Apple Inc. is assembling a high-speed network and upgrading how it builds data centers, a push to be more competitive with Amazon.com Inc., Google Inc. and Microsoft Corp. in cloud services, people familiar with the plans said. Up to now, Apple has relied mostly on traditional network providers and technology suppliers to support consumer services such as iTunes for music and movies, iCloud for storing photos and other content and the Siri voice-activated assistant. Apple will stick with most of its existing vendors, and is mainly seeking to bolster its current infrastructure.