"Michael C" said:
Finally I got the damn voip working. It appears the first provider I chose
was incompatible with my hardware. The second provider I chose was just a
reseller for the first!! The third worked just right as long as I plug the
voip box direct into my cable modem but through my router (DLink DI-804V) it
sounds pretty average. I'm happy to get a new router as I've had it for a
while and have other reasons for replacing it also. Can someone recommend a
router that will work well with voip and a cable modem? I believe it needs
to support QoS to work well with voip.
Thanks,
Michael
http://en.wikipedia.org/wiki/Voip
http://en.wikipedia.org/wiki/H.323
http://www.voip-info.org/wiki/
http://www.voip-info.org/wiki/view/SIP
http://www.voip-info.org/wiki/view/NAT+and+VOIP (phone behind a router)
This page talks about putting a SIPphone in the DMZ, then forwarding
certain ports 5004, 5060, 69 to the phone. But the next Cisco article
makes it seem a bit more complicated than that.
http://support.sipphone.com/index.php?_a=knowledgebase&_j=questiondetails&_i=69&nav2=Troubleshooting
This page has more to say about the protocols involved. RTP
apparently is what carries the actual audio. Some of the
other protocols are being used to set up the session.
http://web.archive.org/web/20031119045017/http://www.cisco.com/warp/public/788/voip/voip-nat.html
I guess the RTP protocol doesn't know about QOS.
My mention of QOS is with respect to how a phone company _could_
send "long distance" packets with a bit set in the header that
says "please forward me before any other data packets". If the
VOIP packets that carry the voice samples (apparently RTP packets)
are given a higher priority, there would be less jitter in the
interarrival time, and the adaptive buffer in the phone would
introduce less latency. That should give a more natural phone
conversation, without the perception of excessive end-to-end
delay. The little I've read so far, does not explain whether
anyone is doing any tricks with available QOS features, to
make one service better than another. Now maybe the collection
of protocols mentioned in that Cisco paper, is already doing
QOS stuff somehow ?
Here is a device that claims to modify QOS for the user.
Lots more research to do, to see if there is any truth to this.
http://support.dlink.com/products/view.asp?productid=DI-102
And the description of this product, makes it sound like you
connect this product to your cable modem, then plug your
normal router into it. A Dlink "Residential Gateway" ...
http://support.dlink.com/products/view.asp?productid=DVG-1120M
Perhaps something like this - router WAN port goes to the LAN
output of the gateway:
WAN LAN (WAN)
--- cable_modem ----- DVG-1120M --------------- router
Residential gateway | | |
Phone 1 Phone 2 | (LAN)
| | |
X X computer(s)
If the device you own is like that "Residential Gateway", perhaps
that is all you need to do to fix it.
Interesting stuff...
Happy reading,
Paul
