How Vonage works, based on IP packet analysis

Ok, too much time on my hands maybe but curiosity got the better of me.  I had problems with only outgoing calls at one point (large delay) and then after numerous complaints to Vonage I think they did something to their network and the delay was much improved.  Like many other Canadians I also continue to have problems with some Canadian 800, 866 etc. numbers so that was a pretty good clue how outgoing works right there.  Anyways, I did some internet searching but found nothing anywhere that described how the Vonage network worked.  Not even in the US.  The Vonage people I was able to get through to did not seem to be too clear on how it all worked either.  I finally decided to do a packet analysis and figure it out.

So here is the deal.  At least in my case. Short and sweet.  Nothing magical about it.  Anyone can do a packet analysis from their Vonage ATA or router and see this for themselves.  In my case, there is constant traffic from my Vonage ATA to/from Vonage servers in LA or NJ on UDP port 10000.  The Vonage servers resolve to DNS names such as "outbound14b.kewr0.s.vonagenetworks.net".  That one is in NJ but I have also seen my ATA talking to similarly named servers in LA after a reboot.  I think it just depends on which servers are available at the time the ATA connects after being plugged in or rebooted or whatever.  This port 10000 UDP traffic is constant back and forth.  I believe this traffic is to/from Vonage proxy servers that do all the administrative things such as authentication, authorization, dialing and ringing. 

Next, there are much less frequent packets that resolve to Vonage DNS servers in LA and NJ.  Outgoing on port 53 and incoming on ports around 2020.  Just standard DNS traffic to allow IP to url resolution.  A third type of traffic is less frequent still.  Maybe every 5 or 10minutes on port 123.  This is likely NTP traffic for time synchronization of the ATA.

Lastly there is the actual voice traffic.  These are RTP packets on seemingly random ports established at the time of the call.  They seem to be on just about any number from mid double digits up to five digit ports.  I am located in Kelowna BC.  Outgoing calls from my local Vonage number to any landline number anywhere in Canada local or long distance tracert through my internet provider (Shaw Cable) to Vancouver and then Seattle where they travel via Level3.net or Alter.net to Vonage Servers in New York.  So that is where all Canadian outgoing calls to Canadian public switched telephone numbers (PSTN) go!  At least in my case.  That obviously includes Canadian 800, 866 etc. numbers.  I guess because there is no way to determine the geographic location of a toll free number like there is with regular toll numbers, and because some Canadian toll free numbers don't work in the US, you will occasionally get number not available messages because the call actually comes from Vonage NJ.  I think they now have some way of routing individual Canadian toll free numbers being called from Canada so they will work in Canada.  I assume they have to manually do this for each toll free number they are made aware of.  I don't know of any toll free Canada only numbers that now work on Vonage to test their routing.  If anyone knows of a Canadian only toll free number that now works on Vonage but did not before please send it to me and I will trace the route.   Curiously, Vonage to Vonage calls go through the same servers except Vonage seems to randomly select LA or NJ servers even though I am calling the same number.  Of course, Vonage to Vonage calls stay on the internet and never enter the PSTN.

US bound calls are apparently handled a bit different.  If I call Seattle or LA the call always goes to a Vonage PSTN gateway in LA which resolves to a url such as rtp64-118-wil2.klax1.s.vonagenetworks.net.  So there are obviously Vonage outgoing PSTN gateways located in several major cities in the US unlike Canada where there are apparently no outgoing PSTN gateways.   Vonage probably has gateways in some other major cities like Atlanta and ? for outgoing.  On the other hand, for whatever reason, ALL outgoing Canadian calls to Canadian PSTN numbers are handled out of Vonage NJ.

Incoming calls to Canadian numbers appear to work differently.  There DO appear to be regional Canadian PSTN gateways for incoming.  Probably due to the fact Vonage needs to provide local numbers and local number portability.  For outgoing, it doesn't matter where the call actually comes from as long as the Caller ID is correct.  In my case living in Kelowna, all incoming calls to my Kelowna number (which I had ported from Telus to Vonage) go to a Vonage incoming PSTN gateway located in a Peer 1 facility in Vancouver.  Shaw probably has a peering arrangement with Peer 1 so from there it appears to connect directly to the Shaw public network and then to my Vonage ATA in Kelowna.  That's all there is to it.

Now that I know all my outgoing Canadian calls (even local calls) have to go to NJ over the internet I am kind of bummed!  My average ping time to the Vonage NJ gateways averages around 100ms round trip which is getting a bit high for voice calls.  Still not that bad IMHO.  Compare that with my ping times to Vonage LA gateways which average around 50ms round trip.  Then there is a bit more delay added when going from there over the phone network.  Probably somewhere around 50ms round trip if it is a local call that has to come back to Kelowna.  So round trip that is maybe 150ms for outgoing calls.  Compare that with incoming which only has to go as far as Vancouver over the internet portion.  My ping times there average about 15ms round trip.  Add maybe 10ms for the phone network portion and your still only looking at about 25ms round trip.  That explains why my outgoing continues to have some delay but incoming seem fine.  Outgoing is still quite acceptable but the perceived quality of the call is obviously going to be a lot less than incoming IMHO.

If Vonage routed my outgoing Canadian calls through Vonage LA PSTN gateways my delay would be a lot less so the perceived quality would probably be a lot better.  I guess it's easier for Vonage to just route all Canadians through NJ.  Quality is likely to suffer for those closer to the west coast.  Time to look for a West Coast VoIP provider that can port my local number I guess.

Update (Aug 01/06).  On request, Vonage has agreed to route all my outgoing calls to my local area code through LA.  I will provide updates as to any noticeble changes in call latency/quality.