VOIP: ekiga, wengophone, twinkle (was What is 'administrivia')

[Fergal Daly]

On 02/01/2008, Mackenzie Morgan <macoafi at gmail.com> wrote:
> On Jan 2, 2008 6:23 AM, Fergal Daly <fergal at esatclear.ie> wrote:
>
> > If your setup is relatively straight-forward or you are able to open
> > ports on your firewall then you don't have be SIP expert to get it
> > working - I know nothing about SIP I got it to work by following the
> > docs,
> >
>
> I'm going to go ahead and lose all my geek points now.  I don't know how to
> open ports on my router.  I certainly don't expect that any normal user
> does.

Then I'm not sure how you got any of the other SIP clients to work. As
I understand it, unless the machine yon which you are running the SIP
client has a publicly accessible IP address, you will not be able to
use SIP unless you have a way to twiddle your router.

The problem is that the voice data travels in UDP packets directly
between you and the other person on the call. If you don't have a
public IP address - say you are using NAT with a wireless router then
the packets will arrive at your router and it will not know what to do
with them - they could be for any of the machines on your wireless
network.

If you "open the port" (or rather "forward the port") on the router,
you are telling your router, if any packets arrive on port number XYZ,
send them to my computer. This will allow SIP to work for you and is
independent of what SIP client you use.

If one of you has a public IP address and the other a NATted one then
if the NATted one startes sending the packets first, their router will
see there is a conversation going on and allow the packets to flow.

If both of you have NATted IP addresses then neither of you can start
the conversation.

With certain routers, there are tricks you can do to get around this
but many many routers have no work around.

Skype gets around this by sending your conversation through a 3rd
computer out on the internet which has a publicly accessible IP
address. All packets between the 2 chat clients go via this computer.
So actually there are 2 UDP packet flows, which this 3rd computer
joins together.

You can also get around this if your router can run a SIP proxy.

I'm curious if you got some other SIP client to work without problems.
I had the same set of problems with twinkle as with ekiga,

F

>
> --
> Mackenzie Morgan
> Linux User #432169
> ACM Member #3445683
> http://ubuntulinuxtipstricks.blogspot.com <-my blog of
> Ubuntu stuff
>  apt-get moo