add overview of MVFST and other info in README

Summary: Adds more info on README

Reviewed By: siyengar

Differential Revision: D15145263

fbshipit-source-id: 93fa6cb37250a08fd78577013d9eb9d20d74430b

README.md

@@ -1,6 +1,45 @@
 
+![alt text](logo.png "MVFST")
+
+## Introduction
+`mvfst` is a client and server implementation of [IETF QUIC](https://tools.ietf.org/html/draft-ietf-quic-transport-20) protocol in C++ by Facebook. QUIC is a UDP based reliable, multiplexed transport protocol that will become an internet standard. The goal of `mvfst` is to build a performant implementation of the QUIC transport protocol that applications could adapt for use cases on both the internet and the data-center. `mvfst` has been tested at scale on android, iOS apps, as well as servers and has several features to support large scale deployments.
+
+## Features
+**Server features**:
+- Multi-threaded UDP socket server with a thread local architecture to be able to scale to multi-core servers
+- Customizable Connection-Id routing. The default Connection-Id routing implementation integrates seamlessly with [katran](https://github.com/facebookincubator/katran)
+- APIs to enable zero-downtime restarts of servers, so that applications do not have to drop connections when restarting.
+- APIs to expose transport and server statistics for debuggability
+- Zero-Rtt connection establishment and customizable zero rtt path validation
+- Support for UDP Generic segmentation offloading (GSO) for faster UDP writes.
+
+**Client features**:
+- Native happy eyeballs support between ipv4 and ipv6 so that applications do not need to implement it themselves
+- Pluggable congestion control and support for turning off congestion control to plug in application specific control algorithms
+- QUIC trace APIs to retrieve deep transport level stats.
+
+## Source Layout
+- `quic/api`:         Defines API that applications can use to interact with the QUIC transport  layer.
+- `quic/client`:      Client transport implementation
+- `quic/server`:      Server transport implementation
+- `quic/codec`:       Read and write codec implementation for the protocol
+- `quic/common`:      Implementation of common utility functions
+- `quic/congestion_control`: Implementation of different congestion control algorithms such  as Cubic and Copa
+- `quic/flowcontrol`: Implementations of flowcontrol functions
+- `quic/handshake`:   Implementations cryptographic handshake layer
+- `quic/loss`:        Implementations of different loss recovery algotithms
+- `quic/logging`:     Implementation of logging framework
+- `quic/happyeyeballs`: Implementation of mechanism to race IPV4 and IPV6 connection and pick a winner
+- `quic/state`:       Defines and implements both connection and stream level state artifacts and state machines
+- `quic/tools`:       Implementation of tools such as one to trace transport events within a connection
+- `quic/sample`:      Example client and server
+
 
-## Building
+## Dependencies
+
+`mvfst` largely depends on two libraries: [folly](https://www.github.com/facebook/folly) and [fizz](https://www.github.com/facebookincubator/fizz).
+
+## Building mvfst
 
 ### Ubuntu 16+
 
@@ -47,7 +86,6 @@ built libraries and binaries for `mvfst`.
 You can also install `mvfst` as well as its dependencies `folly` and `fizz`
 to a custom directory using the build script, by supplying an `INSTALL_PREFIX`
 env var.
-
 ```
 ./build_helper.sh -i /usr/local
 ```
@@ -55,19 +93,34 @@ See `./build_helper.sh --help` for more options
 
 You might need to run the script as root to install to certain directories.
 
+By default the build script `build_helper.sh` enables the building of test target (i.e. runs with `-DBUILD_TEST=ON` option). Since some of tests in `mvfst` require some test artifacts of Fizz, it is necessary to supply the path of the Fizz src directory (via option `DFIZZ_PROJECT`) to correctly build all test targets in `mvfst`.
+
+## Run a sample client and server
+Building the test targets of `mvfst` (or via `build_helper.sh`) should automatically build the sample client and server binaries as well. You can then spin a simple echo server by running:
+```
+./quic/samples/echo -mode=server -host=<ip> -port=<port>
+```
+and to run a client:
+```
+./quic/samples/echo -mode=client  -host=<ip> -port=<port>
+```
+For more options, see
+```
+./quic/samples/echo --help
+```
 ## Contributing
 
-We'd love to have your help in making MVFST better. If you're interested, please
+We'd love to have your help in making `mvfst` better. If you're interested, please
 read our guide to [guide to contributing](CONTRIBUTING.md)
 
 ## License
-MVFST is MIT licensed, as found in the LICENSE file.
+`mvfst` is MIT licensed, as found in the LICENSE file.
 
 ## Reporting and Fixing Security Issues
 
 Please do not open GitHub issues or pull requests - this makes the problem
 immediately visible to everyone, including malicious actors. Security issues in
-MVFST can be safely reported via Facebook's Whitehat Bug Bounty program:
+`mvfst` can be safely reported via Facebook's Whitehat Bug Bounty program:
 
 https://www.facebook.com/whitehat