HP UX 11.x Operating Systems manual Link State Indications

Using HDLC.FRAME Protocol

Link State Indications

•If the “qdown” option is set then the port is set DOWN whenever the hardware detects a loss of synchronization. It is possible for the hardware to alternately re-establish and lose synchronization extremely rapidly with a poor quality line, making it difficult for higher layer protocols to operate. The “qdown” bit should be used only where line quality is known to be very good and with upper layer protocols that need immediate notification of any line problems (SS7 for example).

If an E1/T1 port is configured for external clock, and has no cable connected, it is possible for the hardware to detect framing due to crosstalk from other E1/T1 lines, so HDLC.FRAME terminals on the port may be indicated as UP.

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