Interconnecting ISP networks

The Internet is rife with paradox. For example, new optical switches capable of forwarding terabits of data (in photonic format) must work with a decades-old protocol suite first developed for software-controlled electronic packet switches. Another example is that while IP multicast offers by far the most efficient delivery vehicle for large-scale multiparty communications, few service providers deploy it, choosing instead to consume bandwidth and host resources with multiple point-to-point connections. One of the most interesting Internet-related paradoxes is the relationship between Internet service providers. While competing very publicly for customers using price, value-add services, and performance as leverage, they must privately cooperate among themselves to provide global connectivity. Indeed, without this cooperation each ISP network might devolve into its own separate world with few or none of the global Internet's benefits. Fortunately, this is not the case; in fact, the Internet is a network of networks-a mesh of separately controlled, interconnected networks that form one large, global entity.