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Overflow/Underflow notes
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**Note:** The following overflow/underflow notes do not apply to USRP1,
which does not support the advanced features available in newer products.

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Overflow notes
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When receiving, the device produces samples at a constant rate.
Overflows occurs when the host does not consume data fast enough.
When UHD detects the overflow, it prints an "O" to stdout,
and pushes an inline message packet into the receive stream.

**Network-based devices**:
The host does not back-pressure the receive stream.
When the kernel's socket buffer becomes full, it will drop subsequent packets.
UHD detects the overflow as a discontinuity in the packet's sequence numbers,
and muxes an inline message packet into the receive stream.

**Other devices**:
The host back-pressures the receive stream.
Therefore, overflows always occur in the device itself.
When the device's internal buffers become full, streaming is shutoff,
and an inline message packet is sent to the host.
If the device was in continuous streaming mode,
the UHD will automatically restart streaming.

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Underflow notes
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When transmitting, the device consumes samples at a constant rate.
Underflow occurs when the host does not produce data fast enough.
When the UHD detects underflow, it prints an "U" to stdout,
and pushes a message packet into the async message stream.