Wide area networks, whether running under the ocean, across poles, or buried underground, are crucial to building everything from the global Internet to large-scale corporate networks. Operators who build network-spanning large geographic regions face some unique challenges in right-of-way and managing the physical plant.
Two kinds of providers build these long-haul, or wide area, networks: transit and last-mile providers. While transit providers focus on connecting cities to cities or continents to continents, last-mile, or edge providers focus on building networks connecting individual users to the larger global Internet. Last-mile technologies include solutions like GPON, DOCSIS, and FWA.
The primary topologies these providers use are rings and hub-and-spoke.
One key to doing well on the exams is to perform repetitive-spaced review sessions. Review this chapter’s material using either the tools in the book or interactive tools for the same material found on the book’s companion website. Refer to the online Appendix D, “Study Planner,” element for more details.
Table 12-2 outlines the key review elements and where you can find them. To better track your study progress, record when you completed these activities in the second column.
Table 12-2 Chapter Review Tracking Review All the Key Topics Table 12-3 lists the key topics for this chapter.
Table 12-3 Key Topics for Chapter 12
Key Terms You Should Know
Key terms in this chapter include:
right-of-way TDR FWA GPON DOCSIS MAN last mile PoP CoLo peering point upstream connectivity settlement-free peering open peering ring topology two-connected topologymetro fiber hub-and-spoke topology Concepts and Actions Review the concepts considered in this chapter using Table 12- 4. You can cover the right side of this table and describe each concept or action in your own words to verify your understanding.
Table 12-4 Concepts and Actions
As exciting as addressing, formatting, and carrying data around in packets, the purpose of a computer network is to provide and enable real-world services. Networks use addressing, routing, cables, and wireless signals to carry four kinds of services through the local and wide areas.
Packet transport is the most basic service that networks provide. Transmitters need to format data so the network can carry it and receivers can understand it. Chapter 6, “Network Models,” noted formatting data is called marshaling in the Recursive InterNetwork Architecture (RINA) model.
Networks transport packets from host to host, so this is a “middle layer” construction.
Application transport services are built on packet transport systems. At the application layer, information is again formatted by a transmitter so the receiver can understand it, but network devices do not, in general, need to understand application transport formatting deeply.
Names and time are two more network services crucial to the way applications and humans use a network. Two complex systems, including specialized protocols and servers, provide these services: the Domain Name System (DNS) and Network Time Protocol (NTP).
Applications run on servers, but there is no reason they must run directly on physical servers owned, managed, and controlled by the organization using the application. Selling compute, storage, and networking capacity as a service is called cloud computing.
Each chapter in this part of the book considers one of these kinds of services.
The chapters in this part of the book are as follows:
Chapter 13: Data Centers and Fabrics
Chapter 15: Application Transport
Chapter 13. Data Centers and Fabrics This chapter covers the following exam topics:
1. Standards and Concepts
1.3. Differentiate between LAN, WAN, MAN, CAN, PAN, and WLAN.
Identify and illustrate common physical and logical network topologies Chapter 11, “Local Area Networks,” introduced the idea of local area network (LANs), which are designed and built for short distances. Chapter 11 used building and home networks as two examples of LANs. Chapter 12, “Wide Area Networks, ” introduced wide area networks (WANs). This chapter introduces the third class, or “place,” in modern networks, the data center (DC). As they do with LANs and WANs, engineers often build DCs to support specialized requirements using two or three common topologies.
The chapter begins by considering the kinds of applications engineers design DCs to support, like large-scale retail sites, social media sites, cellular telephone networks, and large-scale Internet interconnection points. The second part of this chapter describes the most common type of topology used to support these applications, the spine-and-leaf fabric. The Clos and butterfly fabrics are both commonly used kinds of spine-and-leaf fabrics.
