  Blockchain has become one of the most attractive technologies for
applications, with a large range of deployments such as production, economy, or
banking. Under the hood, Blockchain technology is a type of distributed
database that supports untrusted parties. In this paper we focus Hyperledger
Fabric, the first blockchain in the market tailored for a private environment,
allowing businesses to create a permissioned network. Hyperledger Fabric
implements a PBFT consensus in order to maintain a non forking blockchain at
the application level. We deployed this framework over an area network between
France and Germany in order to evaluate its performance when potentially large
network delays are observed. Overall we found that when network delay increases
significantly (i.e. up to 3.5 seconds at network layer between two clouds), we
observed that the blocks added to our blockchain had up to 134 seconds offset
after 100 th block from one cloud to another. Thus by delaying block
propagation, we demonstrated that Hyperledger Fabric does not provide
sufficient consistency guaranties to be deployed in critical environments. Our
work, is the fist to evidence the negative impact of network delays on a
PBFT-based blockchain.
