The Proof of Service (PoSe) scoring system helps incentivize masternodes to provide network services. Masternodes that neglect to participate receive an increased PoSe score which eventually results in them being excluded from masternode payment eligibility.

Distributed Key Generation Participation Requirements

The following table lists the aspects of the DKG process a masternode must comply with to avoid receiving a PoSe score increase:

Protocol Version	Proof of Service Requirement
70213+	Exchange required messages (quorum contributions and quorum justifications) with other quorum members during the LLMQ DKG process (Dash Core 0.13.0+)
70218+	Have an open P2P port (Dash Core 0.16.0+). Enforcement of this requirement is dependent on Spork 23 being enabled
70218+	Have a protocol version => `MIN_MASTERNODE_PROTO_VERSION`. During updates where this version is increased, masternodes will begin receiving PoSe score increases once > 80% of masternodes have upgrade (Dash Core 0.16.0+). Enforcement of this requirement is dependent on Spork 23 being enabled

Proof of Service Score Weighting

The current PoSe scoring system is based only on participation in the LLMQ DKG process. This scoring system will expand over time to incorporate additional service requirements in support of the future Dash functionality.

Service	Percent of Score	Requirement
LLMQ DKG	100%	Participate in the DKG process used to establish LLMQs. Requires exchanging messages with other quorum members

PoSe Score Calculation

As shown in the following table, the PoSe Score always decreases by 1 per block as long as a masternode has not been banned. Once banned, the masternode can only be restored by sending a Provider Update Service (ProUpServTx) special transaction.

PoSe Parameter	Value	Example Value
Maximum PoSe Score	Number of registered masternodes	5000
PoSe Score Increases	Maximum PoSe Score * 2/3	3333
PoSe Score Decreases	1 (per block)	Always `1`

The current PoSe scoring algorithm increases the PoSe score by 66% of the maximum score for each failed DKG session. Depending on timing, this allows for no more than 2 failures for a masternode within a payment cycle (i.e a number of blocks equal to the number of registered masternodes).

For example, using the values from above with 5000 masternodes:

In the first 5000 block cycle, two DKG failures occur without the PoSe score exceeding the maximum. This happens since a sufficient number of blocks are mined prior to the second failure to drop the PoSe score below the threshold (< 5000 - 3333) that would result in banning.
In the second 5000 block cycle, the second DKG failure occurs too close to the first and results in the PoSe score exceeding the maximum limit. This results in the masternode receiving a PoSe Ban.

Payment Cycle	Block Number	Event	Score Change	PoSe Score	MN Status
1	1	DKG Failure (1)	+3333	3333	Valid
1	1734	1733 Blocks Mined	-1733	1600	Valid
1	1734	DKG Failure (2)	+3333	4933	Valid
1	5000	3266 Blocks Mined	-3266	1667	Valid
		End of Payment Cycle 1
2	5500	500 Blocks Mined	-500	1167	Valid
2	5500	DKG Failure (3)	+3333	4500	Valid
2	7000	1500 Blocks Mined	-1500	3000	Valid
2	7000	DKG Failure (4)	+3333	6333	PoSe Banned
2	10000	End of Payment Cycle 2	-	6333	PoSe Banned