What is the design pattern to be used to design network file downloader

I want to build network file download manager to be running in the background that support the following features:

• Download multiple files in parallel (max 20 file).
• Re-download the file when the network is disconnected and the file is not filly downloaded.

Please note for HTTP request and local caching, I will be using open source library, what I am looking for is architectural design (design pattern) that can serve building a download manager.