update: tweaks to autonat (#283)

Author: salmad3

content/concepts/nat/autonat.md

@@ -9,45 +9,78 @@ aliases:
 
 ## Background
 
-While the [identify protocol][spec_identify] lets peers inform each other about their observed network
-addresses, however, it is possible that some of these addresses are not accessible from outside the network, as the peer may be located in a private network that is behind a [NAT](overview.md) and therefore unreachable.
+While the [identify protocol](/concepts/introduction/protocols/identify)
+allows peers to inform each other about their observed network addresses,
+sometimes these addresses are inaccessible as the peer may be located in a
+private network (i.e., behind a NAT or a firewall).
 
-To prevent this problem of advertising undialable addresses, libp2p has implemented a protocol called AutoNAT, which allows nodes to determine
-whether or not they are behind a NAT.
-Furthermore, this lays the foundation for nodes to find a way to improve their connectivity to peers in public networks.
+{{< alert icon="" context="info">}}
+Advertising addresses that are not reachable is detrimental for the health of a
+P2P network, as other nodes will unsuccessfully try to dial those addresses wasting
+compute and network resources.
+{{< /alert >}}
+
+To prevent this problem of advertising and dialing unreachable addresses,
+libp2p has implemented a protocol called AutoNAT,
+which allows nodes to determine whether or not they are behind a NAT.
 
 ## What is AutoNAT?
 
-AutoNAT allows a node to request other peers to dial its presumed public addresses. If a few of these
-dial attempts are successful, the node can be reasonably ascertain that it is not behind a NAT. On the other
-hand, if a few of these dial attempts fail, it strongly indicates that a NAT is blocking incoming connections.
+AutoNAT allows a node to request other peers to dial its presumed public addresses.
+
+For private nodes located behind a NAT, it is strongly recommended:
+to:
+
+- Not advertise private addresses
+- Get a reservation with a relay to improve connectivity to public networks
+  and advertise relay addresses instead.
+
+For public nodes, it is suggested to:
 
-The AutoNAT protocol uses the protocol ID `/libp2p/autonat/1.0.0` and involves the exchange of `Dial` and
-`DialResponse` messages.
+- Start a relay to assist other nodes
+- Consider activating DHT server mode to improve connectivity to public
+  networks.
+
+If most of these dial attempts are successful, the node can be reasonably sure
+that it is not behind a NAT. On the other hand, if most of these dial attempts fail,
+it strongly indicates that a NAT is blocking incoming connections.
+
+{{< alert icon="" context="">}}
+Currently, AutoNAT cannot test individual addresses,
+but a [proposal](https://github.com/libp2p/specs/issues/503) for AutoNAT v2 aims to
+add this capability.
+{{< /alert >}}
+
+The AutoNAT protocol uses the protocol ID `/libp2p/autonat/1.0.0` and involves
+the exchange of `Dial` and `DialResponse` messages.
 
 To initiate the protocol, a node sends a `Dial` message to another peer containing
-a list of multiaddresses. The peer then attempts to dial these addresses using a different IP and peer ID
-than it uses for its regular libp2p connection. If at least one of the dials is successful, the peer sends a
-`DialResponse` message with the `ResponseStatus`: `SUCCESS` to the requesting node.
+a list of multiaddresses. The peer then attempts to dial these addresses using a
+different IP and peer ID than it uses for its regular libp2p connection.
+If at least one of the dials is successful, the peer sends a `DialResponse` message
+with the `ResponseStatus`: `SUCCESS` to the requesting node.
 
-If all dials fail, the peer sends a `DialResponse` message with the `ResponseStatus`: `E_DIAL_ERROR`.
-The requesting node can use the response from the peer to determine whether or not it is behind a NAT.
-> If the response indicates success, the node is likely not behind a NAT and does not need to use a relay
-> server to improve its connectivity. If the response indicates an error, the node is likely behind a NAT
-> and may need to use a [relay server](dcutr.md) to communicate with other nodes in the network.
+If all dials fail, the peer sends a `DialResponse` message with the `ResponseStatus`:
+`E_DIAL_ERROR`. The requesting node can use the response from the peer to determine
+whether or not it is behind a NAT.
+> If the response indicates success, the node is likely not behind a NAT and does
+> not need to use a relay server to improve its connectivity. If the response indicates
+> an error, the node is likely behind a NAT and may need to use a
+> [relay server](/concepts/autonat/dcutr) to communicate with other nodes in the network.
 
 {{< alert icon="" context="caution">}}
-To prevent [certain types of attacks](https://www.rfc-editor.org/rfc/rfc3489#section-12.1.1), libp2p implementations of AutoNAT must not dial any multiaddress that
-is not based on the IP address of the requesting node AND must not accept dial requests via relayed
-connections (because it is not possible to validate a node's IP address that arrives via a relayed connection).
+To prevent
+[certain types of attacks](https://www.rfc-editor.org/rfc/rfc3489#section-12.1.1),
+libp2p implementations of AutoNAT must not dial any multiaddress that
+is not based on the IP address of the requesting node AND must not accept dial
+requests via relayed connections (because it is not possible to validate a node's
+IP address that arrives via a relayed connection).
 
-This is to prevent amplification attacks, in which an attacker provides many clients with the same
-faked [MAPPED-ADDRESS](https://www.rfc-editor.org/rfc/rfc3489#section-11.2.1) that points to the intended target, causing all traffic to be focused on the
-target.
+This is to prevent amplification attacks, in which an attacker provides many clients
+with the same faked [MAPPED-ADDRESS](https://www.rfc-editor.org/rfc/rfc3489#section-11.2.1)
+that points to the intended target, causing all traffic to be focused on the target.
 {{< /alert >}}
 
 <!-- ADD DIAGRAM -->
 
 {{< alert icon="💡" context="note" text="See the AutoNAT <a class=\"text-muted\" href=\"https://github.com/libp2p/specs/blob/master/autonat/README.md\">technical specification</a> for more details." />}}
-
-[spec_identify]: https://github.com/libp2p/specs/tree/master/identify