User guide

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LQM Link Quality Monitoring. Optional facility that lets PPP
make policy decisions based on the observed quality of the link
between peers. Documented in RFC 1333.
loopback test. Diagnostic procedure in which data is sent from
a devices's output channel and directed back to its input chan-
nel so that what was sent can be compared to what was
received.
-----M-----
magic number. Random number generated by a router and
included in packets it sends to other routers. If the router
receives a packet with the same magic number it is using, the
router sends and receives packets with new random numbers
to determine if it is talking to itself.
MD5. A 128-bit, message-digest, authentication algorithm used
to create digital signatures. It computes a secure, irreversible,
cryptographically strong hash value for a document. Less
secure than variant SHA-1.
metric. Distance, measured in the number of routers a packet
must traverse, that a packet must travel to go from a router to a
remote network. A route with a low metric is considered more
efficient, and therefore preferable, to a route with a high metric.
See hop count.
modem. Modulator/demodulator. Device used to convert a dig-
ital signal to an analog signal for transmission over standard
telephone lines. A modem at the other end of the connection
converts the analog signal back to a digital signal.
MRU. Maximum Receive Unit. The maximum packet size, in
bytes, that a network interface will accept.