AX.25 has a maximum MTU of 256 bytes I think vs 802.15.4 is 128.
What I find though, having used RFC7959 on large (>100 node) 6LoWPAN networks (which supports a MTU of 1280 on 802.15.4 via L2 fragmentation), is that on congested networks, the fragments get lost causing retransmissions. On good networks, 256 bytes gives good performance, 512 and 1024 byte blocks give diminishing returns. (Great on a small network with nearby nodes, not so great when it's 50+ nodes spread out over a retirement village.)
So on a busy network, there is sometimes a benefit in smaller blocks.
Stuart Longland (VK4MSL) /
npub12n…d9dex
2025-05-18 10:40:09
in reply to nevent1q…cy7u
Author Public Key
npub12n5weher8thl0qlj398tvw2rmwpr33z8j443lpg28xyuzkef9dksnd9dexPublished at
2025-05-18 10:40:09Event JSON
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"content": "AX.25 has a maximum MTU of 256 bytes I think vs 802.15.4 is 128.\n\nWhat I find though, having used RFC7959 on large (\u003e100 node) 6LoWPAN networks (which supports a MTU of 1280 on 802.15.4 via L2 fragmentation), is that on congested networks, the fragments get lost causing retransmissions. On good networks, 256 bytes gives good performance, 512 and 1024 byte blocks give diminishing returns. (Great on a small network with nearby nodes, not so great when it's 50+ nodes spread out over a retirement village.)\n\nSo on a busy network, there is sometimes a benefit in smaller blocks.",
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