Appendix D. SNMP

Every thought is an afterthought.

Hannah Arendt

Managing far-flung networks requires a helping hand. Most network administrators, when given the tasks of running large networks with many leased lines, turn to SNMP, the Simple Network Management Protocol. This appendix presents an overview of two MIBs that may be useful to network administrators with extensive T1 deployments.

RFC 2495: DS1 MIB

RFC 2495 defines the MIB for DS1, DS2, E1, and E2 interfaces. This section will consider only the DS1 portion of RFC 2495.

Differences from T1.231

RFC 2495 was written at the time when a draft revision of T1.231 was working through the ANSI standards process. Some of the definitions in RFC 2495 are based on early drafts of T1.231 and thus are not fully consistent with T1.231. These differences are important because data communications equipment vendors implement the RFC, but telecommunications equipment vendors implement the ANSI specifications. Here are some differences:

  • RFC 2495 defines the out of frame (OOF) defect in exactly the same way that ANSI T1.231 defines the severely errored framing (SEF) defect. In practice, this is only a minor difference because SEF defects are nearly always accompanied by ANSI-defined OOF defects.

  • The definition of a severely errored framing second (SEFS) in RFC 2495 is equivalent to the ANSI definition of a severely errored framing/AIS second (SAS-P).

  • RFC 2495 uses the term “bursty errored second” to refer to ANSI’s errored second type ...

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