How Feasible Is It To Transmit Full Game Replays For Server Validation?

The Storage Challenge

Storing full game replay data on servers requires large investments in storage infrastructure. Replays capture entire game sessions, often lasting hours for complex strategy games, resulting in file sizes ranging from gigabytes to terabytes depending on length and data density. Approximately 5 terabytes of storage would be needed for 1 million 60-minute replays encoded in a highly compressed format at 5 megabits per second, for example. Scaling up to support the player bases of the world’s most popular competitive games with tens of millions of daily users would require petabytes of replay data storage capacity. The associated costs for storage servers and high-bandwidth networks make this prohibitive for most game developers.

Infrastructure Investments

Game developers transmitting full, uncompressed replays would need to invest heavily in specialized storage infrastructure to accommodate capacity demands. This includes high-density storage servers with petabytes of magnetic hard drive capacity or flash solid state drive arrays coupled with networked storage solutions and backup systems. Supporting personnel is also required for hardware maintenance and software configuration. These substantial financial investments put comprehensive replay analysis out of reach for smaller game studios.

Ongoing Operating Expenses

In addition to infrastructure costs, high operating expenses would be incurred for electricity to power servers, network bandwidth to transmit replays, data center real estate, cooling systems, and personnel to keep systems functioning 24/7. These ongoing costs accumulate rapidly with petabytes of replay data from millions of players. Cost reduction strategies are necessary to make feasible the server-side validation that developers seek to implement.

Strategies to Reduce Replay Size

There are several techniques developers can leverage to limit the size of replay files for efficient transmission and storage. By reducing the bandwidth and storage capacity required per replay, game studios can feasibly scale replay analysis to their player base within budget limitations.

Input Logging

Instead of encoding full game simulation data at high precision, replays can solely consist of player input logs and timestamped markers for game events. This input-centric replay format omits unnecessary rendering and positional data while preserving information essential for misuse detection. Input logs paired with timing data enable accurate replay simulations.

Delta Encoding

Delta encoding is an efficient technique that tracks changes between consecutive game states rather than logging full data captures every frame. For example, instead of continually sending positional coordinates for entities that have not moved, delta encoding would transmit the location only once combined with a marker indicating no change for subsequent frames. This significantly reduces unnecessary data.

Compression Algorithms

Applying lossless compression algorithms to replay files can make their transmission and storage more practical. Standard compression libraries reduce file sizes by 40-70% with no data loss. When coupled with efficient encodings tailored to game data like input logs, compression ratios over 90% are achievable. For example, a 2 GB replay could be compressed to 200 MB for easier server processing.

Validating Game Results From Replays

In addition to replay size optimizations, server-side verification procedures ensure that uploaded replays have not been tampered with and accurately represent genuine game results. Cryptographic safeguards and state replicate engines help preserve competitive integrity.

Cryptographic Hashing

All replay files can be fingerprinted with secure cryptographic hashes like SHA-256 fingerprints. A hash uniquely identifies data contents, enabling tamper-proof validation. Altered replay inputs would completely change hashes, allowing illegitimate modifications to be instantly detected before further processing. Fixed salts included during hashing increase security.

Server Replay Engines

Secure server-based replay engines replicate game logic to reproduce sessions from replay inputs. By rerunning matches in a controlled environment, discrepancies between clients can be identified to isolate manipulations. State replication engines tuned to precision timing parameters verify gameplay accuracy.

Handling Divergent Timelines

Margin of error checks should be incorporated in replay analysis to account for minor timeline divergences arising from latency variability or floating point differences that do not meaningfully impact game outcomes. Small state deviations up to certain validated thresholds can be programmatically disregarded to focus solely on significant replay alterations.

When Server Replication is Necessary

While efficient encoding, compression, and hashing strategies enable feasible transmission of massive replay datasets, server-side game state replication is still required in certain situations. When cheating vulnerabilities directly tied to game client authority cannot be fully safeguarded through other protections, server replication is the most robust solution.

Protection Against Client Hacks

Game clients handle much of the real-time simulation calculations, leaving the client vulnerable to hacked modifications granting unfair advantages through techniques like maphacking and fog-of-war reveal cheats. By authoritatively replaying sessions server-side, the results of tampering can be detected and invalidated after the fact through comparative analysis even if hooks to block cheats are not possible.

Anomaly Detection

Statistical analysis models can identify anomalous trends in player performance metrics that indicate cheating is occurring. While metrics alone do not prove cheating, significant deviations from expected distributions warrant further investigation through reconstructed replay analysis. Reference datasets of player inputs help verify normal human capabilities.

Professional Competitions

Maintaining competitive integrity around professional esports requires the highest degree of cheat prevention and validation capabilities. Server-side replication of tournament game sessions allows referees to definitively answer accusations around cheating by reviewing a certified authoritative reference replay not subject to tampering.