DS3/E3
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... value of 0 indicates that this DS1/E1 does not
have a parent DS3/E3."
::= { dsx1ConfigEntry 19 }
...
... Nicklass, O., "Definitions of Managed Objects for the DS3/E3 Interface Type", RFC 3896prop, September 2004. ...
... This document is a companion to the documents that define managed
objects for the DS0 [RFC2494], DS3/E3 [RFC3896], and Synchronous
Optical Network/Synchronous Digital Hierarchy ...