tokens: ['The', 'DCN', 'is', 'a', 'support', 'service', 'that', 'provides', 'the', 'capability', 'to', 'establish', 'paths', 'for', 'information', 'flow', 'between', 'physical', 'blocks', 'in', 'a', 'management', 'environment', 'The', 'DCN', 'may', 'consist', 'of', 'a', 'number', 'of', 'interconnected', 'subnetworks', 'of', 'different', 'types', 'The', 'DCN', 'may', 'be', 'a', 'local', 'path', 'or', 'a', 'widearea', 'connection', 'among', 'distributed', 'physical', 'blocks', 'The', 'DCN', 'is', 'technologyindependent', 'and', 'may', 'employ', 'any', 'single', 'or', 'combination', 'of', 'transmission', 'technologies', 'In', 'order', 'for', 'two', 'or', 'more', 'physical', 'blocks', 'to', 'exchange', 'management', 'information', 'they', 'must', 'be', 'connected', 'by', 'a', 'communications', 'path', 'and', 'each', 'element', 'must', 'support', 'the', 'same', 'interface', 'onto', 'that', 'communications', 'path', 'Physical', 'blocks', 'communicate', 'using', 'a', 'common', 'communication', 'mechanism', 'which', 'provides', 'a', 'set', 'of', 'Application', 'Programming', 'Interfaces', 'APIs', 'that', 'include', 'the', 'services', 'of', 'the', 'upper', 'three', 'protocol', 'layers', 'of', 'the', 'OSI', 'Reference', 'Model', 'Some', 'of', 'these', 'API', 'services', 'expose', 'the', 'communications', 'capabilities', 'of', 'the', 'DCN', 'and', 'others', 'expose', 'common', 'platform', 'functions', 'eg', 'Directory']