NetworkPerformanceSystem

NetworkPerformanceSystem

Network Performance Systems is a general networking overhaul, designed to tackle the problem created by high ping.

In Valheim, most objects are simulated by users. So a single high ping user in an area can make everything or all sorts of things feel terrible. This mod aims to address that in a number of ways.

Why this is different from the other networking mods

Every other Valheim networking mod treats multiplayer performance as a bandwidth problem — compression, bigger buffers, higher send rates, filtered broadcasts. That is the right diagnosis for ten people in one base saturating a shared cap. It does not handle a larger distributed server, or multiple players from vastly different goegraphic locations.

NPS addresses these issues in a number of ways

• Each peer gets their own Round Trip timing (RTT), Healthcheck and bandwidth estimates
• This allows dynamic adjustments to route around a poor connection
• This higher ping players with decent bandwidth allow the server to send more aggressively to these players in compensation
• Object ownership can be dynamically adjusted around players with poor connections to provide the best experience for all players in the area
• Objects which need network calls to interact with get ownership transferred ahead of time, delay scenarios much less likely
• Objects that change ownership during active requests get their requests properly re-targeted against the new owner, and an item that still cannot be delivered is dropped at the station instead of lost
• Digging and other changes to the ground reach whoever owns that ground, so the ground does not split open along tile borders when nearby players own neighbouring ground
• Objects which are locally important (footsteps for example) are only network broadcast locally, instead of globally around the server
• Server Garbage collection churn is significantly reduced compared to vanilla

Installing

Server-only works. Vanilla clients get the send window, ownership, scheduler, station-request and creature-hit fixes with nothing installed on their end, and the server follows where they actually are rather than where they were two seconds ago. Picking up a dropped item, and opening chests and doors, picking berries, using item stands, beds, wards, portals, map tables and beehives, and commanding tames, reach whoever owns the object now instead of being lost on a player who owned it a moment ago, and an item is sent to the player the moment it is theirs. The server times every player's ping itself, from the game's own ping to their answer (Ping / Use In-Game Ping), so crossplay players have one too and who runs what is decided by each player's best ping rather than one inflated by a busy fight. The server also sends settled or distant creatures, fish and birds, and drifting ice, logs and dropped items in water, to each player less often, holds back building, tree and rock updates that change nothing a player can see, and sends the world's list of past players only when it has actually changed. Damage numbers go only to players close enough to see them, and Routed RPC / Damage Numbers can limit them to the player who landed the hit, or stop sending them at all. The server finds its own send rate, too: above the game's 150 KB/s per player while somebody's connection is full - in a big fight - up to Auto Send Rate Max KBps (500), and only as far as its own line has shown it can carry, shared among however many players are on (Steam Transport / Auto Send Rate).

Installing on clients too adds latency compensation, live position reporting and the clean exit from a dead session for those clients, and lets a ship they own pass to whoever takes its helm. Creatures they simulate stop re-sending themselves while standing still, which matters most next to a pen of tamed animals, and fish, birds and anything floating in water they simulate are sent a few times a second instead of every frame, which matters most by water - a Jotun invasion on a coast, or a ship in sea ice (Creature Updates / Quiet Floating Objects; anything a player stands on or is next to still goes out every frame). Their game also tells the server how smoothly it is running, so a player whose machine slows down in a big fight is given fewer creatures to run, and how much of their own upload is waiting, so the server can let them upload faster than the game's 150 KB/s while it is full (Steam Transport / Auto Player Uploads), or give them fewer creatures when that is not enough. Other players' icons on their map jump straight to where somebody went after a portal trip or a respawn, instead of sliding there for up to a minute, and players near them are shown where they are right now (Player List / Map Pins Follow Players). With the mod on the server as well, a player's new position reaches everyone as soon as their icon is 20 m out of date (Map Position Accuracy), instead of on the game's 2-second player list, and a portal trip goes out at once (Send Map Positions Right Away). Mixed groups are fine — benefits are per-player, and a client without the mod behaves exactly as vanilla. There is no version lock: nobody gets kicked for not having it.

Works on dedicated servers and on player-hosted games.

Diagnosing and Reporting a problem

An easy way to start is enabling the nps_stats display Run nps_stats_collect (needs devcommands, since sampling costs a Steam call per peer per tick), play, then nps_stats.

A player the link-pressure table marks as LOSSY is already being dealt with: the server steps that one player's send rate down until their connection stops losing packets, and back up once it is clean, without changing anyone else's rate (Steam Transport / Enable Loss Backoff). A player whose loss does not improve - once their rate is below what their connection was already carrying, or at the lowe