Every change Nyx can make

Mechanism

Windows implements delayed ACK (RFC 1122): instead of acknowledging every segment it waits up to 200 ms hoping to piggyback the ACK on outgoing data or to cover a second segment. A game sends small packets continuously, so there is rarely anything to piggyback on, and the server sits waiting for an acknowledgement it could have had immediately. TcpAckFrequency=1 acknowledges every segment as it arrives.

Mechanism

Nagle's algorithm holds a small outbound segment until the previous one has been acknowledged, so it can coalesce several writes into one full-size packet. Combined with delayed ACK on the other side this produces the classic 200 ms stall. Most games set TCP_NODELAY on their own sockets, but TCPNoDelay=1 guarantees it for the interface regardless of what the application asked for.

Mechanism

When a TCP segment is lost and there is no duplicate ACK to trigger fast retransmit, the sender waits for the retransmission timeout before trying again. Windows starts that timer at 3000 ms and retries up to 5 times. For a game that is a visible freeze. Lowering the initial RTO to 2000 ms and the retry count to 3 turns a multi-second stall into a short hitch, and makes a genuinely dead connection fail fast instead of hanging.

Mechanism

RSC lets the NIC or the stack merge several incoming TCP segments into one larger buffer before handing it up, which cuts per-packet CPU cost substantially on a busy server. To merge, it has to wait for the next segment. That wait is pure added latency and, worse, it is variable — which is jitter. On a gaming desktop the CPU saving is irrelevant and the wait is not.

Mechanism

AFD is the kernel driver behind every Winsock socket. Its default send and receive windows are sized for throughput, which means data can sit in a kernel buffer while the stack decides whether more is coming. Reducing the windows to 16 KB and setting FastSendDatagramThreshold to 1500 routes anything MTU-sized or smaller — every game packet — down the fast path, and clearing IgnorePushBitOnReceives makes the stack honour the sender's PSH flag and deliver immediately.

Mechanism

Four separate things. Tcp1323Opts=1 enables RFC 1323 window scaling (needed for any throughput over a long path) while leaving timestamps off, saving 12 bytes of option space in every single segment. SackOpts=1 enables selective acknowledgement so one lost packet does not force a retransmit of everything after it. TcpTimedWaitDelay=30 releases closed sockets after 30 s instead of 240 s, and MaxUserPort=65534 widens the ephemeral range — together they stop port exhaustion on a machine that opens a lot of connections. DefaultTTL=64 is the Linux/BSD value and avoids the rare middlebox that treats 128 as suspicious.

Mechanism

When the peer does not support selective acknowledgement, Windows applies a resiliency heuristic that holds back on retransmitting to avoid flooding a path it cannot measure well. Every server a game client talks to supports SACK, so the heuristic only ever fires on a misread and when it does it lengthens recovery.

Mechanism

Windows 11 defaults to CUBIC, which is the same algorithm Linux uses and is a sensible default. Compound TCP grows the window using a delay signal as well as loss, which on some high-latency paths recovers throughput faster after a drop. Honest assessment: this changes bulk transfer behaviour far more than it changes game latency, the effect is path-dependent, and on a short low-latency route it does nothing. It is here because it is measurably useful on long international routes, and it is marked experimental because for most people it will not move a single millisecond.

Mechanism

This tweak exists to undo damage, not to add anything. Windows sizes the TCP receive window dynamically based on the measured bandwidth-delay product. A very popular piece of advice is to set autotuninglevel=disabled or highlyrestricted, which pins the window to 64 KB and caps throughput at roughly 64KB/RTT — about 5 Mbit/s on a 100 ms path. It does nothing for latency and it wrecks downloads. Nyx sets it back to `normal` and additionally disables the scaling heuristics, which can silently clamp the window based on past observations of a different network.

Mechanism

RFC 1323 timestamps let a sender measure RTT precisely and protect against wrapped sequence numbers on very fast long paths. They cost 12 bytes of TCP option space per segment. Neither property matters for a game on a consumer link, so the bytes are better spent on payload. This is small — one or two percent of header overhead, not a ping fix.

Mechanism

URO is RSC for UDP, introduced in Windows 11. The stack coalesces multiple inbound datagrams into one indication to save CPU. FiveM state sync and Minecraft Bedrock RakNet are high-rate UDP: coalescing means a datagram that arrived on time sits in a buffer waiting for a sibling that may be 5-10 ms behind it. Every datagram in the batch is then delivered late, and the delay varies with traffic rate — which is exactly the profile of jitter players describe as rubber-banding.

Mechanism

PnPCapabilities is the bitfield behind the power checkboxes on the adapter's Power Management tab. Bit 3 (value 8) disables "allow the computer to turn off this device", bit 4 (16) disables wake-on-LAN management; 24 sets both. With power management on, the adapter can be suspended during an idle moment and the resume shows up as a one-to-several-second stall — the classic "my internet drops for a second every few minutes".

Mechanism

By default a NIC waits a short interval, or until a few packets have arrived, before interrupting the CPU — one interrupt for many packets instead of one each. That saves a lot of CPU on a server pushing millions of packets per second. On a desktop receiving a few hundred game packets per second it means each packet waits for the moderation timer, typically 10-100 microseconds but driver-dependent and load-dependent. Disabling it gives the shortest, most consistent delivery path at the cost of more interrupts.

Mechanism

Nyx binary-searches the largest ICMP payload that reaches the game server with the Don't-Fragment bit set, then sets the interface MTU to that plus 28 bytes of headers. Why it matters: if your MTU is larger than some link on the path — very common on PPPoE, where the real limit is 1492, and on any VPN or tunnel — routers either fragment your packets or drop them. A fragmented packet is lost entirely if any one fragment is lost, so a 0.5% loss rate becomes a 1% stall rate. If path MTU discovery is blocked by a firewall that eats ICMP, which is common, the connection instead hangs on large packets with no error at all.

Mechanism

Ethernet flow control lets a device whose receive buffer is filling send a PAUSE frame telling the other end to stop transmitting for a period. It prevents drops — by stalling the whole link, all traffic, including the game. A dropped packet costs one retransmit; a PAUSE frame costs every packet queued behind it. Modern TCP recovers from loss far more gracefully than a game recovers from a link freeze.

Mechanism

Without RSS every received packet is processed on a single CPU, almost always CPU 0 — the same core Windows loads with timers and other driver work. When that core is busy, packets queue behind whatever it is doing, which shows up as jitter that has nothing to do with your connection. RSS hashes each flow to one of several queues and spreads them across cores. This is on by default on most hardware; Nyx sets it because a surprising number of "optimiser" scripts turn it off.

Mechanism

Antivirus suites, old VPN clients and "gaming network" utilities install Layered Service Providers that sit in the Winsock chain and see every packet. A dead or buggy one adds latency to every socket operation and is a classic cause of unexplained lag that survives every other tweak. This re-registers the catalog in its default order.

Mechanism

IEEE 802.3az puts the physical layer into Low Power Idle whenever the link is quiet, and wakes it when a packet needs to move. Wake-up takes tens of microseconds, and because game traffic is bursty the PHY sleeps constantly — so a large share of packets pay the wake penalty. The variance is the problem more than the absolute cost. Realtek, Intel and Killer each spell the keyword differently, so Nyx writes all the known variants and skips the ones the driver does not expose.

Mechanism

The receive and transmit rings are the small arrays of descriptors the NIC uses to hand packets to the driver. If a burst arrives while the CPU is briefly busy and the ring is full, those packets are dropped at the hardware — invisible to any software counter you would normally look at. Raising the rings to 512 gives roughly four times the headroom. This is a trade: a deeper queue means a packet at the back waits longer, so Nyx uses 512 rather than the maximum.

Mechanism

A jumbo frame is larger than the 1500-byte Ethernet MTU. It helps only if every device on the path supports it, which no path to a game server does. If it is enabled locally, oversized packets either get fragmented — doubling the chance that a single loss destroys the whole payload — or silently dropped by the first hop that will not forward them.

Mechanism

LSO lets the stack hand the NIC a buffer far larger than one packet and have the hardware split it. It cuts CPU on uploads. The side effect is that your game packet can end up queued behind a 64 KB burst the NIC is still segmenting — a few milliseconds of head-of-line blocking on the transmit path, which matters while you are also uploading anything.

Mechanism

Computing a TCP/UDP checksum in software costs CPU cycles on the critical path of every packet. Every NIC made this century does it in hardware at zero latency cost. Disabling checksum offload is near the top of every bad tweak list and it is strictly worse — more CPU, no benefit. Nyx sets the keywords back to 3 (RX and TX enabled).

Mechanism

NetBIOS name resolution broadcasts to the whole subnet whenever a name cannot be resolved by DNS, and answers everyone else's broadcasts too. Nothing a game does needs it. Setting NetbiosOptions=2 per interface turns it off and removes that chatter, which matters most on Wi-Fi where every broadcast is sent at the lowest common data rate and occupies the air for everybody.

Mechanism

Most game servers are IPv4-only. When IPv6 is preferred, Windows tries an IPv6 route first and falls back after a timeout, which adds dead time to connect and reconnect. DisabledComponents=0x20 changes only the prefix policy so IPv4 is tried first — IPv6 stays fully functional. Nyx deliberately does not use 0xFF (disable IPv6 entirely), which breaks Xbox networking, Teredo, some Discord voice paths and an increasing number of CGNAT setups.

Mechanism

Creates a Windows QoS policy that stamps DSCP 46 (Expedited Forwarding) on outbound packets for the selected game's ports and gives them throughput priority in the local scheduler. Honest limits: the local scheduling part always works, so a game packet jumps the queue ahead of a Windows Update upload on your own machine. The DSCP marking only helps beyond your network if your router honours it and your ISP does not clear it — most consumer ISPs clear it at the edge. Worth doing, not magic.

Mechanism

The QoS Packet Scheduler can reserve up to 20% of link bandwidth for applications that explicitly request a reservation. Honest caveat: on a normal machine nothing requests one, so this is usually already zero in practice and you should not expect a ping change. Nyx sets NonBestEffortLimit=0 because it costs nothing and removes the question entirely — not because it is the ping fix the internet claims it is.

Mechanism

Windows caches negative DNS answers for 15 minutes by default. When a lookup fails transiently — which happens on reconnect, on Wi-Fi roaming, or when an ISP resolver hiccups — every retry for the next quarter of an hour fails instantly from cache without ever touching the network. Setting the negative TTLs to zero makes each attempt a real attempt; raising the positive cache TTL to a day keeps successful lookups local. This does not touch in-game ping: what it removes is the dead time between clicking reconnect and actually reconnecting.

Mechanism

Nyx races Cloudflare, Google, Quad9, AdGuard and your current resolver with real queries and sets the fastest pair on the active adapter. Read this part carefully, because every competitor lies about it: DNS resolves a hostname to an address before you connect. It has zero effect on your ping once you are in a game. What it does affect is how fast the FiveM server list loads, how quickly a Minecraft server address resolves when you click join, and whether a slow ISP resolver adds a second of dead time to every reconnect.

Mechanism

Not an optimisation — maintenance. Clears stale entries that can point you at a dead server address or an old gateway MAC. Nyx runs this after any DNS or MTU change so the next connection starts clean. Nothing to undo.

Mechanism

When any process registers a multimedia thread with MMCSS — which includes most games, Discord voice and every browser playing audio — Windows throttles non-multimedia network traffic to roughly 10 packets per millisecond so the audio path cannot be starved. It is a reasonable default for a media PC and an active handicap for a game, because the game's own network traffic is not what MMCSS considers multimedia. Setting the index to 0xFFFFFFFF disables the throttle.

Mechanism

Windows' default timer tick is 15.6 ms. A thread that sleeps waiting for the next frame or the next network poll can therefore wake up to 15.6 ms late. Nyx calls NtSetTimerResolution to request 0.5 ms and holds that request for as long as it runs. There is a catch nobody mentions: since Windows 10 2004, a timer resolution request only applies to the requesting process unless the global policy is set, so the registry value here is what makes it apply to the game too.

Mechanism

SystemResponsiveness is the percentage of CPU time MMCSS guarantees to low-priority background work. The default is 20. Lowering it to 10 hands that time to foreground threads, which shortens the worst-case wait before the game thread runs after a packet arrives. Nyx uses 10 rather than 0 deliberately: at 0 the MMCSS audio threads can be starved on a loaded system, which is where the "set it to zero" advice gets people audio stutter and blames it on something else.

Mechanism

MMCSS keeps a profile per task category. The Games category controls the priority, GPU priority and scheduled I/O priority of any thread a game registers under it. The defaults are conservative. Raising Priority to 6, GPU Priority to 8 and both scheduling categories to High means the game thread gets picked sooner after an interrupt, and its I/O is not queued behind background disk work. Clock Rate 10000 asks for a 1 ms scheduling granularity for those threads.

Mechanism

Win32PrioritySeparation packs three settings into one value: quantum length, whether it is fixed or variable, and how much extra quantum a foreground thread gets. The desktop default (2) is a long, variable quantum with a 3:1 foreground ratio — tuned so a background compile does not get starved. The value 38 (0x26) selects a short variable quantum with the same 3:1 boost: threads are preempted more often, so the game thread never waits a full long quantum behind something else. The trade is more context switches.

Mechanism

On the Balanced plan Windows lowers the CPU multiplier whenever load drops, and raising it back takes tens of microseconds to a few milliseconds depending on the platform. A game loop is bursty — idle, spike, idle — so the governor is constantly guessing wrong and the spike runs at a low clock before it ramps. High performance holds the clock up. Nyx records your current plan GUID before switching so the restore puts you back exactly where you were.

Mechanism

Sets the processor's minimum performance state to 100% on AC power, so the CPU never drops below its base clock. This removes frequency ramp latency entirely rather than shortening it. It is genuinely effective and genuinely expensive: the CPU runs at full clock while you read a web page.

Mechanism

PCIe Active State Power Management lets the link between the chipset and a device drop into L0s or L1 when idle. Coming back out of L1 takes a few microseconds, and the NIC is the one device where that happens on the arrival path of every packet after a quiet moment. Setting ASPM off for the AC profile keeps the link at L0.

Mechanism

Windows suspends an idle USB device to save power. For a USB Ethernet or Wi-Fi adapter the resume adds latency to the first packet after any gap; for a mouse or keyboard it shows up as the first input after a pause being late. Turning selective suspend off on the AC profile removes both.

Mechanism

By default Windows may page out parts of the kernel and driver code that have not been touched recently. If the network driver's receive path gets paged out while you are in a menu, the next packet triggers a disk read before it can be processed. DisablePagingExecutive=1 keeps it all resident. On a machine with 16 GB this costs a few hundred megabytes of RAM you were not using anyway.

Mechanism

Delivery Optimization turns your PC into a peer that uploads Windows and Store updates to other machines on the internet. It saturates a consumer uplink with no regard for what else is running, and a saturated uplink delays your outbound game packets by however deep the modem queue is — often 100-500 ms. This is not a micro-optimisation: it is usually the single largest avoidable source of lag spikes on a Windows gaming PC. Mode 0 restricts it to direct HTTP download only.

Mechanism

Store apps keep running background tasks that poll for mail, news, weather and updates on a timer. Each one is tiny, but they fire unpredictably, and on a connection where the uplink queue is the bottleneck a handful of simultaneous requests is enough to add a visible spike.

Mechanism

The Customer Experience Improvement Program and Application Experience tasks run on a schedule, read a lot of disk and upload the result. They are small, but they fire without regard for what you are doing, and the disk activity plus the upload is enough to produce a spike. These are diagnostics only — disabling them does not affect Windows Update or security.

Mechanism

The DODownloadMode policy stops the peer-to-peer behaviour, but the service still starts and holds network state. Setting it to manual start means it only runs when Windows Update actually needs it, so nothing is listening the rest of the time.

Mechanism

While the game is running Nyx raises its priority class so the scheduler picks its threads first, and — for the process that actually owns the network thread — keeps it off CPU 0, which on most consumer boards also services the network interrupt. The result is that the thread processing a packet is not competing with the interrupt that delivered it. Nyx deliberately does not offer Realtime priority: it can starve the kernel's own threads and freeze the machine.

Mechanism

Background recording keeps an encoder running continuously so you can save the last few minutes. That encoder costs GPU time and, more importantly, inserts itself into the present path — which raises frame time variance. Frame time variance is not network latency, but it is indistinguishable from it to a player: both make your shot land late.

Mechanism

HAGS moves GPU queue management from the driver on the CPU to a dedicated processor on the GPU. On paper that removes a CPU hop from every submission. In practice the result depends on your GPU generation, driver version and game: it reliably reduces CPU overhead, and it sometimes increases frame latency because the driver loses the ability to reorder work. Nyx includes it as an experiment with a before/after measurement, not as a recommendation.

Mechanism

Windows transparently converts exclusive fullscreen into a borderless window composited by the desktop window manager, which makes alt-tab instant. That composition step adds one frame of latency and puts the DWM in your present path. Turning it off restores true exclusive fullscreen for games that ask for it, at the cost of a slower alt-tab.