📄 rfc1232.txt
字号:
Network Working Group F. Baker
Request for Comments: 1232 Advanced Computer Communications, Inc.
C. Kolb
Performance Systems International, Inc.
Editors
May 1991
Definitions of Managed Objects
for the DS1 Interface Type
Status of this Memo
This memo defines objects for managing DS1 Interface objects for use
with the SNMP protocol. This memo is a product of the Transmission
MIB Working Group of the Internet Engineering Task Force (IETF).
This RFC specifies an IAB standards track protocol for the Internet
community, and requests discussion and suggestions for improvements.
Please refer to the current edition of the "IAB Official Protocol
Standards" for the standardization state and status of this protocol.
Distribution of this memo is unlimited.
Table of Contents
1. Abstract .............................................. 1
2. The Network Management Framework....................... 2
3. Objects ............................................... 2
3.1 Format of Definitions ............................... 3
4. Overview .............................................. 3
4.1 Binding between Interfaces and CSUs ................. 3
4.2 Objectives of this MIB Module ....................... 4
4.3 DS1 Terminology ..................................... 4
5. Definitions ........................................... 6
5.1 The DS1 Configuration Group ......................... 6
5.2 The DS1 Interval Group .............................. 13
5.3 The DS1 Current Group ............................... 16
5.4 The DS1 Total Group ................................. 19
5.5 The DS1 Fractional Group ............................ 22
6. Acknowledgements ...................................... 25
7. References ............................................ 26
8. Security Considerations................................ 27
9. Authors' Addresses..................................... 28
1. Abstract
This memo defines an experimental portion of the Management
Information Base (MIB) for use with network management protocols in
TCP/IP-based internets. In particular, this memo defines MIB objects
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RFC 1232 DS1 Interface Objects May 1991
for representing DS1 physical interfaces. Implementors should
consult in addition to this memo the companion document that
describes that DS3 managed objects.
2. The Network Management Framework
The Internet-standard Network Management Framework consists of three
components. They are:
RFC 1155 which defines the SMI, the mechanisms used for describing
and naming objects for the purpose of management. RFC 1212
defines a more concise description mechanism, which is wholly
consistent with the SMI.
RFC 1156 which defines MIB-I, the core set of managed objects for
the Internet suite of protocols. RFC 1213, defines MIB-II, an
evolution of MIB-I based on implementation experience and new
operational requirements.
RFC 1157 which defines the SNMP, the protocol used for network
access to managed objects.
The Framework permits new objects to be defined for the purpose of
experimentation and evaluation.
3. Objects
Managed objects are accessed via a virtual information store, termed
the Management Information Base or MIB. Objects in the MIB are
defined using the subset of Abstract Syntax Notation One (ASN.1) [7]
defined in the SMI. In particular, each object has a name, a syntax,
and an encoding. The name is an object identifier, an
administratively assigned name, which specifies an object type. The
object type together with an object instance serves to uniquely
identify a specific instantiation of the object. For human
convenience, we often use a textual string, termed the OBJECT
DESCRIPTOR, to also refer to the object type.
The syntax of an object type defines the abstract data structure
corresponding to that object type. The ASN.1 language is used for
this purpose. However, the SMI [3] purposely restricts the ASN.1
constructs which may be used. These restrictions are explicitly made
for simplicity.
The encoding of an object type is simply how that object type is
represented using the object type's syntax. Implicitly tied to the
notion of an object type's syntax and encoding is how the object type
is represented when being transmitted on the network.
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RFC 1232 DS1 Interface Objects May 1991
The SMI specifies the use of the basic encoding rules of ASN.1 [8],
subject to the additional requirements imposed by the SNMP.
3.1. Format of Definitions
Section 5 contains contains the specification of all object types
contained in this MIB module. The object types are defined using the
conventions defined in the SMI, as amended by the extensions
specified in [13].
4. Overview
These objects are used when the particular media being used to
realize an interface is a DS1 physical interface. At present, this
applies to these values of the ifType variable in the Internet-
standard MIB:
ds1 (18)
e1 (19)
The definitions contained herein are based on the AT&T T-1
specifications and Extended Superframe (ESF) format [9, 10], the
latter of which conforms to proposed ANSI specifications [14, 15].
The various T1 and E1 line disciplines are similar enough that
separate MIBs are unwarranted, although there are some differences.
For example, Loss of Frame is defined more rigorously in the ESF
specification than in the D4 specification, but it is defined in
both.
4.1. Binding between Interfaces and CSUs
It should be noted that it is possible to multiplex multiple bit
streams onto a single DS1 physical interface (CSU), realizing
multiple interfaces from the perspective of the Internet-standard
MIB. It is also possible to concatenate physical interfaces to
provide a single logical interface. As such, it is important to be
able to distinguish between the indices used to identify the CSUs
attached to a node and the indices used to identify an interface (in
the MIB sense) attached to a node.
Each agent which resides on a host which uses DS1 physical interfaces
is required to assign a small, positive integer uniquely to each CSU.
This is known as the "CSUIndex", and is used to distinguish between
different CSUs attached to a node. The CSUIndex is also used as the
"key" when accessing tabular information about DS1 physical
interfaces.
The potentially many-to-one binding between CSU indices and the
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RFC 1232 DS1 Interface Objects May 1991
ifIndex value assigned to each MIB interface are defined in the
ds1ConfigTable table defined in the next section.
4.2. Objectives of this MIB Module
There are numerous things that could be included in a MIB for DS1
Interfaces: the management of multiplexors, CSUs, DSUs, and the like.
The intent of this document is to facilitate the common management of
CSUs, both in-chassis and external via proxy. 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 CSUs that are currently
deployed, which is to say ESF CSUs conforming to AT&T specifications.
However, by simple generalization of these objects, the MIB is also
made applicable to D4 and G.704 devices.
To meet a requirement not easily satisfied in other places, there is
one additional group present, the Fractional DS1 group. This is
intended to facilitate the use of fractional DS1 devices (i.e.,
devices which utilize a subset of the 8 bit channels available in the
frame) over the managed CSUs.
4.3. DS1 Terminology
The terminology used in this document to describe error conditions on
a T1 or E1 circuit monitored by a CSU are from references [10], [11],
[14], and [15].
Out of Frame event
An Out of Frame event is declared when the receiver
detects two or more framing-bit errors within a 3
millisecond period, or two or more errors out of five or
less consecutive framing-bits. At this time, the framer
enters the Out of Frame State, and starts searching for a
correct framing pattern. The Out of Frame state ends
when reframe occurs.
Loss of Signal
This event is declared upon observing 175 +/- 75
contiguous pulse positions with no pulses of either
positive or negative polarity (also called keep alive).
Code Violation Error Event
A Code Violation Error Event is the occurrence of a
received Cyclic Redundancy Check code that is not
identical to the corresponding locally-calculated code.
Bipolar Violation
A Bipolar Violation, for B8ZS-coded signals, is the
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RFC 1232 DS1 Interface Objects May 1991
occurrence of a received bipolar violation that is not
part of a zero-substitution code. It also includes other
error patterns such as: eight or more consecutive zeros
and incorrect parity.
Errored Seconds
An Errored Second is a second with one or more Code
Violation Error Events OR one or more Out of Frame
events. In D4 and G.704 section 2.1.3.2 (eg, G.704 which
does not implement the CRC), the presence of Bipolar
Violations also triggers an Errored Second.
Severely Errored Seconds
A Severely Errored Second is a second with 320 or more
Code Violation Error Events OR one or more Out of Frame
events.
Severely Errored Framing Second
An Severely Errored Framing Second is a second with one
or more Out of Frame events.
Unavailable Signal State
This state is declared at the onset of 10 consecutive
Severely Errored Seconds. It is cleared at the onset of
10 consecutive seconds with no Severely Errored Second.
Unavailable Seconds
Unavailable Seconds are calculated by counting the number
of seconds that the CSU is in the Unavailable Signal
State, including the initial 10 seconds to enter the
state but not including the 10 seconds to exit the state.
Note that any second that may be counted as an
Unavailable Second may not be counted as an Errored
Second, a Severely Errored Second. Since the 10 Severely
Errored Seconds that comprise the transition from the
available to Unavailable Signal State may also be counted
as Errored Seconds, and Severely Errored Seconds previous
to entering the state, these three counters are adjusted
so that any second counted during this transition is then
subtracted. The 10 seconds in the transition from
unavailable to available may be counted as Errored
Seconds.
A special case exists when the 10 or more second period
crosses the 900 second statistics window boundary, as the
foregoing description implies that the Severely Errored
Second and Unavailable Second counters must be adjusted
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RFC 1232 DS1 Interface Objects May 1991
when the Unavailable Signal State is entered. Clearly,
successive GETs of the affected ds1IntervalSES and
ds1IntervalUAS objects will return differing values if
the first GET occurs during the first few seconds of the
window. This is viewed as an unavoidable side-effect of
selecting the presently deployed AT&T objects as a basis
for this memo.
Yellow Alarm
A Yellow Alarm is declared because of an incoming Yellow
Signal from the far-end. In effect, the circuit is
declared to be a one way link.
Red Alarm
A Red Alarm is declared because of an incoming Loss of
Signal, Loss of Framing, Alarm Indication Signal. After
a Red Alarm is declared, the device sends a Yellow Signal
to the far-end. The far-end, when receives the Yellow
Signal, declares a Yellow Alarm.
Circuit Identifier
This is a character string specified by the circuit
vendor, and is useful when communicating with the vendor
during the troubleshooting process.
5. Definitions
RFC1232-MIB DEFINITIONS ::= BEGIN
IMPORTS
experimental, Counter
FROM RFC1155-SMI
DisplayString
FROM RFC1158-MIB
OBJECT-TYPE
FROM RFC-1212;
-- This MIB module uses the extended OBJECT-TYPE macro as
-- defined in [13].
-- this is the MIB module for ds1 objects
ds1 OBJECT IDENTIFIER ::= { experimental 2 }
-- the DS1 Configuration group
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RFC 1232 DS1 Interface Objects May 1991
-- Although the objects in this group are read-only, at the
-- agent's discretion they may be made read-write so that the
-- management station, when appropriately authorized, may
-- change the behavior of the CSU, e.g., to place the device
-- into a loopback state or emit a QRSS BER test.
-- Implementation of this group is mandatory for all systems
-- that attach to a ds1.
ds1ConfigTable OBJECT-TYPE
SYNTAX SEQUENCE OF DS1ConfigEntry
ACCESS not-accessible
STATUS mandatory
DESCRIPTION
"The DS1 Configuration table."
::= { ds1 1 }
ds1ConfigEntry OBJECT-TYPE
SYNTAX DS1ConfigEntry
ACCESS not-accessible
STATUS mandatory
DESCRIPTION
"An entry in the DS1 Configuration table."
INDEX { ds1CSUIndex }
::= { ds1ConfigTable 1 }
DS1ConfigEntry ::=
SEQUENCE {
ds1CSUIndex
INTEGER,
ds1Index
INTEGER,
ds1TimeElapsed
INTEGER (1..900),
ds1ValidIntervals
INTEGER (0..96),
ds1LineType
INTEGER,
ds1ZeroCoding
INTEGER,
ds1Loopback
INTEGER,
ds1SendCode
INTEGER,
ds1YellowAlarm
INTEGER,
ds1RedAlarm
INTEGER,
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