📄 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
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