rfc2495.txt

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Fowler, Ed.                 Standards Track                     [Page 6]

RFC 2495                   DS1/E1/DS2/E2 MIB                January 1999


         +-----+
   |     |     |
   |     |     |               +---------------------+
   |E    |     |  1.544  MBPS  |              Line#A | DS1 Link
   |t    |  R  |---------------+ - - - - -  - - -  - +------>
   |h    |     |               |                     |
   |e    |  O  |  1.544  MBPS  |              Line#B | DS1 Link
   |r    |     |---------------+ - - - - - - - - - - +------>
   |n    |  U  |               |  CSU Shelf          |
   |e    |     |  1.544  MBPS  |              Line#C | DS1 Link
   |t    |  T  |---------------+ - - - -- -- - - - - +------>
   |     |     |               |                     |
   |-----|  E  |  1.544  MBPS  |              Line#D | DS1 Link
   |     |     |---------------+ -  - - - -- - - - - +------>
   |     |  R  |               |_____________________|
   |     |     |
   |     +-----+

   The assignment of the index values could for example be:

           ifIndex  Description
           1        Ethernet
           2        Line#A Router
           3        Line#B Router
           4        Line#C Router
           5        Line#D Router
           6        Line#A CSU Router
           7        Line#B CSU Router
           8        Line#C CSU Router
           9        Line#D CSU Router
           10       Line#A CSU Network
           11       Line#B CSU Network
           12       Line#C CSU Network
           13       Line#D CSU Network

   The ifStackTable is then used to show the relationships between the
   various DS1 interfaces.

           ifStackTable Entries
           HigherLayer   LowerLayer
           2             6
           3             7
           4             8
           5             9
           6             10
           7             11
           8             12
           9             13



Fowler, Ed.                 Standards Track                     [Page 7]

RFC 2495                   DS1/E1/DS2/E2 MIB                January 1999


   If the CSU shelf is managed by itself by a local SNMP Agent, the
   situation would be identical, except the Ethernet and the 4 router
   interfaces are deleted.  Interfaces would also be numbered from 1 to
   8.

           ifIndex  Description
           1        Line#A CSU Router
           2        Line#B CSU Router
           3        Line#C CSU Router
           4        Line#D CSU Router
           5        Line#A CSU Network
           6        Line#B CSU Network
           7        Line#C CSU Network
           8        Line#D CSU Network

           ifStackTable Entries

           HigherLayer   LowerLayer
           1             5
           2             6
           3             7
           4             8

2.2.2.  Usage of ifStackTable for DS1/E1 on DS2/E2

   An example is given of how DS1/E2 interfaces are stacked on DS2/E2
   interfaces.  It is not necessary nor is it always desirable to
   represent DS2 interfaces.  If this is required, the following
   stacking should be used.  All ifTypes are ds1.  The DS2 is determined
   by examining ifSpeed or dsx1LineType.

        ifIndex  Description
        1        DS1 #1
        2        DS1 #2
        3        DS1 #3
        4        DS1 #4
        5        DS2

        ifStackTable Entries

        HigherLayer   LowerLayer
        1             5
        2             5
        3             5
        4             5






Fowler, Ed.                 Standards Track                     [Page 8]

RFC 2495                   DS1/E1/DS2/E2 MIB                January 1999


2.2.3.  Usage of Channelization for DS3, DS1, DS0

   An example is given here to explain the channelization objects in the
   DS3, DS1, and DS0 MIBs to help the implementor use the objects
   correctly. Treatment of E3 and E1 would be similar, with the number
   of DS0s being different depending on the framing of the E1.


   Assume that a DS3 (with ifIndex 1) is Channelized into DS1s (without
   DS2s).  The object dsx3Channelization is set to enabledDs1.  There
   will be 28 DS1s in the ifTable.  Assume the entries in the ifTable
   for the DS1s are created in channel order and the ifIndex values are
   2 through 29. In the DS1 MIB, there will be an entry in the
   dsx1ChanMappingTable for each ds1.  The entries will be as follows:

           dsx1ChanMappingTable Entries

           ifIndex  dsx1Ds1ChannelNumber   dsx1ChanMappedIfIndex
           1        1                      2
           1        2                      3
           ......
           1        28                     29

   In addition, the DS1s are channelized into DS0s.  The object
   dsx1Channelization is set to enabledDS0 for each DS1.   When this
   object is set to this value, 24 DS0s are created by the agent. There
   will be 24 DS0s in the ifTable for each DS1.  If the
   dsx1Channelization is set to disabled, the 24 DS0s are destroyed.

   Assume the entries in the ifTable are created in channel order and
   the ifIndex values for the DS0s in the first DS1 are 30 through 53.
   In the DS0 MIB, there will be an entry in the dsx0ChanMappingTable
   for each DS0.  The entries will be as follows:

           dsx0ChanMappingTable Entries

           ifIndex   dsx0Ds0ChannelNumber  dsx0ChanMappedIfIndex
           2         1                     30
           2         2                     31
           ......
           2         24                    53

2.2.4.  Usage of Channelization for DS3, DS2, DS1

   An example is given here to explain the channelization objects in the
   DS3 and DS1 MIBs to help the implementor use the objects correctly.





Fowler, Ed.                 Standards Track                     [Page 9]

RFC 2495                   DS1/E1/DS2/E2 MIB                January 1999


   Assume that a DS3 (with ifIndex 1) is Channelized into DS2s.  The
   object dsx3Channelization is set to enabledDs2.  There will be 7 DS2s
   (ifType of DS1) in the ifTable.  Assume the entries in the ifTable
   for the DS2s are created in channel order and the ifIndex values are
   2 through 8. In the DS1 MIB, there will be an entry in the
   dsx1ChanMappingTable for each DS2.  The entries will be as follows:

           dsx1ChanMappingTable Entries

           ifIndex  dsx1Ds1ChannelNumber   dsx1ChanMappedIfIndex
           1        1                      2
           1        2                      3
           ......
           1        7                      8

   In addition, the DS2s are channelized into DS1s.  The object
   dsx1Channelization is set to enabledDS1 for each DS2.  There will be
   4 DS1s in the ifTable for each DS2.  Assume the entries in the
   ifTable are created in channel order and the ifIndex values for the
   DS1s in the first DS2 are 9 through 12, then 13 through 16 for the
   second DS2, and so on.  In the DS1 MIB, there will be an entry in the
   dsx1ChanMappingTable for each DS1.  The entries will be as follows:

           dsx1ChanMappingTable Entries

           ifIndex   dsx1Ds1ChannelNumber  dsx1ChanMappedIfIndex
           2         1                     9
           2         2                     10
           2         3                     11
           2         4                     12
           3         1                     13
           3         2                     14
           ...
           8         4                     36


2.2.5.  Usage of Loopbacks

   This section discusses the behaviour of objects related to loopbacks.

   The object dsx1LoopbackConfig represents the desired state of
   loopbacks on this interface.  Using this object a Manager can
   request:
       LineLoopback
       PayloadLoopback (if ESF framing)
       InwardLoopback
       DualLoopback (Line + Inward)
       NoLoopback



Fowler, Ed.                 Standards Track                    [Page 10]

RFC 2495                   DS1/E1/DS2/E2 MIB                January 1999


   The remote end can also request loopbacks either through the FDL
   channel if ESF or inband if D4.  The loopbacks that can be request
   this way are:
       LineLoopback
       PayloadLoopback (if ESF framing)
       NoLoopback

   To model the current state of loopbacks on a DS1 interface, the
   object dsx1LoopbackStatus defines which loopback is currently applies
   to an interface.  This objects, which is a bitmap, will have bits
   turned on which reflect the currently active loopbacks on the
   interface as well as the source of those loopbacks.

   The following restrictions/rules apply to loopbacks:

   The far end cannot undo loopbacks set by a manager.

   A manager can undo loopbacks set by the far end.

   Both a line loopback and an inward loopback can be set at the same
   time.  Only these two loopbacks can co-exist and either one may be
   set by the manager or the far end.  A LineLoopback request from the
   far end is incremental to an existing Inward loopback established by
   a manager.  When a NoLoopback is received from the far end in this
   case, the InwardLoopback remains in place.

2.3.  Objectives of this MIB Module

   There are numerous things that could be included in a MIB for DS1
   signals:  the management of multiplexors, CSUs, DSUs, and the like.
   The intent of this document is to facilitate the common management of
   all devices with DS1, E1, DS2, or E3 interfaces.  As such, a design
   decision was made up front to very closely align the MIB with the set
   of objects that can generally be read from these types devices that
   are currently deployed.

   J2 interfaces are not supported by this MIB.

2.4.  DS1 Terminology

   The terminology used in this document to describe error conditions on
   a DS1 interface as monitored by a DS1 device are based on the late
   but not final draft of what became the ANSI T1.231 standard [11].  If
   the definition in this document does not match the definition in the
   ANSI T1.231 document, the implementer should follow the definition
   described in this document.





Fowler, Ed.                 Standards Track                    [Page 11]

RFC 2495                   DS1/E1/DS2/E2 MIB                January 1999


2.4.1.  Error Events

   Bipolar Violation (BPV) Error Event
       A BPV error event for an AMI-coded signal is the occurrence of a
       pulse of the same polarity as the previous pulse.  (See T1.231
       Section 6.1.1.1.1) A BPV error event for a B8ZS- or HDB3- coded
       signal is the occurrence of a pulse of the same polarity as the
       previous pulse without being a part of the zero substitution
       code.

   Excessive Zeroes (EXZ) Error Event
       An Excessive Zeroes error event for an AMI-coded signal is the
       occurrence of more than fifteen contiguous zeroes.  (See T1.231
       Section 6.1.1.1.2) For a B8ZS coded signal, the defect occurs
       when more than seven contiguous zeroes are detected.

   Line Coding Violation (LCV) Error Event
       A Line Coding Violation (LCV) is the occurrence of either a
       Bipolar Violation (BPV) or Excessive Zeroes (EXZ) Error Event.
       (Also known as CV-L; See T1.231 Section 6.5.1.1)

   Path Coding Violation (PCV) Error Event
       A Path Coding Violation error event is a frame synchronization
       bit error in the D4 and E1-noCRC formats, or a CRC or frame
       synch. bit error in the ESF and E1-CRC formats. (Also known as
       CV-P; See T1.231 Section 6.5.2.1)

   Controlled Slip (CS) Error Event
       A Controlled Slip is the replication or deletion of the payload
       bits of a DS1 frame.  (See T1.231 Section 6.1.1.2.3) A Controlled
       Slip may be performed when there is a difference between the
       timing of a synchronous receiving terminal and the received
       signal.  A Controlled Slip does not cause an Out of Frame defect.

2.4.2.  Performance Defects