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authorschmidt <douglascraigschmidt@users.noreply.github.com>2004-03-10 17:45:15 +0000
committerschmidt <douglascraigschmidt@users.noreply.github.com>2004-03-10 17:45:15 +0000
commit15263f460b0b69f1812195aeeb5099ddae007233 (patch)
tree73dff6c97837648ecce30da00fdcd22c2b892d76 /protocols
parentac98b3872fc737300c207bf3bc50b05f5bb2088f (diff)
downloadATCD-15263f460b0b69f1812195aeeb5099ddae007233.tar.gz
ChangeLogTag:Wed Mar 10 11:29:13 UTC 2004 Johnny Willemsen <jwillemsen@remedy.nl>
Diffstat (limited to 'protocols')
-rw-r--r--protocols/ace/TMCast/README41
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