The legal tussle between Cisco Systems Inc. and Apple Inc. over the “iPhone” brand name could boil down to whether the products are judged dissimilar enough and competing in separate enough markets to both use Cisco’s trademarked name.

Cisco claims in its federal trademark-infringement lawsuit that Apple’s iPod-cell phone hybrid is “deceptively and confusingly similar” to the line of cordless Internet-enabled phones from its Linksys division.