Over time the use of multiple paths within the modern corporate network has increased. Using both paths of an active/backup pair adds bandwidth. We’ve gone through a whole series of phases, and now are emerging into the 4th generation of the technology. This is Hybrid Network Unification, the linkage of MPLS and Internet VPN as a seamless network. I’ve had the (good?) fortune to experience all of these at various points, and to design networks around these technologies, and speak from experience that this isn’t a particularly easy thing to do.
Let’s look at some of the options:
- static host routing
- application specific routing (Policy Based routing)
- path selection technology
- application path selection against objectives using smart|path
The static routing option was quick and easy to implement. Using both paths was OK in theory, but was terrible from an operational standpoint. A link failure somewhere in the network would most likely cause the traffic to blackhole, (since the static routes invariably wouldn’t fail out of the network, causing traffic to be discarded.)
Policy-Based routing was more successful, especially if you wrapped the traffic in a GRE tunnel across the network. In later Cisco IOS releases this could be set up to send keepalives. If these are not received, the GRE tunnel fails if there is an issue in the network. The policy-based explicit route would then fail out, directing traffic back to the default route within the network. However, like the static routing, it’s still a bit of a nightmare trying to isolate the faults. Scaling the solution is a challenge since you’d need to change 100’s or 1000’s of routers in large networks. Changes to the PBR rules are local to each router and need to be set for both paths. The changes to the PBR rules are necessary if you change an application or host.
Only recently has the software and equipment been available to make this easier, and now it’s possible using Ipanema to use both paths (e.g. MPLS and Internet, or dual supplier MPLS), and still gain all the objective based application benefits.
Admittedly, we’re not first to market with a path-selection routine, most notably Juniper JNPR 30,15 +0,57 +1,93% has a similar feature in their WX platform. But we are the first to extend our network-wide per-flow objective-based management into an autonomous multi-path solution.
Selecting specific user classes, (a group of applications with similar performance requirements) makes smart|path route traffic over up to 3 paths in the network. This means that you could have all the benefits of a path-selection technology to split traffic onto multiple routes. This activates those expensive tail circuits used for backup. (Your network provider may want to charge you for the additional IP bandwidth in use in the network core too!).
Unlike traditional path selection techniques, which force traffic down a single link until either delay or packet-loss or failure cause it to reroute; the Ipanema solution will dynamically select a path based on the delay, jitter and loss requirements of the user class. This means that should all the paths in the network be capable of delivering an application, it could route separate flows over up to three different links. The security-minded control this on an application group basis, so that sensitive information never leaves a more secure route.
So smart|path provides the following benefits to an organisation:
- use the expensive tails that were for backup as active links
- objective based management of user classes to deliver applications against business requirements
- comprehensive monitoring and reporting on traffic
- the ability to send different traffic flows over multiple links at the same time
(other technologies limit this to a single path)
