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+Software Architecture
+=====================
+
+The fd.io vpp implementation is a third-generation vector packet
+processing implementation specifically related to US Patent 7,961,636,
+as well as earlier work. Note that the Apache-2 license specifically
+grants non-exclusive patent licenses; we mention this patent as a point
+of historical interest.
+
+For performance, the vpp dataplane consists of a directed graph of
+forwarding nodes which process multiple packets per invocation. This
+schema enables a variety of micro-processor optimizations: pipelining
+and prefetching to cover dependent read latency, inherent I-cache phase
+behavior, vector instructions. Aside from hardware input and hardware
+output nodes, the entire forwarding graph is portable code.
+
+Depending on the scenario at hand, we often spin up multiple worker
+threads which process ingress-hashes packets from multiple queues using
+identical forwarding graph replicas.
+
+VPP Layers - Implementation Taxonomy
+------------------------------------
+
+![image](/_images/VPP_Layering.png)
+
+-   VPP Infra - the VPP infrastructure layer, which contains the core
+    library source code. This layer performs memory functions, works
+    with vectors and rings, performs key lookups in hash tables, and
+    works with timers for dispatching graph nodes.
+-   VLIB - the vector processing library. The vlib layer also handles
+    various application management functions: buffer, memory and graph
+    node management, maintaining and exporting counters, thread
+    management, packet tracing. Vlib implements the debug CLI (command
+    line interface).
+-   VNET - works with VPP\'s networking interface (layers 2, 3, and 4)
+    performs session and traffic management, and works with devices and
+    the data control plane.
+-   Plugins - Contains an increasingly rich set of data-plane plugins,
+    as noted in the above diagram.
+-   VPP - the container application linked against all of the above.
+
+It's important to understand each of these layers in a certain amount of
+detail. Much of the implementation is best dealt with at the API level
+and otherwise left alone.