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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Can you explain why paths to same host diverge?
Folks,
We've been seeing some large latencies to sites inside of UUNET lately.
In trying to figure out where the latency is coming from (UUNET or our
provider, Sprint), I observed something which has me baffled.
I have two hosts on the same subnet. One of them is 128.114.2.53 and the
other is 128.114.2.91. Here are ping results from these machines to
www.uu.net:
from 128.114.2.91:
PING www.uu.net (199.170.0.30): 56 data bytes, 100 packets
100 packets transmitted, 100 packets received, 0% packet loss
round-trip (ms) min/avg/max = 362/548/778 (std = 103)
from 128.114.2.53:
PING www.uu.net (199.170.0.30): 56 data bytes, 100 packets
100 packets transmitted, 100 packets received, 0% packet loss
round-trip (ms) min/avg/max = 92.9/107/139 (std = 8.43)
The RTT from 128.114.2.91 are always much higher (many times a full order
of magnitude) than those of 128.114.2.53. The explanation for the
differing RTTs turns out to be that the paths between each of my machines
and www.uu.net are different. In the below traceroutes, everything
agrees up through hop five. But at hop six, the paths diverge:
from 128.114.2.53:
traceroute to www.uu.net (199.170.0.30): 1-30 hops, 38 byte packets
1 comm-g.UCSC.EDU (128.114.2.252) 4.52 ms
2 frontdoor.UCSC.EDU (128.114.103.1) 1.15 ms
3 UC-net-dmz.ucsc.edu (208.1.176.6) 1.45 ms
4 bgty-lata01.ucnet.net (192.35.219.2) 7.79 ms
5 sl-gw10-stk-11-0-T3.sprintlink.net (144.228.146.49) 8.70 ms
6 sl-bb10-stk-2-1-155M.sprintlink.net (144.232.4.78) 30.2 ms
7 sl-bb3-stk-0-0-0-155M.sprintlink.net (144.232.4.42) 33.0 ms
8 Hssi8-1-0.BR1.SFO1.ALTER.NET (137.39.166.121) 42.3 ms
9 114.ATM3-0-0.XR1.SCL1.ALTER.NET (146.188.145.222) 76.9 ms
10 100.ATM2-0-0.TR1.SCL1.ALTER.NET (146.188.145.226) 41.3 ms
11 107.ATM8-0-0.TR1.DCA1.ALTER.NET (146.188.136.221) 110 ms (ttl=242!)
12 199.ATM4-0-0.XR1.TCO1.ALTER.NET (146.188.161.161) 223 ms (ttl=243!)
13 193.ATM5-0-0.GW2.FFX1.ALTER.NET (146.188.160.209) 158 ms (ttl=242!)
14 UUNET7-GW.UU.NET (137.39.12.162) 214 ms (ttl=241!) 163 ms (ttl=241!)
15 www.uu.net (199.170.0.30) 155 ms (ttl=240!)
from 128.114.2.91:
traceroute to www.uu.net (199.170.0.30): 1-30 hops, 38 byte packets
1 comm-g.UCSC.EDU (128.114.2.252) 1.29 ms
2 frontdoor.UCSC.EDU (128.114.103.1) 1.7 ms
3 UC-net-dmz.ucsc.edu (208.1.176.6) 2.82 ms
4 bgty-lata01.ucnet.net (192.35.219.2) 7.75 ms
5 sl-gw10-stk-11-0-T3.sprintlink.net (144.228.146.49) 10.6 ms
6 sl-bb11-stk-1-1-155M.sprintlink.net (144.232.4.98) 11.2 ms
7 sl-bb3-stk-4-0-0.sprintlink.net (144.232.4.14) 9.27 ms
8 Hssi8-1-0.BR1.SFO1.ALTER.NET (137.39.166.121) 609 ms
9 114.ATM3-0-0.XR2.SCL1.ALTER.NET (146.188.145.210) 541 ms
10 100.ATM3-0-0.TR2.SCL1.ALTER.NET (146.188.145.246) 578 ms
11 107.ATM8-0-0.TR2.DCA1.ALTER.NET (146.188.136.225) 633 ms
12 198.ATM8-0-0.XR2.TCO1.ALTER.NET (146.188.161.185) 683 ms (ttl=243!)
13 192.ATM12-0-0.GW2.FFX1.ALTER.NET (146.188.160.221) 622 ms (ttl=242!)
14 UUNET7-GW.UU.NET (137.39.12.162) 569 ms (ttl=241!) 534 ms (ttl=241!)
15 www.uu.net (199.170.0.30) 579 ms (ttl=240!)
Can anyone explain to me why paths would diverge in this fashion? These
traceroutes aren't aberrations - the packets follow these forward paths
consistently.
Clues greatly appreciated.
thanks,
mb
---
Mark Boolootian
UC Santa Cruz
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