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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
+------------------------------------
+
+.. figure:: /_images/VPP_Layering.png
+   :alt: image
+
+   image
+
+-  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.