page 68
innovaphone IP DECT
The number of ports to be released cannot be restricted if the device has to
communicate with third-party products. It is thus necessary to release all
ports to and from the device.
•
The device is placed in front of the firewall, so that the data stream does
not have to pass the firewall. In this case, you will not be able to set up any
voice connections from within the network to the device (for example, with
innovaphone Softphone PCs).
If the network is operated in NAT mode and the product you are using does not
support H.323 NAT, then it is not possible to operate beyond the firewall.
VoIP and heavily loaded WAN links
If voice data is transmitted over heavily loaded, narrowband WAN links, the voice
quality can be affected if the respective links can no longer ensure adequate
transmission quality.
Prioritisation of voice data on the WAN links can help here. This can usually be
achieved by the routers used.
Direct use can be made of the "
Prioritisation of H.323 voice data
" function, if it
is supported by your router.
If you router is able to prioritise on the basis of the ToS field (
T
ype
o
f
S
ervice),
you can use this function. The VoIP device sets the ToS
Priority field to the value
0x10
for all IP packets that it sends. This value can be changed, if necessary,
under the chapter “
Configuration/IP/Settings
”
.
If this is not the case, the function “
Prioritisation according to source/destination
address
” can be used, if available. In this way, data packets from and to the
device are prioritised. This in effect corresponds to the prioritisation of voice data
as above.
In any case, the maximum size of packets transmitted over the WAN link (often
referred to as
MTU size
) should be restricted to a value smaller than 800 bytes.
This ensures that, in spite of the prioritisation of voice data, larger data packets
Tip
You can specify hexadecimal, octal or decimal values: the entries
0x10
,
020
and
16
are all equivalent. The value set for the ToS Priority field should be
the same on all used devices.
