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1. Message  - transaction message (...FinishRequest for 2PC, ...PrepareResponse for 1PC)
   1. it is guaranteed that it's sent after all transaction DataRecords are written into WAL on sending node.
2. Channel  - TCP communication connection from one node to another, by that the Messages is sent.
3. ChannelState  - for single channel it's a set of Messages that was sent, but not committed yet on receiver.
   1. In Ignite we can think that ChannelState is represented by active transactions in PREPARING, and greater, states.
4. IncrementalSnapshot  - on Ignite node it is represented with 2 WAL records (ConsistentCutStartRecord  commits the WAL state, ConsistentCutFinishRecord  describes the ChannelState ). It guarantees that every node in cluster includes in the snapshot:
   1. transactions committed before ConsistentCutStartRecord  and weren't included into ConsistentCutFinishRecord#after() ;
   2. transactions committed between ConsistentCutStartRecord  and ConsistentCutFinishRecord and were included into ConsistentCutFinishRecord#before() .
5. Marker  - mark that piggy backs on the Message, and notifies a node about running snapshot.

   1. After IS start and before finish all PrepareRequest , FinishRequest  are wrapper by ConsistentCutMarkerMessage  instead of regular Message . This is done to notify target node ⁣⁣via communication channel about running IS .

In terms of Ignite, there are additional definitions:

1. Consistent Cut  - Successful attempt of creating IncrementalSnapshot.
2. Inconsistent Cut  - Failed attempt of creating a IncrementalSnapshot, due to inability to correctly describe a ChannelState .

Note, ConsistentCut  can't guarantee that specific transaction that runs concurrently with the algorithm will land before or after cut, it only guarantees that set of the transactions before(or after) the cut will be the same on the each node in cluster.

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