Voice over IP (VoIP) VoIP System Telephones
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2. An IP address, network mask and the default gateway for the start procedure
are sent from the DHCP server. Via the “Next server” option, the DHCP server
also provides the TFTP server’s IP address and the operations software’s file
name. The DHCP server uses the MAC address to select the operations software
file which matches the type of device.
3. The boot loader loads the operations software file from the specified TFTP
server. The TFTP server’s IP address and the file’s name are shown in the display.
The loaded operations software is started.
4. The operations software sends a DHCP request on the broadcast address
255.255.255.255. The VoIP system telephone now receives an IP address,
network mask and default gateway for operations from the DHCP server. Using
“Option 43”, which is reserved for this purpose, the DHCP server also provides
the IP address of the communication system and port number 8100 for regist-
ration.
5. The VoIP system telephone creates a TCP connection to the supplied IP-
address/port-number combination and sends a registration query. The
OpenCom 510 checks the MAC address sent with the registration and confirms
the registration request if the VoIP system telephone is listed in the menu
PBX Configuration: Devices: VoIP Phones. The keep-alive time, port number
(8101) for telephony signalling and the value to use for the TOS byte are also
communicated in the registration answer.
6. The VoIP system telephone creates a second TCP connection using the sig-
nalling port number 8101 and sends a registration analogue to the U
pn
system
telephones.
7. Extra connections are created using the IP protocol RTP (“Realtime Transport
Protocol”) for call data when a call is created. For calls between two VoIP system
telephones, port numbers above 8200 are used. For transmission to a Media
Gateway card, a port in the range 1024 – 1087 is used.
If you wish to operate a VoIP system telephone via a routed IP connection (for
example VPN or RAS) it may be necessary to configure an external DHCP server
accordingly. Please note the selection of the codec and keep-alive time for RAS
connections. This can be done by selecting the default profile RAS in the
PBX Configuration: Devices: VoIP Phones for the VoIP system telephone. The
operations software provided via TFTP must match the type of device and com-
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