On 15 Aug 2007, at 08:07, Chengchen Hu wrote:
Just suppose no business fators (like multiple ASes belongs to a same ISP), is it always possible for BGP to automatically find an alternative path when failure occurs if exist one? If not, what may be the causes?
I think everyone here has already covered a lot of the bases to do with your original question (i.e. 'Because kit might not be configured to re-converge in an optimal way'), but if I can summarise the question you are trying to answer as "how can we improve convergence times", you might like to look at the notes that Nate Kushman presented in Toronto this year http://www.nanog.org/mtg-0702/kushman.html Summary Many studies show that when Internet links go up or down, the dynamics of BGP may cause several minutes of packet loss. The loss occurs even when multiple paths between the sender and receiver domains exist, and is unwarranted given the high connectivity of the Internet. Instead, we would like to ensure that Internet domains stay connected as long as the underlying network is connected. Andy