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Heres an interesting puzzle.



 
 
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  #1  
Old January 8th 13, 06:53 PM posted to uk.telecom.broadband,uk.d-i-y,uk.telecom.broadband
The Natural Philosopher
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Posts: 2,728
Default Heres an interesting puzzle.

At 5 a.m. my internet connection went 'weird'



Traceroute revealed that some internet sites were inaccessible whilst
others going via the same router were just fine.

I reported it to my ISP, sincere problem seemed to be in one of their
boundary routers, and patched into a proxy on a machine I COULD reach,
and (most) traffic was restored.

At 3pm the problem still existed, so I reported it to them by email

At 4 pm I lost patience and phoned. They admitted the problem, but said
that the router in question had been rebooted and the problem had gone,
but 'the solution seems to be to restart the customer router'

I did, and full connectivity was restored.

But the puzzle remains: how could a problem on a machine miles away
reflect itself in corrupted router NAT tables? As this is the only thing
that I can see that could have produced this behaviour.

I am honestly stumped on this.

Anyone provide a rationale?



--
Ineptocracy

(in-ep-toc'-ra-cy) - a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

  #2  
Old January 8th 13, 08:42 PM posted to uk.telecom.broadband
alexd
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Posts: 1,765
Default Heres an interesting puzzle.

The Natural Philosopher (for it is he) wrote:

Anyone provide a rationale?


Perhaps the router [or datacentre] that your session terminated on had a
problem and rebooting the router got you on to a different router/DC.

--
http://ale.cx/ (AIM:troffasky) )
20:40:35 up 22 days, 23:12, 7 users, load average: 1.45, 1.28, 1.27
Qua illic est reprehendit, illic est a vindicatum
  #3  
Old January 8th 13, 09:03 PM posted to uk.telecom.broadband,cam.misc,uk.telecom.broadband
The Natural Philosopher
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Posts: 2,728
Default Heres an interesting puzzle.

On 08/01/13 20:42, alexd wrote:
The Natural Philosopher (for it is he) wrote:

Anyone provide a rationale?


Perhaps the router [or datacentre] that your session terminated on had a
problem and rebooting the router got you on to a different router/DC.

Nope. traceroute reveals an identical route. IP is static

I have got as far as conjecturing that the NAT tables for even broken
routes are preserved after dropping the TCP connection.

So that e.g I would be using the same source port every time.

OTOH its possible that routes BACK to me - OSPF or similart - were
broken in some way and reconnecting deleted those.

BUT those operate on IP address alone, not destination (my source) port,
as such. So that falls apart.


--
Ineptocracy

(in-ep-toc'-ra-cy) - a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

  #4  
Old January 8th 13, 09:03 PM posted to uk.telecom.broadband,cam.misc,uk.telecom.broadband
The Natural Philosopher
external usenet poster
 
Posts: 2,728
Default Heres an interesting puzzle.

On 08/01/13 20:42, alexd wrote:
The Natural Philosopher (for it is he) wrote:

Anyone provide a rationale?


Perhaps the router [or datacentre] that your session terminated on had a
problem and rebooting the router got you on to a different router/DC.

Nope. traceroute reveals an identical route. IP is static

I have got as far as conjecturing that the NAT tables for even broken
routes are preserved after dropping the TCP connection.

So that e.g I would be using the same source port every time.

OTOH its possible that routes BACK to me - OSPF or similart - were
broken in some way and reconnecting deleted those.

BUT those operate on IP address alone, not destination (my source) port,
as such. So that falls apart.


--
Ineptocracy

(in-ep-toc'-ra-cy) - a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

  #5  
Old January 9th 13, 12:42 PM posted to uk.d-i-y,uk.telecom.broadband
The Natural Philosopher
external usenet poster
 
Posts: 2,728
Default Heres an interesting puzzle.

On 09/01/13 11:44, Plusnet Support Team wrote:
On 08/01/2013 21:03, The Natural Philosopher wrote:
On 08/01/13 20:42, alexd wrote:
The Natural Philosopher (for it is he) wrote:

Anyone provide a rationale?

Perhaps the router [or datacentre] that your session terminated on had a
problem and rebooting the router got you on to a different router/DC.

Nope. traceroute reveals an identical route. IP is static

I have got as far as conjecturing that the NAT tables for even broken
routes are preserved after dropping the TCP connection.

So that e.g I would be using the same source port every time.

OTOH its possible that routes BACK to me - OSPF or similart - were
broken in some way and reconnecting deleted those.

BUT those operate on IP address alone, not destination (my source) port,
as such. So that falls apart.


Plusnet by any chance? If so, BGP was flapping on one of the routers in
our core network. The reboot of your router was probably a coincidence.

If it wasn't Plusnet then ignore me

No, it was in fact IDnet.
But it confirms one suspicion, that there was something odd going on in
the peering between major ISPs.


--
Ineptocracy

(in-ep-toc'-ra-cy) - a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

 




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