Chapter 2: Network devices
The chapter introduction uses offices connected over a distance to distinguish local area networks from wide area networks.
After this chapter you will be able to
- LAN and WAN distinction. Distinguish a LAN from a WAN using the offices in figure 2.1: each office is a LAN, while the connection between offices is a WAN.
- Computer network definition. Explain that a computer network connects devices so they can share resources.
- Client and server roles. Explain that a client accesses a service provided by a server, and that these are roles rather than fixed kinds of physical device. Describe how the same device can take either role depending on the exchange.
- Switch role within a LAN. Explain that a switch connects devices within a LAN so they can communicate through it, rather than typically communicating with the switch itself. Distinguish this role from providing connectivity between LANs or to external networks.
- Router role at LAN edges. Explain why a router is used at the edge of a LAN and distinguish its role from a switch's role within a LAN.
- Network firewall protection. Explain why connecting a network to the internet creates security risks and how a network firewall protects it by inspecting traffic and allowing or denying it according to configured rules.
Section by section
Introduction
The chapter introduction uses offices connected over a distance to distinguish local area networks from wide area networks.
- LAN and WAN distinction: Distinguish a LAN from a WAN using the offices in figure 2.1: each office is a LAN, while the connection between offices is a WAN.
Why it matters: This distinction helps you describe whether a network is within one location or connects distant locations.
Key terms: local area network (LAN), wide area network (WAN)
2.1 What is a network?
Defines a computer network and explains the nodes and shared resources in that definition.
- Computer network definition: Explain that a computer network connects devices so they can share resources.
Why it matters: This definition gives you a starting point for understanding what network devices connect and why. - Meaning of a node: Describe what counts as a node, including both devices people use and devices that make up the network infrastructure.
Why it matters: Recognizing both end devices and infrastructure as nodes makes the network definition more useful. - Meaning of a resource: Explain what a network resource is and give examples beyond files.
Why it matters: Resources explain what connected devices can share or use through a network.
Key terms: computer network, nodes, resources, node, network infrastructure, routers, switches, firewalls, resource, webpage
2.2 Types of network devices
Introduces the upcoming discussion of nodes that share resources and infrastructure nodes that facilitate that sharing.
2.2.1 Clients and servers
Defines clients and servers by their roles in providing and accessing services, then distinguishes these end hosts from network infrastructure devices.
- Client and server roles: Explain that a client accesses a service provided by a server, and that these are roles rather than fixed kinds of physical device. Describe how the same device can take either role depending on the exchange.
Why it matters: Thinking in terms of roles lets you identify the client and server even when both devices are PCs. - End hosts and infrastructure: Distinguish client and server nodes, also called endpoints or end hosts, from the infrastructure devices that connect them and facilitate communication.
Why it matters: This distinction clarifies which devices are communicating and which devices connect them.
Key terms: client, server, service, endpoints, end hosts, network infrastructure
2.2.2 Switches
This section explains how switches connect end hosts within a LAN and defines the ports used to connect devices.
- Switch role within a LAN: Explain that a switch connects devices within a LAN so they can communicate through it, rather than typically communicating with the switch itself. Distinguish this role from providing connectivity between LANs or to external networks.
Why it matters: This distinction helps you identify what a switch does in a network and where another type of device is needed. - Ports as physical interfaces: Describe a port as a physical connector where a cable attaches a device to another device, and explain why the section also calls it an interface.
Why it matters: Recognizing ports as physical interfaces makes the section’s description of devices connecting to a switch concrete.
Key terms: switch, LAN, end hosts, port, interface, cable
2.2.3 Routers
Explains how routers connect LANs to external networks, what a home wireless router combines, and what a cloud icon means in a network diagram.
- Router role at LAN edges: Explain why a router is used at the edge of a LAN and distinguish its role from a switch's role within a LAN.
Why it matters: This distinction helps you identify which device connects a local network to networks beyond it. - Home wireless router roles: Describe why a home wireless router is more than a router and where this combined device is suitable.
Why it matters: It explains why the device called a router in a home often does more than the router role described here. - Cloud icon diagram meaning: Explain what a cloud icon conveys in the network diagram.
Why it matters: It helps you read the figure without mistaking omitted network details for missing connections.
Key terms: router, switch, LAN, external networks, wireless router, Wi-Fi router, home router, wireless access point, firewall, SOHO
2.2.4 Firewalls
This section explains why networks use firewalls and distinguishes network firewalls from host-based firewalls.
- Network firewall protection: Explain why connecting a network to the internet creates security risks and how a network firewall protects it by inspecting traffic and allowing or denying it according to configured rules.
Why it matters: This explains how a network can communicate over the internet while blocking traffic its rules do not allow. - Host and network firewalls: Distinguish a host-based firewall from a network firewall by where each operates and the traffic each examines.
Why it matters: The distinction clarifies which kind of firewall this section discusses.
Key terms: network firewall, configured rules, allow, deny, host-based firewall, hardware appliance
2.3 Summary
Where this is used later
- Local area networks (chapter 6) · The discussion of local area networks builds on the basic meaning of a LAN.
- How end hosts send packets (chapter 9) · Identifying end hosts and what they are doing provides context for how they send packets.
- Frame switching (chapter 6) · Provides the basic purpose before the book explains frame switching.
- (chapter intro) (chapter 6) · The basic role of switches as network devices.
- Copper UTP connections (chapter 3) · Builds on the idea of physical cable connections between device ports.
- Configuring interfaces (chapter 8) · Uses the term interface for connections on routers and switches.
- The basics of routing (chapter 9) · Builds on the router's role in connecting networks when introducing routing fundamentals.
- The layers of the TCP/IP model (chapter 4) · Routers are introduced as network devices.
Concepts explained in this chapter
- local networkA local area network is a network that connects devices within a limited geographic area such as an office or building.
- networkA computer network is a set of interconnected devices that communicate and share resources.
- routerA network device that forwards packets between different networks based on network-layer addressing.
- network switchA Layer 2 switch is a switch that forwards frames within a local network without performing network-layer routing.
- port numberA port number is a transport-layer identifier ranging from 0 to 65535 that directs network data to a particular application process on a host.
- network interfaceA network interface is a connection point through which a device communicates with other devices in a network.
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