Time_Exc_0.seq - check Time Exceeded 0
Router
When test starts, states of Neighbor Cache Entry for TN's
addresses are reachable.
This test verifies that NUT sends valid ICMPv6 Time Exceeded (code 0)
in response to a packet which can not be forwarded.
And this test verifies that the message processing rule,
- If the message is a response to a message sent to one of the
node's unicast addresses, the Source Address of the reply must
be that same address.
- If the message is a response to a message sent to an address
that does not belong to the node, the Source Address should be
that unicast address belonging to the node that will be most
helpful in diagnosing the error. For example, if the message is
a response to a packet forwarding action that cannot complete
successfully, the Source Address should be a unicast address
belonging to the interface on which the packet forwarding
failed.
TN NUT
---------------------------
1.
=== echo request packet ===>
src address : TN global address
dst address : NUT global address
hop limit : 0 or 1
2.
<< JUDGMENT >>
<=== ICMPv6 Time Exceeded ===
src address : NUT global address
dst address : TN global address
Code is 0
<< PASS >>
NUT send ICMPv6 Time Exceeded.
<< FAIL >>
NUT do not send ICMPv6 Time Exceeded.
RFC2463 3.3 Time Exceeded Message
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unused |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| As much of invoking packet |
+ as will fit without the ICMPv6 packet +
| exceeding the minimum IPv6 MTU [IPv6] |
IPv6 Fields:
Destination Address
Copied from the Source Address field of the invoking
packet.
ICMPv6 Fields:
Type 3
Code 0 - hop limit exceeded in transit
1 - fragment reassembly time exceeded
Unused This field is unused for all code values.
It must be initialized to zero by the sender
and ignored by the receiver.
Description
If a router receives a packet with a Hop Limit of zero, or a router decrements a packet's Hop Limit to zero, it MUST discard the packet and send an ICMPv6 Time Exceeded message with Code 0 to the source of the packet. This indicates either a routing loop or too small an initial Hop Limit value.
The rules for selecting the Source Address of this message are defined in section 2.2.
perldoc V6evalTool