  Quantum mechanics is the current best description of the world as we know it.
Experiments have shown that quantum predictions are accurate up ten places of
decimal. In quantum cryptography much work has been devoted to the study of
Quantum Key Distribution (QKD). The purpose of QKD is to securely distribute
secret keys between the users in a network. As a result, several quantum
cryptographic protocols have been implemented and tested after the advent of
quantum computing. In this paper, we have given a brief overview of QKD, and
some practical networks that integrate QKD in the current Internet security
architecture. We have also discussed some aspects of quantum network security
with particular attention to Byzantine Agreement Protocol.
