Sorry for an off-topic post about network bandwidth... Everything seems
slow lately and I want to make sure I understand some issues. Below is a
traceroute and ping to Yahoo. Usually, Yahoo is about 200 to 300 ms
distant. Today (right now) it appears to be about 10 times that
distant. I tried other hosts and had similar results (although
occasionally the time would drop for a second or two and then rise again).
It seems like there are big jumps in the latencies going from hop 3 to 4
and 4 to 5 and again in the 8,9,10 area then 11 looks pretty fast, 12-13
slow, then Yahoo itself looks about normal.
So: (1) I obviously don't fully understand traceroute; These are round
trips between me and that node, right? So how can latencies on successive
hops get bigger and smaller? Is this a sign of wildly unstable network
latencies? Or are there "slow hops" and "fast hops"? Or something
else? (2) Similarly, how could latencies to hop 12 be so large and then to
Yahoo itself so small? Why are the latencies on hop 14 so different from
those of the subsequent ping?
Part 2: It takes me about 29 minutes to transfer some 345 megabyte files
from one host to another over our LAN using scp. So I'm getting about 1.6
Mb throughput, right? It's a 10Mb hubbed segment so I'm getting about 32%
of the realistic maximum, right? We are going to replace the hub with a
100Mb switch so I'm expecting transfers to be 6000% faster soon.
Part 3: I used scp to transfer a *whole* lot of dissertation data from a
computer on my home LAN to a computer here at work. I started the
transfer at 9AM. Here are some snapshots of the progress:
kbytes time elapsed (Kb/s)
-------- ---------- ------- ----------
103360 11:51:45 10305 10.03
144980 13:09:23 14963 9.69
154340 13:26:06 15966 9.67
359524 21:59:00 46740 7.69
412700 00:20:48 55248 7.47
Did I calculate the throughput correctly? So in terms of modem speeds,
this would be a sustained throughput of 60 kilo-baud? Which would be
phenomenal if I had a modem but I have a cable modem at home and we have
(only) a dedicated 128K ISDN line here at work. Does a 128K ISDN translate
to transferring about 16 Kb/s? So I was getting about 63% of our maximum
just before lunch and the average had dropped to only 48% towards the end
of the transfer? If traffic to/from my work network were the cause, I
would expect the numbers to stay pretty constant during the day and then
jump up at night. Since the opposite seems to happen, can I conclude that
there is a bottleneck on my cable network or in between? Or is there
anything about scp that would cause it to progressively slow during a long
transfer? The traffic at home passed through a Linux gateway; should
masquerading using a Celron 400 with 128 MB RAM cause a lot of
latency? Should I be happy with these speeds?
Your thoughts, corrections, etc. are appreciated,
-Alan Mead
[amead@hera amead]$ traceroute www.yahoo.com
traceroute: Warning: www.yahoo.com has multiple addresses; using 216.32.74.52
traceroute to www.yahoo.akadns.net (216.32.74.52), 30 hops max, 38 byte packets
1 ipatrtr (64.5.73.1) 1.803 ms 1.843 ms 1.621 ms
2 its-1.soltec.net (206.148.208.4) 379.762 ms 144.834 ms 30.339 ms
3 gw.soltec.net (206.148.208.1) 30.347 ms 186.326 ms 191.611 ms
4 * * 63.238.135.69 (63.238.135.69) 58.856 ms
5 * chi-core-03.inet.qwest.net (205.171.20.153) 64.578 ms 333.373 ms
6 chi-brdr-03.inet.qwest.net (205.171.20.138) 53.553 ms 64.983
ms 116.843 ms
7 ibr02-p0-1.okbr01.exodus.net (205.171.4.50) 79.681 ms 60.430
ms 83.002 ms
8 * bbr01-g3-0.okbr01.exodus.net (216.34.183.65) 50.619 ms 60.761 ms
9 bbr02-p6-0.jrcy01.exodus.net (216.32.132.110) 80.145 ms 645.017 ms *
10 bbr01-p5-0.stng01.exodus.net (209.185.9.98) 1141.746 ms 997.142
ms 462.167 ms
11 dcr04-g9-0.stng01.exodus.net (216.33.96.146) 226.203 ms 142.618
ms 69.571 ms
12 * 216.33.98.19 (216.33.98.19) 609.612 ms 874.789 ms
13 216.35.210.126 (216.35.210.126) 871.602 ms 600.034 ms 286.730 ms
14 www3.dcx.yahoo.com (216.32.74.52) 328.424 ms 96.569 ms 127.680 ms
[amead@hera amead]$ ping www.yahoo.com
PING www.yahoo.akadns.net (216.32.74.50) from 64.5.73.33 : 56(84) bytes of
data.
64 bytes from 216.32.74.50: icmp_seq=0 ttl=242 time=2191.2 ms
64 bytes from 216.32.74.50: icmp_seq=1 ttl=242 time=1659.6 ms
64 bytes from 216.32.74.50: icmp_seq=2 ttl=242 time=674.5 ms
64 bytes from 216.32.74.50: icmp_seq=3 ttl=242 time=1479.0 ms
64 bytes from 216.32.74.50: icmp_seq=4 ttl=242 time=1654.7 ms
64 bytes from 216.32.74.50: icmp_seq=5 ttl=242 time=1888.6 ms
64 bytes from 216.32.74.50: icmp_seq=6 ttl=242 time=1673.6 ms
64 bytes from 216.32.74.50: icmp_seq=7 ttl=242 time=1838.1 ms
64 bytes from 216.32.74.50: icmp_seq=8 ttl=242 time=1470.3 ms
64 bytes from 216.32.74.50: icmp_seq=9 ttl=242 time=1190.0 ms
64 bytes from 216.32.74.50: icmp_seq=10 ttl=242 time=381.6 ms
64 bytes from 216.32.74.50: icmp_seq=11 ttl=242 time=697.2 ms
--- www.yahoo.akadns.net ping statistics ---
13 packets transmitted, 12 packets received, 7% packet loss
round-trip min/avg/max = 381.6/1399.8/2191.2 ms
---
Alan Mead, Ph.D. / Research Scientist / [EMAIL PROTECTED]
Institute for Personality and Ability Testing
1801 Woodfield Dr / Savoy IL 61874 USA
217-352-4739 (v) / 217-352-9674 (f)
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