Connected: An Internet Encyclopedia
4.3.2.8 Rate Limiting
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4. INTERNET LAYER - PROTOCOLS
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4.3 INTERNET CONTROL MESSAGE PROTOCOL - ICMP
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4.3.2 GENERAL ISSUES
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4.3.2.8 Rate Limiting
4.3.2.8 Rate Limiting
A router which sends ICMP Source Quench messages MUST be able to
limit the rate at which the messages can be generated. A router
SHOULD also be able to limit the rate at which it sends other sorts
of ICMP error messages (Destination Unreachable, Redirect, Time
Exceeded, Parameter Problem). The rate limit parameters SHOULD be
settable as part of the configuration of the router. How the limits
are applied (e.g., per router or per interface) is left to the
implementor's discretion.
- DISCUSSION
-
Two problems for a router sending ICMP error message are:
- The consumption of bandwidth on the reverse path, and
- The use of router resources (e.g., memory, CPU time)
To help solve these problems a router can limit the frequency with
which it generates ICMP error messages. For similar reasons, a
router may limit the frequency at which some other sorts of
messages, such as ICMP Echo Replies, are generated.
- IMPLEMENTATION
-
Various mechanisms have been used or proposed for limiting the
rate at which ICMP messages are sent:
- Count-based - for example, send an ICMP error message for
every N dropped packets overall or per given source host.
This mechanism might be appropriate for ICMP Source Quench,
if used, but probably not for other types of ICMP messages.
- Timer-based - for example, send an ICMP error message to a
given source host or overall at most once per T milliseconds.
- Bandwidth-based - for example, limit the rate at which ICMP
messages are sent over a particular interface to some
fraction of the attached network's bandwidth.
Next: 4.3.3 SPECIFIC ISSUES
Connected: An Internet Encyclopedia
4.3.2.8 Rate Limiting