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Latency/ping
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Latency/ping
13-09-2014 6:35 PM
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(Have separated out this query I posted elsewhere)
Remind me, please, why is there such a disparity in latency depending on who reports it::
BTW - 47
Thinkbroadband - 32
Speedtest (ookla) - 24
OK, I know there's going to be a brief time lag between them but that difference seems excessive! Who do I believe?
RF suggested it was due to variations in the distant server, which seemed feasible. However I'm not now sure. Speedtest/ookla gives you a choice and previously I was using xylo, only about 5 miles from chez Dent as the drone flies. But I've just selected others much more distant and got similarly lower speedtest/ookla figures:
BTW - 41
Thinkbroadband - 31
Speedtest/ookla - averages 26
Pinging plusnet averages 35
What can one deduce from all this please?
Remind me, please, why is there such a disparity in latency depending on who reports it::
BTW - 47
Thinkbroadband - 32
Speedtest (ookla) - 24
OK, I know there's going to be a brief time lag between them but that difference seems excessive! Who do I believe?
RF suggested it was due to variations in the distant server, which seemed feasible. However I'm not now sure. Speedtest/ookla gives you a choice and previously I was using xylo, only about 5 miles from chez Dent as the drone flies. But I've just selected others much more distant and got similarly lower speedtest/ookla figures:
BTW - 41
Thinkbroadband - 31
Speedtest/ookla - averages 26
Pinging plusnet averages 35
What can one deduce from all this please?
Message 1 of 7
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6 REPLIES 6
Re: Latency/ping
13-09-2014 8:48 PM
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All of them use java/flash and I don't rate any of them for ping response times.
A much better way is to use the ping command (e.g. ping bbc.co.uk) from the command prompt.
A much better way is to use the ping command (e.g. ping bbc.co.uk) from the command prompt.
Message 2 of 7
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Re: Latency/ping
13-09-2014 9:24 PM
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I was looking at this earlier and I located and tested the severs as follows.
[tt]
BT
193.113.8.193
193.113.4.154
22 ping
ThinkBroadband
80.249.107.221
80.249.106.133
64 bytes from 80.249.107.221: icmp_seq=5 ttl=59 time=16.6 ms
64 bytes from 80.249.107.221: icmp_seq=6 ttl=59 time=17.3 ms
64 bytes from 80.249.107.221: icmp_seq=7 ttl=59 time=16.9 ms
64 bytes from 80.249.107.221: icmp_seq=8 ttl=59 time=16.7 ms
Speedtest.net london server
85.233.160.167
64 bytes from 85.233.160.167: icmp_seq=1 ttl=58 time=19.6 ms
64 bytes from 85.233.160.167: icmp_seq=2 ttl=58 time=19.0 ms
64 bytes from 85.233.160.167: icmp_seq=3 ttl=58 time=19.1 ms
64 bytes from 85.233.160.167: icmp_seq=5 ttl=58 time=19.1 ms
[/tt]
The BT server doesn't give priority for ping
[tt]
1. 192.168.0.254 0.0% 69 48.0 50.7 4.2 99.3 30.9
2. lo0.10.central10.pcl-bng01.plus.net 0.0% 69 17.2 18.2 16.1 43.4 4.9
3. irb.10.pcl-cr02.plus.net 0.0% 68 16.8 20.3 16.0 54.2 9.3
irb.10.pcl-cr01.plus.net
4. ae1.ptw-cr02.plus.net 0.0% 68 16.8 19.8 16.2 65.1 7.7
ae1.ptw-cr01.plus.net
ae2.pcl-cr01.plus.net
ae2.pcl-cr02.plus.net
5. ae2.ptw-cr01.plus.net 0.0% 68 17.6 20.0 16.5 54.2 6.0
ae1.ptw-cr01.plus.net
195.99.126.182
195.99.126.138
ae1.ptw-cr02.plus.net
ae2.ptw-cr02.plus.net
6. 195.99.126.138 0.0% 68 17.8 21.1 16.8 41.6 3.9
core1-te0-15-0-10.ealing.ukcore.bt.net
core1-te0-3-0-7.ilford.ukcore.bt.net
core1-te0-15-0-10.ilford.ukcore.bt.net
195.99.126.182
194.72.31.148
core2-te0-15-0-4.ealing.ukcore.bt.net
core2-te0-3-0-12.ealing.ukcore.bt.net
7. core2-te0-15-0-10.ealing.ukcore.bt.net 0.0% 68 22.6 34.3 17.9 211.6 38.3
core1-te0-3-0-7.ilford.ukcore.bt.net
core1-pos1-1.birmingham.ukcore.bt.net
core1-te0-0-0-11.ealing.ukcore.bt.net
core2-pos1-1.birmingham.ukcore.bt.net
core1-pos1-0.birmingham.ukcore.bt.net
core2-pos1-0.birmingham.ukcore.bt.net
core1-te0-15-0-10.ealing.ukcore.bt.net
8. core2-pos1-0.birmingham.ukcore.bt.net 0.0% 68 22.6 29.7 21.0 192.3 25.3
iar1-gig5-4.birmingham.ukcore.bt.net
core1-pos1-1.birmingham.ukcore.bt.net
iar1-gig5-5.birmingham.ukcore.bt.net
core1-pos1-0.birmingham.ukcore.bt.net
core2-pos1-1.birmingham.ukcore.bt.net
9. iar1-gig5-5.birmingham.ukcore.bt.net 0.0% 68 22.1 23.3 21.0 57.1 4.8
iar1-gig5-4.birmingham.ukcore.bt.net
62.172.57.218
10. 62.172.57.218 46.3% 68 22.5 23.1 21.1 32.6 2.7
11. ?
12. ?
13. ?
14. ?
15. 193.113.8.193 47.8% 68 7377. 6357. 5388. 7377. 587.5
[/tt]
[tt]
BT
193.113.8.193
193.113.4.154
22 ping
ThinkBroadband
80.249.107.221
80.249.106.133
64 bytes from 80.249.107.221: icmp_seq=5 ttl=59 time=16.6 ms
64 bytes from 80.249.107.221: icmp_seq=6 ttl=59 time=17.3 ms
64 bytes from 80.249.107.221: icmp_seq=7 ttl=59 time=16.9 ms
64 bytes from 80.249.107.221: icmp_seq=8 ttl=59 time=16.7 ms
Speedtest.net london server
85.233.160.167
64 bytes from 85.233.160.167: icmp_seq=1 ttl=58 time=19.6 ms
64 bytes from 85.233.160.167: icmp_seq=2 ttl=58 time=19.0 ms
64 bytes from 85.233.160.167: icmp_seq=3 ttl=58 time=19.1 ms
64 bytes from 85.233.160.167: icmp_seq=5 ttl=58 time=19.1 ms
[/tt]
The BT server doesn't give priority for ping
[tt]
1. 192.168.0.254 0.0% 69 48.0 50.7 4.2 99.3 30.9
2. lo0.10.central10.pcl-bng01.plus.net 0.0% 69 17.2 18.2 16.1 43.4 4.9
3. irb.10.pcl-cr02.plus.net 0.0% 68 16.8 20.3 16.0 54.2 9.3
irb.10.pcl-cr01.plus.net
4. ae1.ptw-cr02.plus.net 0.0% 68 16.8 19.8 16.2 65.1 7.7
ae1.ptw-cr01.plus.net
ae2.pcl-cr01.plus.net
ae2.pcl-cr02.plus.net
5. ae2.ptw-cr01.plus.net 0.0% 68 17.6 20.0 16.5 54.2 6.0
ae1.ptw-cr01.plus.net
195.99.126.182
195.99.126.138
ae1.ptw-cr02.plus.net
ae2.ptw-cr02.plus.net
6. 195.99.126.138 0.0% 68 17.8 21.1 16.8 41.6 3.9
core1-te0-15-0-10.ealing.ukcore.bt.net
core1-te0-3-0-7.ilford.ukcore.bt.net
core1-te0-15-0-10.ilford.ukcore.bt.net
195.99.126.182
194.72.31.148
core2-te0-15-0-4.ealing.ukcore.bt.net
core2-te0-3-0-12.ealing.ukcore.bt.net
7. core2-te0-15-0-10.ealing.ukcore.bt.net 0.0% 68 22.6 34.3 17.9 211.6 38.3
core1-te0-3-0-7.ilford.ukcore.bt.net
core1-pos1-1.birmingham.ukcore.bt.net
core1-te0-0-0-11.ealing.ukcore.bt.net
core2-pos1-1.birmingham.ukcore.bt.net
core1-pos1-0.birmingham.ukcore.bt.net
core2-pos1-0.birmingham.ukcore.bt.net
core1-te0-15-0-10.ealing.ukcore.bt.net
8. core2-pos1-0.birmingham.ukcore.bt.net 0.0% 68 22.6 29.7 21.0 192.3 25.3
iar1-gig5-4.birmingham.ukcore.bt.net
core1-pos1-1.birmingham.ukcore.bt.net
iar1-gig5-5.birmingham.ukcore.bt.net
core1-pos1-0.birmingham.ukcore.bt.net
core2-pos1-1.birmingham.ukcore.bt.net
9. iar1-gig5-5.birmingham.ukcore.bt.net 0.0% 68 22.1 23.3 21.0 57.1 4.8
iar1-gig5-4.birmingham.ukcore.bt.net
62.172.57.218
10. 62.172.57.218 46.3% 68 22.5 23.1 21.1 32.6 2.7
11. ?
12. ?
13. ?
14. ?
15. 193.113.8.193 47.8% 68 7377. 6357. 5388. 7377. 587.5
[/tt]
Message 3 of 7
(787 Views)
Re: Latency/ping
13-09-2014 9:43 PM
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Mind u this is interesting..
[tt]
Connected to 193.113.4.154: time=28.78ms protocol=TCP port=80
Connected to 193.113.4.154: time=29.15ms protocol=TCP port=80
Connected to 193.113.4.154: time=27.21ms protocol=TCP port=80
Connection statistics:
Attempted = 3, Connected = 3, Failed = 0 (0.00%)
Approximate connection times:
Minimum = 27.21ms, Maximum = 29.15ms, Average = 28.38ms
Connected to 193.113.8.193: time=29.83ms protocol=TCP port=80
Connected to 193.113.8.193: time=28.20ms protocol=TCP port=80
Connected to 193.113.8.193: time=28.50ms protocol=TCP port=80
Connection statistics:
Attempted = 3, Connected = 3, Failed = 0 (0.00%)
Approximate connection times:
Minimum = 28.20ms, Maximum = 29.83ms, Average = 28.84ms
[/tt]
[tt]
Connected to 193.113.4.154: time=28.78ms protocol=TCP port=80
Connected to 193.113.4.154: time=29.15ms protocol=TCP port=80
Connected to 193.113.4.154: time=27.21ms protocol=TCP port=80
Connection statistics:
Attempted = 3, Connected = 3, Failed = 0 (0.00%)
Approximate connection times:
Minimum = 27.21ms, Maximum = 29.15ms, Average = 28.38ms
Connected to 193.113.8.193: time=29.83ms protocol=TCP port=80
Connected to 193.113.8.193: time=28.20ms protocol=TCP port=80
Connected to 193.113.8.193: time=28.50ms protocol=TCP port=80
Connection statistics:
Attempted = 3, Connected = 3, Failed = 0 (0.00%)
Approximate connection times:
Minimum = 28.20ms, Maximum = 29.83ms, Average = 28.84ms
[/tt]
Message 4 of 7
(787 Views)
Re: Latency/ping
13-09-2014 9:48 PM
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I don't think the BT Wholesale speedtest even uses ICMP ping packets to measure latency - I didn't see any in wireshark. It probably just puts a timestamp in a URL, and compares the sent timestamp with when the request arrives at the server.
I concur that it's better to use ping at a command prompt for measuring latency.
I concur that it's better to use ping at a command prompt for measuring latency.
Message 5 of 7
(787 Views)
Re: Latency/ping
16-09-2014 11:03 AM
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Many thanks! That's way too technical for me, but I'll follow your suggestion and use ping, just looking for any major change.
Message 6 of 7
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Re: Latency/ping
16-09-2014 12:54 PM
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It's true that the latency measures from the various online speed testers shouldn't be given much credence, but it's also worth remembering that modern networks, including PlusNet's Juniper platform and the underlying BT Wholesale infrastructure, are so heavily shaped and buffered that ICMP echo replies (ie. the ping command) may not give a particularly accurate picture of the real latency (nor the variation in it) across traffic classes either.
Ping is more usefully seen as an end-to-end link integrity (and possibly routing) check - provided the other end is set to reply. It will generally show up serious problems too, and on the flip side of that coin give an indication of the minimum achievable latency when things are running smoothly. But that minimum may not be what actual real-world traffic over other protocols experiences. It may often be: but not necessarily.
There's an interesting knowledge base article which explains why pinging the PlusNet gateways themselves is not a reliable measure of latency; and whilst it doesn't directly apply to pinging other sites on the internet, it does illustrate that various factors can be at work which cause different traffic to be treated differently in all sorts of places.
It is handy to use something like hping (or even Wireshark) to compare pings using TCP and UDP to build up a more accurate picture, but even then if DPI is being employed all bets are off.
I've had an opportunity to compare a PlusNet 40/20 FTTC connection with a 100/15 FTTP connection on a different exchange recently. The ICMP pings are a little higher on the FTTC (which is close to the cabinet) - around 5-6ms rather than 3-4ms on FTTP to 80.249.99.164 (ThinkBroadband) - and the bandwidth is obviously lower, yet my general subjective impression so far has been that the FTTC connection is snappier. Hard to put my finger on objective metrics, as ever, and I haven't had chance to do any serious testing, but real-world browsing latency seems as if it may be lower. Certainly not consistently higher, anyway.
So latency is indeed all a bit technical - or opaque and subjective, at any rate.
Ping is more usefully seen as an end-to-end link integrity (and possibly routing) check - provided the other end is set to reply. It will generally show up serious problems too, and on the flip side of that coin give an indication of the minimum achievable latency when things are running smoothly. But that minimum may not be what actual real-world traffic over other protocols experiences. It may often be: but not necessarily.
There's an interesting knowledge base article which explains why pinging the PlusNet gateways themselves is not a reliable measure of latency; and whilst it doesn't directly apply to pinging other sites on the internet, it does illustrate that various factors can be at work which cause different traffic to be treated differently in all sorts of places.
It is handy to use something like hping (or even Wireshark) to compare pings using TCP and UDP to build up a more accurate picture, but even then if DPI is being employed all bets are off.
I've had an opportunity to compare a PlusNet 40/20 FTTC connection with a 100/15 FTTP connection on a different exchange recently. The ICMP pings are a little higher on the FTTC (which is close to the cabinet) - around 5-6ms rather than 3-4ms on FTTP to 80.249.99.164 (ThinkBroadband) - and the bandwidth is obviously lower, yet my general subjective impression so far has been that the FTTC connection is snappier. Hard to put my finger on objective metrics, as ever, and I haven't had chance to do any serious testing, but real-world browsing latency seems as if it may be lower. Certainly not consistently higher, anyway.
So latency is indeed all a bit technical - or opaque and subjective, at any rate.
Message 7 of 7
(787 Views)
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