[Asterisk-Users] MGCP service from Free Télécom

[Stewart Nelson]

I'd like to use the VoIP service from Free with Asterisk,
but am having a couple of problems.  Here are some details:

ADSL from Free Télécom comes bundled with VoIP and TV
services.  Most users access the VoIP via the supplied
Freebox, which is an integrated DSL modem, router, ATA, and
media player.  It is of course possible to connect the
Freebox to Asterisk via an X100P or other FXO interface.
However, to improve quality, reliability, control, etc., I'd
like to have Asterisk directly access the underlying MGCP
service.

Since this will take quite a bit of work (chan_mgcp
presently acts only as Call Agent and cannot function as an
endpoint), I first tried to configure an old Cisco ATA-186
to use the Free service.  Although international and
domestic long distance calls (both outgoing and incoming)
work fine, there are problems with local calls.  When
calling some locations in Paris, the ATA user hears a severe
echo (though there is no echo if Freebox is used).  The 186,
like most ATAs, has echo cancellation only for the analog
line.  That is working as expected; the remote party does
not hear an echo.  I would think that the far side echo
would be canceled by the remote media gateway, but that does
not seem to be the case.  I don't believe that the caller
has any control over this (the CA sends out requests and the
endpoint obeys them), so it appears that the Freebox must be
doing echo cancellation for both ends.  Can someone confirm
this?  If it's true, is it possible for Asterisk to cancel
echo from the remote end?

On calls to nearby locations, such as my own POTS line or
Free's voicemail service, there is no outgoing audio from the
ATA.  It appears to be a routing problem, because I can't
ping these media gateways, typically 172.16.254.x, but can
ping those where the audio is ok, typically 172.25.x.x.
Packets do arrive *from* 172.16.254.x, and incoming audio is
ok.  However, the ATM protocol is RFC 1483 routed, VC mux, so
there is no way to specify a gateway other than using the
proper PVC, which I assume is 8/35 for all the private
addresses used for VoIP, and 8/36 for Internet IPs.  I'd
like to see what the Freebox is doing differently, but don't
know how, because this traffic does not appear on its
Ethernet port.  Is there a reasonably inexpensive tool that
can monitor the packets on a DSL line?  Or some other way to
find out what is happening?

Thanks in advance,

Stewart