BGP or PFR for WAN Survivability

Are you considering redundancy to protect your network for a fiber cut or local network failure?  While using an internet VPN as a secondary network is a common backup solution (using BGP), the right SD-WAN solution can provide a more seamless fail-over in less than a second.  Some SD-WAN technologies will even maintain a VoIP or video session with absolutely no loss of contact, pretty valuable if you route customer calls over the network. You should consider using LTE as a solid protection against the catastrophic fiber cut that might take out all your connections.  If a facility does not have two MPOEs, LTE is a no-brainer.  Even if you do have two points of entry, LTE for fail-over is a bargain, if it supports your bandwidth requirements, which is dependent on reception conditions.

BGP is a common routing protocol for WAN survivability. For mission critical network applications, the availability and performance of applications vital. When it comes to network related issues, BGP, which is used for end-to-end routing, was not designed to consider certain metrics related to performance of applications when selecting best paths. This is exactly where PFR comes into the picture.

By doing so, PFR allows network administrators to minimize bandwidth cost, do intelligent load distribution, and most importantly, improve the availability of applications in their network.  This makes PFR superior  to BGP. Cisco provides PFR at no charge as part of its IOS.

Cisco PFR policies can be based on the following real-time parameters:
• WAN out-bound performance (traffic exiting from an enterprise): Delay, loss, reachability, throughput, jitter, and MOS.
• WAN in-bound performance (traffic arriving into an enterprise): Delay, loss, reachability, and throughput.
• WAN and Internet path parameters: Reachability, throughput, load, and link usage cost.
Cisco Performance Routing consists of two distinct elements: border routers and a master controller. The border routers connect enterprises to the WAN; the master controller is a software entity supported by Cisco IOS Software on a router platform. Border routers gather traffic and path information and send this information to a master controller, which places all received information into a database. The master controller is configured with the requested service policies, so it is aware of everything that happens at the network edge and can automatically detect and take action when certain parameters are out-of-policy.

OER or optimized edge routing is the predecessor to PFR. PFR encompasses all the OER features, but also PFR greatly expands application intelligence and has a broader technology scope than OER. It has many more advanced features and has extensive reporting capabilities through CLI, Syslog, SNMP, and Netflow.


Looking at the network here, notice that the traditional routing, in this case, BGP, chooses the path with the least number of AS hops as the best path. But if there is a condition in that path that hurts network performance, such as some packets being dropped because of a bad interface, it is highly unlikely for BGP to detect the condition and reroute the traffic. Even if BGP does reroute the traffic, it is likely that the protocol timers are not set aggressively which means there will be a significant performance degradation from the perspective of the application end user. This is exactly the type of problem that PFR was designed to address. It can detect black-outs or soft errors very quickly in the end-to-end path and force path changes to route around the fault. This is how PFR guarantees application availability and performance. In fact, this is just one of the typical problems that PFR can help solve.  If you use Cisco routers, you should consider PFR as an alternative to BGP.

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