Rapid Network Reconvergence technologies?

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Aug 16th, 2009
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Are there commercial technologies offered that provide very fast network reconvergence? By that I mean the ability to mover data from one network path to another if that path fails? I see from our network several seconds for OSPF to reconverge. Are there technologies that would support a simple 2 path reconvergence to occur much faster, say in milliseconds?

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paolo bevilacqua Sun, 08/16/2009 - 13:36
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Actually a properly designed OSPF network can reconverge in 200ms.


The real problem is that sometime you have the "black-hole" type of failures where your L1 is down but upper layer is not notified, for these you need some reasonable keepalive timeout to expire.


However you should state what is the application that brings you to ask the question because there millions of networks worldwide, including very sensitive ones, happily running the traditional routing protocols without issue whatsoever.



c.captari Sun, 08/16/2009 - 17:26
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Yes. There is: "Bidirectional Forwarding Detection"


http://cco.cisco.com/en/US/docs/ios/12_0s/feature/guide/fs_bfd.html


http://en.wikipedia.org/wiki/Bidirectional_Forwarding_Detection


BFD provides fast BFD peer failure detection times independently of all media types, encapsulations, topologies, and routing protocols BGP, EIGRP, IS-IS, and OSPF. By sending rapid failure detection notices to the routing protocols in the local router to initiate the routing table recalculation process, BFD contributes to greatly reduced overall network convergence time. Figure 1 shows a simple network with two routers running OSPF and BFD. When OSPF discovers a neighbor (1) it sends a request to the local BFD process to initiate a BFD neighbor session with the OSPF neighbor router (2). The BFD neighbor session with the OSPF neighbor router is established (3).



Otherwise a specific solution for OSPF would be: OSPF Support for Fast Hellos

http://www.cisco.com/en/US/docs/ios/12_0s/feature/guide/fasthelo.html

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