Incoming Delay buffers player actions before applying them so that actions arrive (and are applied) at all clients simultaneously.
The figure below depicts an example of incoming delay. The figure depicts downward timelines on a server and 2 clients, Client A and Client B. At time t0, player A responds to the game with an action. That action is immediately sent to the Server and then to Client B. Because of the latency for Client A to the Server and the Server to Client B, that action does not arrive at Client B until time t1. In order to have the action executed simultaneously on both clients, Client A adds a incoming delay equal to the latency from Client A to the Server plus the latency from the Server to Client B before applying the action so that Client A also applies the action at time t1. Note, while the extra delay is shown at the client in this example, it can also be used at the server. Incoming delay is called local lag by some researchers.
Christophe Diot and Laurent Gautier, 1999. A Distributed Architecture for Multiplayer Interactive Applications on the Internet
Martin Mauve, 2000. Consistency in Replicated Continuous Interactive Media
Yow-Jian Lin, Katherine Guo and Sanjoy Paul, 2002. Sync-MS: Synchronized Messaging Service for Real-Time Multi-Player Distributed Games
Martin Mauve, Jurgen Vogel, Volker Hilt and Wolfgang Effelsberg, 2004. Local-Lag and Timewarp: Providing Consistency for Replicated Continuous Applications
Jeremy Brun, Farzad Safaei, Paul Boustead, 2006. Managing Latency and Fairness in Networked Games
Yi Zhang, Ling Chen and Gencai Chen, 2006. Globally Synchronized Dead-Reckoning with Local Lag for Continuous Distributed Multiplayer Games
Dingliang Liang and Paul Boustead, 2006. Using Local Lag and Timewarp to Improve Performance for Real Life Multi-Player Online Games
Ling Chen, Gen-Cai Chen, Hong Chen, Jack March, Steve Benford and Zhi-Geng Pan, 2007. An HCI Method to Improve the Human Performance Reduced by Local-lag Mechanism
Anh Le and Yanni Ellen Liu, 2007. Fairness in Multi-Player Online Games on Deadline-Based Networks
Dane Stuckel and Carl Gutwin, 2008. The Effects of Local Lag on Tightly-Coupled Interaction in Distributed Groupware
Doowon Paik, Chung-Ha Yun and Jooyeon Hwang, 2008. Effective Message Synchronization Methods for Multiplayer Online Games with Maps
Naoki Ishii, Yutaka Ishibashi and Shinji Sugawara, 2009. Enhancement of Adaptive Delta-Causality Control with Adaptive Dead-reckoning for Multiplayer Online Games
Sili Zhao, DuLi, Hansu Gu, BinShao and NingGu, 2009. An Approach to Sharing Legacy TV/Arcade Games for Real-Time Collaboration
Cheryl Savery, T.C. Nicholas Graham and Carl Gutwin, 2010. The Human Factors of Consistency Maintenance in Multiplayer Computer Games
Yusuke Hara, Yutaka Ishibashi, Norishige Fukushima, and Shinji Sugawara, 2012. Adaptive Delta-Causality Control Scheme with Dynamic Control of Prediction Time in Networked Haptic Game
Yuji Kusunose, Yutaka Ishibashi, Norishige Fukushima, and Shinji Sugawara, 2012. Adaptive Delta-Causality Control with Prediction in Networked Real-Time Game Using Haptic Media
Cheryl Savery, T.C. Nicholas Graham, 2013. Timelines: Simplifying the Programming of Lag Compensation for the Next Generation of Networked Games
Jingxi Xu and Benjamin Wah, 2013. Concealing Network Delays in Delay-Sensitive Online Interactive Games Based on Just-Noticeable Differences
Cheryl Savery, T.C. Nicholas Graham, Carl Gutwin and Michelle Brown, 2014. The Effects of Consistency Maintenance Methods on Player Experience and Performance in Networked Games
David Aldbridge, 2011. I Shot You First: Networking the Gameplay of Halo:Reach
Glenn Fiedler, 2015. Physics for Game Programmers : Networking for Physics Programmers
Tim Ford and Philip Orwig, 2016. Developer Update - Let's Talk Netcode
Michael Stallone, 2018. 8 Frames in 16ms: Rollback Networking in 'Mortal Kombat' and 'Injustice 2'
Paul Haile and Mitch Sanborn, 2019. Call of Duty: Modern Warfare Netcode Explained!
Ricky Pusch, 2019. Explaining How Fighting Games Use Delay-Based and Rollback Netcode
Timothy Ford, 2019. Overwatch Gameplay Architecture and Netcode
Matt deWet and David Straily, 2020. Peeking into Valorant's Netcode
Shengmei Liu, Xiaokun Xu and Mark Claypool. A Survey and Taxonomy of Latency Compensation Techniques for Network Computer Games, ACM Computing Surveys, Article 243, Volume 54, Issue 11S, DOI https://doi.org/10.1145/3519023, September 9, 2022. Online at: http://www.cs.wpi.edu/~claypool/papers/lag-taxonomy/