Multiple ISP Load Balancing

Drew Weaver drew.weaver at thenap.com
Wed Dec 14 13:28:34 CST 2011


I've asked several times about this in the past; although I learned quickly to stop asking.

It seems that the consensus has generally been that the best way to handle traffic engineering in networks where you have multiple full-feed up-streams is to do it manually (i.e. set preference for your top N AS/prefix destinations) or don't do it at all (let BGP figure it out..?).

Suggesting that a "route optimization system" has any value generally makes people cranky.

Thanks,
-Drew

-----Original Message-----
From: Holmes,David A [mailto:dholmes at mwdh2o.com] 
Sent: Wednesday, December 14, 2011 2:07 PM
To: nanog at nanog.org
Subject: Multiple ISP Load Balancing

>From time to time some have posted questions asking if BGP load balancers such as the old Routescience Pathcontrol device are still around, and if not what have others found to replace that function. I have used the Routescience device with much success 10 years ago when it first came on the market, but since then a full BGP feed has become much larger, Routescience has been bought by Avaya, then discontinued, and other competitors such as Sockeye, Netvmg have been acquired by other companies.

Doing some research on how load balancing can be accomplished in 2011, I have come across Cisco's performance routing feature, and features from load balancing companies such as F5's Link Controller. I have always found BGP to be easy to work with, and an elegant, simple solution to load balancing using a route-reflector configuration in which one BGP client (Routescience Pathcontrol in my background) learns the best route to destination networks, and then announces that best route to BGP border routers using common and widely understood BGP concepts such as communities and local pref, and found this to lead to a deterministic Internet routing architecture. This required a knowledge only of IETF standards (common BGP concepts and configurations), required no specialized scripting, or any other knowledge lying outside IETF boundaries, and it seemed reasonable to expect that network engineers should eagerly and enthusiastically want to master this technology, just as any other technology must be mastered to run high availability networks.

So I am wondering if anyone has experience with implementing load balancing across multiple ISP links in 2011, and if there have been any comparisons between IETF standards-based methods using BGP, and other proprietary methods which may use a particular vendor's approach to solving the same problem, but involves some complexity with more variables to be plugged in to the architecture.

David



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