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Logging H.248 Messages

You can use the traceoptions feature to log H.248 messages exchanged between a VPG and its associated PGC. These messages include all transactions, transaction replies, and transaction acknowledgements. Corrupted messages, messages with invalid syntax, and messages that fail interim AH validation are also logged. The captured data includes both the raw H.248 message (as it appears on the wire) and associated metadata.

The captured data is stored by default in the pgcpd file in the /var/log directory. In addition to H.248 messages, this file contains all other PGCP operations that you have chosen to trace. To make it easier to find H.248 messages in the file, there is a BEGIN field and an END field, each with a matching sequence number.

When you enable logging of H.248 messages, the software logs messages for all VPGs on the router. To determine which VPG exchanged the message, use the 5–tuple field in the H.248 message.

Fields in the H.248 Messages

Each H.248 message contains the following fields:

TRACE_TIMESTAMP
[BEGIN #SEQNUM  TIMESTAMP  5-TUPLE  DIRECTION  MSG_SIZE]
MegacoMessage
[END #SEQNUM]

The following is a sample ServiceChange message:

Oct 10 09:32:28
[BEGIN #778  Oct 10 09:32:28  UDP:10.50.40.100:2944->172.16.1.1:2944  TX  168]
AU=0x00000000:0x00000000:0x000000000000000000000000
!/1 [10.50.40.100]:2944
T=1{
C=-{
SC=ROOT{
SV{MT=RS,RE="901",AD=2944,PF=JNPR_PGCP/1,V=3,20071010T09322800}}}}
[END #778]

Table 16 describes the fields in H.248 messages.

Table 16: Description of Fields in H.248 Messages

Field	Description
TRACE_TIMESTAMP	Time the messaged was captured. The timestamp is in the format HH:MM:SS.mmmmmm
BEGIN	Constant string BEGIN that indicates the beginning of a message.
#SEQNUM	Sequential number of the message used to correlate the BEGIN header with the END footer.
TIMESTAMP	Date and time of the message. Time is displayed in the format HH:MM:SS.mmmmmm
5-TUPLE	UDP or TCP packet’s 5-tuple (transport protocol, source address and port, destination address and port). Used to identify the VPG and the PGC that exchanged the message.
DIRECTION	Direction message was sent from the VPG: TX for an outgoing H.248 message. RX for an incoming H.248 message.
MSG_SIZE	Size of message in bytes excluding transport protocol (UDP/TCP/IP) overhead.
MegacoMessage	Captured data including the interim authentication header (if any).
END	Constant string END that indicates the end of a captured message.

Messages That Exceed Output Buffer Limit

The trace file has a limit on the size of a single output buffer. Messages longer than this limit are divided into several trace buffers. Messages divided into buffers use the following template:

TRACE_TIMESTAMP
  [BEGIN #SEQNUM  TIMESTAMP  5-TUPLE  DIRECTION  MSG_SIZE]
  MegacoMessage (1st part)
  TRACE_TIMESTAMP (--- contd ---)
  MegacoMessage (2nd part)
  ...
  TRACE_TIMESTAMP (--- contd ---)
  MegacoMessage (n'th part)
  [END #SEQNUM]

Here is an example of a divided message:

Oct 10 09:32:56
  [BEGIN #779  Oct 10 09:32:56  UDP:22.0.0.6:2944->10.50.40.100:2944  RX  436]
  AU=0x00000000:0x00000000:0x000000000000000000000000
  MEGACO/3 [22.0.0.6]:2944
  Transaction = 12567418{
      Context = 65323 {
         Modify=ip/4/vif-0/3 {
            Media{
               Stream=1{
                  LocalControl{Mode=SR,DS/DSCP=00,TMAN/POL=on}}}},
         Modify=ip/4/vif-0/3 {
            Media{
               Stream=1{
  Oct 10 14:13:19 (--- contd ---)
                  LocalControl{Mode=SR,DS/DSCP=00,TMAN/POL=on}}}}}}
  [END #779]

Configuring Logging of H.248 Messages

The captured data is stored by default in the pgcpd file in the /var/log directory.

Step-by-Step Procedure

To enable logging of H.248 messages:

Access the PGCP traceoptions configuration.[edit] user@host#edit services pgcp traceoptions
Set the flag that enables logging of H.248 messages.[edit services pgcp traceoptions] user@host#set flag pgcp-stack-h248
Set the maximum number of trace files. If you specify a maximum number of files, you also must specify a maximum file size.[edit services pgcp traceoptions] user@host#set file files 10
Set the maximum size of the trace files. [edit services pgcp traceoptions] user@host#set file pgcpd size 10000k

Logging H.248 Messages

Fields in the H.248 Messages

Messages That Exceed Output Buffer Limit

Configuring Logging of H.248 Messages

Related Topics