14.7 LOOKING AHEAD

This chapter focused on networking within a confined local domain—devices connected through switches, access points, and structured topologies. Yet most communication systems do not terminate within a single LAN. Enterprises interconnect multiple buildings. Service providers connect metropolitan networks. The Internet links millions of autonomous networks across the globe.

The challenge therefore shifts from networking to internetworking.

Networking concerns communication within a single broadcast or switching domain. Internetworking concerns communication between networks—potentially using different technologies, address structures, and administrative policies. This requires:

Logical addressing independent of physical location,
Routing mechanisms to determine packet paths across multiple hops,
Transport protocols to provide end-to-end reliability and flow control,
Mechanisms for fragmentation, encapsulation, and interoperability.

Where Ethernet switches forward frames based on MAC addresses within a local domain, routers forward packets based on IP addresses across multiple domains. The scope expands from Layer 2 to Layer 3 and beyond.

Chapter 15 therefore examines the principles of internetworking. We will explore IP addressing (IPv4 and IPv6), subnetting, routing algorithms, transport-layer protocols, and the architecture of the Internet itself. We will see how hierarchical addressing enables global scalability, how routing tables grow and are managed, and how end-to-end transport services provide reliability across heterogeneous paths.

If this chapter explained how devices communicate within a local fabric, the next explains how those fabrics are stitched together into a global system.

The progression now moves from local connectivity to global interconnection—from LANs to the Internet.