Is running VOIP between sites feasible within the US over VPN connections?? I realise that once on the internet there is no QOS more best effort etc.
I have been studying the Cisco SNF 2.0 configuration templates for SMB and Cisco's Validated Design Templates which provide guidace for configuring VPN between sites with QOS applied within the VPN.
I just wondered if anyone out there can share there experience with the voice quality and reliability using VOIP over VPN. It seems like a cost effective solution for SMB customers using the public Internet as a transport for intersite voice calls.
We currently have over 30 remote sites in Europe running VoIP over VPNs without any issues. Our HQ is in London and we have VoIP to countries which have pretty poor links i.e 512kbps and RTT of 300ms+, due to the distances (+5 hours from London) and on the whole it is fine.
We have rolled out Riverbed WAN Accelerators to a few countries and this has improved the voice quality.
It can be done. Think Skype
Just for consideration - like you said - no quality guarantees.
Most people tolerate slight call quality issues with Skype because it is free, and a big money saver.
Business users are not so tolerant usually.
So you need to have a fallback to allow them to dial out the PSTN if they have issues on a call.
A couple of points to consider..
1. Take into account your RTT's - usually people say 150ms maximum, but we usually prefer it to be less. If you are over this, it will still work, but the experience may not be that good. Think users on the end of Satelite links. Sometimes we have up 700ms RTT and they still manage to use Sat phones and even VoIP in some cases. They just adjust the way they converse, more like a 2 way radio!
2. Make sure you can use a codec designed for lossy links - iLBC for example - http://en.wikipedia.org/wiki/Internet_Low_Bit_Rate_Codec (Cisco supports this in all the new gear)
3. It is most likely your access links that there will be congestion. You can still perform QoS here on the egress. You dont have full control over the ingress though. Using the best quality links and providers here will help. Using the same ISP usually helps, but probably difficult internationally.
4. Packeteer Packetshapers (Now Bluecoat) do a good job of bandwidth control on internet links. They do things like intercept TCP sessions and adjust the windowing size to reduce bandwidth consumption for hogs like FTP, P2P etc. You need to be very careful about what sort of other traffic you allow on the links, and how you control it.
5. Protocols like SIP and MGCP will perform better over higher latency links. If you end up with H323, you may have delayed audio cut through issues, in which case you should look at H323 fast start options.
6. Make sure you figure out how many calls you can support, and use call admission control to limit the number of simultaneous calls you allow.
I have customers running from Australia to parts of Asia using this scenario, they find it acceptable, considering the cost of the call.
Is running VOIP between sites feasible within the US over VPN connections??
Yes, and actually works very well. It is actually very popular across vendors and applications.