, as well as the cdcc(2,174,4). It's helpful to highlight these in the trace as well.

Through the dmpidreq and dmpidres (Request and Response) we can get the Process ID (pid) of the party we're going to extend the call to: 06/24/2010 11:45:32.096 CCM|Digit analysis: wait_DmPidRes- Partition=[] Pattern=[801XXXX] Where=[], cmDeviceType=[AccessDevice], OutsideDialtone =[1], DeviceOverride=[0], PID=RouteListControl(1,100,61,2)

We see that the Route Pattern I matched was 801XXXX, and that this pattern points to RouteListControl. The Process ID for this is (1,100,61,2).

Track the called process to the correct node The Route List Control process exists on Node 1 (the publisher) and we're currently on the subscriber. It exists inside the CUCM process (100). This means the subscriber will now have to send a message to Route List Control on the publisher.

I typically match Node IDs to server names by looking at the SDL trace files. For example, here we can see that cucm7-sub1 is Node 2 (SDL002_*.txt)

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Tracking H.323 Calls in CUCM SDI Traces

Since we know the signal was sent to Node 1, and Node 2 is the subscriber, we can search the SDL trace folders for Node 1. Node 1 is always the publisher server (but your publisher might not always be Node1 based on your CCM version and whether or not you've activated and deactivated servces).

Let's open the CCM trace on the publisher at the time in question, 11:45:32.096

cucm7-pub\2010-06-24_11-47-15\cm\trace\ccm\sdi\ccm00000002.txt 06/24/2010 11:45:32.100 CCM|RouteListControl::idle_CcSetupReq - RouteList(ICT_RL)

Here is the inbound request from the sub to the pub. We can see the call is going to a Route List named "ICT_RL".

The Route List parses through the Route Groups, and you can see we pick a member of the RG in the following trace 06/24/2010 11:45:32.101 CCM|SMDMSharedData::findLocalDevice - Name=ICTto801 Key=005cee5b-ef72-4919-4855-5983ba8b23f2 isActvie=1 Pid=(1,153,7) found

Lucky for us the PID of this device inside the Route Group is also on node 1. If we scroll down a bit in the traces we should see the outbound H.323 call over this InterClusterTrunk.

Find the Outbound H.225 Setup Here we see the process created for this H.225 outbound session. The CUCM is trying to establish an outbound TCP connection. 06/24/2010 11:45:32.188 CCM|H225D::restart0_TcpConnectionInfo: H225Cdpc(1,100,154,3)

Next we'll see the actal H.323 outbound setup:

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Tracking H.323 Calls in CUCM SDI Traces

06/24/2010 11:45:32.193 CCM|SPROCRas - { h323-uu-pdu { h323-message-body setup : { protocolIdentifier { 0 0 8 2250 0 5 }, sourceAddress { dialedDigits : "7021004", h323-ID : {"7021004", {0, 0, 0, 0}, ...} }, sourceInfo { vendor { vendor { t35CountryCode 181, t35Extension 0, manufacturerCode 18 }, productId '436973636F43616C6C4D616E61676572'H, versionId '31'H }, terminal { }, mc FALSE, undefinedNode FALSE }, destinationAddress { dialedDigits : "8011000" }, activeMC FALSE, conferenceID '807B41849C7D31C2030003010E302CCF'H, conferenceGoal create : NULL, callType pointToPoint : NULL, sourceCallSignalAddress ipAddress : { ip '0E302C15'H, port 1720 }, | 06/24/2010 11:45:32.193 CCM|callIdentifier { guid '807B41849C7D31C2030003010E302CCF'H

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Tracking H.323 Calls in CUCM SDI Traces

The most important part of this message for tracking the rest of the call is the guid '807B41849C7D31C2030003010E302CCF'H. This is an identifier unique to the call. We can use grep or wingrep now to search on this guid. We can find out how many traces this guid appears in and then open all of these traces in our editor of choice.

Along with the exploded H.225 message body there is also a compact printout of the H.225 message:

11:45:32.193 CCM|Out Message -- H225SetupMsg -- Protocol= H225Protocol 11:45:32.193 CCM|Ie - H225BearerCapabilityIe IEData= 04 03 80 90 A2 11:45:32.193 CCM|Ie - H225CallingPartyIe IEData= 6C 09 00 81 37 30 32 31 30 30 34 11:45:32.193 CCM|Ie - Q931CalledPartyIe IEData= 70 08 80 38 30 31 31 30 30 30 11:45:32.194 CCM|IsdnMsgData2= 08 02 00 03 05 04 03 80 90 A2 6C 09 00 81 37 30 32 11:45:32.212 CCM|In Message -- H225CallProceedingMsg -- Protocol= H225Protocol 11:45:32.212 CCM|IsdnMsgData1= 08 02 80 03 02 7E 00 55 05 21 80 06 00 08 91 4A 00

This gives us an extremely succinct way to track all of the messages in a call. We can see the first message is an Outbound Setup and it contains the ASCII values of the called and calling numbers.

Calling 37 30 32 31 30 30 34 Called 38 30 31 31 30 30 30

Since these are in ASCII and they're digits all you need to do to get he numbers is just remove the leading 3 from each group of numbers. This is very handy for double checking which number gets sent to the far end H.323 device.

The second message is a Inbound Proceeding message.

We tie these messages together based on the ISDN identifier, which starts at the third octet.

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Tracking H.323 Calls in CUCM SDI Traces

The identifier portion is 0 03. The first character indicates direction. 0 stands for the outbound direction in this case. The outbound direction will be inbound + 8 (hex), or 8 in this case.

Find the Negotiated H.245 Port Messages like Setup, Proceeding, Alerting, Connect, and Release Complete will be exchanged over the H.225 protocol. These messages are for call control. There is a completely different protocol called H.245 that is used to negotiate the IP addresses, UDP Port numbers, and codec that will be used for the media streams of the call.

In either the Alerting, or Connect message the called endpoint will put in a section called H.245 address. This port triggers the calling party to setup a new TCP session to the called party for the purposes of exchanging H.245 messages.

I used Notepad++ to search for the guid in all trace files, then browsed through all of the H.225 messages until I find the one with the port:

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Tracking H.323 Calls in CUCM SDI Traces

Here you can see that the H.245 port is 58820 and it comes in the Connect message at 11:45:34 (when the called party answered). I've highlighted this port as it is crucial to our next step.

Locate the H.245 TTPid based on H.245 Port Now that we have the H.245 Port we can look for the process identifier that will allow us to find all H.245 messages for this call.

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Tracking H.323 Calls in CUCM SDI Traces

Note This procedure below only applies to "Slow Start" calls. I will document "Fast Start" at another point in time.

If the H.245 port comes on an Inbound H.225 message, search down in the traces for the port number. We have to do post processing to create the H.245 process. If the H.245 port is sent on an Outbound H.225 message, search up in the traces for the port number. We have already done the processing to make the H.245 process and THEN we send out the message with the port number.

This is an Inbound H.225 message in our example, so we will search down for the H.245 port number until we see a line that looks like this: 06/24/2010 11:45:34.167 CCM|H245Interface(3)::start_Transition, (H245Client session) ip = (14.48.44.80), port = 58820, TA provided by Callee

In this instance we see that the H.245 interface created has a process ID of 3 H245Interface(3). All H.245 message for this call will be exchanged on that process. Search down until you see a message like the following to get the full process ID: 06/24/2010 11:45:34.181 CCM|H245ASN - TtPid=(1,100,16,3) -Outgoing -value MultimediaSystemControlMessage ::= request : terminalCapabilitySet

This is an Outbound TCS. The identifier that we'll use as our future search string is TtPid=(1,100,16,3). Go ahead and make this some other interesting color.

Use Notepad++ "Find in all Open Documents" (or similar search in your text editor) to get the full H.245 session output from the start of the call to the end:

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Tracking H.323 Calls in CUCM SDI Traces

Find the Capabilities in the Terminal Capability Set Each side will advertise the supported capabilities in the Terminal Capability Set (TCS) message. One side will initially advertise all capabilities supported. The responding side will respond with the matching supported capabilities.

Here the outbound TCS advertises support for:

{ capabilityTableEntryNumber 3, capability receiveAudioCapability : g711Ulaw64k : 40 }, { capabilityTableEntryNumber 4, capability receiveAudioCapability : g711Alaw64k : 40 }, { capabilityTableEntryNumber 5, capability receiveAudioCapability : g729wAnnexB : 6 }, { capabilityTableEntryNumber 6, capability receiveAudioCapability : g729AnnexAwAnnexB : 6 }, {

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Tracking H.323 Calls in CUCM SDI Traces

capabilityTableEntryNumber 7, capability receiveAudioCapability : g729 : 6 }, { capabilityTableEntryNumber 8, capability receiveAudioCapability : g729AnnexA : 6 }, { capabilityTableEntryNumber 9, capability receiveAndTransmitUserInputCapability : dtmf : NULL

G.711U/A @ up to 40 msec packetization (4 data samples per frame with each sample taking 10msec) G.729/A/B @ 6 data samples per frame (60 msec packetization, since each sample takes 10msec)

Note:

G.711 uses the msec packetization interval between RTP packets in the TCS G.729 uses the number of 10msec data samples per RTP packet inside the TCS

If you understand that each sample is 10msec in length then the conversion between the two is pretty simple.

The most common packetization is 20msec, or 2 voice samples per RTP packet.

If we look at the capabilities Inbound we see that all of the same capabilities are supported.

Find the Codec, IP addresses, and UDP Ports used When we go back to the subscriber traces, where the calling phone is registered, we can see that Region configurations are setup for G.711 (64kbps as printed in the traces)

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Tracking H.323 Calls in CUCM SDI Traces

06/24/2010 11:45:34.194 CCM|RegionsServer::MatchCapabilities -- kbps=64, capACount=6, capBCount=8

On the publisher we tell the far end H.323 node we're using G.711 @ 20 msec 06/24/2010 11:45:34.246 CCM|H245ASN - TtPid=(1,100,16,3) -Outgoing -value MultimediaSystemControlMessage ::= request : openLogicalChannel : { forwardLogicalChannelNumber 1, forwardLogicalChannelParameters { dataType audioData : g711Ulaw64k : 20,

We also get an inbound message for G.711 @ 20msec

On the subscriber we can go back to our TCP Handle and see that the SCCP calling phone is told to Open a G.711 audio channel. The phone responds (StationInit) saying it will listen on UDP port 24418. 06/24/2010 11:45:34.255 CCM|StationInit: (0000003) OpenReceiveChannelAck Status=0, IpAddr=IpAddr.type:0 ipAddr:0x0e302ccf000000000000000000000000(14.48.44.207), Port=24418, PartyID=33554435

If we go back to the node where the H.245 session is ongoing, we see the following outgoing OpenLogicalChannelAck. Notice that the UDP RTP port number we send out on the H.323 leg is the exact port that the phone responded with in the SCCP ORCAck, 24418. 06/24/2010 11:45:34.257 CCM|H245ASN - TtPid=(1,100,16,3) -Outgoing -value MultimediaSystemControlMessage ::= response : openLogicalChannelAck : { forwardLogicalChannelNumber 1, forwardMultiplexAckParameters h2250LogicalChannelAckParameters : { sessionID 1, mediaChannel unicastAddress : iPAddress : { network '0E302CCF'H, tsapIdentifier 24418 },

The incoming OpenLogicalChannelAck says the called party will be listening on 23362

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Tracking H.323 Calls in CUCM SDI Traces

06/24/2010 11:45:34.259 CCM|H245ASN - TtPid=(1,100,16,3) -Incoming -value MultimediaSystemControlMessage ::= response : openLogicalChannelAck : { forwardLogicalChannelNumber 1, forwardMultiplexAckParameters h2250LogicalChannelAckParameters : { sessionID 1, mediaChannel unicastAddress : iPAddress : { network '0E302CCC'H, tsapIdentifier 23362 },

Going back to the publisher server where the Calling SCCP phone is registered we see CUCM instructing to send RTP to this new IP and port using the previously established codec. 06/24/2010 11:45:34.260 CCM|StationD: (0000003) startMediaTransmission conferenceID=42514739 passThruPartyID=33554435 remoteIpAddress=IpAddr.type:0 ipAddr:0x0e302ccc000000000000000000000000(14.48.44.204) remotePortNumber=23362 milliSecondPacketSize=20 compressType=4(Media_Payload_G711Ulaw64k)

Further on in the call the Called party presses Hold, Resume, and End Call. You can use all of the previously discussed techniques to track through the behavior of these steps in detail.

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