1Network fundamentals and TCP/IP basics

• 1.1The OSI reference model and TCP/IP layers

  Covers the correspondence between the OSI reference model, which divides communication into seven roles, and the four-layer TCP/IP model used in practice; encapsulation, which wraps upper-layer data in lower-layer headers, and the PDU (frame/packet/segment) at each layer; and the judgment skill of isolating which layer—L2/L3/L4/L7—a given communication failure belongs to.

• 1.2LANs, Ethernet, and switching

  Covers Ethernet standards and CSMA/CD, full-duplex communication, the 48-bit MAC address, an L2 switch's MAC address learning and flooding, choosing devices that separate collision domains and broadcast domains, and the judgment skill of deciding whether to use a hub, an L2 switch, or an L3 switch.

• 1.3IP addressing and subnet design

  Covers the structure of IPv4 addresses and the classful concept, CIDR notation and the subnet mask, VLSM, which splits address space into variable-length blocks sized to the required host count, private addresses that must not leak externally, and the judgment skill of designing network segments while manually verifying subnet calculations.

• 1.4IPv6 and address resolution

  Covers 128-bit IPv6 address notation and global unicast addresses/link-local addresses, ARP, which resolves MAC addresses for IPv4, and its IPv6 counterpart NDP, dual stack, which runs IPv4 and IPv6 side by side, and the judgment skill of deciding how to respond to IPv4 address exhaustion.

• 1.5Data transmission and the physical layer

  Covers transmission coding, which puts digital signals onto an analog transmission medium, multiplexing (TDM/FDM/WDM), which consolidates multiple communications onto a single line, error control for handling transmission errors, the difference between full duplex and half duplex, and the relationship between bandwidth and effective transmission speed.