In the realm of blockchain and distributed ledger technologies, congestion control has long been a pivotal concern. The continuous surge in transaction activity, coupled with the growing need for scalability and fairness, calls for innovative solutions. In response to this, IOTA 2.0 introduces a groundbreaking Congestion Control Mechanism, which is a dynamic and fair approach that revolutionizes the way transactions are processed in a permissionless system.
This article delves into the workings of IOTA 2.0’s Congestion Control Mechanism, its components, and the problems it aims to address.
Addressing Congestion in Permissionless Systems
According to the IOTA Foundation, its overhauled protocol acknowledges the inherent challenges of managing congestion in permissionless systems, particularly the unpredictability of delays and escalating fees that often plague traditional blockchains.
To tackle these issues, IOTA 2.0’s Congestion Control Mechanism endeavors to provide a solution that is fair, efficient, secure, and transparent.

Dynamic Allocation Based on Mana Holdings
IOTA 2.0 takes a unique approach to congestion control by dynamically allocating throughput to users based on their Mana holdings. Mana, a reward generated automatically by holding IOTA tokens, plays a pivotal role in this system.
Users’ Mana holdings become the key to determining how much they can transact and how quickly their transactions are processed.
Anti-Spam Mechanism with Traffic Awareness
One of the key components of IOTA 2.0’s congestion control is the Mana burn mechanism. When users create a block, they are required to specify an amount of Mana that will be deducted from their balance.
This amount is calculated objectively, taking into account block characteristics and the Reference Mana Cost, which is influenced by recent traffic activity. The said mechanism effectively acts as an anti-spam measure, preventing users from overloading the network.
If a user’s Mana balance becomes negative due to misbehavior, the protocol imposes punitive actions.
The Role of the Scheduler
The scheduler in IOTA 2.0 is responsible for deciding which block should be processed next. Instead of relying on bidding, which can lead to unpredictable auction-like systems with escalating fees, IOTA 2.0’s scheduler operates on a dynamic approach. It links each block issuer to a queue, iterating through them in a round-robin fashion.
The scheduler schedules blocks based on the issuer’s deficit, a quantity proportional to their Mana holdings. This approach ensures fairness and minimizes delays in block processing and dissemination.
Tip Selection for Enhanced Consensus
IOTA 2.0 also introduces a unique concept of “tips,” which are blocks that haven’t yet been referenced by later blocks. Nodes maintain a pool of local tips, and when a new block is created, the node randomly selects two to eight eligible tips from its pool.
These eligible tips must belong to the same slot commitment chain chosen by the node and meet specific time constraints. The act of blocks referencing other blocks is crucial for consensus, and it enhances the probability of approval and confirmation.
Final Thoughts
IOTA 2.0’s Congestion Control Mechanism is a significant departure from traditional blockchain congestion management. By leveraging Mana and implementing a dynamic allocation system, it aims to create a secure and scalable decentralized network where fairness, efficiency, and predictability reign.
With these, the new design is undoubtedly poised to reshape the landscape of distributed ledger technologies going forward.