Almost all network circuit load balancing systems use some kind of
(src/dst) hash in order to attempt to keep end-to-end packet ordering
the same. What the hash is built upon (ip, tcp/udp port, etc) is up to
the local admin.
So if one path is borked and sending packets to a blackhole (but the
dynamic routing doesn't detect that), then you'll see things like what
you mention.
Also you can see drops like this in active/active firewalls that aren't
properly synchronized, so return packets get dropped as they can arrive
on the wrong device.
Not knowing AWS infrastructure, I'm guessing it's a combo of the above.
And yes, BGP is still the core routing protocol for the internet.
Cheers,
Ross.
On 02/07/15 12:44 PM, Edward Ned Harvey (lopser) wrote:
I don't know anything about how BGP works, or even, if BGP is what's currently
used on the Internet.
I found it very weird, that two machines in the same LAN (with public IP's),
pinging the same target IP address far away, one of them got a response while
the other didn't. And it was even more weird that the results would toggle from
minute to minute.
Suppose there's more than one possible route between my LAN and the destination
IP. I know there's no guarantee that any particular route will be chosen -
Suppose a single packet leaves Host A, and follows a good route, but another
packet leaves Host B and follows a route that has a broken segment. This could
possibly explain a single ping succeeding for Host A and failing for Host B.
But why would *all* the packets from Host B get routed along the broken path,
while all the packets from Host A get routed along the good path? Is this
possible or impossible, or somewhere in between? This is ICMP Echo and Response
we're talking about.
Could the explanation be, simply, some network segment was broken on the
internet, and for some reason, all the packets from Host B would get routed
over that segment (and fail), and the routes would readjust themselves once
every few minutes, making the problem intermittent, and independent of traffic
from Host A?
_______________________________________________
Tech mailing list
Tech@lists.lopsa.org
https://lists.lopsa.org/cgi-bin/mailman/listinfo/tech
This list provided by the League of Professional System Administrators
http://lopsa.org/
_______________________________________________
Tech mailing list
Tech@lists.lopsa.org
https://lists.lopsa.org/cgi-bin/mailman/listinfo/tech
This list provided by the League of Professional System Administrators
http://lopsa.org/
