Broadband cross country link d 50ms r 10 mbps

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Unformatted text preview: The main prefixes we use: Prefix Exp. K(ilo) 103 M(ega) 106 G(iga) 109 prefix exp. m(illi) 10-3 µ(micro) 10-6 n(ano) 10-9 •  Use powers of 10 for rates, 2 for storage –  1 Mbps = 1,000,000 bps, 1 KB = 1024 bytes •  “B” is for bytes, “b” is for bits 8 4 10/6/13 Latency Examples •  “Dialup” with a telephone modem: –  D = 5ms, R = 56 kbps, M = 1250 bytes •  Broadband cross- country link: –  D = 50ms, R = 10 Mbps, M = 1250 bytes 9 Latency Examples (2) •  “Dialup” with a telephone modem: D = 5ms, R = 56 kbps, M = 1250 bytes L = 5ms + (1250 x 8)/(56 x 103) sec = 184ms! •  Broadband cross- country link: D = 50ms, R = 10 Mbps, M = 1250 bytes L = 50ms + (1250 x 8) / (10 x 106) sec = 51ms •  A long link or a slow rate means high latency –  Oien, one delay component dominates CSE 461 University of Washington 10 5 10/6/13 Bandwidth- Delay Product •  Messages take space on the wire! •  The amount of data in flight is the bandwidth- delay (BD) product –  Measure in bits, or in messages –  Small for LANs, big for “long fat” pipes 11 Bandwidth- Delay Example •  Fiber at home, cross- country R=40 Mbps, D=50ms BD = 40 x 50 x 103 bits = 250 KB 110101000010111010101001011 •  That’s quite a lot of data “in the network”! 12 6 10/6/13 Introduc8on to Computer Networks Media (Wires, etc.) (§2.2, 2.3) Computer Science & Engineering Types of Media •  Media propagate signal...
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This document was uploaded on 04/04/2014.

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