Add example to readme

README.md

@@ -143,6 +143,42 @@ fn main() -> Result<(), NetworkError> {
 }
 ```
 
+This library contains networks from [TopologyZoo](http://www.topology-zoo.org) and convenient builder functions to quickly generate random configurations.
+Notice, that this requires the features `topology_zoo` and `rand`.
+
+```rust
+use bgpsim::prelude::*;
+use bgpsim::builder::*;
+
+type Prefix = SimplePrefix;           // Use non-overlapping prefixes.
+type Queue = BasicEventQueue<Prefix>; // Use a basic FIFO event queue
+type Ospf = GlobalOspf;               // Use global OSPF without message passing
+type Net = Network<Prefix, Queue, Ospf>;
+
+# #[cfg(feature = "topology_zoo, rand")]
+fn main() -> Result<(), NetworkError> {
+
+    // create the Abilene network
+    let mut net: Net = TopologyZoo::Abilene.build(Queue::new());
+    // Create 5 random external routers
+    net.build_external_routers(extend_to_k_external_routers, 5)?;
+    // Assign random link weights between 10 and 100.
+    net.build_link_weights(random_link_weight, (10.0, 100.0))?;
+    // Generate an iBGP full-mesh topology.
+    net.build_ibgp_full_mesh()?;
+    // Generate all eBGP sessions
+    net.build_ebgp_sessions()?;
+    // Generate route-maps to implement Gao-Rexford routing policies, with probability 20% that
+    // an external network will be treated as a customer, 30% that it will be treated as peer,
+    // and 50% that it will be a provider.
+    let _peer_types = net.build_gao_rexford_policies(GaoRexfordPeerType::random, (0.2, 0.3))?;
+
+    Ok(())
+}
+# #[cfg(not(feature = "topology_zoo, rand"))]
+# fn main() {}
+```
+
 ## Disclaimer
 
 This library is a research project.