changing routes while packets are still moving
i’ve been thinking more about what it actually takes to change a running network. choosing a better route is one problem. getting traffic onto that new route, while the network is still carrying packets is whole different ball game. i hadn’t given that second part much thought until lately. my first instinct was pretty straightforward: calculate the new routes, check that they work, and push the forwarding rules to the switches. this instinct was without consideration that the switches probably won’t all apply those rules at the same time, and while they’re updating, packets are still moving between them. ...