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3.2.2.8 Timestamp and Timestamp Reply: RFC-792
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3.2.2.8 Timestamp and Timestamp Reply: RFC-792
3.2.2.8 Timestamp and Timestamp Reply: RFC-792
A host MAY implement Timestamp and Timestamp Reply. If they
are implemented, the following rules MUST be followed.
- The ICMP Timestamp server function returns a Timestamp
Reply to every Timestamp message that is received. If
this function is implemented, it SHOULD be designed for
minimum variability in delay (e.g., implemented in the
kernel to avoid delay in scheduling a user process).
The following cases for Timestamp are to be handled
according to the corresponding rules for ICMP Echo:
- An ICMP Timestamp Request message to an IP broadcast or
IP multicast address MAY be silently discarded.
- The IP source address in an ICMP Timestamp Reply MUST
be the same as the specific-destination address of the
corresponding Timestamp Request message.
- If a Source-route option is received in an ICMP Echo
Request, the return route MUST be reversed and used as
a Source Route option for the Timestamp Reply message.
- If a Record Route and/or Timestamp option is received
in a Timestamp Request, this (these) option(s) SHOULD
be updated to include the current host and included in
the IP header of the Timestamp Reply message.
- Incoming Timestamp Reply messages MUST be passed up to
the ICMP user interface.
The preferred form for a timestamp value (the "standard
value") is in units of milliseconds since midnight Universal
Time. However, it may be difficult to provide this value
with millisecond resolution. For example, many systems use
clocks that update only at line frequency, 50 or 60 times
per second. Therefore, some latitude is allowed in a
"standard value":
- A "standard value" MUST be updated at least 15 times
per second (i.e., at most the six low-order bits of the
value may be undefined).
- The accuracy of a "standard value" MUST approximate
that of operator-set CPU clocks, i.e., correct within a
few minutes.
Next: 3.2.2.9 Address Mask Request/Reply: RFC-950
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3.2.2.8 Timestamp and Timestamp Reply: RFC-792