You’re right that a lot of enterprise customers tend to use 4G as a fail-over circuit only - this is normally because they are just looking for cellular fail-over if their main fixed links go down -so buy cheaper data packages for that purpose. However we have lots of customers using our MAX multi-cellular routers with just 4G/3G connectivity for temporary site deployments and in vehicles, so the choice of how you use a cellular WAN link is very much down to what you need to get out of it and the deployment scenario.
In answer to your questions:
- There is an algorithm to allow a link to seamlessly burst across to secondary link if latency becomes high?
A. Yes and No. When using session based load balancing we have a lowest latency rule so that the lowest latency link will always be favoured when sending traffic. This isn’t technically ‘seamless’ though since load balancing works at a session level - it is an automatic process however, and depending on the application/traffic in use, can appear seamless to the end user. If you want true seamless fail-over between WAN links then you need to use SpeedFusion our VPN Bonding technology.
With SpeedFusion, WAN links are given usage priorities where only available WAN connections with the highest priority will be utilized. So if you have a fixed line set to Priority 1 and a cellular link set to priority 2, the cellular link will only be used if the fixed line connection fails (saying that, the cellular link does have some keep alive traffic running over it to make sure its ready when needed). This hot fail-over is performed at a packet level and is seamless.
If you had both a fixed line and a cellular connection set to priority 1 (so active/active) we will always favour the healthiest lowest latency link in the tunnel, so if the fixed line WAN latency rises above the latency of the cellular link, traffic will effectively burst across the cellular link. Since SpeedFusion works at a packet level this is a seamless process.
- Know how bonded cellular connections perform, in particular latency management in an active/active scenario?
A. In an active/active bonded cellular scenario, traffic is sent down the lowest latency cellular WAN link. If the traffic saturates that first link, it will overflow to any available additional higher latency links, at which point overall latency across the VPN bonded tunnel will rise. You can of course use QoS within the SpeedFusion Tunnel to prioritise any type of traffic to improve the end user experience for time sensitive applications like VoIP over a bonded cellular connection.
Ultimately though, no matter how clever SpeedFusion is, the end user experience will naturally always be governed by the quality and bandwidth availability of the WAN links connected, and dependant on what applications are in use. For example I have personally used VoIP over bonded 3G services here in the UK when I moved house and was waiting for my fixed line internet to be connected. This worked great. I have also used VoIP and Citrix in a moving vehicle (I wasn’t driving of course) using the same bonded cellular set up which also worked great until we entered a tunnel where the Voip call dropped but Citrix just temporarily froze and then recovered.
Therefore its important to set customer expectations correctly when deploying any VPN bonding solution depending on the applications they want to use and their deployment scenario, SpeedFusion will do its best with any type of WAN link that’s connected, but it will struggle to provide a high quality VPN connection if the underlying WAN links are themselves of a very low quality. When using cellular links then, any improvements you can make to cell reception are well worth the effort. Nearly all of our partners who specialise in cellular bonding will use additional high gain external antennas and perform cellular provider surveys before customer deployments to guarantee they are providing the best quality cellular connections possible for SpeedFusion.
As for QoS, we have inbuilt application profiles for most traffic types to make things quick and easy to configure, or you can create custom rules based on protocol/port/IP or use DSCP values as required.
If you haven’t already, I recommend logging into the demo web interfaces for both the MAX and the Balance that we have on our website. You can see the full webui for WAN, SpeedFusion and QoS settings there and get a great feel for what’s possible.
MAX Demo: http://www.peplink.com/products/max-cellular-router/max-live-demo/
Balance Demo: http://www.peplink.com/products/balance/live-demo/