Hi,
I have added 2 new destination unreachable codes that
Bob suggested in the ICMPv6 draft.
(me and Bob had a discussion offline and the text is
outcome of that)
Here is the new text. I would appreciate everyone's
comments.
==============
ICMPv6 Fields:
Type 1
Code 0 - no route to destination
1 - communication with destination
administratively prohibited
2 - beyond scope of source address
3 - address unreachable
4 - port unreachable
5 - source address failed ingress policy
6 - reject route to destination
Unused This field is unused for all code values.
It must be initialized to zero by the sender
and ignored by the receiver.
Description
A Destination Unreachable message SHOULD be generated by a router, or
by the IPv6 layer in the originating node, in response to a packet
that cannot be delivered to its destination address for reasons other
than congestion. (An ICMPv6 message MUST NOT be generated if a
packet is dropped due to congestion.)
If the reason for the failure to deliver is lack of a matching entry
in the forwarding node's routing table, the Code field is set to 0
(NOTE: this error can occur only in nodes that do not hold a "default
route" in their routing tables).
If the reason for the failure to deliver is administrative
prohibition, e.g., a "firewall filter", the Code field is set to 1.
If the reason for the failure to deliver is that the destination is
beyond the scope of the source address, the Code field is set to 2.
This condition can occur only when the scope of the source address is
smaller than the scope of the destination address (e.g., when a
packet has a link-local source address and a global-scope destination
address) and the packet cannot be delivered to the destination
without leaving the scope of the source address.
If the reason for the failure to deliver can not be mapped to any of
the specific codes listed above, the Code field is set to 3. The
example of such cases are inability to resolve the IPv6 destination
address into a corresponding link address, or a link-specific problem
of some sort.
One specific case in which a Destination Unreachable message with a
code 3 is sent is in response to a packet received by a router from a
point-to-point link, destined to an address within a subnet assigned
to that same link (other than one of the receiving router's own
addresses). In such a case, the packet MUST NOT be forwarded back
onto the arrival link.
A destination node SHOULD send a Destination Unreachable message with
Code 4 in response to a packet for which the transport protocol
(e.g., UDP) has no listener, if that transport protocol has no
alternative means to inform the sender.
If the reason for the failure to deliver is that packets with this
source address is not allowed due to ingress filtering policies, the
Code field is set to 5.
If the reason for the failure to deliver is that the route to the
destination is a reject route, the Code field is set to 6. This may
occur if the router has been configured to reject all the traffic for
a specific prefix.
Upper layer notification
A node receiving the ICMPv6 Destination Unreachable message MUST
notify the upper-layer process.
==============
Regards
Mukesh
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