Iptables breaks a working VoIP phone?

Shane Hathaway shane at hathawaymix.org
Tue Oct 30 17:10:11 MDT 2007


Kenneth Burgener wrote:
> Do you think there is a
> possibility that BroadVoice would give me the admin password to their
> hardware?

I imagine not, because that's their lock-in strategy.  I used a
SunRocket gizmo for a week, and it turns out they were pretty cunning:

- The default configuration (after you push the reset button) is not
functional and only retrieves a replacement configuration from a URL.
- The configuration information was encrypted using RC4 with a secret
key, probably involving the device's serial number.
- Once configured, the device hid the configuration from me.
- Although I could gain administrator access by pushing the reset button
while shielding the device from the Internet, I could not find out my
SIP password to register with SunRocket.

I returned the gizmo right away after discovering that SunRocket sees
its customers as adversaries.  I imagine BroadVoice does similar tricks.

> 1. The firewall box was the oldest box I had laying around, so it isn't
> beefy.  Doesn't the audio encoding consume quite a bit of processing
> power? (That is if I can solve #3)

I don't think so.  When I run a conference call with 4 participants on
Asterisk, it has to decode and encode a stream for each of the 4
connections, yet the whole conference consumes a whopping 2% of the CPU.
 The CPU is an AMD64 3000.

> 2. The Sipura ATA required ZERO configuration to get my analog phones to
> just work.  The asterisk box will require configuring and tuning.
> (Which is more of an inconvenience than a problem)

Very true.  Asterisk has its own configuration language that you'd have
to decipher.  OTOH, it's surprisingly fun to play with phones, like
making your telephone answer with an official-sounding "Nobody here but
us chickens."  Also, Asterisk is a good way to tap into incredibly
inexpensive VOIP options such as:

http://icall.com/carriers/
http://les.net

Your best option right now is probably to dig in with tcpdump /
wireshark and see the SIP messages directly.  Note that SIP looks a lot
like HTTP, so it's easy to read.  Once you're armed with the SIP
headers, you'll be able to ask the right questions on the Shorewall
mailing lists.

Shane




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