Write readme

README.md

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-# \#lang uwu BGP Router
 
+          __ __  __
+       __/ // /_/ /___ _____  ____ _   __  ___      ____  __
+      /_  _  __/ / __ `/ __ \/ __ `/  / / / / | /| / / / / /
+     /_  _  __/ / /_/ / / / / /_/ /  / /_/ /| |/ |/ / /_/ /
+      /_//_/ /_/\__,_/_/ /_/\__, /   \__,_/ |__/|__/\__,_/
+                           /____/
+
+## High level approach
+
+The design of this "BGP" router is based on an internal radix tree structure containing the routing
+database. Routes are indexed in the tree based on the bit pattern of their subnet, and route lookup
+walks the tree to find the most specific route node corresponding to the requested destination
+address. The router itself is based on Racket's built-in I/O multiplexing to automatically manage
+I/O between multiple sockets.
+
+## Challenges
+
+ - **No existing radix tree package in Racket.**
+   Due to Racket's unfortunate lack of adoption in the networks field, nobody has written any public
+   radix tree library for Racket that we could find, so we had to implement our own. This went
+   through approximately 3 iterations and it's still mildly spaghetti code.
+ - **No stdlib `SOCK_SEQPACKET` support.**
+   There's no support for `SOCK_SEQPACKET` in the standard UNIX domain socket module, so we pulled
+   the source code for this module and added a mode for `SOCK_SEQPACKET`.
+ - **Interesting simulator dependencies.**
+   The provided simulator has a hard dependency on Python 3.6, which neither of us actually had
+   installed or were capable of installing, and it did not work with Python 3.8.
+
+## Testing
+
+For the milestone submission, we included some basic internal unit tests but there isn't a lot of
+code coverage on those yet.  We also ran the simulator milestone tests against the current router
+implementation and both milestone tests are passing.

router

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 #!/usr/bin/env racket
 #lang racket
-; vim:syntax=racket
 ; vim:ft=racket
 
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