As per given, TNT is the largest independent logistics company in the world (4pl). (4pl) means a forth party logistics is neutral and will manage the logistics process, regardless of what carriers, forwarders, or warehouses are used. The 4PL can and will even manage 3PLs that the customer is already currently using. Many 4PLs have addressed the huge requirements of electronic interface between numerous companies exactly as TNT logistics. The (3pl) mentioned above stands for third party logistics, and that is to involve using external organizations to execute logistics activities that have traditionally been performed within an organization itself. According to this definition, third-party logistics includes any form of outsourcing of logistics activities previously performed in house. For example, if a company with its own warehousing facilities decides to employ external transportation, this would be an example of third-party logistics. Logistics is an emerging business area in many countries. Whereas the concept of a fourth-party logistics (4PL) assembles the resources, planning capabilities, and technology of its own organization and other organizations to design, build, and run comprehensive supply chain
References: : 1- http://www.informore.com/control-tower.php 2- http://www.inboundlogistics.com/cms/article/supply-chain-control-towers-offer-a-birds-eye-view/