[strongSwan] Performance (latency) in a Hub and Spoke setup

Sat Dec 30 22:47:30 CET 2017

Hi Noel

Thanks for the advice. I installed tcpdump and wireshark and added a 
rule to log ICMP errors.
This is an excerpt from the log file. I assume this line shows something 
is sent to port 80 but I cannot find the corresponding iptables entry.

Dec 30 21:42:11 localhost kernel: [1423944.393321] IN= OUT=eth0 
SRC=210.211.212.213 DST=192.168.2.135 LEN=88 TOS=0x00 PREC=0xC0 TTL=64 
ID=38805 PROTO=ICMP TYPE=11 CODE=0 [SRC=192.168.2.135 DST=192.168.1.130 
LEN=60 TOS=0x00 PREC=0x00 TTL=1 ID=63979 DF PROTO=TCP SPT=47511 DPT=80 
WINDOW=5840 RES=0x00 SYN URGP=0 ]

Best regards
Martin

On 28.12.2017 01:43, Noel Kuntze wrote:
> Hi,
>
> Looks like your firewall rules on the hub are broken and cause the problems or you need to configure an additional CHILD_SA to tunnel ICMP errors from the hub, because it has no IP in the local TS.
> Check both those suspicions.
>
> Kind regards
>
> Noel
>
> On 27.12.2017 23:00, Martin Sand wrote:
>> Thanks again Noel.
>>
>> I have executed `traceroute -T --mtu <destination>` and `mtr -rw <destination>` on machines at both locations.
>> I did not do further investigation on the MSS yet since I have this strange packet loss.
>> Based on the route, I assume this happens at the hub which is in between the two routers?
>> Could this be the root cause I need to further investigate?
>>
>> Kind regards
>> Martin
>>
>> traceroute -T --mtu pi-frankfurt
>> traceroute to pi-frankfurt (192.168.2.135), 30 hops max, 60 byte packets
>>   1  router-freiburg (192.168.1.1)  0.263 ms  0.179 ms  0.172 ms
>>   2  * * *
>>   3  router-frankfurt (192.168.2.1)  41.762 ms  41.182 ms  36.716 ms
>>   4  pi-frankfurt (192.168.2.135)  36.693 ms  43.629 ms  37.051 ms
>>
>> traceroute -T --mtu pi-freiburg
>> traceroute to pi-freiburg (192.168.1.130), 30 hops max, 60 byte packets
>>   1  router-frankfurt (192.168.2.1)  0.489 ms  0.381 ms  0.287 ms
>>   2  * * *
>>   3  router-freiburg (192.168.1.1)  38.368 ms  47.673 ms  35.441 ms
>>   4  pi-freiburg (192.168.1.130)  39.456 ms  54.566 ms  36.117 ms
>>
>> mtr -rw pi-frankfurt
>> Start: 2017-12-27T22:57:40+0100
>> HOST: workstation              Loss%   Snt   Last   Avg  Best Wrst StDev
>>    1.|-- router-freiburg         0.0%    10    0.2   0.2   0.2 0.3   0.0
>>    2.|-- ???                      100.0    10    0.0   0.0   0.0 0.0   0.0
>>    3.|-- router-frankfurt        0.0%    10   33.3  35.5  32.5 42.0   2.7
>>    4.|-- pi-frankfurt              0.0%    10   33.5  34.4  32.7 36.7   1.5
>>
>>
>> On 27.12.2017 21:08, Noel Kuntze wrote:
>>> Hi,
>>>
>>> You can test the convergence speed using `traceroute -T --mtu <destination>`, but that only gives you the MTU. You need to manually discover the MSS
>>> using `traceroute -T -O mss=<mss> <destination>`.
>>>
>>> The best way to check if the problem continues is to just run tcpdump/wireshark and check for ICMP Fragmenation needed packets and TCP errors or timeouts.
>>>
>>> Kind regards
>>>
>>> Noel
>>>
>>> On 27.12.2017 17:12, Martin Sand wrote:
>>>> Thanks Noel. Sorry, I had to travel to the other location (350 km).
>>>>
>>>> I adapted the iptable rules. It improved, but I have the impression it only improved a bit.
>>>> Is there a way to measure MTU discovery time?
>>>>
>>>> Kind regards
>>>> Martin
>>>>
>>>>
>>>> On 14.12.2017 13:51, Noel Kuntze wrote:
>>>>> Hi,
>>>>>
>>>>>> VPN internal http requests to a web server of another spoke take some time until the page is rendered.
>>>>>> I assume this is due to the latency.
>>>>> Nah. It's extremely more likely that the path MTU discovery takes some time (maybe due to some missing/wrong firewall rules on some host(s) in your network topology).
>>>>> Try lowering the MTU and MSS of the tunneled traffic[1].
>>>>>
>>>>> Kind regards
>>>>>
>>>>> Noel
>>>>>
>>>>> [1] https://wiki.strongswan.org/projects/strongswan/wiki/ForwardingAndSplitTunneling#MTUMSS-issues
>>>>>
>>>>> On 14.12.2017 13:41, Martin Sand wrote:
>>>>>> Hi all
>>>>>>
>>>>>> I have a Hub and Spoke setup. Connections are working perfectly fine.
>>>>>> Throughput is almost reaching the maximum rate of the upload channel speed, 10 MBit/s.
>>>>>>
>>>>>> Unfortunately the latency is not fulfilling my objectives. I have an average ping time of 39 ms (see below) when pinging clients on other spokes.
>>>>>> VPN internal http requests to a web server of another spoke take some time until the page is rendered.
>>>>>> I assume this is due to the latency.
>>>>>>
>>>>>> Is there any chance to improve the latency? Or is the latency perfectly good?
>>>>>>
>>>>>> Best regards
>>>>>> Martin
>>>>>>
>>>>>> Hub internet address
>>>>>> 64 bytes from vpn.example.com (217.122.5.6): icmp_seq=1 ttl=57 time=15.2 ms
>>>>>>
>>>>>> Internal address of Hub
>>>>>> PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data.
>>>>>> 64 bytes from 192.168.1.1: icmp_seq=1 ttl=62 time=40.4 ms
>>>>>>
>>>>>> Client on another spoke
>>>>>> PING 192.168.1.130 (192.168.1.130) 56(84) bytes of data.
>>>>>> 64 bytes from 192.168.1.130: icmp_seq=1 ttl=61 time=108 ms
>>>>>> 64 bytes from 192.168.1.130: icmp_seq=2 ttl=61 time=41.8 ms
>>>>>> 64 bytes from 192.168.1.130: icmp_seq=3 ttl=61 time=38.0 ms
>>>>>> 64 bytes from 192.168.1.130: icmp_seq=4 ttl=61 time=35.2 ms
>>>>>> 64 bytes from 192.168.1.130: icmp_seq=5 ttl=61 time=36.4 ms
>>>>>> 64 bytes from 192.168.1.130: icmp_seq=6 ttl=61 time=39.1 ms
>>>>>> 64 bytes from 192.168.1.130: icmp_seq=7 ttl=61 time=38.1 ms
>>>>>> 64 bytes from 192.168.1.130: icmp_seq=8 ttl=61 time=41.6 ms
>>>>>> 64 bytes from 192.168.1.130: icmp_seq=9 ttl=61 time=36.0 ms
>>>>>> 64 bytes from 192.168.1.130: icmp_seq=10 ttl=61 time=36.7 ms
>>>>>>
>>>>>> --- 192.168.1.130 ping statistics ---
>>>>>> 10 packets transmitted, 10 received, 0% packet loss, time 9013ms
>>>>>> rtt min/avg/max/mdev = 35.295/45.159/108.281/21.146 ms
>>>>>>