Watched a CBT Nugget video and it was said that BGP protocol was slow. So if you brought up a domain it would take days for the domain to be fully accessible. However while at work a change was made on the router concerning BGP routes and it took minutes for the change to seen. So is the BGP protocol slow or is it fast. Thanks
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A paper on how BGP is used in data centers, where it needs to converge fast: https://www.usenix.org/system/files/nsdi21-abhashkumar.pdf – Bruno Rijsman Apr 14 '23 at 17:50
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It’s common knowledge that BGP has no ability to make performance-based routing decisions and often routes traffic through paths that are congested or affected by routing anomalies.
Since BGP is focused on reachability and its own stability, in case some problems occur the traffic may only be rerouted due to hard failures. Hard failures are total losses of reachability as opposed to degradation. This means that even though service may be so degraded that it is unusable for an end user, BGP will continue to assume that a degraded route is valid until and unless the route is invalidated by a total lack of reachability.
One way to detect this problem is to monitor reachability of key remote services.
Another is looking at total traffic, which will be much lower than usual in the presence of a black hole. Once detected, recovering from routing black hole affecting one ISP/peer is very SIMPLE: shut down the BGP session towards that provider until they’ve fixed the problem.
Alternatively you can automate the process of selecting the best performing transit provider or peer by deploying a route optimizer which evaluates all ISPs, IXes, and partial peers in terms of packet loss and latency and automatically reroutes traffic through the most reliable path.
So, BGP can be fast if correctly configured and optimized.
Dgitsss
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Considering the recent changes done in few minutes as you mention, It actually while working with the ISPs, it depends on how large their network is and based on their topologies they have to make a decision based on the AS. The larger the AS the more time it will take. By larger, I meant the hops and advertisements and network Segments. While working on Simulation environment it takes around 30seconds. But the production network is different.
Keyur
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But it's not as fast as EIGRP or OSPF. Though, OSPF / EIGRP are not recommended for external production environment. – Keyur Dec 06 '16 at 00:43
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In general it is about the definition of "fast".
Compared to IGPs, BGP is really slow.
Inside a production network where you may need subsecond reconvergence of your network, that is very fast compared to some minutes (iBGP is not discussed here, because this can be highly optimized (IGPs/BFD/Timers).
eBGP can't because you lose control at the border of your AS). Your delay gets bigger with every hop (maybe the next provider) your route has to be propagated. You might have seen your change after minutes, but that does not mean, that this change was propagated around the globe.
You can check the changes here with some kind of history:
