Re: [homenet] DNCP/HNCP Revisited

Juliusz Chroboczek <jch@irif.fr> Thu, 19 September 2019 23:06 UTC

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Date: Fri, 20 Sep 2019 01:06:40 +0200
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From: Juliusz Chroboczek <jch@irif.fr>
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Subject: Re: [homenet] DNCP/HNCP Revisited
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> I notice in the current Openwrt code that the max UDP packet size is set at 9000 octets with the comment:

> /* Very arbitrary. On some implementations, I have seen some issues
>  * with 10+kb frames so we use this for now. It MUST be significantly
>  * more than 4k, due to how code is written at the moment. */
> #define HNCP_MAXIMUM_UNICAST_SIZE 9000

> With current code (without expanding the TLV data set), and my sample
> test routers, that sets a current maximum network size of approx. 12
> nodes.

I don't think that the limit applies to the total network size, it applies to
the maximum size of a single NODE-STATE TLV.  If memory serves, HNCP is
able to send each NODE-STATE in a separate datagram, so the network can
grow without bound; it's the amount of data published by a single node
that is limited to slightly less than 9kB.

However, I agree that this could prove problematic if you build a very
dense network (a single node with a lot of neighbours) or if you have
large numbers of external connections terminating at a single node.

-- Juliusz