Specifications

Chapter 4 - MGCP Protocol Features Firewall Traversal
78
Mediatrix 4100
Figure 25: Conference Message Flow – Part 3
Firewall Traversal
The Mediatrix 4100 may be used in a private domain that is not directly connected to the IP network. For
instance, this may be the case for ITSP (Internet Telephony Service Provider) clients that have a small private
network. This private network is connected to the public IP network through a firewall.
When a Mediatrix 4100 controlled with the MGCP protocol is deployed behind a firewall, the Media Gateway
Controller (MGC) should be allowed to control the unit. To keep the firewall connection alive, signalling packets
must be exchanged between the Mediatrix 4100 and MGC within a specified period of time called the keep-
alive timeout. If no packets are exchanged for the specified period, then the connection will be closed.
To keep the connection alive, the Mediatrix 4100 uses the RSIP RM : x-keepalive command to indicate that
its inactivity timer has timed-out. The RSIP keep-alive command is sent at the gateway level.
The RSIP keep-alive command does not require any 200 OK from the MGC. It is launched immediately after
the activation of the MGCP stack. It is then possible to see a RSIP keep-alive command preceding the initial
RSIP restart if the registration initial delay period is larger than the inactivity timer. Furthermore, the RSIP
keep-alive is not submitted to the disconnection procedure.
Note that voice packets cannot be used to keep the connection opened because they are transmitted on
another channel.
 To enable the firewall keep-alive timeout mechanism:
1. In the mgcpMIB, define the keep-alive timeout value (in seconds) in the mgcpFwKeepAliveTimeout
variable.
The default value is 300 seconds.
2. Set the mgcpFwKeepAliveEnable variable to enable.
This enables the firewall keep-alive timeout mechanism. The RSIP keep-alive is sent every time the
timeout is reached.
MGC
Port 2727
X: 113
O: L/hf
C: 2
I: 483408421
M: inactive
R: L/hu(N),G/ft(N),G/mt(N)
S:
X: 114
C: 2
I: 483408421
M: inactive
R: L/hu(N),G/ft(N),G/mt(N)
S:
X: 1141
C: 1
I: 483408420
M: confrnce
R: L/hf(N),L/hu(N),G/ft(N),G/mt(N)
S:
X: 115
C: 2
I: 483408421
M: confrnce
R: L/hf(N),L/hu(N),G/ft(N),G/mt(N)
S:
X: 116
NTFY 522191983 aaln/[e-mail] MGCP 1.0
200 522191983 OK
MDCX 26 aaln/[e-mail] MGCP 1.0
200 26 OK
MDCX 126 aaln/[e-mail] MGCP 1.0
200 126 OK
MDCX 27 aaln/[e-mail] MGCP 1.0
200 27 OK
MDCX 28 aaln/[e-mail] MGCP 1.0
200 28 OK
User A User B User C