Today, the fundamentals of the Internet design are no longer suitable for current and future applications. Transport Control Protocol (tcp) is the main reliable transport protocol found in the Internet. tcp offers great performance while remaining fair with the other connections. tcp uses a congestion control plane based on windows mechanisms. Despite its advantages, tcp has many limitations and is not well suited to all application models. The last decade has seen the advent of large bandwidth network and heavy multimedia applications. Many electronic devices have multiple interfaces to connect to the Internet, the end-users wish to use all of them to improve the transfer speed and the tolerance to failures. However, operate in a multipath environment is not trivial and several potential issues could result from an unaware use of a reliable transport protocol. This book study, analyzes the proposed reliable transport protocols and compare them. It then performs a set of experiments on the Concurrent Multipath Transfer transport protocol in the NS-1 software simulator. These experiments have allowed us to highlight some unfair behavior with external tcp sources.