Ticket #11: De-registration when returning home [Vijay Devarapalli
<vijay at wichorus.com>]
RFC 3775 currently says the mobile node "SHOULD" send a de-registration
BU when it returns home. This is kind of odd because, without the
de-registration BU, the home agent continues defending the mobile node's
home address and keeps tunneling the packets to the last known care-of
address. The BCE must be deleted for the mobile node to be able to send/
receive packets from the home link. I am not sure why we went with
"SHOULD" in the first place.
From the interop events I have attended, I know that all mobile node
implementations send a de-registration BU as soon as they detect they
are on the home link. The use of "SHOULD" instead of "MUST" caused some
confusion during the PMIPv6-MIPv6 interactions discussion. So we need to
fix this.
Here is the proposed change.
OLD:
A mobile node detects that it has returned to its home link through
the movement detection algorithm in use (Section 11.5.1), when the
mobile node detects that its home subnet prefix is again on-link.
The mobile node SHOULD then send a Binding Update to its home agent,
to instruct its home agent to no longer intercept or tunnel packets
for it.
NEW:
A mobile node detects that it has returned to its home link through
the movement detection algorithm in use (Section 11.5.1), when the
mobile node detects that its home subnet prefix is again on-link.
The mobile node MUST then send a Binding Update to its home agent,
to instruct its home agent to no longer intercept or tunnel packets
for it.
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Gerardo Giaretta <gerardog at qualcomm.com>
This was discussed also in Philadelphia and in general I agree a
MUST is more appropriate.
However we should make clear that the MN MUST send the deregistration
BU only when it wants the HA to stop intercepting packets and
forwarding them to the CoA.
Let's assume for example the MN has two active interfaces, it is using
interface with CoA1 registered at the HA. Then it switches interface2
on and detects interfaces2 is connected to the home link. This should
not immediately trigger the MN to send the BU, unless the MN wants all
traffic destined to the HoA routed to interface2 (the MN may still
want to have the traffic destined to interface1).
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Sri Gundavelli <sgundave at cisco.com>
We discussed this issue in the last meeting and I thought
the conclusion there was, if the mobile node attaches to
the home link and *if* it decides to use the home address
i.e., defend the home address on the home link, then it
MUST send a dereg BU. This will avoid the Proxy ND contention.
Note that it is possible the MN is attached to the home,
but may choose to send the dereg bit later. So, the wording
has to reflect this aspect.
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Ahmad Muhanna <amuhanna at nortel.com>
IMO, the best for RFC3775 and RFC3775bis is to maintain "SHOULD" because
my understanding of "SHOULD" is that the MN MUST send de-registration
UNLESS there is a condition that makes it impossible on the MN to send
de-registration, e.g. MN lost coverage, or lost power, etc.
The usefulness of SHOULD in base RFC3775 that it can be become "MUST"
in a specific scenario where that is possibly described in a different
doc, like the case that Gerardo mentioned. IMO, that "MUST" should be
captured in the Multi-CoA doc not in RFC3775bis.
On the other hand, the latest change defeats the original purpose of
RFC3775, because RFC3775 mandates on the MN to send de-registration,
however, the last change, proposed here, makes it based on the MN
discretion and that is very dangerous.
I disagree with this change and I favor maintaining "SHOULD" in
the base document and if "MUST" is needed in a specific scenarios
let us capture that in the respected document.
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George Tsirtsis <tsirtsis at googlemail.com>
... it does not make sense to require
that the MN sends a dereg BU when it connects to its home link.
Instead this is a MIPv6 layer decision that has nothing to do with
whether the MN has connection only to the home link or to one or more
other links at the same time.
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Sri Gundavelli <sgundave at cisco.com>
...I'm ok leaving the initial SHOULD
wording, however, the technical issue that I see and as I
said before is that we should clearly document and state
that the MN MUST send a dereg message before it can start
using its hoa on the home link and that will avoid any ND
contentions between the HA and the MN. This is not implicit
and cannot be left to the reader and so must be documented.
Generally, it can be stated the MN must send a dereg. But,
the issue related to power down ...etc. ..etc are probably
valid and there may be valid reasons as why MN may not be
able to send a dereg message. So, we can always qualify
that requirement and state that the MN must send a dereg
before it can start using its home address on the home link
and also leave the option for it not to send any dereg
message in some situations and when it has no need to use
its HoA.
Bottom line:
- Leave the SHOULD as a strong recommendation for the MN
to send dereg, as it is currently written.
- Add additional text and state the MN MUST send a dereg
before it can use its hoa on the home link.
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George Tsirtsis <tsirtsis at googlemail.com>
Sri/Ben, IMHO combining SHOULDs/MAYs and MUSTs with "if" statements
does not result in good specs. For example, the MUST in Ben's proposal
is to be followed only if the MN *intends* to get its traffic to flow
on the home link and, not following the MUST does not really break the
protocol. In any case, *intentions* are not easy to evaluate during
interoperability testing. So, maybe we should simply try to clarify
the SHOULD. Here is a proposal:
OLD Text:
A mobile node detects that it has returned to its home link through
the movement detection algorithm in use (Section 11.5.1), when the
mobile node detects that its home subnet prefix is again on-link.
The mobile node SHOULD then send a Binding Update to its home agent,
to instruct its home agent to no longer intercept or tunnel packets
for it.
NEW Text:
A mobile node detects that it has returned to its home link through
the movement detection algorithm in use (Section 11.5.1), when the
mobile node detects that its home subnet prefix is again on-link.
The mobile node SHOULD then send a Binding Update to its home agent,
to instruct its home agent to no longer intercept or tunnel packets
for it. Until the mobile node sends a de-registration Binding Update,
it will not be able to send and receive packets using its home
address from the home link. The home agent will continue to intercept
all packets sent to the mobile's home address and tunnel to the
previously registered care-of address.
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Reporter: charliep at computer.org | Owner: charliep at computer.org
Type: defect | Status: new
Priority: minor | Milestone:
Component: draft-ietf-mext-rfc3775bis | Version:
Severity: Active WG Document | Keywords:
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