Return-Path: william@bourbon.usc.edu Delivery-Date: Sun Oct 19 20:01:40 2008 X-Spam-Checker-Version: SpamAssassin 3.2.3 (2007-08-08) on merlot.usc.edu X-Spam-Level: X-Spam-Status: No, score=-2.3 required=5.0 tests=AWL,BAYES_00 autolearn=ham version=3.2.3 Received: from bourbon.usc.edu (bourbon.usc.edu [128.125.9.75]) by merlot.usc.edu (8.14.1/8.14.1) with ESMTP id m9K31eBg003883 for ; Sun, 19 Oct 2008 20:01:40 -0700 Received: from bourbon.usc.edu (localhost.localdomain [127.0.0.1]) by bourbon.usc.edu (8.14.2/8.14.1) with ESMTP id m9K3AioQ024456 for ; Sun, 19 Oct 2008 20:10:44 -0700 Message-Id: <200810200310.m9K3AioQ024456@bourbon.usc.edu> To: cs551@merlot.usc.edu Subject: Re: Multihoming Date: Sun, 19 Oct 2008 20:10:44 -0700 From: Bill Cheng Someone wrote: > Lecture 12 slide 11 has a bullet that says ISP1 routes directly. But I > didn't see how that related to the discussion. To reach Customer from ISP1, ISP1 has two choices. One has AS_PATH length of 1 and the other one has AS_PATH length of 2. So, it chooses the one with AS_PATH length of 1. ISP1 does not experience the same thing as ISP3 where longest prefix match will steer the traffic in the wrong direction. -- Bill Cheng // bill.cheng@usc.edu