inter-domain link recovery

Chengchen Hu huc at
Wed Aug 15 07:11:14 UTC 2007

Thank you for comments. I know there are economic/contractual relationships between two networks, and BGP cannot find a path that the business rules forbid.  But when in these cases, how to recover it? The network operators just wait for physically reparing the link or they may manully configure an alternative path by paying another network for transit service or finding a peering network? 

C. Hu 

From: Patrick W. Gilmore
Data: 2007-08-15 13:59:16
To: nanog
CC: Patrick W. Gilmore
Subject: Re: inter-domain link recovery

On Aug 15, 2007, at 12:06 AM, Chengchen Hu wrote:

> I find that the link recovery is sometimes very slow when failure  
> occures between different ASes. The outage may last hours. In such  
> cases, it seems that the automatic recovery of BGP-like protocol  
> fails and the repair is took over manually.
> We should still remember the taiwan earthquake in Dec. 2006 which  
> damaged almost all the submarine cables. The network condition was  
> quit terrible in the following a few days. One may need minutes to  
> load a web page in US from Asia. However, two main cables luckly  
> escaped damage. Furthermore, we actually have more routing paths,  
> e.g., from Asia and Europe over the trans-Russia networks of  
> Rostelecom and TransTeleCom. With these redundent path, the  
> condition should not be that horrible.
> And here is what I'd like to disscuss with you, especially the  
> network operators,
> 1. Why BGP-like protocol failed to recover the path sometimes? Is  
> it mainly because the policy setting by the ISP and network operators?

Why do you think BGP was supposed to find the remaining path?  Is it  
possible that the remaining fibers were not owned or leased by the  
networks in question?  Or are you suggesting that any capacity should  
be available to anyone who "needs" it, whether they pay or not?

BGP cannot find a path that the business rules forbid.


> 2. What is the actions a network operator will take when such  
> failures occures? Is it the case like that, 1)to find (a)  
> alternative path(s); 2)negotiate with other ISP if need; 3)modify  
> the policy and reroute the traffic. Which actions may be time  
> consuming?
> 3. There may be more than one alternative paths and what is the  
> criterion for the network operator to finally select one or some of  
> them?
> 4. what infomation is required for a network operator to find the  
> new route?
> Thank you.
> C. Hu

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