On Fri, 22 Jun 2007, Proinnsias Breathnach wrote:
> and even how long the return path for ICMP packets is. It cannot be
> considered a useful measure of latency on the link, as ICMP may (or
> indeed may not) be subject to the same QoS restrictions as other
> traffic.
Right..
ICMP directed at a host, and conditions that require ICMP
control messages to be sent (like TTL running out on a packet
being forwarded - traceroute) tend to be:
- handled in slow paths, for higher-end routers this may mean it gets
processed and sent by a seperate piece of hardware (the hardware
that runs host software, as opposed to the hardware that does the
forwarding for the path(s) whose latency you're interested in)
- rate-limited, possibly globally across all host-directed/generated
ICMP.
regards,
--
Paul Jakma paul at clubi.iepaul at jakma.org Key ID: 64A2FF6A
Fortune:
The intelligence of any discussion diminishes with the square of the
number of participants.
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