IPv6 packet drops

eduPERT case ticket: 
[DFN#2016091610000414] GGUS-Ticket-ID: #123930 ASSIGNED to "EDUPERT"
Author: DFN-NOC - Robert Stoy



Problem Description: ----------------------- end users observes on MTR ouptut packet drops on ipv6 traffic between cea.fr and other international sites, In addition end user observes unexpected routing when using ipv6, expectation is that the LHCONE should be used, instead user sees ipv6 path through open internet. Example is shown on path cea.fr <-> desy.de

End systems
--------------
end system A:
 perfsonar01.datagrid.cea.fr 
   192.54.207.250
   2001:660:3031:110:ffff::221

end system B:
 perfsonar-ps-02.desy.de
   131.169.98.29  
   2001:638:700:1062::1:1d

Paths (and MTR measurements) on both directions
---------------------------------------------------------

A -> B

My traceroute  [v0.75]
perfsonar01.datagrid.cea.fr (::)                                  Wed Sep 14 10:38:36 2016
Keys:  Help   Display mode   Restart statistics   Order of fields   quit
                                                  Packets               Pings
 Host                                           Loss%   Snt   Last   Avg  Best  Wrst StDev
 1. ipv6test.datagrid.cea.fr                     0.0%    96    0.3   1.2   0.2  50.3   6.1
 2. 2001:660:7904:142:1::1                       7.3%    96    0.7   0.7   0.6   1.4   0.1
 3. te0-1-0-5-paris1-rtr-001.noc.renater.fr     17.7%    96    6.3  20.3   2.1 143.6  26.5
 4. 2001:660:7903:186:2::2                      13.5%    96    8.2   8.7   6.7  12.4   1.1
 5. renater.mx1.gen.ch.geant.net                 0.0%    96    8.9   9.1   8.8  23.3   1.5
 6. ae1.mx1.fra.de.geant.net                     0.0%    95   17.3  17.4  17.2  26.9   1.1
 7. cr-fra1.x-win.dfn.de                        49.5%    95   17.8  17.8  17.6  18.2   0.2
 8. cr-han2-be6-7.x-win.dfn.de                  28.4%    95   24.6  24.8  24.6  25.1   0.1
 9. cr-ham1-hundredgige0-6-0-1.x-win.dfn.de      2.1%    95   30.2  28.9  28.6  30.2   0.2
10. xr-ham1-pc3.x-win.dfn.de                     0.0%    95   28.4  29.1  28.3  56.8   3.8
11. xr-des1-pc2.x-win.dfn.de                     0.0%    95   29.5  29.7  29.0  65.0   3.7
12. kr-desy.x-win.dfn.de                         0.0%    95   28.9  29.0  28.8  37.3   1.1
13. fw-197-22-reth-0.desy.de                    10.5%    95   28.8  28.9  28.7  29.2   0.2
14. rt-dc-04-svi-804.desy.de                     0.0%    95   29.3  29.4  29.2  29.9   0.2
    rt-dc-03-svi-803.desy.de
15. perfsonar-ps-02.desy.de                      0.0%    95   28.8  28.9  28.7  29.4   0.2
 
B -> A

My traceroute  [v0.75]
perfsonar01.datagrid.cea.fr (0.0.0.0)                             Wed Sep 14 10:36:41 2016
Keys:  Help   Display mode   Restart statistics   Order of fields   quit
                                                  Packets               Pings
 Host                                           Loss%   Snt   Last   Avg  Best  Wrst StDev
 1. cvm14.datagrid.cea.fr                        0.0%   153    0.2   1.1   0.2  43.3   5.4
 2. 193.51.191.234                               0.0%   153    1.5   1.5   1.1  41.6   3.3
 3. geant-lhcone-gw.mx1.par.fr.geant.net         0.0%   153    1.1   1.2   1.0  11.2   0.9
 4. ae2.mx1.gen.ch.geant.net                     0.0%   153    8.6   8.6   8.4  14.4   0.5
 5. geant-lhcone-gw.mx1.fra.de.geant.net         0.0%   153   16.7  16.8  16.6  25.2   0.9
 6. dfn-lhcone-gw.fra.de.geant.net               0.0%   153   17.0  17.4  16.8  36.7   1.9
 7. cr-han2-be6-82.x-win.dfn.de                  0.0%   152   26.4  26.2  25.9  27.0   0.2
 8. kr-des51-2.x-win.dfn.de                      0.0%   152   25.8  25.9  25.8  46.1   1.6
 9. fw-197-22-reth-0.desy.de                    12.5%   152   26.0  26.0  25.9  26.8   0.1
10. rt-dc-04-svi-804.desy.de                     0.0%   152   26.2  26.4  26.2  26.7   0.1
11. perfsonar-ps-02.desy.de
 
Analysis:
------------

Endsystems VPN (VRF) membership
  endsystems A ipv4 and ipv6 prefixes are visible in VRF LHCONE *and* in open Internet routing tables
  endsystems A ipv4 and ipv6 prefixes are visible in VRF LHCONE *and* in open Internet routing tables

This deciscon is made at the end sites.

Path A -> B  
 mtr shows IPv6 path through open internet

Path B -> A
 mtr shows IPv4 path through LHCONE

Packet Loss:
Packet losses are shown only on intermediate routers. There is no packet loss shown end-to-end on both directions
This indicates that rate limits for icmp respectively icmpv6 traffic are active at this time on these routers.
These rate limits protect the router CPU and control plane on the router.
There is no limit on the forwarding path through the router.

Routing:
The analysis shows differences on on the path directions with regard to the protocol family used (IPv4,IPv6) and
differences on the VPN/open internet usage.
The MTR output does not clearly show if the ipv6 or the ipv4 address has been explicitely used as destination addresses.
Assumption is that on the MTR commande intentionally on A->B the ipv6 destination address has been used 
and on on B->A the ipv4 destination address.

The reason  why the ipv6 path is through the open internet is most probably caused on the routing decision
made directly at the end site A on the first hop "ipv6test.datagrid.cea.fr". 
The second hop 2001:660:7904:142:1::1 is not shown in the routing table of the VRF LHCONE but only on the open internet routing
table:
Therefore the ipv6 path A->B is using the open internet.
This problem should be fixed locally a the end site A.


-- Kurt Baumann - 2016-10-24

Comments

Topic revision: r1 - 2016-10-24 - KurtBaumann
 
This site is powered by the TWiki collaboration platform Powered by PerlCopyright © 2004-2009 by the contributing authors. All material on this collaboration platform is the property of the contributing authors.