network: Sync peerstore constants between libp2p and litep2p (#4906)

Counterpart of: https://github.com/paritytech/polkadot-sdk/pull/4031

cc @paritytech/networking

---------

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>
Co-authored-by: Sebastian Kunert <skunert49@gmail.com>

substrate/client/network/src/litep2p/peerstore.rs

@@ -42,14 +42,20 @@ use std::{
 const LOG_TARGET: &str = "sub-libp2p::peerstore";
 
 /// We don't accept nodes whose reputation is under this value.
-pub const BANNED_THRESHOLD: i32 = 82 * (i32::MIN / 100);
+pub const BANNED_THRESHOLD: i32 = 71 * (i32::MIN / 100);
 
 /// Relative decrement of a reputation value that is applied every second. I.e., for inverse
-/// decrement of 50 we decrease absolute value of the reputation by 1/50. This corresponds to a
-/// factor of `k = 0.98`. It takes ~ `ln(0.5) / ln(k)` seconds to reduce the reputation by half,
-/// or 34.3 seconds for the values above. In this setup the maximum allowed absolute value of
-/// `i32::MAX` becomes 0 in ~1100 seconds (actually less due to integer arithmetic).
-const INVERSE_DECREMENT: i32 = 50;
+/// decrement of 200 we decrease absolute value of the reputation by 1/200.
+///
+/// This corresponds to a factor of `k = 0.995`, where k = 1 - 1 / INVERSE_DECREMENT.
+///
+/// It takes ~ `ln(0.5) / ln(k)` seconds to reduce the reputation by half, or 138.63 seconds for the
+/// values above.
+///
+/// In this setup:
+/// - `i32::MAX` becomes 0 in exactly 3544 seconds, or approximately 59 minutes
+/// - `i32::MIN` escapes the banned threshold in 69 seconds
+const INVERSE_DECREMENT: i32 = 200;
 
 /// Amount of time between the moment we last updated the [`PeerStore`] entry and the moment we
 /// remove it, once the reputation value reaches 0.
@@ -362,7 +368,7 @@ mod tests {
 	#[test]
 	fn decaying_max_reputation_finally_yields_zero() {
 		const INITIAL_REPUTATION: i32 = i32::MAX;
-		const SECONDS: u64 = 1000;
+		const SECONDS: u64 = 3544;
 
 		let mut peer_info = PeerInfo::default();
 		peer_info.reputation = INITIAL_REPUTATION;
@@ -377,7 +383,7 @@ mod tests {
 	#[test]
 	fn decaying_min_reputation_finally_yields_zero() {
 		const INITIAL_REPUTATION: i32 = i32::MIN;
-		const SECONDS: u64 = 1000;
+		const SECONDS: u64 = 3544;
 
 		let mut peer_info = PeerInfo::default();
 		peer_info.reputation = INITIAL_REPUTATION;