Does SD-WAN maintain a session?

[WarrenG]

Does Meraki SD-WAN maintain a session across both Internet connections? For example if someone inside the network is on a VoIP phone call and the WAN connection that their call was using goes down, will the phone call automatically switch over to the other WAN connection, or will the phone call get dropped?

[Inderdeep · Accepted solution]

@WarrenG : yes it will switch automatically to other link as it maintains the algorithm of dynamic path. Dynamic path selection allows a network administrator to configure performance criteria for different types of traffic. Path decisions are then made on a per-flow basis based on which of the available VPN tunnels meet these criteria, determined by using packet loss, latency, and jitter metrics that are automatically gathered by the MX. So if your primary link has packet loss it will automatically switch to the second link for traffic flow 

[cmr]

For a lot of traffic @Inderdeep is correct, however with SIP it must be TCP SIP for this to work well, some SIP is UDP and then you will likely get a dropped call and have to redial.

[WarrenG]

Thanks to both @Inderdeep and @cmr  for your responses. I am specifically interested in this feature as it relates to RingCentral, who I believe have transitioned to SIP/TCP. So my understanding from both of your responses, this should work pretty well? Thanks again!

[ww]

I think it only works for traffic inside the autovpn.

On internet traffic outside the vpn when it moves from wan1 to wan2 you get a different public ip so the phone will need to register a new session to the cloud provider

[WarrenG]

Okay, so wait you're saying it doesn't work?

[cmr]

@WarrenG I was replying in an SD-WAN context (where both ends have an MX) as we run that setup and it works fine with TCP SIP inside the auto-VPN tunnels.

As @ww said, if you go for a pure internet connection, as opposed to SD-WAN then you will get a drop from one ISP to another, but it should survive an MX HA failover.

[WarrenG]

Okay it seems that we're using the term SD-WAN differently. You're referring to site-to-site VPN, while I'm referring to  an MX router using two Internet connections simultaneously for load-balanced Internet access.

[cmr]

@WarrenG what you are referring to is internet load balancing, not SD-WAN.  SD-WAN always needs a service or device at each termination point (location), hence the initial confusion.

[WarrenG]

I'll respectfully disagree with you on this. SD-WAN simply means software defined, which leaves it open to a broad interpretation of what that means in practice. In a nutshell, SD-WAN refers to network connectivity that is controlled and managed via a software abstraction layer. There is no definition of SD-WAN that says it is only for site-to-site VPN.

Regardless, I appreciate the clarification as it relates to the original question i.e. that VoIP would not work correctly in my scenario 👍

[cmr]

@WarrenG no offence taken, I was merely explaining the confusion 🙂