[e2e] What's wrong with this picture?

Glen Turner gdt at gdt.id.au
Tue Sep 8 05:29:21 PDT 2009

Steinar Haug wrote:
> Do you know of *any* ISPs that explicitly prioritize ICMP a lot lower
> than TCP for traffic *through* the ISP's routers? Note that this is
> different from ICMP to/from the router itself.

Yes, I did the QoS policy for one -- AARNet.  We had a lot of ping
flooding from our fast network of smaller ISPs we peer with. So
into the Scavenger class went ICMP Echo and Echo Reply.

There's no need for diagnostic features to run in the Best Effort
class. Can't say that anyone has noticed, yet alone complained.
We did send out a warning about the use of ICMP Echo as a heartbeat
protocol for STONITH.

Alexandre Grojsgold wrote:
 > no network should hold a packet for long 8 or 9 seconds, and yet  deliver it to somewhere

Actually, lots of hosts and routers will deliver queued packets that
were present when the interface went offline when the interface comes
back online. Operationally speaking, cyclical bursts of packets O(10s)
old are indicative of a clocking issue or a forever-negotiating ethernet
interface, we've also seen a variant of delay behaviour on devices
suffering RAM ECC errors.

Best wishes, Glen

  Glen Turner   <http://www.gdt.id.au/~gdt/>

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