Figure 7-3: Full Mesh and Pure Hub-and-Spoke Topologies for Leased Line Data Networks Site A Full Mesh Topology Site B 田中 OC 3 Leased Line In a full mesh topology there is a leased line eased between each pair of sitesLine Highly reliable eased Line Leased ighly expensive Line LEaSEE Line Site c Site D 7-11
7-11 Figure 7-3: Full Mesh and Pure Hub-and-Spoke Topologies for Leased Line Data Networks Full Mesh Topology OC3 Leased Line T1 Leased Line Site A Site B Site C Site D T1 Leased Line T3 Leased Line T3 Leased Line In a full mesh topology, there is a leased line between each pair of sites Highly reliable Highly expensive
Figure 7-3: Full Mesh and Pure Hub-and-Spoke Topologies for Leased Line Data Networks Site A Pure Hub-and-Spoke Topology Site B In a pure hub-and-spoke 田 o topology, there is only one leased line from the hub site to each other site Very inexpensive Very unreliable Leased Leased Line Site D Few companies use either of these extreme topologies They have some backup links uu site C 7-12
7-12 Figure 7-3: Full Mesh and Pure Hub-and-Spoke Topologies for Leased Line Data Networks Pure Hub-and-Spoke Topology OC3 Leased Line Site A Site B Site C Site D T3 Leased Line T3 Leased Line In a pure hub-and-spoke topology, there is only one leased line from the hub site to each other site. Very inexpensive. Very unreliable. Few companies use either of these extreme topologies. They have some backup links
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 7-13
7-13 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
7-14 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 7-15
7-15 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