Juliusz Chroboczek <[email protected]> wrote:
    >>> If the latter, I can see some opportunities for transient routing loops
    >>> if not done carefully.  (And you certainly don't want a routing loop on
    >>> a link with low-power nodes.)

    >> That’s interesting. Could you try explaining what could happen ?

    > I hope I'm just being paranoid, since I rather like the idea of
    > redistribution through HNCP.

    > A and B are homenet nodes.  L is a low power node.

>   A-----B
>    \   /
>     \ /
>      L
>      |
>      |
>     LLN

Not a valid topology.   This is the correct topology:

>   A-----B
>    \   /
>     \ /
>   LLNgate (aka Thermostat)
>      |
>  L---+---L
>    L-+-L

the low power nodes are not the gateway.  That just doesn't work.

    > A and B are both announcing the LLN route.  L crashes.  A and B both
    > notice that L is no longer reachable, so each of them attempts to route
    > through the other one.  You have a transient routing loop that lasts until
    > A and B agree on the fact that L is unreachable.

There is no impact on the low power nodes or the gateway. This is inevitable.

    > On a wired network, the routing loop will be extremely short-lived (one
    > successful packet exchange for both Babel and OSPF, not sure about IS-IS).
    > I'm not sure what will happen on a wireless network, but I've learnt to be
    > pessimistic about the behaviour of 802.11.  I could imagine cases where
    > the looping data traffic prevents A and B from communicating successfully,
    > especially if L had more than just two Homenet neighbours.

So you are saying you think that the looping L traffic will consume all of
the bandwidth of the wireless network, and that will keep the routing
protocol from converging again.

-- 
]               Never tell me the odds!                 | ipv6 mesh networks [ 
]   Michael Richardson, Sandelman Software Works        | network architect  [ 
]     [email protected]  http://www.sandelman.ca/        |   ruby on rails    [ 
        

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