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ttl value has changed

Blim
Grafter
Posts: 462
Registered: ‎06-03-2012

ttl value has changed

Ive not touched a thing but my TTL value has half what it used to be.
Could this shed any light on my connection problems or is everyone seeing a slowdown even out of peak times now?
5 REPLIES
Community Veteran
Posts: 5,177
Thanks: 482
Fixes: 20
Registered: ‎10-06-2010

Re: ttl value has changed

TTL = Time To Live
What says it's lower? To where? If the value has changed (and you haven't changed the starting TTL), that just means the routing has changed, if the final TTL value is lower, there must be more hops along the route. The routing could have changed in Plusnet's network, within some peering network in the middle, or nearer the destination.
Blim
Grafter
Posts: 462
Registered: ‎06-03-2012

Re: ttl value has changed

Its changed around the same time the problem started.
A simple ping test shows the change.
from around 244 to 120. That's pinging out bbci.
My RWIN has also changed and seems to be stuck at 16698. That's for a 78mb connection and when its stable 12ms ping to bbci.
Community Veteran
Posts: 5,177
Thanks: 482
Fixes: 20
Registered: ‎10-06-2010

Re: ttl value has changed

Since it's somewhat unlikely that there are an extra 124 hops between you and bbci, it must be that the starting ttl on your computer has changed. You can verify the number of hops by doing a traceroute (there appear to be 6 or 7 hops between mine and static.bbci.co.uk).
ping static.bbci.co.uk
PING a1638.g.akamai.net (23.61.255.216) 56(84) bytes of data.
64 bytes from a23-61-255-216.deploy.akamaitechnologies.com (23.61.255.216): icmp_seq=1 ttl=57 time=19.3 ms
64 bytes from a23-61-255-216.deploy.akamaitechnologies.com (23.61.255.216): icmp_seq=2 ttl=57 time=20.5 ms
The ttl starts at 64 on my computer (Linux), and the result shown by ping is the value that remains after the ttl is decreased by one at each hop along the route.
I can't imagine changing the starting ttl from 250 to 128 would make any difference to anything, since there won't be any servers 129 or more hops away. I think TTL is mainly to guard against packets going around forever in accidental routing loops.
Blim
Grafter
Posts: 462
Registered: ‎06-03-2012

Re: ttl value has changed

I agree,TTL on its own should not affect my connection, but the change took place around the same time problems started happening. Maybe it would suggest some tweaks where done on my connection/line that has resulted in the problem I'm having. Forget the RWIN, I was just interested in why it was so low. But turns out it has nothing to do with this problem.
Community Veteran
Posts: 5,177
Thanks: 482
Fixes: 20
Registered: ‎10-06-2010

Re: ttl value has changed

I was wrong about the TTL shown by the ping reply. It's just the TTL of the echo reply packet received, and that could start at any value depending on the remote server you're pinging. I tried pinging www.bbc.co.uk with TTL set to 20, 200 and 255, in each case the replies had TTL of 55.