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MODE
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1991-09-18
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==== NOSview [137]
mode
====
_________________________________________________________________
mode <interface> [vc | datagram] Default: datagram
_________________________________________________________________
Display or set the default transmission mode on the specified
AX.25 interface.
In 'vc' (virtual circuit) mode, IP packets are encapsulated in
AX.25 I-frames and are acknowledged at the link level according
to the AX.25 protocol. Link level connections are opened if
necessary. This is the conventional mode used by TNCs operating
in native mode.
In 'datagram' mode, IP packets are encapsulated in AX.25 UI-
frames and transmitted without any other link level mechanisms,
such as connections or acknowledgements.
In both modes, ARP is used to map IP to AX.25 addresses. The
defaults can be overridden with the type-of-service (TOS) bits in
the IP header. Turning on the "reliability" bit causes I-frames
to be used, while turning on the "low delay" bit uses UI-frames.
(The effect of turning on both bits is undefined and subject to
change).
In both modes, IP-level fragmentation is done if the datagram is
larger than the interface MTU. In virtual circuit mode, however,
the resulting datagrams (or fragments) are further fragmented at
the AX.25 layer if they are still larger than the AX.25 'paclen'
parameter.
In AX.25 fragmentation, datagrams are broken into several I-
frames and reassembled at the receiving end before being passed
to IP. This is preferable to IP fragmentation whenever possible
because of decreased overhead (the IP header isn't repeated in
each fragment) and increased robustness (a lost fragment is
immediately retransmitted by the link layer).
>> Example: mode tnc0 vc
_________________________________________________________________
mode netrom [vc | datagram] Default: datagram
_________________________________________________________________
Display or set the default transmission mode for NET/ROM
transmissions.
>> Example: mode netrom vc