Configuring your home
network for SIP-based callerID
If you already have an
IP-based voice provider (Vonage, VoicePulse, Lingo, etc), you can reduce the callerID
notification latency using the information sent in the
IP traffic from the provider versus that provided by the
PSTN adapater. Typically, you'll have the data on the
first ring!
Unfortunately, you'll probably have to make a few changes
to your home network to be able to make things work. These
directions assume you have at least two devices (your
computer and the PSTN adapter) behind a NATing router
(Linksys, Netgear, D-Link etc). You may also have a PSTN adapter
with built-in routing functionality - that will also
work. I also assume you have a properly configured and
working installation of NCID. We will be using the included
"sip2ncid" utility to pull callerID information from the
SIP traffic.
The root of the problem is that the NATing router has an
internal switch that forwards traffic only the system it is
destined for. This has several major benefits including
eliminating ethernet collision domains and increasing
security. It also means that your NCID server will not see
SIP traffic that is not destined to it (although there are
reports that the Linksys RT31P2 router broadcasts SIP
control messages).
ncidsip uses the SIP control traffic (specifically, the SIP
REGISTER messages) to gather information about the caller.
In order for ncidsip to "see" this traffic, you will need a
way to put the ncidsip in the data path or get a copy of
the traffic to it.
Option 1 is fairly straight-forward, although I don't
recommend it. If you are running ncidd on a Linux system,
you can add an ethernet interface to the system, connect
the PSTN adapter to it, and enable NAT. A major drawback to
doing this is that you inserting a fairly complicated piece
of equipment into the critical path. There's no questioning
the stability of Linux routing and NATing functionality,
but a home linux system (usually meant for tinkering after
hours) may not have the uptime you need for your phone
service.
Option 2 is even easier, although it will involve an
additional piece of equipment. You will need to purchase an
ethernet hub and insert it between your cable/DSL modem and
your router (if you have an all-in-one model, this method
won't work). Ethernet hubs are fairly archaic technology
and you need to be very careful in selecting one. Many
recent "hubs" are actually switches, which we don't want.
Two models I can recommend from personal experience are the
Netgear DS104 10/100Mbps hub and the Netgear EN104 10Mpbs
hub. They both have a nice metal casing and a cool retro
look. If you have a high-speed connection, I would stay
away from the EN104. My downlink is 16Mbps, but putting the
EN104 in-line dropped it to a pathetic 3Mbps. The DS104,
since it's a 100Mbps device, worked much better and does
not bottleneck my traffic. Be aware that the DS104 is
actually two hubs - a 10Mbps and a 100Mbps - connected
internally by a switch. If you have mixed interface speeds,
this hub will probably not work for you. You can pick up
either on eBay for $15-20.
Run an ethernet cable from it to the system running ncidsip
and you're good to go!
