RFC 1315 PROPOSED STANDARD INFRASTRUCTURE · SNMP · MANAGEMENT
Frame Relay MIB: Management Information Base for Frame Relay DTEs
SNMP management objects for Frame Relay data terminal equipment.
RFC EDITOR
Brown, C., Baker, F., and C. Carvalho, "Management Information Base for Frame Relay DTEs", RFC 1315, DOI 10.17487/RFC1315, April 1992, <https://www.rfc-editor.org/info/rfc1315>.
BIBTEX
@misc{rfc1315,
series = {Request for Comments},
number = 1315,
howpublished = {RFC 1315},
publisher = {RFC Editor},
doi = {10.17487/RFC1315},
url = {https://www.rfc-editor.org/info/rfc1315},
author = {C. Brown and F. Baker and C. Carvalho},
title = {{Management Information Base for Frame Relay DTEs}},
pagetotal = 19,
year = 1992,
month = apr,
} LINEAGE · FROM THE RFC INDEXOpen full graph →
RFC text
Contents
Network Working Group C. Brown
Request for Comments: 1315 Wellfleet Communications, Inc.
F. Baker
Advanced Computer Communications
C. Carvalho
Advanced Computer Communications
April 1992
Management Information Base for Frame Relay DTEs
Status of this Memo
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.
Abstract
This memo defines a portion of the Management Information Base (MIB)
for use with network management protocols in TCP/IP-based internets.
In particular, it defines objects for managing Frame Relay.
Table of Contents
1. The Network Management Framework ............................ 2
2. Objects ..................................................... 2
2.1 Format of Definitions ...................................... 3
3. Overview .................................................... 3
3.1 Frame Relay Operational Model .............................. 3
3.2 Textual Conventions ........................................ 3
3.3 Structure of MIB ........................................... 3
4. Definitions ................................................. 4
4.1 Data Link Connection Management Interface .................. 4
4.2 Circuit Table .............................................. 9
4.3 Error Table ................................................ 14
5. Acknowledgements ............................................ 17
6. References .................................................. 17
7. Security Considerations...................................... 18
8. Authors' Addresses........................................... 19
1. 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.
2. 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.
The SMI specifies the use of the basic encoding rules of ASN.1 [8],
subject to the additional requirements imposed by the SNMP.
2.1. Format of Definitions
Section 4 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 [9,10].
3. Overview
3.1. Frame Relay Operational Model
For the purposes of understanding this document, Frame Relay is
viewed as a multi-access media, not as a group of point-to-point
connections. This model proposes that Frame Relay is a single
interface to the network (physical connection) with many destinations
or neighbors (virtual connections). This view enables a network
manager the ability to group all virtual connections with their
corresponding physical connection thereby allowing simpler
diagnostics and trouble shooting.
3.2. Textual Conventions
Several new data types are introduced as a textual convention in this
MIB document. These textual conventions enhance the readability of
the specification and can ease comparison with other specifications
if appropriate. It should be noted that the introduction of the
these textual conventions has no effect on either the syntax nor the
semantics of any managed objects. The use of these is merely an
artifact of the explanatory method used. Objects defined in terms of
one of these methods are always encoded by means of the rules that
define the primitive type. Hence, no changes to the SMI or the SNMP
are necessary to accommodate these textual conventions which are
adopted merely for the convenience of readers and writers in pursuit
of the elusive goal of clear, concise, and unambiguous MIB documents.
The new data types are Index and DLCI. Index refers to the range
1..ifNumber, and is used to establish the correspondence between
ifEntries and Frame Relay Interfaces. DLCI refers to the range
0..DLCINumber, and is used to refer to the valid Data Link Connection
Indices. DLCINumber is, by definition, the largest possible DLCI
value possible under the configured Q.922 Address Format.
3.3. Structure of MIB
The MIB is composed of three groups, one defining the Data Link
Connection Management Interface (DLCMI), one describing the Circuits,
and a third describing errors.
During normal operation, Frame Relay virtual circuits will be added,
deleted and change availability. The occurrence of such changes is
of interest to the network manager and therefore, one trap is
defined, intended to be corollary to the SNMP "Link Up" and "Link
Down" traps.
4. Definitions
RFC1315-MIB DEFINITIONS ::= BEGIN
IMPORTS
OBJECT-TYPE
FROM RFC-1212
transmission
FROM RFC1213-MIB
TimeTicks
FROM RFC-1155
TRAP-TYPE
FROM RFC-1215;
-- Frame Relay DTE MIB
frame-relay OBJECT IDENTIFIER ::= { transmission 32 }
--
-- the range of ifIndex
--
Index ::= INTEGER -- 1..ifNumber
--
-- the range of a Data Link Connection Identifier
--
DLCI ::= INTEGER -- 0..DLCINumber
-- Data Link Connection Management Interface
-- The variables that configure the DLC Management Interface.
frDlcmiTable OBJECT-TYPE
SYNTAX SEQUENCE OF FrDlcmiEntry
ACCESS not-accessible
STATUS mandatory
DESCRIPTION
"The Parameters for the Data Link Connection Management
Interface for the frame relay service on this
interface."
REFERENCE
"Draft American National Standard T1.617-1991, Annex D"
::= { frame-relay 1 }
frDlcmiEntry OBJECT-TYPE
SYNTAX FrDlcmiEntry
ACCESS not-accessible
STATUS mandatory
DESCRIPTION
"The Parameters for a particular Data Link Con-
nection Management Interface."
INDEX { frDlcmiIfIndex }
::= { frDlcmiTable 1 }
FrDlcmiEntry ::=
SEQUENCE {
frDlcmiIfIndex
Index,
frDlcmiState
INTEGER,
frDlcmiAddress
INTEGER,
frDlcmiAddressLen
INTEGER,
frDlcmiPollingInterval
INTEGER,
frDlcmiFullEnquiryInterval
INTEGER,
frDlcmiErrorThreshold
INTEGER,
frDlcmiMonitoredEvents
INTEGER,
frDlcmiMaxSupportedVCs
INTEGER,
frDlcmiMulticast
INTEGER
}
frDlcmiIfIndex OBJECT-TYPE
SYNTAX Index
ACCESS read-only
STATUS mandatory
DESCRIPTION
"The ifIndex value of the corresponding ifEn-
try."
::= { frDlcmiEntry 1 }
frDlcmiState OBJECT-TYPE
SYNTAX INTEGER {
noLmiConfigured (1),
lmiRev1 (2),
ansiT1-617-D (3), -- ANSI T1.617 Annex D
ansiT1-617-B (4) -- ANSI T1.617 Annex B
}
ACCESS read-write
STATUS mandatory
DESCRIPTION
"This variable states which Data Link Connec-
tion Management scheme is active (and by impli-
cation, what DLCI it uses) on the Frame Relay
interface."
REFERENCE
"Draft American National Standard T1.617-1991"
::= { frDlcmiEntry 2 }
frDlcmiAddress OBJECT-TYPE
SYNTAX INTEGER {
q921 (1), -- 13 bit DLCI
q922March90 (2), -- 11 bit DLCI
q922November90 (3), -- 10 bit DLCI
q922 (4) -- Final Standard
}
ACCESS read-write
STATUS mandatory
DESCRIPTION
"This variable states which address format is
in use on the Frame Relay interface."
::= { frDlcmiEntry 3 }
frDlcmiAddressLen OBJECT-TYPE
SYNTAX INTEGER {
two-octets (2),
three-octets (3),
four-octets (4)
}
ACCESS read-write
STATUS mandatory
DESCRIPTION
"This variable states which address length in
octets. In the case of Q922 format, the length
indicates the entire length of the address in-
cluding the control portion."
::= { frDlcmiEntry 4 }
frDlcmiPollingInterval OBJECT-TYPE
SYNTAX INTEGER (5..30)
ACCESS read-write
STATUS mandatory
DESCRIPTION
"This is the number of seconds between succes-
sive status enquiry messages."
REFERENCE
"Draft American National Standard T1.617-1991,
Section D.7 Timer T391."
DEFVAL { 10 }
::= { frDlcmiEntry 5 }
frDlcmiFullEnquiryInterval OBJECT-TYPE
SYNTAX INTEGER (1..255)
ACCESS read-write
STATUS mandatory
DESCRIPTION
"Number of status enquiry intervals that pass
before issuance of a full status enquiry mes-
sage."
REFERENCE
"Draft American National Standard T1.617-1991,
Section D.7 Counter N391."
DEFVAL { 6 }
::= { frDlcmiEntry 6 }
frDlcmiErrorThreshold OBJECT-TYPE
SYNTAX INTEGER (1..10)
ACCESS read-write
STATUS mandatory
DESCRIPTION
"This is the maximum number of unanswered
Status Enquiries the equipment shall accept be-
fore declaring the interface down."
REFERENCE
"Draft American National Standard T1.617-1991,
Section D.5.1 Counter N392."
DEFVAL { 3 }
::= { frDlcmiEntry 7 }
frDlcmiMonitoredEvents OBJECT-TYPE
SYNTAX INTEGER (1..10)
ACCESS read-write
STATUS mandatory
DESCRIPTION
"This is the number of status polling intervals
over which the error threshold is counted. For
example, if within 'MonitoredEvents' number of
events the station receives 'ErrorThreshold'
number of errors, the interface is marked as
down."
REFERENCE
"Draft American National Standard T1.617-1991,
Section D.5.2 Counter N393."
DEFVAL { 4 }
::= { frDlcmiEntry 8 }
frDlcmiMaxSupportedVCs OBJECT-TYPE
SYNTAX INTEGER
ACCESS read-write
STATUS mandatory
DESCRIPTION
"The maximum number of Virtual Circuits allowed
for this interface. Usually dictated by the
Frame Relay network.
In response to a SET, if a value less than zero
or higher than the agent's maximal capability
is configured, the agent should respond bad-
Value"
::= { frDlcmiEntry 9 }
frDlcmiMulticast OBJECT-TYPE
SYNTAX INTEGER {
nonBroadcast (1),
broadcast (2)
}
ACCESS read-write
STATUS mandatory
DESCRIPTION
"This indicates whether the Frame Relay inter-
face is using a multicast service."
::= { frDlcmiEntry 10 }
-- A Frame Relay service is a multiplexing service. Data
-- Link Connection Identifiers enumerate virtual circuits
-- (permanent or dynamic) which are layered onto the underlying
-- circuit, represented by ifEntry. Therefore, each of the entries
-- in the Standard MIB's Interface Table with an IfType of
-- Frame Relay represents a Q.922 interface. Zero or more
-- virtual circuits are layered onto this interface and provide
-- interconnection with various remote destinations.
-- Each such virtual circuit is represented by an entry in the
-- circuit table.
-- Circuit Table
-- The table describing the use of the DLCIs attached to
-- each Frame Relay Interface.
frCircuitTable OBJECT-TYPE
SYNTAX SEQUENCE OF FrCircuitEntry
ACCESS not-accessible
STATUS mandatory
DESCRIPTION
"A table containing information about specific Data
Link Connection Identifiers and corresponding virtual
circuits."
::= { frame-relay 2 }
frCircuitEntry OBJECT-TYPE
SYNTAX FrCircuitEntry
ACCESS not-accessible
STATUS mandatory
DESCRIPTION
"The information regarding a single Data Link
Connection Identifier."
INDEX { frCircuitIfIndex, frCircuitDlci }
::= { frCircuitTable 1 }
FrCircuitEntry ::=
SEQUENCE {
frCircuitIfIndex
Index,
frCircuitDlci
DLCI,
frCircuitState
INTEGER,
frCircuitReceivedFECNs
Counter,
frCircuitReceivedBECNs
Counter,
frCircuitSentFrames
Counter,
frCircuitSentOctets
Counter,
frCircuitReceivedFrames
Counter,
frCircuitReceivedOctets
Counter,
frCircuitCreationTime
TimeTicks,
frCircuitLastTimeChange
TimeTicks,
frCircuitCommittedBurst
INTEGER,
frCircuitExcessBurst
INTEGER,
frCircuitThroughput
INTEGER
}
frCircuitIfIndex OBJECT-TYPE
SYNTAX Index
ACCESS read-only
STATUS mandatory
DESCRIPTION
"The ifIndex Value of the ifEntry this virtual
circuit is layered onto."
::= { frCircuitEntry 1 }
frCircuitDlci OBJECT-TYPE
SYNTAX DLCI
ACCESS read-only
STATUS mandatory
DESCRIPTION
"The Data Link Connection Identifier for this
virtual circuit."
REFERENCE
"Draft American National Standard T1.618-1991,
Section 3.3.6"
::= { frCircuitEntry 2 }
frCircuitState OBJECT-TYPE
SYNTAX INTEGER {
invalid (1),
active (2),
inactive (3)
}
ACCESS read-write
STATUS mandatory
DESCRIPTION
"Indicates whether the particular virtual cir-
cuit is operational. In the absence of a Data
Link Connection Management Interface, virtual
circuit entries (rows) may be created by set-
ting virtual circuit state to 'active', or
deleted by changing Circuit state to 'invalid'.
Whether or not the row actually disappears is
left to the implementation, so this object may
actually read as 'invalid' for some arbitrary
length of time. It is also legal to set the
state of a virtual circuit to 'inactive' to
temporarily disable a given circuit."
DEFVAL { active }
::= { frCircuitEntry 3 }
frCircuitReceivedFECNs OBJECT-TYPE
SYNTAX Counter
ACCESS read-only
STATUS mandatory
DESCRIPTION
"Number of frames received from the network in-
dicating forward congestion since the virtual
circuit was created."
REFERENCE
"Draft American National Standard T1.618-1991,
Section 3.3.3"
::= { frCircuitEntry 4 }
frCircuitReceivedBECNs OBJECT-TYPE
SYNTAX Counter
ACCESS read-only
STATUS mandatory
DESCRIPTION
"Number of frames received from the network in-
dicating backward congestion since the virtual
circuit was created."
REFERENCE
"Draft American National Standard T1.618-1991,
Section 3.3.4"
::= { frCircuitEntry 5 }
frCircuitSentFrames OBJECT-TYPE
SYNTAX Counter
ACCESS read-only
STATUS mandatory
DESCRIPTION
"The number of frames sent from this virtual
circuit since it was created."
::= { frCircuitEntry 6 }
frCircuitSentOctets OBJECT-TYPE
SYNTAX Counter
ACCESS read-only
STATUS mandatory
DESCRIPTION
"The number of octets sent from this virtual
circuit since it was created."
::= { frCircuitEntry 7 }
frCircuitReceivedFrames OBJECT-TYPE
SYNTAX Counter
ACCESS read-only
STATUS mandatory
DESCRIPTION
"Number of frames received over this virtual
circuit since it was created."
::= { frCircuitEntry 8 }
frCircuitReceivedOctets OBJECT-TYPE
SYNTAX Counter
ACCESS read-only
STATUS mandatory
DESCRIPTION
"Number of octets received over this virtual
circuit since it was created."
::= { frCircuitEntry 9 }
frCircuitCreationTime OBJECT-TYPE
SYNTAX TimeTicks
ACCESS read-only
STATUS mandatory
DESCRIPTION
"The value of sysUpTime when the virtual cir-
cuit was created, whether by the Data Link Con-
nection Management Interface or by a SetRe-
quest."
::= { frCircuitEntry 10 }
frCircuitLastTimeChange OBJECT-TYPE
SYNTAX TimeTicks
ACCESS read-only
STATUS mandatory
DESCRIPTION
"The value of sysUpTime when last there was a
change in the virtual circuit state"
::= { frCircuitEntry 11 }
frCircuitCommittedBurst OBJECT-TYPE
SYNTAX INTEGER
ACCESS read-write
STATUS mandatory
DESCRIPTION
"This variable indicates the maximum amount of
data, in bits, that the network agrees to
transfer under normal conditions, during the
measurement interval."
REFERENCE
"Draft American National Standard T1.617-1991,
Section 6.5.19"
DEFVAL { 0 } -- the default indicates no commitment
::= { frCircuitEntry 12 }
frCircuitExcessBurst OBJECT-TYPE
SYNTAX INTEGER
ACCESS read-write
STATUS mandatory
DESCRIPTION
"This variable indicates the maximum amount of
uncommitted data bits that the network will at-
tempt to deliver over the measurement interval.
By default, if not configured when creating the
entry, the Excess Information Burst Size is set
to the value of ifSpeed."
REFERENCE
"Draft American National Standard T1.617-1991,
Section 6.5.19"
::= { frCircuitEntry 13 }
frCircuitThroughput OBJECT-TYPE
SYNTAX INTEGER
ACCESS read-write
STATUS mandatory
DESCRIPTION
"Throughput is the average number of 'Frame Re-
lay Information Field' bits transferred per
second across a user network interface in one
direction, measured over the measurement inter-
val.
If the configured committed burst rate and
throughput are both non-zero, the measurement
interval
T=frCircuitCommittedBurst/frCircuitThroughput.
If the configured committed burst rate and
throughput are both zero, the measurement in-
terval
T=frCircuitExcessBurst/ifSpeed."
REFERENCE
"Draft American National Standard T1.617-1991,
Section 6.5.19"
DEFVAL {0} -- the default value of Throughput is
-- "no commitment".
::= { frCircuitEntry 14 }
-- Error Table
-- The table describing errors encountered on each Frame
-- Relay Interface.
frErrTable OBJECT-TYPE
SYNTAX SEQUENCE OF FrErrEntry
ACCESS not-accessible
STATUS mandatory
DESCRIPTION
"A table containing information about Errors on the
Frame Relay interface."
::= { frame-relay 3 }
frErrEntry OBJECT-TYPE
SYNTAX FrErrEntry
ACCESS not-accessible
STATUS mandatory
DESCRIPTION
"The error information for a single frame relay
interface."
INDEX { frErrIfIndex }
::= { frErrTable 1 }
FrErrEntry ::=
SEQUENCE {
frErrIfIndex
Index,
frErrType
INTEGER,
frErrData
OCTET STRING,
frErrTime
TimeTicks
}
frErrIfIndex OBJECT-TYPE
SYNTAX Index
ACCESS read-only
STATUS mandatory
DESCRIPTION
"The ifIndex Value of the corresponding ifEn-
try."
::= { frErrEntry 1 }
frErrType OBJECT-TYPE
SYNTAX INTEGER {
unknownError(1),
receiveShort(2),
receiveLong(3),
illegalDLCI(4),
unknownDLCI(5),
dlcmiProtoErr(6),
dlcmiUnknownIE(7),
dlcmiSequenceErr(8),
dlcmiUnknownRpt(9),
noErrorSinceReset(10)
}
ACCESS read-only
STATUS mandatory
DESCRIPTION
"The type of error that was last seen on this
interface."
::= { frErrEntry 2 }
frErrData OBJECT-TYPE
SYNTAX OCTET STRING
ACCESS read-only
STATUS mandatory
DESCRIPTION
"An octet string containing as much of the er-
ror packet as possible. As a minimum, it must
contain the Q.922 Address or as much as was
delivered. It is desirable to include all in-
formation up to the PDU."
::= { frErrEntry 3 }
frErrTime OBJECT-TYPE
SYNTAX TimeTicks
ACCESS read-only
STATUS mandatory
DESCRIPTION
"The value of sysUpTime at which the error was
detected."
::= { frErrEntry 4 }
-- Frame Relay Globals
frame-relay-globals OBJECT IDENTIFIER ::= { frame-relay 4 }
frTrapState OBJECT-TYPE
SYNTAX INTEGER { enabled(1), disabled(2) }
ACCESS read-write
STATUS mandatory
DESCRIPTION
"This variable indicates whether the system
produces the frDLCIStatusChange trap."
DEFVAL { disabled }
::= { frame-relay-globals 1 }
-- Data Link Connection Management Interface Related Traps
frDLCIStatusChange TRAP-TYPE
ENTERPRISE frame-relay
VARIABLES { frCircuitIfIndex, frCircuitDlci, frCircuitState }
DESCRIPTION
"This trap indicates that the indicated Virtual
Circuit has changed state. It has either been
created or invalidated, or has toggled between
the active and inactive states."
::= 1
END
5. Acknowledgements
This document was produced by the IP Over Large Public Data Networks
(IPLPDN) Working Group.
The following people provided additional comments and suggestions:
Art Berggreen of Advanced Computer Communications, and Jim Philippou
of Xyplex Communications.
6. References
[1] Cerf, V., "IAB Recommendations for the Development of Internet
Network Management Standards", RFC 1052, NRI, April 1988.
[2] Cerf, V., "Report of the Second Ad Hoc Network Management Review
Group", RFC 1109, NRI, August 1989.
[3] Rose M., and K. McCloghrie, "Structure and Identification of
Management Information for TCP/IP-based internets", RFC 1155,
Performance Systems International, Hughes LAN Systems, May 1990.
[4] McCloghrie K., and M. Rose, "Management Information Base for
Network Management of TCP/IP-based internets", RFC 1156, Hughes
LAN Systems, Performance Systems International, May 1990.
[5] Case, J., Fedor, M., Schoffstall, M., and J. Davin, "Simple
Network Management Protocol", RFC 1157, SNMP Research,
Performance Systems International, Performance Systems
International, MIT Laboratory for Computer Science, May 1990.
[6] McCloghrie K., and M. Rose, Editors, "Management Information Base
for Network Management of TCP/IP-based internets", RFC 1213,
Performance Systems International, March 1991.
[7] Information processing systems - Open Systems Interconnection -
Specification of Abstract Syntax Notation One (ASN.1),
International Organization for Standardization, International
Standard 8824, December 1987.
[8] Information processing systems - Open Systems Interconnection -
Specification of Basic Encoding Rules for Abstract Notation One
(ASN.1), International Organization for Standardization,
International Standard 8825, December 1987.
[9] Rose, M., and K. McCloghrie, Editors, "Concise MIB Definitions",
RFC 1212, Performance Systems International, Hughes LAN Systems,
March 1991.
[10] Rose, M., Editor, "A Convention for Defining Traps for use with
the SNMP", RFC 1215, Performance Systems International, March
1991.
7. Security Considerations
Security issues are not discussed in this memo.
8. Authors' Addresses
Caralyn Brown
Wellfleet Communications, Inc.
15 Crosby Drive
Bedford, Massachusetts 01730
Phone: (617) 275-2400
EMail: cbrown@wellfleet.com
Fred Baker
Advanced Computer Communications
315 Bollay Drive
Sannta Barbara, California 93117
Phone: (805) 685-4455
EMail: fbaker@acc.com
Charles Carvalho
Advanced Computer Communications
315 Bollay Drive
Sannta Barbara, California 93117
Phone: (805) 685-4455
EMail: charles@acc.com
AI ELI5
On this page
PROBLEMNetwork administrators managing Frame Relay services needed a standard way to monitor and configure the equipment at the edge of Frame Relay connections across different vendors.
MECHANISMRFC 1315 defines SNMP managed objects organized into three groups: Data Link Connection Management Interface (DLCMI) configuration, virtual circuit state and statistics, and error tracking.
WHY IT WAS REPLACEDThis MIB provided essential Frame Relay management but was superseded by RFC 2115 as Frame Relay technology matured.
§1Introduction
Frame Relay is a packet-switching protocol optimized for data communications over Wide Area Networks. It operates at the data-link layer and offers lower overhead than earlier protocols by eliminating error correction and retransmission at each hop. RFC 1315 defines SNMP managed objects for Frame Relay Data Terminal Equipment (DTEs)—the equipment at the edge of a Frame Relay network that users control.
The RFC treats Frame Relay as a single physical interface layered with multiple virtual circuits identified by Data Link Connection Identifiers (DLCIs). Each DLCI represents a logical connection to a remote destination, whether permanent (configured in advance) or dynamic (created on demand). This view simplifies network management by grouping virtual connections with their underlying physical connection.
Frame Relay links are fast, lean highways for data. Each company plugs equipment (a DTE) into the Frame Relay network and creates virtual circuits (like numbered lanes) to reach distant offices. This RFC explains how to ask that equipment questions via SNMP.
§2MIB Structure and Management Groups
The Frame Relay MIB has three main components. The DLCMI (Data Link Connection Management Interface) group manages the protocol used to communicate with the Frame Relay network about virtual circuit status. It includes configuration parameters such as the polling interval (how often to ask the network for status), error thresholds (how many missed responses trigger an alarm), and the maximum number of virtual circuits allowed.
The Circuit group contains a table of information about each active or inactive virtual circuit. For each DLCI, the table records the circuit state, counters for frames and octets sent and received, congestion notification counts (FECN and BECN fields), and quality-of-service parameters such as committed burst rate and throughput. The Error group tracks the last error seen on the interface, its type, the data received, and the time of occurrence.
The MIB has three drawers: one for negotiating with the Frame Relay network (DLCMI), one for tracking each virtual circuit's traffic and status, and one for recording what went wrong.
§3Virtual Circuit Management
Each virtual circuit is represented as a row in the circuit table, indexed by the interface number and the DLCI. The frCircuitState object can be set by the administrator to 'active', 'inactive', or 'invalid' to control the circuit's operational state. When a circuit is created or deleted by the network (via the Data Link Connection Management Interface), the DLCMI automatically updates the table; managers can also create or delete circuits manually via SNMP.
The circuit table includes counters for frames and octets sent and received on that circuit since its creation. Two fields record congestion notification bits (FECN and BECN) received from the network: FECN signals forward congestion (the path to the destination is congested), while BECN signals backward congestion (the path back is congested). These counters help administrators detect when the network is overloaded and may trigger traffic shaping or rerouting policies.
Each virtual circuit has a status light (active, inactive, or off) and counters for traffic. Congestion bits tell whether the line ahead is busy or the line back is busy—like traffic signals on a highway.
§4DLCI and Address Formats
A Data Link Connection Identifier (DLCI) is a 10- to 13-bit number that uniquely identifies a virtual circuit on a Frame Relay interface. The RFC supports multiple address formats standardized by ITU-T: Q.921 (13-bit DLCI), Q.922 March 90 (11-bit), Q.922 November 90 (10-bit), and final Q.922. The address length (two, three, or four octets) is configurable per interface to match the network's standard. The RFC allows administrators to set the maximum supported DLCI value and the maximum number of concurrent virtual circuits, accommodating different service levels and network capabilities.
The DLCMI also tracks the Link Management Interface type in use. Common types include 'noLmiConfigured' (no automatic discovery), 'lmiRev1' (Cisco's proprietary extension), and ANSI T1.617 variants (standards-based management). The polling interval and error thresholds ensure that equipment can detect when the connection to the network has failed and halt traffic accordingly.
Each virtual circuit gets a number (DLCI). Different Frame Relay standards use different-sized numbers. Managers set the maximum expected circuits and choose how often to check if the network is still reachable.
§5Error Tracking and Traps
The Error group records problems encountered on the Frame Relay interface. The frErrType object identifies the last error, distinguishing between various failure modes: 'receiveShort' (frame too small), 'receiveLong' (frame exceeds maximum size), 'illegalDLCI' (unknown DLCI), 'dlcmiProtoErr' (protocol violation), and others. The frErrData field contains the offending packet or frame, and frErrTime records when the error occurred.
RFC 1315 defines one trap: frDLCIStatusChange, which fires when a virtual circuit transitions between active, inactive, or invalid states. Administrators can enable or disable this trap via the frTrapState object. This trap alerts management systems to circuit failures or recoveries so they can investigate or trigger failover procedures.
When something goes wrong—a frame is too big, a circuit drops—the equipment remembers what happened. It can also send a signal (a trap) to the manager when a circuit changes status.
§6References
[1]RFC 1155Rose, M., and K. McCloghrie, "Structure and Identification of Management Information for TCP/IP-based internets", RFC 1155, May 1990.May 1990[2]RFC 1213McCloghrie, K., and M. Rose, "Management Information Base for Network Management of TCP/IP-based internets", RFC 1213, March 1991.March 1991[3]RFC 1157Case, J., Fedor, M., Schoffstall, M., and J. Davin, "Simple Network Management Protocol", RFC 1157, May 1990.May 1990