On Thu, 8 Jan 2004 [EMAIL PROTECTED] wrote:
Let me take my stab at trying the wording of this text:
=====
(f) Finally, in order to limit the bandwidth and forwarding costs
incurred sending ICMPv6 error messages, an IPv6 node MUST limit
the rate of ICMPv6 error messages it sends. This situation may
occur when a source sending a stream of erroneous packets fails
to heed the resulting ICMPv6 error messages.
One good way to implement the rate-limiting function is a token
bucket, allowing up to B back-to-back error messages to
be transmitted in a burst, but limiting the average rate of
transmission to N, where N can either be packets/seconds or a
fraction of the attached link's bandwidth.
Rate-limiting mechanisms which cannot cope with bursty traffic
(e.g., traceroute) are not recommended; thus a simple timer-based
implementation, allowing an error message every T
milliseconds (even with low values for T), is not reasonable.
The rate-limiting parameters SHOULD be configurable. In the case
of a token-bucket implementation, the best defaults depend on where
the implementation is expected to be deployed (e.g., a high-end
router vs. an embedded host). For example, in a small/mid -sized
device, the possible defaults could be B=10, N=10/s.
=====
Reasoning:
- RFC1918 states rate-limiting SHOULD be configurable. A MUST seems
too heavy in case the implementation and the defaults have been chosen
properly.
- Pure bandwidth-based mechanism doesn't seem to be useful at all, so
for simplicit, omit it from here (can be coupled with a token bucket
still).
- It's rather difficult to recommend good values for B and N, as
different kinds of nodes may have entirely different deployment
scenarios. I don't feel particularly strongly on this, just invented
some values which would probably be OK for all but the biggest
routers.
--
Pekka Savola "You each name yourselves king, yet the
Netcore Oy kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings
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