echo reply
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... an MPLS "echo request" and "echo reply", and mechanisms for
transporting the echo reply. The first part aims at providing enough
...
... echo request" and "echo reply", and mechanisms for
transporting the echo reply. The first part aims at providing enough
information to check correct operation of the data plane, as well as
...
... echo request, i.e., an IPv4 encapsulated echo reply is sent
in response to an IPv4 encapsulated ...
... sender, and returned
unchanged by the receiver in the echo reply (if any). There are no
semantics associated with this handle, although a sender ...
... NTP] when the MPLS
echo request is sent. The TimeStamp Received in an echo reply is the
time-of-day (according to the receiver ...
... Downstream Mapping object is a
request that Downstream Mapping objects be included in the echo
reply. If the replying router is the destination of the FEC ...
... Downstream Mapping TLV SHOULD NOT be included in the echo reply.
Otherwise the replying router SHOULD include a Downstream ...
... router SHOULD include an Interface and Label Stack
Object in the echo reply message.
N Treat as a Non-IP ...
... The following TLV is a TLV that MAY be included in an echo reply to
inform the sender of an echo request ...
... TLV MAY be used by the originator of the echo request to request
that an echo reply be sent with the IP header TOS byte set to the
...
... formed, LSR X SHOULD send an MPLS Echo Reply with the Return Code
set to "Malformed echo request ...
... Timestamp Sent are not examined, but are
included in the MPLS echo reply message.
The algorithm ...
...
Best-return-code: contains the return code for the echo reply packet
as currently best known. As algorithm progresses,
...
... further checks that it performs.
Best-rtn-subcode: similar to Best-return-code, but for the Echo
Reply Subcode.
FEC ...
... A Downstream Mapping TLV SHOULD be included in the echo
reply (see section 3.3) filled in with information about
the current ECMP path.
...
...
Send an MPLS echo reply with a Return Code of Best-return-code,
and a Return Subcode of Best-rtn-subcode. Include any TLVs ...
... created during the above process. The procedures for sending
the echo reply are found in subsection 4.4.1.
...
... Sending an MPLS Echo Reply ...
...
An MPLS echo reply is a UDP packet. It MUST ONLY be sent in response
to an MPLS echo request ...
... An LSR X should only receive an MPLS echo reply in response to an
MPLS echo request that it sent. Thus, on receipt of an MPLS ...
... MPLS echo request that it sent. Thus, on receipt of an MPLS echo
reply, X should parse the packet to ensure that it is well-formed,
then attempt to match up the echo reply ...
... echo
reply, X should parse the packet to ensure that it is well-formed,
then attempt to match up the echo reply with an echo request that it
had previously sent, using the destination ...
... UDP port and the Sender's
Handle. If no match is found, then X jettisons the echo reply;
otherwise, it checks the Sequence Number to see if it matches.
...
... Sequence Number to see if it matches.
If the echo reply contains Downstream Mappings, and X wishes to
traceroute ...
... TLV. Furthermore, the "Validate FEC Stack" flag
SHOULD NOT be set until an echo reply packet with a Downstream
Mapping TLV ...
... attacks involving faking or
replaying MPLS echo reply messages are unlikely to be effective.
These replies would have to match the Sender's Handle and Sequence
Number ...
... filtering the
addresses to which echo reply messages may be sent.
Although this document makes special use of 127/8 address ...