[c-nsp] BGP and load balancing... kinda

[Justin M. Streiner]

On Fri, 23 Feb 2007, Shaun wrote:

> Say i had a ethernet 1000mbit uplink to ISP_A and ISP_B and DS3 uplink
> to ISP_C... doing bgp with all 3.  What would happen if the DS3 started
> to reach capacity, would the router know and start pushing traffic out
> ISP_A or B? or is this somthing i have to try to balance on my own?

No, you would have to alter your routing policies to push traffic away 
from the saturated link.

The other thing is that people often have an assumption that 
inter-provider load balancing works like server load balancing.  This is 
for the most part not the case.  The tools in BGP to shift traffic aren't 
designed to give super-fine control over traffic distribution, the way you 
can through a server load balancer or some other type of packet-shaping 
appliance.  If you take full feeds or something close to it, you can 
exercise a goot bit of control over your traffic, it just depends on how 
much time you want to spend tweaking routing policies...

jms