Subject: [Mobike] issue 10: changing addresses or paths?

From: Jari Arkko <[email-masked]>
Date: Tue, 30 Nov 2004 06:23:02 +0200

Our earlier resolution of issue 17 (if both parties have
several addresses, do we assume that all pairs have
connectivity between them?) was that we should NOT
assume full connectivity in these cases.

I believe the above resolution implies that upon
a problem, we may have to switch paths, not just
an address. I also explained the issue in Washington
in my presentation.

So I think its pretty clear that the answer to this
question is that we need to be able to change paths.
Suggested text below:

Change design draft from

6.  Changing addresses or changing the paths (issue #10, #14)

    The question here is, if it is enough for the MOBIKE to detect the
    dead-address, or do it need to detect also dead-paths. Dead-address
    detection means that we only detect that we cannot get packets
    through to that remote address by using the local IP-address given by
    the local IP-stack (i.e. local address selected normally by the
    routing information). Dead-path detection means that we need to try
    all possible local interfaces/IP-addresses for each remote addresses,
    i.e. find all possible paths between the hosts and try them all to
    see which of them work (or at least find one working path).

    Doing the dead-address detection is simpler, and there is less probe
    packets to be sent, thus it does not cause that much stress to the
    network. It also is enough for the scenarios where the connection
    problems are local (i.e. interfaces going down, WLAN access
    disappearing etc). It does not help if some router somewhere along
    the path breaks down, in which case rerouting the packets along
    another path might get around that broken router. The question is,
    whether rerouting around that problem inside the core network is a
    problem that MOBIKE needs to solve.

to

6. Changing addresses or changing the paths (issue #10, #14)

    The question here is, if it is enough for the MOBIKE to detect the
    dead-address, or do it need to detect also dead-paths. Dead-address
    detection means that we only detect that we cannot get packets
    through to that remote address by using the local IP-address given by
    the local IP-stack (i.e. local address selected normally by the
    routing information). Dead-path detection means that we need to try
    all possible local interfaces/IP-addresses for each remote addresses,
    i.e. find all possible paths between the hosts and try them all to
    see which of them work (or at least find one working path).

    While performing just an address change is simpler, the existence
    of locally operational addresses are not, however, a guarantee
    that communications can be established with the peer.  A
    failure in the routing infrastructure can prevent the sent packets
    from reaching their destination. Or a failure of an interface on
    one side can be related to the failure of an interface on the
    other side, making it necessary to change more than one address
    at a time.

--Jari

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