We propose a new hybrid fault model for clock synchronization and
single-round (approximate) agreement in synchronous distributed
systems (This research has been conducted in our SynUTC-project,
see http://www.auto.tuwien.ac.at/Projects/SynUTC/, supported by the
Austrian START programme Y41-MAT.), which accurately captures both
node and link faults. Unlike conventional ``global'' fault models,
which rest upon the total number of faulty nodes in the system, it
solely relies upon the number of faults in any two non-faulty nodes'
``perceptions'' ---conveyed by the messages from all other nodes---
of the system.  This way, arbitrary node and communication faults,
including receiver-caused omission and time/value faults, can be
modeled properly. As an example (Lacking space did not allow us to
include the analysis of convergence-function-based algorithms in this
paper; consult (Schmid 2000, TR 183/1-108) for a more comprehensive
treatment.}, we show that the consistent broadcast primitive ---and
hence the clock synchronization algorithms--- of Srikanth & Toueg can be
analyzed under this model. As far as link faults are concerned, our
analysis reveals that as few as 4\ia+2\is+2\io+1 nodes are sufficient for
tolerating at most \ia, \is, and \io asymmetric, symmetric, and
omission link faults at any receiving node.

Keywords: Fault-tolerant distributed systems, fault models,
link failures, consistent broadcasting, clock synchronization.