diff options
Diffstat (limited to 'protocols')
| -rw-r--r-- | protocols/ace/TMCast/README | 41 |
1 files changed, 19 insertions, 22 deletions
diff --git a/protocols/ace/TMCast/README b/protocols/ace/TMCast/README index 43e35c52388..9e6299d8c2c 100644 --- a/protocols/ace/TMCast/README +++ b/protocols/ace/TMCast/README @@ -1,17 +1,15 @@ - - Architecture TMCast (stands for Transaction MultiCast) is an implementation of a transactional multicast protocol. In essence, the idea is to represent -each message delivery to members of a multicast group as a transaction - -an atomic, consistent and isolated action. A multicast transaction can -be viewed as an atomic transition of the group members to a new state. -If we define [Mo] as a set of operational (non-faulty) members of the -group, [Mf] as a set of faulty members of the group, [Ma] as a set of -members that view transition [Tn] as aborted and [Mc] as a set of members -that view transition [Tn] as committed, then this atomic transition [Tn] -should satisfy one of the following equations: +each message delivery to members of a multicast group as a transaction +- an atomic, consistent and isolated action. A multicast transaction +can be viewed as an atomic transition of the group members to a new +state. If we define [Mo] as a set of operational (non-faulty) members +of the group, [Mf] as a set of faulty members of the group, [Ma] as a +set of members that view transition [Tn] as aborted and [Mc] as a set +of members that view transition [Tn] as committed, then this atomic +transition [Tn] should satisfy one of the following equations: Mo(Tn-1) = Ma(T) U Mf(T) Mo(Tn-1) = Mc(T) U Mf(T) @@ -20,21 +18,20 @@ Or, in other words, after transaction T has been committed (aborted), all operational (before transaction T) members are either in the committed (aborted) or failed state. -Thus, for each member of the group, outcome of the transaction can -be commit, abort or a member failure. It is important for a member -to exhibit a failfast (error latency is less than transaction cycle) -behavior. Or, in other words, if a member transitioned into a wrong +Thus, for each member of the group, outcome of the transaction can be +commit, abort or a member failure. It is important for a member to +exhibit a failfast (error latency is less than transaction cycle) +behavior. Or, in other words, if a member transitioned into a wrong state, it is guaranteed to fail instead of delivering a wrong result. -In order to achieve such an error detection in a decentralized -environment, certain limitations were imposed. One of the most -user-visible limitation is the fact that the lifetime of the group -with only one member is very short. This is because there is not way +In order to achieve such an error detection in a decentralized +environment, certain limitations were imposed. One of the most +user-visible limitation is the fact that the lifetime of the group +with only one member is very short. This is because there is not way for a member to distinguish "no members yet" case from "my link to the -group is down". In such a situation, the member assumes the latter case. -There is also a military saying that puts it quite nicely: two is one, -one is nothing. - +group is down". In such a situation, the member assumes the latter +case. There is also a military saying that puts it quite nicely: two +is one, one is nothing. State of Implementation |