vault backup: 2022-10-22 10:43:05

content/notes/25-advanced-topics.md

@@ -33,6 +33,37 @@ network elements
 
 application-layer routing
 - load balancer: app-layer routing
-- recieves
+- recieves external client requests
+- directs workload within data center
+- returns results to client (data center internals are hidden)
+- ![](https://i.imgur.com/Z33ZvcS.png)
+
+protocols
+- similar to TCP/IP protocols
+- link layer
+	- RoCE: remote DMA (RDMA) over converged internet
+		- direct memory access
+		- communcation between memory of different computers
+- transport layer
+	- ECN (explicit congestion notification) used in transport layer congestion control
+	- experimentation with hop-by-hop (backpressure) congestion
+- routing management
+	- SDN widely used
+	- place related servers, as close as possible together 
 
 # Software Defined networks
+- separate control plane and data plane
+	- monollithic router contains switching hardware, runs proprietary implementation of internet standard protocols in proprietary router
+	- different "middleboxes" for different network layer functions:
+		- firewalls, load balancers, NAT boxes
+
+![mainframe to pc analogy](https://i.imgur.com/S8FAfkD.png)
+
+logically centralized control plane
+- easier network management: avoid router misconfigs, greater flexibility of traggic flows
+- table based forwarding allows "programming" routers
+	- compute tables centrally and distribute
+- open implementation of control plane
+
+
+