On Wed, 20 Feb 2008, Jason Schiller wrote:
=== Slide 16 and 17 === Smaller ISPs who purchase transit from one or more up streams often use TE towards their transit providers. They may do this to optimize on best performance, low latency, high reachability, or to squeeze as much traffic out of their expensive transit links. Imagine a large South American ISP that has 16 STM-1s to each of its two transit providers with half of the links on two different cable systems. Imagine that the STM-1s are expensive and as a result, in general, the ISP wants to load them ass full as possible. Additionally, one of the oceanic cable systems has better performance, and one of the two up stream providers has better service and support. It is important some critical customers be guaranteed to be on the better performing cable system and be delivered to the higher performance and better supported up stream provider.
Maybe one thing that should be noted in this context about transit contracts (I guess this is pretty common, but not sure): 1) you have to pay for the higher of up/downlink, and 2) you have a contracted basic rate which you will pay whether you have traffic on the link or not (and then the rate you pay for exceeding that).
If you want to optimize costs (and optimization could be very significant here), you may need to 1) balance both in/outbound traffic to a particular transit ISP to be as close to each other as possible, and 2) be able to put roughly the desired amount of load on different transit providers.
-- Pekka Savola "You each name yourselves king, yet the Netcore Oy kingdom bleeds." Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings -- to unsubscribe send a message to rrg-request@psg.com with the word 'unsubscribe' in a single line as the message text body. archive: <http://psg.com/lists/rrg/> & ftp://psg.com/pub/lists/rrg