Radix Mainnet (Xi’an)

Xi’an [ /ʃi’æn/ ] will be the next major release of the Radix network. Xi’an will allow an unlimited number of shard groups, enabling Radix’s sharded state model to be fully utilized.

State Model

The Radix 'universe' exists on a fixed space of 2^256 data shards, served by a distributed network of validators called Shard Groups. Shard coverage for Xi’an will be allocated according to processing power, storage and bandwidth. A fixed ledger space allows wallet addresses to be deterministically mapped to a shard and, hence, for the global state of the network to be a derived sum of shard states. With so many shards, the likelihood of two substates being mapped to the same hash (a hash collision) at 1m transactions per second (tps), has been estimated as one every 3.67^63 years. The Radix protocol assumes that 256 bits are enough to avoid "almost all" collisions in shard addresses. In the rare event of a collision, the corresponding transaction would fail and the user would simply retry, automatically resulting in different shard addresses.

A proto-implementation of Xi’an is currently being built in the Cassandra project.

Radix’s founder, Dan Hughes, has said that the first release of Xi’an might begin with 8-16 shard groups, which will be increased as the network throughput grows.

Consensus

Radix's consensus protocol is called Cerberus. It will allow an effectively unlimited number of shards to operate independently without losing atomic composability.

Validator Nodes in Xi'an

It remains unclear if every Xi'an wallet will be given the software to run a validator node. The consensus algorithm's operation is also uncertain when most nodes are powered down. Power drain and feasibility of running mobile validators are additional concerns.

Xi'an Proof of Concept

The Xi'an protocol for the Radix network is a speculative concept, aimed at increasing the number of validator sets and shard groups for better transaction processing. The number of validator sets may be double the amount required to satisfy the demand for transactions per second (TPS). Each validator set may consist of up to 3000 validators, with a minimum of 100 validators for security purposes.

The Xi'an protocol allows the number of validators in each validator set to vary between 100 and 3000 while maintaining the same number of shard groups. Only when TPS demand increases to utilize the whole 3000 validators will it be necessary to add a shard or split existing shard groups.