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what is an acceptable packet drop level for traffic leaving the plusnet network?

btsimonh
Hooked
Posts: 9
Thanks: 1
Registered: ‎07-10-2016

what is an acceptable packet drop level for traffic leaving the plusnet network?

I'm having issues with http request failures; which I believe I have isolated to occur only for sites outside of the plusnet network.

 

My actual application is node.js based, and I suspected the libraries and lost a day, but in actuality, the packets are lost when leaving plusnet.

two simple text batch files which use 'wget' (https://sourceforge.net/projects/gnuwin32/files/wget/1.11.4-1/) to test:

testplus.bat:

:continue
wget http://www.plus.net/robots.txt -t 1
set ERRLEV=%ERRORLEVEL%
ECHO.%ERRORLEVEL%
ECHO.%ERRLEV%
del robots.txt

set /A count=%count%+1

echo count is %count%
if %ERRLEV% equ 0 goto continue

 

testbt.bat:

:continue
wget http://www.bt.com/robots.txt -t 1
set ERRLEV=%ERRORLEVEL%
ECHO.%ERRORLEVEL%
ECHO.%ERRLEV%
del robots.txt

set /A count=%count%+1

echo count is %count%
if %ERRLEV% equ 0 goto continue

 

when running testplus,bat, I have not had it stop in a few minutes, no failures, timeouts, etc.

when running testbt.bat, I can see count anything from 1 to 75, after which it stops, and wget states:

--2017-05-24 10:25:53-- http://www.bt.com/robots.txt
Resolving www.bt.com... 193.113.9.162
Connecting to www.bt.com|193.113.9.162|:80... failed: Connection timed out.
Giving up.

 

The result is the same for other websites, e.g. http://www.facebook.com/robots.txthttp://www.broadbandspeedchecker.co.uk/robots.txt

In my real application, because I'm asking for more data, I see failure to connect, but also timeouts reading the data.  It has highlighted that I need to deal with this type of failure, but the failures I'm seeing are too frequent in my opinion.

 

So, Question:

what is an acceptable failure level, and is there a problem on the plusnet network in routing packets externally?

10 REPLIES
btsimonh
Hooked
Posts: 9
Thanks: 1
Registered: ‎07-10-2016

Re: what is an acceptable packet drop level for traffic leaving the plusnet network?

interestingly, testplus.bat just stopped at count=3454.

but the stop was I believe a failure in wget Smiley, log was:

--2017-05-24 10:34:23-- http://www.plus.net/robots.txt
Resolving www.plus.net... 212.159.9.2, 212.159.8.2
Connecting to www.plus.net|212.159.9.2|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 334 [text/plain]
robots.txt has sprung into existence.
Giving up.

 

Community Veteran
Posts: 5,587
Thanks: 1,524
Fixes: 35
Registered: ‎16-10-2014

Re: what is an acceptable packet drop level for traffic leaving the plusnet network?

Just a word of caution, if you continue to hit the plus.net site like that you risk being blocked assuming you haven't been already.

Community Veteran
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Thanks: 1,524
Fixes: 35
Registered: ‎16-10-2014

Re: what is an acceptable packet drop level for traffic leaving the plusnet network?


btsimonh wrote:

So, Question:

what is an acceptable failure level, and is there a problem on the plusnet network in routing packets externally?


I wouldn't have thought so as this would have been raised before. To give a better understanding can you give a brief description as to what your code does and the errors being returned by it.

 

 

btsimonh
Hooked
Posts: 9
Thanks: 1
Registered: ‎07-10-2016

Re: what is an acceptable packet drop level for traffic leaving the plusnet network?

It's pretty much described in the first post.

I was writing an application which makes ~800 https requests to retrieve a sequence of data from an http interface.

Each request asks for some work to be done, which takes a few hundred ms and then responds.  Immediately I either ask for the same work to be done again with different parameters, or download the result.  Once I have the result, I immediately send the next request.

I believe each request opens a new TCP connection....

I was finding that they regularly failed with either connection timeout, or response timeout.  I spent a day suspecting the nodejs libraries I was using, but then re-created the tests with wget, illustrated by the batch files provided, hence excluding the libraries & node.js.  I determined that the site I was making requests from was not the issue (and apologised for raising a ticket with them...) by testing against other sites.  When I found that the plusnet site did not exhibit the issue, but most (all I tested) did, I wondered what I should expect from the service.

 

In wireshark, I'm seeing quite a few

2999 16.998881 193.132.104.187 192.168.1.189 TCP 443 [TCP Out-Of-Order] 80 → 49465 [PSH, ACK] Seq=1 Ack=83 Win=14720 Len=389

and

3183 17.900177 193.132.104.187 192.168.1.189 TCP 1506 [TCP Out-Of-Order] [TCP segment of a reassembled PDU]

 

and finally when it has a connection timeout:

6282 35.451509 192.168.1.189 193.132.104.187 TCP 66 [TCP Retransmission] 49520 → 80 [SYN] Seq=0 Win=8192 Len=0 MSS=1460 WS=4 SACK_PERM=1

7177 41.452041 192.168.1.189 193.132.104.187 TCP 62 [TCP Retransmission] 49520 → 80 [SYN] Seq=0 Win=8192 Len=0 MSS=1460 SACK_PERM=1

 

It does not seem to matter whether I add 400ms between requests or not...

The wireshark logs against http://www.plus.net/robots.txt are completely clean.

 

So it would seem that my LAN is ok, my broadband is OK, plusnet's network is ok, but routing out of plusnet is not?

 

Community Veteran
Posts: 5,587
Thanks: 1,524
Fixes: 35
Registered: ‎16-10-2014

Re: what is an acceptable packet drop level for traffic leaving the plusnet network?

OK, I see the logic to your reasoning here but you have to remember that Plusnet will get 100s if not 1000s of hits a second so I guess there would be some contention there which may lead to the re-tries, you won't be the only user on the PN network!

Also the size of data you are asking for needs to be considered so as you are getting PDU notices then that tells me that the data won’t fit a single segment, and is nothing to worry about.

btsimonh
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Registered: ‎07-10-2016

Re: what is an acceptable packet drop level for traffic leaving the plusnet network?

I've now done some further tests.

From a machine on a BT fibre connection, I don't see any failures against websites I have tested against (don't have wireshark over there, so it may be there are recoverable packet drops).  (I did get a 429 - too many requests, rate limiting).

From the same machine (in the BT network) to MY webserver, I get similar issues to outgoing connections; connection timeouts and response timeouts.

The difference is chalk and cheese.

Community Veteran
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Registered: ‎16-10-2014

Re: what is an acceptable packet drop level for traffic leaving the plusnet network?

@btsimonh - As none of us are perfect I have to raise the issue of your code, it is running away with itself? Is the logic and flow correct?

I run clusters of client PCs here that I use to offload work from a central server, as I know how many of these clients are available my load balancing code (C++) rate limits the client task dispatch depending on how may clients there are. The less there are the slower it goes to allow the client time to process the task. OK, we're only taking 25ms here but it was causing me issues until I sorted out the timing.

btsimonh
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Registered: ‎07-10-2016

Re: what is an acceptable packet drop level for traffic leaving the plusnet network?

@Mook - did you try running the batch files?

Just download the zip of wget plus the zip of it's dependencies, combine the content of the two zips (no installation to do), then create the two batch files in the bin folder, and test.

I would be VERY interested to know if this is related to *my* plusnet connection or if it is a general issue? - although I put the location of the drops as being at the point of plusnet network's external routing, such routing will not be exactly the same for all...

Although I'm primarily concerned about the work I do, this issue is likely to be the cause of regular dropouts on uktvplayer that we see, and kick-offs from netflix and amazon.

 

Community Veteran
Posts: 5,587
Thanks: 1,524
Fixes: 35
Registered: ‎16-10-2014

Re: what is an acceptable packet drop level for traffic leaving the plusnet network?

Sorry @btsimonh I haven't nor have I any intention to either having been IP blocked the last time I tickled their network. Maybe someone else will do it for you but not me, sorry.

P.S. You also need Windows to run .bat files as well. Wink

btsimonh
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Posts: 9
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Registered: ‎07-10-2016

Re: what is an acceptable packet drop level for traffic leaving the plusnet network?

This:

https://www.elifulkerson.com/projects/tcping.php

also shows the issue.

e.g.

tcping -t -w 10 -i 0.1 www.example.com

....

Ping statistics for 93.184.216.34:80
457 probes sent.
446 successful, 11 failed.
Approximate trip times in milli-seconds (successful connections only):
Minimum = 82.376ms, Maximum = 1159.542ms, Average = 92.063ms

 

tcping -t -w 10 -i 0.1 www.plus.net

......

Probing 212.159.9.2:80/tcp - Port is open - time=22.226ms
Control-C
Probing 212.159.9.2:80/tcp - No response - time=11.583ms

Ping statistics for 212.159.9.2:80
385 probes sent.
384 successful, 1 failed.
Approximate trip times in milli-seconds (successful connections only):
Minimum = 20.873ms, Maximum = 157.923ms, Average = 27.486ms

(the '1 fail' was when I hit ctrl-c).