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As stated earlier the key issue in the packet radio network is transmission
capacity, and from the discussion above it is clear that AX.25 doesn't use
this capacity efficiently because:
- The virtual circuit functionality is strictly not the responsibility
of the link layer. It should form part of the network layer which is
separated from the link layer.
- Similarly, source routing is strictly not the responsibility of
the link layer. It should form part of the network layer which is
separated from the link layer.
- Callsigns are transmitted in every packet, although most amateur
services require a transmitter to broadcast their callsign at larger
intervals (e.g 10 minutes). As each callsign is 7 octets long, and
there are at least two in each packet, this forms a large overhead.