docs: Rewrite the what is VPP (first) section, also fix the build

Signed-off-by: John DeNisco <jdenisco@cisco.com>
Change-Id: Ifb558171f8976a721703e74afea997d006273b5f
Signed-off-by: Dave Barach <dave@barachs.net>

1 files changed, 26 insertions, 0 deletions

diff --git a/docs/whatisvpp/hoststack.rst b/docs/whatisvpp/hoststack.rst
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+.. _hoststack:
+
+==============
+TCP Host Stack
+==============
+
+VPP’s host stack leverages VPP’s graph based forwarding model and vectorized packet
+processing to ensure high throughput and scale transport protocol termination. It
+exposes apis that apart from allowing for efficient user-space app consumption and
+generation of data, also enables highly efficient local inter-app communication. 
+ 
+At a high level VPP’s host stack consists of 3 major components: 
+
+* A session layer that facilitates interaction between transport protocols and applications
+* Pluggable transport protocols, including TCP, QUIC, TLS, UDP
+* VCL (VPPComs library) a set of libraries meant to ease the consumability of the stack from application perspective
+ 
+All of these components were custom built to fit within VPP’s architecture and to
+leverage its speed. As a result, a significant amount of effort was invested into:
+
+*  building a transport pluggable session layer that abstracts the interaction between applications and transports using a custom-built shared memory infrastructure. Notably, this also allows for transport protocols that are typically implemented in applications, like QUIC and TLS, to be implemented within VPP. 
+* a clean slate TCP implementation that supports vectorized packet processing and follows VPP’s highly scalable threading model. The implementation is RFC compliant, supports a high number of high-speed TCP protocol features and it was validated using Defensic’s Codenomicon 1M+ tests suite. 
+* VCL, a library that emulates traditional asynchronous communication functions in user-space, all while allowing for new patterns to be developed, if needed. 
+* implementing a high performance “cut-through” communication mode that enables applications attached to vpp to transparently exchange data over shared memory without incurring the extra cost of a traditional transport protocol. Testing has shown this to be much more efficient than traditional inter-container networking.
+
+For developer features press next.