packet loss question

Ken Chase math at sizone.org
Thu Jul 7 19:52:47 UTC 2016


No offence, but i swear that mtr should come with a license to use it. I get more
questions from people accusing us of network issues with mtr in hand...

You shoudlnt care that there's 80% packet loss in the middle of your route, unless
you have actual traffic to lag-101.ear3.miami2.level3.net. I suspect you dont.
(If you did, you'd have mtr'd to it directly of course.)

As for your second trace, the sudden jump from 0% on 2nd last hop to 100% last
hop packetloss seems like firewalling to me. (long discussion about the
probabilities of getting 5 0%pl hops in a row and 100% on an unfirewalled
endpoint elided. TL;DR: use more packets in your test -i 0.1 -c 100 thanks).

If you have 0% packetloss to your target endpoint, is there an issue here?
What caused you to mtr?  0% pl is pretty good. You could play quake 1.0
through that pl and ping time. The +20ms ATL<>CHI jump in the route you'd have
to take up with einstein/bill nye/$deity. 

For the 2nd trace, the 1st hop is your latency issue (plus the big jump from
miami<>ashburn, again the limit is c.)

ICMP is allowed to be dropped by intervening routers. Someone will quote an RFC
at us shortly.

Mtr without a return route is not that useful in figuring out packetloss
because pl requires the packet make it there and back. Pl could be anywhere on
the return route, which is probably not symmetrical. The internet stopped
being symetrical about 20+ years ago (if it ever even loosely was), so get a friend
to send you an mtr to your ip from the farside.

(I remember a project long ago, some cgi-bin (yeah that long ago) that was
basically a full-path forward+reverse traceroute you could hit on a selected
server at the provider.  Rather handy. not sure if its still a thing, or what it was
called.)

/kc


On Thu, Jul 07, 2016 at 03:17:40PM -0400, Phillip Lynn said:
  >Hi all,
  >
  >  I am writing because I do not understand what is happening.  I ran mtr
  >against our email server and www.teco.comand below are the results.  I am
  >not a network engineer so I am at a loss.  I think what I am seeing is
  >maybe a hand off issue, between Frontier and Level3Miami2. If I am correct
  >then what can I do?
  >
  >  My system is running Centos 6.5 Linux.
  >
  >Thanks,
  >
  >Phillip
  >
  >
  >
  >(! 1011)-> sudo mtr -r netwolves.securence.com
  >HOST: xxxxx at netwolves.comLoss%   Snt   Last   Avg Best  Wrst StDev
  >  1. 172.24.109.1                  0.0%    10    0.6 0.6 0.6   0.7   0.0
  >  2. lo0-100.TAMPFL-VFTTP-322.gni  0.0%    10    3.2 2.0 1.0   4.3   1.2
  >  3. 172.99.44.214                 0.0%    10    4.0 4.9 2.3   6.9   1.5
  >  4. ae8---0.scr02.mias.fl.fronti  0.0%    10    9.3 9.1 7.5   9.8   1.0
  >  5. ae1---0.cbr01.mias.fl.fronti  0.0%    10    8.9   9.1   7.6 9.7 0.7
  >  6. lag-101.ear3.Miami2.Level3.n 80.0%    10    9.0   8.9   8.8 9.0 0.1
  >  7. 10ge9-14.core1.mia1.he.net    0.0%    10   14.3 13.0 7.6  18.1   4.3
  >  8. 10ge1-1.core1.atl1.he.net     0.0%    10   25.6  33.2 22.4  99.7  23.6
  >  9. 10ge10-4.core1.chi1.he.net    0.0%    10   45.6  51.8 45.5  82.7  12.5
  > 10. 100ge14-2.core1.msp1.he.net   0.0%    10   53.6  63.9 53.6 125.2  21.8
  > 11. t4-2-usi-cr02-mpls-usinterne  0.0%    10   53.2  73.1 53.2 225.6  54.0
  > 12. v102.usi-cr04-mtka.usinterne  0.0%    10   53.2  53.9 53.2  55.3   0.6
  > 13. netwolves.securence.com       0.0%    10   53.4  53.9 53.4  55.4   0.7
  >
  >(! 1014)-> sudo mtr -r www.teco.com
  >HOST: xxxxx at netwolves.comLoss%   Snt   Last   Avg Best  Wrst StDev
  >  1. 172.24.109.1                  0.0%    10    0.6 0.6 0.6   0.7   0.0
  >  2. lo0-100.TAMPFL-VFTTP-322.gni  0.0%    10  104.8 81.4 1.1 113.2  43.2
  >  3. 172.99.47.198                 0.0%    10  115.0 77.8 2.9 115.0  40.2
  >  4. ae7---0.scr01.mias.fl.fronti  0.0%    10  111.1 80.2 8.5 113.5  41.3
  >  5. ae0---0.cbr01.mias.fl.fronti  0.0%    10  105.9  82.2   7.6 115.4 33.8
  >  6. lag-101.ear3.Miami2.Level3.n 70.0%    10  116.1  80.2   8.5 116.1 62.0
  >  7. NTT-level3-80G.Miami.Level3.  0.0%    10  110.0 81.5 9.0 120.3  41.9
  >  8. ae-3.r20.miamfl02.us.bb.gin.  0.0%    10  119.8  84.0 10.0 119.8  38.5
  >  9. ae-4.r23.asbnva02.us.bb.gin. 10.0%    10  137.4 107.6 30.1 142.7  45.7
  > 10. ae-2.r05.asbnva02.us.bb.gin.  0.0%    10  135.0 109.9 36.6 140.0  39.1
  > 11. xe-0-9-0-8.r05.asbnva02.us.c  0.0%    10  147.5 125.6 49.4 165.5  41.1
  > 12. 24.52.112.21                  0.0%    10  158.6 124.0 49.6 161.3  41.5
  > 13. 24.52.112.42                  0.0%    10  151.0 127.7 52.2 159.0  41.2
  > 14. ???                          100.0    10    0.0 0.0 0.0   0.0   0.0
  >
  >-- 
  >Phillip Lynn
  >Software Engineer III
  >NetWolves
  >Phone:813-579-3214
  >Fax:813-882-0209
  >Email: phillip.lynn at netwolves.com
  >www.netwolves.com
  >

-- 
Ken Chase - ken at heavycomputing.ca skype:kenchase23 +1 416 897 6284 Toronto Canada
Heavy Computing - Clued bandwidth, colocation and managed linux VPS @151 Front St. W.



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