复旦大学：《计算机网络 Computer Networking》课程教学资源（PPT课件讲稿）Wide Area Networks（WANs）

Wide area networks (WANS) Chapte Updated Dec 2009 XU Zhengchuan Fudan University

Wide Area Networks (WANs) Chapter 7 Updated Dec. 2009 XU Zhengchuan Fudan University

Orientation Single Networks Layers 1 and 2(so osI standards dominate) Chapters 4-7: Local to long-distance for single networks Chapter 4: Wired Ethernet LANS Chapter 5: Wireless LANS WLANs) Chapter 6: Telecommunications(and Internet Access Chapter 7: Wide Area Networks (WANs) Chapter 8: TCP/IP Internetworking To link multiple single networks 7-2

7-2 Orientation • Single Networks – Layers 1 and 2 (so OSI standards dominate) – Chapters 4-7: Local to long-distance for single networks • Chapter 4: Wired Ethernet LANs • Chapter 5: Wireless LANs (WLANs) • Chapter 6: Telecommunications (and Internet Access) • Chapter 7: Wide Area Networks (WANs) • Chapter 8: TCP/IP Internetworking – To link multiple single networks

/ WAN Concepts Wide Area Networks(WANs) Single networks that connect different sites So Layer 1 and Layer 2 operation WAN Purposes Internet access( Chapter 6) Link sites within the same corporation Provide remote access individuals who are off site 1.Point-to-point Leased Line Network 2. Public Switched Data Networks(PSDNs 7-3

7-3 WAN Concepts • Wide Area Networks (WANs) – Single networks that connect different sites – So Layer 1 and Layer 2 operation • WAN Purposes – Internet access (Chapter 6) – Link sites within the same corporation – Provide remote access to individuals who are off site 1.Point-to-point Leased Line Network 2.Public Switched Data Networks (PSDNs)

Leased Line Networks

Leased Line Networks

Figure 7-2: Leased Line Networks for Voice and Data eased Line voice Network Site A Site B OC3 Leased Line PBⅩ PBX Leased T1 Line Leased Leased line voice Networks Have a 56 kbps Site C Leased PBX at each Site Line 56 kbps PBX Leased Ine Leased 56 kbps Line PBX PBX Leased Line Site D Site e 7-5

7-5 Figure 7-2: Leased Line Networks for Voice and Data OC3 Leased Line T1 Leased Line T1 Leased Line T3 Leased Line 56 kbps Leased Line 56 kbps Leased Line 56 kbps Leased Line Site A Site B Site D Site E Site C Leased Line Voice Network PBX PBX PBX PBX PBX Leased Line Voice Networks Have a PBX at Each Site

Figure 7-2: Leased Line Networks for Voice and Data eased Line data Network Site a Site B 田 outer OC3 Leased Line Router Leased T1 Line Leased line data Networks Have a 56 kbps Site C Router at each Site Leased Line Router Leased 56 kbps Ine Leased Router/56 kbps Line Leased Router Line Site D ite e 7-6

7-6 Figure 7-2: Leased Line Networks for Voice and Data OC3 Leased Line T1 Leased Line T1 Leased Line T3 Leased Line 56 kbps Leased Line 56 kbps Leased Line 56 kbps Leased Line Site A Site B Site D Site E Site C Leased Line Data Network Router Router Router Router Router Leased Line Data Networks Have a Router at Each Site

Leased Lines: Recap Leased line characteristics Point-to-point circuits Always on High speeds: 64 kbps (rare) to several gigabits per second Leased for a minimum period of time Usually offered by telephone companies

7-7 Leased Lines: Recap • Leased Line Characteristics – Point-to-point circuits – Always on – High speeds: 64 kbps (rare) to several gigabits per second – Leased for a minimum period of time – Usually offered by telephone companies

Figure 7-4: Leased Line Speeds North American Digital Hierarchy Line Speed Typical Transmission Medium 56 kbps 56 kbps 2-Pair Data-Grade UTP T1 1.544 Mbps 2-Pair Data-Grade UTP 56 kbps leased lines are hardly used today because they are so slow T1 lines are very widely used because they are in the speed range of greatest corporate demand- 128 kbps to a few megabits per second 7-8

7-8 Figure 7-4: Leased Line Speeds Line Speed Typical Transmission Medium 56 kbps 56 kbps 2-Pair Data-Grade UTP T1 1.544 Mbps 2-Pair Data-Grade UTP North American Digital Hierarchy 56 kbps leased lines are hardly used today because they are so slow. T1 lines are very widely used because they are in the speed range of greatest corporate demand— 128 kbps to a few megabits per second

I Figure 7-4: Leased Line Speeds, Continued North American Digital hierarchy Line Speed Typical Transmission Medium 1.544 Mbps 2-Pair Data-Grade UTP Fractional t1 128 kbps, 256 kbps, 2-Pair Data-Grade UTP 384 kbps, 512 kbps 768 kbps Bonded T1s(multiple A few multiples of2-Pair Data-Grade UTP T1s acting as a single 544 Mbps line) T1 lines are very widely used Fractional t1 lines offer lower speeds for companies that need them Two or three T1 lines can be bonded for higher speeds T1, Fractional T1, and Bonded T 1s are the most widely used leased lines

7-9 Figure 7-4: Leased Line Speeds, Continued Line Speed Typical Transmission Medium Fractional T1 128 kbps, 256 kbps, 384 kbps, 512 kbps, 768 kbps 2-Pair Data-Grade UTP T1 1.544 Mbps 2-Pair Data-Grade UTP North American Digital Hierarchy Bonded T1s (multiple T1s acting as a single line) A few multiples of 1.544 Mbps 2-Pair Data-Grade UTP T1 lines are very widely used. Fractional T1 lines offer lower speeds for companies that need them. Two or three T1 lines can be bonded for higher speeds. T1, Fractional T1, and Bonded T1s are the most widely used leased lines

Figure 7-4: Leased Line Speeds, Continued North American Digital Hierarchy Line peed Typical Transmission Medium 1.544 Mbps 2-Pair Data-Grade UTP T3 44.736 Mbps Optical Fiber The jump from T 1 to T3 speeds is extremely large Few firms need T3 speeds, and they only need these speeds for some of their leased lines Some carriers offer fractional T3 lines to bridge the T1-T3 gap T3 lines and all faster leased lines use optical fiber 7-10

7-10 Figure 7-4: Leased Line Speeds, Continued Line Speed Typical Transmission Medium North American Digital Hierarchy T3 44.736 Mbps Optical Fiber The jump from T1 to T3 speeds is extremely large. Few firms need T3 speeds, and they only need these speeds for some of their leased lines. Some carriers offer fractional T3 lines to bridge the T1-T3 gap. T3 lines and all faster leased lines use optical fiber. T1 1.544 Mbps 2-Pair Data-Grade UTP