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Your comment, to me, only points out that the OSI layer model is nonsense. Envoy in DSR mode routes traffic based on application features, at "layer 7".
by jeffbee 1y ago
Your comment, to me, only points out that the OSI layer model is nonsense. Envoy in DSR mode routes traffic based on application features, at "layer 7".
- nyrikki 1y agoEnvoy calls it Layer 4 https://blog.envoyproxy.io/introduction-to-modern-network-load-balancing-and-proxying-a57f6ff80236 https://blog.envoyproxy.io/introduction-to-modern-network-lo...
- jeffbee 1y agoThat's fair. Of course that post also calls the OSI model "unfortunate" and "a poor approximation".
- nyrikki 1y agoAll models are wrong, some are useful. Layer 4 to 7 is useful in this case, as layer 4 involves forging tcp/udp packets, which is vastly different than say a http level reverse proxy.
- thequux 1y agoIf you actually read ITU T-REC X.200, which specifies the OSI model, you'll find that it doesn't match the modern internet at all. E.g., we don't have an OSI-style transport protocol at all (connections themselves aren't addressable independent of the SSAPs), TCP and UDP are actually layer 5, the presentation layer is protocol-specific, and pretty much the entire stack falls to bits if the network layer isn't packet switched. There's a separate term for the bits of the OSI model that are actually relevant; it's called the IETF model.
- philwelch 1y agoThe model itself isn’t nonsense because it’s not a model of load balancers; it’s a model of network protocols. Load balancers might handle multiple levels of the stack for the same traffic, but so does any other networked program, eg handling cross-domain redirects.