  The goal of Byzantine Broadcast (BB) is to allow a set of fault-free nodes to
agree on information that a source node wants to broadcast to them, in the
presence of Byzantine faulty nodes. We consider design of efficient algorithms
for BB in {\em synchronous} point-to-point networks, where the rate of
transmission over each communication link is limited by its "link capacity".
The throughput of a particular BB algorithm is defined as the average number of
bits that can be reliably broadcast to all fault-free nodes per unit time using
the algorithm without violating the link capacity constraints. The {\em
capacity} of BB in a given network is then defined as the supremum of all
achievable BB throughputs in the given network, over all possible BB
algorithms.
  We develop NAB -- a Network-Aware Byzantine broadcast algorithm -- for
arbitrary point-to-point networks consisting of $n$ nodes, wherein the number
of faulty nodes is at most $f$, $f<n/3$, and the network connectivity is at
least $2f+1$. We also prove an upper bound on the capacity of Byzantine
broadcast, and conclude that NAB can achieve throughput at least 1/3 of the
capacity. When the network satisfies an additional condition, NAB can achieve
throughput at least 1/2 of the capacity.
  To the best of our knowledge, NAB is the first algorithm that can achieve a
constant fraction of capacity of Byzantine Broadcast (BB) in arbitrary
point-to-point networks.
