When we have to do maintenance on the network or an uplink, we try to do this with the smallest possible impact. Sometimes that means that we have to shut down a BGP session before the maintenance. This should not be a problem; routers will automatically find another route to reach other networks, but it still can mean that there is temporary packet loss. So what if we could let the Internet know that there is maintenance coming up? Well, we now can. And we will!
My colleague Sven recently visited the RIPE meeting in Dubai – there are worse places to attend a conference, right? One of the main things that was talked about, was standardizing a new BGP community feature called Graceful Shutdown. The idea of this is to let routers know in advance that a particular BGP session will be down soon, so the routers can already start rerouting the traffic.
Border Gateway Protocol
Border Gateway Protocol, or BGP, is the protocol used for routing traffic between different ISPs. A BGP session between a client’s network and ours, lets the routers on both sides know that they can reach each other, as well as which traffic they can route across the link. Depending on the needs, it is the internal routing of the client that chooses the best way to connect to us. If we are doing maintenance on an uplink, that BGP session is ‘shut down’ and the customer’s internal routing protocol will have to find another way to reach us. Especially for less sophisticated technologies it means it can take some time to set up a connection, which can lead to packet loss.
So what if we were to warn you that a BGP session will shut down, before it actually closes? It gives your internal routing protocol a chance to make the necessary arrangements to reroute the traffic in advance.
That is why we and other major ISP’s like GTT and NTT, will implement the BGP community ‘Graceful Shutdown’ feature in our systems. This feature reduces or eliminates the loss of inbound or outbound traffic flows that were initially forwarded along the peering link that is being shut down for maintenance. It also allows a graceful shutdown mechanism that does not require any router reconfiguration at maintenance time. The benefits of the BGP Graceful Shutdown feature are: fewer lost packets and less time spent reconfiguring devices. This way we ‘warn’ you when their will be maintenance so that your routing is prepared.
It is like the slogan the government uses for drivers when there are roadworks: Plan your journey in advance, so that you can get ‘from A to Better’.