diff --git a/src/handler/mod.rs b/src/handler/mod.rs
index 625582402..52a47a8a9 100644
--- a/src/handler/mod.rs
+++ b/src/handler/mod.rs
@@ -471,7 +471,7 @@ impl Handler {
             trace!("Request queued for node: {}", node_address);
             self.pending_requests
                 .entry(node_address)
-                .or_insert_with(Vec::new)
+                .or_default()
                 .push(PendingRequest {
                     contact,
                     request_id,
diff --git a/src/handler/request_call.rs b/src/handler/request_call.rs
index b91c7643e..42506aa76 100644
--- a/src/handler/request_call.rs
+++ b/src/handler/request_call.rs
@@ -1,4 +1,4 @@
-pub use crate::node_info::{NodeAddress, NodeContact};
+pub use crate::node_info::NodeContact;
 use crate::{
     packet::Packet,
     rpc::{Request, RequestBody},
diff --git a/src/ipmode.rs b/src/ipmode.rs
index de66fd195..f2dbe48da 100644
--- a/src/ipmode.rs
+++ b/src/ipmode.rs
@@ -69,6 +69,17 @@ impl IpMode {
     }
 }
 
+/// Copied from the standard library. See <https://github.com/rust-lang/rust/issues/27709>
+/// The current code is behind the `ip` feature.
+pub const fn to_ipv4_mapped(ip: &std::net::Ipv6Addr) -> Option<std::net::Ipv4Addr> {
+    match ip.octets() {
+        [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xff, 0xff, a, b, c, d] => {
+            Some(std::net::Ipv4Addr::new(a, b, c, d))
+        }
+        _ => None,
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -230,14 +241,3 @@ mod tests {
             .test();
     }
 }
-
-/// Copied from the standard library. See <https://github.com/rust-lang/rust/issues/27709>
-/// The current code is behind the `ip` feature.
-pub const fn to_ipv4_mapped(ip: &std::net::Ipv6Addr) -> Option<std::net::Ipv4Addr> {
-    match ip.octets() {
-        [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xff, 0xff, a, b, c, d] => {
-            Some(std::net::Ipv4Addr::new(a, b, c, d))
-        }
-        _ => None,
-    }
-}
diff --git a/src/kbucket/entry.rs b/src/kbucket/entry.rs
index 1e0304048..97be95de1 100644
--- a/src/kbucket/entry.rs
+++ b/src/kbucket/entry.rs
@@ -25,9 +25,7 @@
 //! representing the nodes participating in the Kademlia DHT.
 
 pub use super::{
-    bucket::{
-        AppliedPending, ConnectionState, InsertResult, Node, NodeStatus, MAX_NODES_PER_BUCKET,
-    },
+    bucket::{AppliedPending, ConnectionState, InsertResult, Node, NodeStatus},
     key::*,
     ConnectionDirection,
 };
diff --git a/src/packet/mod.rs b/src/packet/mod.rs
index f071263bd..ef7ad63c0 100644
--- a/src/packet/mod.rs
+++ b/src/packet/mod.rs
@@ -29,16 +29,25 @@ pub const MESSAGE_NONCE_LENGTH: usize = 12;
 /// The Id nonce length (in bytes).
 pub const ID_NONCE_LENGTH: usize = 16;
 
+pub struct Nat;
+
+impl ProtocolIdentity<3> for Nat {
+    const PROTOCOL_ID_BYTES: [u8; 6] = *b"discv5";
+    const PROTOCOL_VERSION_BYTES: [u8; 2] = 0x0001_u16.to_be_bytes();
+    const IMPLEMENTATION_FEATURES: [u8; 3] = *b"nat";
+}
 pub struct DefaultProtocolId {}
 
 impl ProtocolIdentity for DefaultProtocolId {
     const PROTOCOL_ID_BYTES: [u8; 6] = *b"discv5";
     const PROTOCOL_VERSION_BYTES: [u8; 2] = 0x0001_u16.to_be_bytes();
+    const IMPLEMENTATION_FEATURES: [u8; 0] = *b"";
 }
 
-pub trait ProtocolIdentity {
+pub trait ProtocolIdentity<const N: usize = 0>: Sync + Send {
     const PROTOCOL_ID_BYTES: [u8; 6];
     const PROTOCOL_VERSION_BYTES: [u8; 2];
+    const IMPLEMENTATION_FEATURES: [u8; N];
 }
 
 pub(crate) const MAX_PACKET_SIZE: usize = 1280;
diff --git a/src/service/test.rs b/src/service/test.rs
index b2860700e..d02f8394c 100644
--- a/src/service/test.rs
+++ b/src/service/test.rs
@@ -173,7 +173,7 @@ async fn test_connection_direction_on_inject_session_established() {
     let ip = std::net::Ipv4Addr::LOCALHOST;
     let enr = EnrBuilder::new("v4")
         .ip4(ip)
-        .udp4(10001)
+        .udp4(10003)
         .build(&enr_key1)
         .unwrap();
 
@@ -181,7 +181,7 @@ async fn test_connection_direction_on_inject_session_established() {
     let ip2 = std::net::Ipv4Addr::LOCALHOST;
     let enr2 = EnrBuilder::new("v4")
         .ip4(ip2)
-        .udp4(10002)
+        .udp4(10004)
         .build(&enr_key2)
         .unwrap();