Re: inter-domain link recovery

[Andy Davidson <andy () nosignal org>]

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