Confusion with multiple upstream eBGP peers (Routing beyond our control)

Question:

I am imagining WS-C3750V2-24PS-S a smallish networking (AS1234) with say three full BGP table peers that provide transit to the network (just to keep the maths simple here);

Lets say AS100 and AS200 are preferred transit providers with AS300 as a backup/least prefered (AS prepends or similar stop us from using this network by default). So in this scenario our little network gets two different paths across the Internet, as not to rely solely on one provided, with a backup provider to hand also.

How do you mange issues like packet loss somewhere in AS100's or AS200's network?

So lets say a host on our AS1234 network is talking to host in AS888 and the preferred route is through AS100 but somewhere deep in AS100 a link is flapping (for example) and I can't get to AS888 reliably through there anymore, but I can through to other peers of AS100 OK. We can postulate that AS100 is the best path for 50% of the Internet and AS200 for the other 50% (this is a best case fictional scenario). I can't ping 50% of the internet via AS100 and then in the event a ping fails (or some other more reliable test) tear down the BGP session to use AS100 until it's fixed again, nor vice versa with AS200.

So what do you do?

First of all, I asume you don't know about the issue between AS100 and AS888 until someome moans about it to you? Secondly, do you then some how modify the route(s) to AS888 that come from AS100 (route map for example to change the weight or preference) so AS200 is now preferred for AS888? Do you infact shut down the AS100 peering and now use AS200 & AS300? How do you rectify these situations that are beyond you control using what is in your control?

Answer:

OER sounds like what you'll need. With OER (Optimized Edge Routing) or PFR (Performance Routing), you can sense latency, packet drops, etc, and move traffic to another circuit. OER uses BGP or static routing to perform the changes, but it can automatically move traffic to another circuit if one starts to exhibit issues.

http://www.cisco.com/en/US/docs/ios-xml/ios/oer/configuration/12-4t/oer-overview.html

For futher information, please refer to http://www.3anetwork.com/cisco-ws-c3750v2-48ps-s-price_p110.html