Understanding MGCP Packets: A brief overview and example with debugs

Mijanur Rahman's Blog

While studying MGCP protocol messages from debugs my head was spinning like ‘what the c**p message are those!’, had an weird idea to generate the call and capture all MGCP packets and write down explanation of each of the terms. I am weak on the MGCP debugs packets from the beginning of starting voice, now I just wanted to nail it down and wished to learn whole conversations between MGCP GW and the Call Agents. Tough one for me I know but who doesn’t want to learn something new? Took the challenge and I think now it’s quite easy for me.🙂

Before starting the derivation let’s write down the MGCP Packet verbs and code explanations:

Code Verb
AUCX    AuditConnection.
AUEP    AuditEndpoint.
CRCX    CreateConnection.
DLCX    DeleteConnection.
EPCF    EndpointConfiguration.
MDCX    ModifyConnection.
RQNT    NotificationRequest.
NTFY    Notify.
RSIP    RestartInProgress.

CodeDescription
200    The requested transaction was executed normally.
250    The connection was deleted.

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Windows 7 NTP Server enabling

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\NTPServer\Enabled
Changing the ‘Enabled’ flag to the value 1 enables the NTP Server.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Parameters\Type
Change the server type to NTP by specifying ‘NTP’ in the ‘Type’ registry entry.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Config\AnnounceFlags
Set the ‘Announce Flags’ registry entry to 5, to indicate a reliable time source.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Config\LocalClockDispersion
Set ‘LocalClockDispersion’ to 0

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\VMICTimeProvider\
Enabled Value data type 0

Command prompt: net stop w32time then net start w32time.

Don’t forget to disable Windows firewall or enable the following port to flow through.

NTP (and SNTP) uses UDP port 123.

Note: If you try to telnet this port, you will not be able because it is an UDP port. So, go-ahead and try to Sync…