lec-3 - Today's Agenda Network Structure Delays in networks...

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7 Aug 2008  BITS C481 (Computer Networks) 1 Today’s Agenda Network Structure Delays in networks cont… Access Networks ISPs and Internet Backbones
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7 Aug 2008  BITS C481 (Computer Networks) 2 Nodal delay d proc = processing delay typically a few microsecs or less d queue = queuing delay depends on congestion d trans = transmission delay = L/R, significant for low-speed links d prop = propagation delay a few microsecs to hundreds of msecs prop trans queue proc nodal d d d d d + + + =
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7 Aug 2008  BITS C481 (Computer Networks) 3      Queuing delay (revisited) R=link bandwidth (bps) L=packet length (bits) a=average packet arrival rate traffic intensity = La/R La/R ~ 0: average queueing delay small La/R <= 1: delays become large La/R > 1: more “work” arriving than can be serviced, average delay infinite!
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7 Aug 2008  BITS C481 (Computer Networks) 4 “Real” Internet delays and routes What do “real” Internet delay & loss look like? Traceroute program: provides delay measurement from source to router along end-to-end Internet path towards destination. For all i: Sends three packets that will reach router i on path towards destination Router i will return packets to sender Sender times interval between transmission and reply. Read RFC 1393 for more detail !!! 3 probes
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7 Aug 2008  BITS C481 (Computer Networks) 5 Example: MIT to BITS Pilani 1 W92-RTR-1-W92SRV21.MIT.EDU (18.7.21.1) 0.511 ms 0.342 ms 0.283 ms 2 EXTERNAL-RTR-1-BACKBONE-2.MIT.EDU (18.168.1.18) 0.474 ms 0.465 ms 0.472 ms
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This note was uploaded on 07/20/2009 for the course INFORMATIO BITS C481 taught by Professor Prof.virendrasinghshekhawat during the Fall '08 term at Birla Institute of Technology & Science, Pilani - Hyderabad.

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lec-3 - Today's Agenda Network Structure Delays in networks...

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