One very basic question. We have a MPLS line to a remote site and a DSL line to the same remote site. When i ping these sites, we are getting almost the same response times for both the circuits. eg:320ms for MPLS and 390 for DSL. Shouldn't the MPLS repsonse be way better. Around how much can i expect?
As I have mentioned, MPLS is mainly used as a service enabler. The advantage you could get for using MPLS is you can have better services like traffic engineering QoS, VPNs etc. So if you are comparing dsl and mpls without any service, they both would work the same. But with mpls, you might have better redundancy with features like Fast-reroute, traffic engineering to have guarantees etc.
If your service provider is not giving you any services, then dsl and mpls would be the same as far as response times are concerned. And you still can run voip over that too but the problem would be during congestion. It is the worst case scenarios that you pay for. May be during congestion times or when there are problems in the SP core, you could see the difference in the response times for mpls and regular DSL. And again if you are using the connection for VPNs, then mpls provides many more features. And moreover mpls can use traffic engineering which can help your traffic take lesser congested path or a specific path to maintain constant delay avoiding jitter. Hense, mpls.