explain inner workings

README.md

@@ -393,7 +393,35 @@ Then simply run
 This will build the weave router, produce a docker image
 `zettio/weave` and export that image to /tmp/weave.tar
 
-If you are interested in the inner workings of weave, read the
+## How does it work?
+
+Weave creates a network bridge on the host. Each container is
+connected to that bridge via a veth pair, the container side of which
+is given the IP address & netmask supplied in 'weave run'. Also
+connected to the bridge is the weave router container, which is given
+the IP address & netmask supplied in 'weave launch'.
+
+A weave router captures Ethernet packets from its bridge-connected
+interface in promiscuous mode, using 'pcap'. It forwards these packets
+over UDP to weave router peers running on other hosts. On receipt of
+such a packet, a router injects the packet on its bridge interface
+using 'pcap' and/or forwards the packet to peers.
+
+Weave routers learn which peer host a particular MAC address resides
+on. They combine this knowledge with topology information in order to
+make routing decisions and thus avoid forwarding every packet to every
+peer. The topology information captures which peers are connected to
+which other peers; weave can route packets in partially connected
+networks with changing topology.
+
+Weave routers establish TCP connections to each other, over which they
+perform a protocol handshake and subsequently exchange topology
+information. These connections are encrypted if so configured. Peers
+also establish UDP "connections", possibly encrypted, for the
+aforementioned packet forwarding. These "connections" are duplex and
+can traverse firewalls.
+
+More details on the inner workings of weave can be found in the
 [architecture documentation](docs/architecture.txt).
 
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