GMPLS - Communication of Alarm Information :: RFC4783
Network Working Group L. Berger, Ed.
Request for Comments: 4783 LabN
Updates: 3473 December 2006
Category: Standards Track
GMPLS - Communication of Alarm Information
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The IETF Trust (2006).
Abstract
This document describes an extension to Generalized MPLS (Multi-
Protocol Label Switching) signaling to support communication of alarm
information. GMPLS signaling already supports the control of alarm
reporting, but not the communication of alarm information. This
document presents both a functional description and GMPLS-RSVP
specifics of such an extension. This document also proposes
modification of the RSVP ERROR_SPEC object.
This document updates RFC 3473, "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation Protocol-Traffic
Engineering (RSVP-TE) Extensions", through the addition of new,
optional protocol elements. It does not change, and is fully
backward compatible with, the procedures specified in RFC 3473.
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RFC 4783 GMPLS - Communication of Alarm Information December 2006
Table of Contents
1. Introduction ....................................................3
1.1. Background .................................................3
2. Alarm Information Communication .................................4
3. GMPLS-RSVP Details ..............................................5
3.1. ALARM_SPEC Objects .........................................5
3.1.1. IF_ID ALARM_SPEC (and ERROR_SPEC) TLVs ..............5
3.1.2. Procedures ..........................................9
3.1.3. Error Codes and Values .............................10
3.1.4. Backwards Compatibility ............................11
3.2. Controlling Alarm Communication ...........................11
3.2.1. Updated Admin_Status Object ........................11
3.2.2. Procedures .........................................11
3.3. Message Formats ...........................................12
3.4. Relationship to GMPLS UNI .................................13
3.5. Relationship to GMPLS E-NNI ...............................14
4. Security Considerations ........................................14
5. IANA Considerations ............................................15
5.1. New RSVP Object ...........................................15
5.2. New Interface ID Types ....................................16
5.3. New Registry for Admin-Status Object Bit Fields ...........16
5.4. New RSVP Error Code .......................................16
6. References .....................................................17
6.1. Normative References ......................................17
6.2. Informative References ....................................17
7. Acknowledgments ................................................18
8. Contributors ...................................................18
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RFC 4783 GMPLS - Communication of Alarm Information December 2006
1. Introduction
GMPLS signaling provides mechanisms that can be used to control the
reporting of alarms associated with a label switched path (LSP).
This support is provided via Administrative Status Information
[RFC3471] and the Admin_Status object [RFC3473]. These mechanisms
only control if alarm reporting is inhibited. No provision is made
for communication of alarm information within GMPLS.
The extension described in this document defines how the alarm
information associated with a GMPLS LSP may be communicated along the
path of the LSP. Communication both upstream and downstream is
supported. The value in communicating such alarm information is that
this information is then available at every node along the LSP for
display and diagnostic purposes. Alarm information may also be
useful in certain traffic protection scenarios, but such uses are out
of the scope of this document. Alarm communication is supported via
a new object, new error/alarm information TLVs, and a new
Administrative Status Information bit.
The communication of alarms, as described in this document, is
controllable on a per-LSP basis. Such communication may be useful
within network configurations where not all nodes support
communication to a user for reporting of alarms and/or communication
is needed to support specific applications. The support of this
functionality is optional.
The communication of alarms within GMPLS does not imply any
modification in behavior of processing of alarms, or for the
communication of alarms outside of GMPLS. Additionally, the
extension described in this document is not intended to replace any
(existing) data plane fault propagation techniques.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
1.1. Background
Problems with data plane state can often be detected by associated
data plane hardware components. Such data plane problems are
typically filtered based on elapsed time and local policy. Problems
that pass the filtering process are normally raised as alarms. These
alarms are available for display to operators. They also may be
collected centrally through means that are out of the scope of this
document.
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RFC 4783 GMPLS - Communication of Alarm Information December 2006
Not all data plane problems cause the LSP to be immediately torn
down. Further, there may be a desire, particularly in optical
transport networks, to retain an LSP and communicate relevant alarm
information even when the data plane state has failed completely.
Although error information can be reported using PathErr, ResvErr,
and Notify messages, these messages typically indicate a problem in
signaling state and can only report one problem at a time. This
makes it hard to correlate all of the problems that may be associated
with a single LSP and to allow an operator examining the status of an
LSP to view a full list of current problems. This situation is
exacerbated by the absence of any way to communicate that a problem
has been resolved and a corresponding alarm cleared.
The extensions defined in this document allow an operator or a
software component to obtain a full list of current alarms associated
with all of the resources used to support an LSP. The extensions
also ensure that this list is kept up-to-date and synchronized with
the real alarm status in the network. Finally, the extensions make
the list available at every node traversed by an LSP.
2. Alarm Information Communication
A new object is introduced to carry alarm information details. The
details of alarm information are much like the error information
carried in the existing ERROR_SPEC objects. For this reason the
communication of alarm information uses a format that is based on the
communication of error information.
The new object introduced to carry alarm information details is
called an ALARM_SPEC object. This object has the same format as the
ERROR_SPEC object, but uses a new C-Num to avoid the semantics of
error processing. Also, additional TLVs are defined for the IF_ID
ALARM_SPEC objects to support the communication of information
related to a specific alarm. These TLVs may also be useful when
included in ERROR_SPEC objects, e.g., when the ERROR_SPEC object is
carried within a Notify message.
While the details of alarm information are like the details of
existing error communication, the semantics of processing differ.
Alarm information will typically relate to changes in data plane
state, without changes in control state. Alarm information will
always be associated with in-place LSPs. Such information will also
typically be most useful to operators and applications other than
control plane protocol processing. Finally, while error information
is communicated within PathErr, ResvErr, and Notify messages
[RFC3473], alarm information will be carried within Path and Resv
messages.
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RFC 4783 GMPLS - Communication of Alarm Information December 2006
Path messages are used to carry alarm information to downstream
nodes, and Resv messages are used to carry alarm information to
upstream nodes. The intent of sending alarm information both
upstream and downstream is to provide the same visibility to alarm
information at any point along an LSP. The communication of multiple
alarms associated with an LSP is supported. In this case, multiple
ALARM_SPEC objects will be carried in the Path or Resv messages.
The addition of alarm information to Path and Resv messages is
controlled via a new Administrative Status Information bit.
Administrative Status Information is carried in the Admin_Status
object.
3. GMPLS-RSVP Details
This section provides the GMPLS-RSVP [RFC3473] specification for
communication of alarm information. The communication of alarm
information is OPTIONAL. This section applies to nodes that support
communication of alarm information.
3.1. ALARM_SPEC Objects
The ALARM_SPEC objects use the same format as the ERROR_SPEC object,
but with class number of 198 (assigned by IANA in the form 11bbbbbb,
per Section 3.1.4).
o Class = 198, C-Type = 1
Reserved. (C-Type value defined for ERROR_SPEC, but is not
defined for use with ALARM_SPEC.)
o Class = 198, C-Type = 2
Reserved. (C-Type value defined for ERROR_SPEC, but is not
defined for use with ALARM_SPEC.)
o IPv4 IF_ID ALARM_SPEC object: Class = 198, C-Type = 3
Definition same as IPv4 IF_ID ERROR_SPEC [RFC3473].
o IPv6 IF_ID ALARM_SPEC object: Class = 198, C-Type = 4
Definition same as IPv6 IF_ID ERROR_SPEC [RFC3473].
3.1.1. IF_ID ALARM_SPEC (and ERROR_SPEC) TLVs
The following new TLVs are defined for use with the IPv4 and IPv6
IF_ID ALARM_SPEC objects. They may also be used with the IPv4 and
IPv6 IF_ID ERROR_SPEC objects. See [RFC3471] Section 9.1.1 for the
original definition of these values. Note the length provided below
is for the total TLV. All TLVs defined in this section are OPTIONAL.
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The defined TLVs MUST follow any interface identifying TLVs. No
rules apply to the relative ordering of the TLVs defined in this
section.
Type Length Description
----------------------------------
512 8 REFERENCE_COUNT
513 8 SEVERITY
514 8 GLOBAL_TIMESTAMP
515 8 LOCAL_TIMESTAMP
516 variable ERROR_STRING
The Reference Count TLV has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reference Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Reference Count: 32 bits
The number of times this alarm has been repeated as determined
by the reporting node. This field MUST NOT be set to zero, and
TLVs received with this field set to zero MUST be ignored.
Only one Reference Count TLV may be included in an object.
The Severity TLV has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |Impact | Severity |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Reserved: 20 bits
This field is reserved. It MUST be set to zero on generation,
MUST be ignored on receipt, and MUST be forwarded unchanged and
unexamined by transit nodes.
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RFC 4783 GMPLS - Communication of Alarm Information December 2006
Impact: 4 bits
Indicates the impact of the alarm indicated in the TLV. See
[M.20] for a general discussion on classification of failures.
The following values are defined in this document. The details
of the semantics may be found in [M.20].
Value Definition
----- ---------------------
0 Unspecified impact
1 Non-Service Affecting (Data traffic not interrupted)
2 Service Affecting (Data traffic is interrupted)
Severity: 8 bits
Indicates the impact of the alarm indicated in the TLV. See
[RFC3877] and [M.3100] for more information on severity. The
following values are defined in this document. The details of
the semantics may be found in [RFC3877] and [M.3100]:
Value Definition
----- ----------
0 Cleared
1 Indeterminate
2 Critical
3 Major
4 Minor
5 Warning
Only one Severity TLV may be included in an object.
The Global Timestamp TLV has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Global Timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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RFC 4783 GMPLS - Communication of Alarm Information December 2006
Global Timestamp: 32 bits
An unsigned fixed-point integer that indicates the number of
seconds since 00:00:00 UT on 1 January 1970 according to the
clock on the node that originates this TLV. This time MAY
include leap seconds if they are used by the local clock and
SHOULD contain the same time value as used by the node when the
alarm is reported through other systems (such as within the
Management Plane) if global time is used in those reports.
Only one Global Timestamp TLV may be included in an object.
The Local Timestamp TLV has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Local Timestamp: 32 bits
Number of seconds reported by the local system clock at the
time the associated alarm was detected on the node that
originates this TLV. This number is expected to be meaningful
in the context of the originating node. For example, it may
indicate the number of seconds since the node rebooted or may
be a local representation of an unsynchronized real-time clock.
Only one Local Timestamp TLV may be included in an object.
The Error String TLV has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Error String (NULL padded display string) //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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RFC 4783 GMPLS - Communication of Alarm Information December 2006
Error String: 32 bits minimum (variable)
A string of characters in US-ASCII, representing the type of
error/alarm. This string is padded to the next largest 4-byte
boundary using null characters. Null padding is not required
when the string is 32-bit aligned. The contents of error
string are implementation dependent. See the condition types
listed in Appendices of [GR833] for a list of example strings.
Note length includes padding.
Multiple Error String TLVs may be included in an object.
3.1.2. Procedures
This section applies to nodes that support the communication of alarm
information. ALARM_SPEC objects are carried in Path and Resv
messages. Multiple ALARM_SPEC objects MAY be present.
Nodes that support the extensions defined in this document SHOULD
store any alarm information from received ALARM_SPEC objects for
future use. All ALARM_SPEC objects received in Path messages SHOULD
be passed unmodified downstream in the corresponding Path messages.
All ALARM_SPEC objects received in Resv messages SHOULD be passed
unmodified upstream in the corresponding Resv messages. ALARM_SPEC
objects are merged in transmitted Resv messages by including a copy
of all ALARM_SPEC objects received in corresponding Resv Messages.
To advertise local alarm information, a node generates an ALARM_SPEC
object for each alarm and adds it to both the Path and Resv messages
for the impacted LSP.
In all cases, appropriate Error Node Address, Error Code, and Error
Values MUST be set (see below for a discussion on Error Code and
Error Values). As the InPlace and NotGuilty flags only have meaning
in ERROR_SPEC objects, they SHOULD NOT be set. TLVs SHOULD be
included in the ALARM_SPEC object to identify the interface, if any,
associated with the alarm. The TLVs defined in [RFC3471] for
identifying interfaces in the IF_ID ERROR_SPEC object [RFC3473]
SHOULD be used for this purpose, but note that TLVs type 4 and 5
(component interfaces) are deprecated by [RFC4201] and SHOULD NOT be
used. TLVs SHOULD also be included to indicate the severity
(Severity TLV), the time (Global Timestamp and/or Local Timestamp
TLVs), and a (brief) string (Error String TLV) associated with the
alarm. The reference count TLV MAY also be included to indicate the
number of times an alarm has been repeated at the reporting node.
ALARM_SPEC objects received from other nodes are not impacted by the
addition of local ALARM_SPEC objects, i.e., they continue to be
processed as described above. The choice of which alarm or alarms to
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advertise and which to omit is a local policy matter, and may be
configurable by the user.
There are two ways to indicate time. A global timestamp TLV is used
to provide an absolute time reference for the occurrence of an alarm.
The local timestamp TLV is used to provide time reference for the
occurrence of an alarm that is relative to other information
advertised by the node. The global timestamp SHOULD be used on nodes
that maintain an absolute time reference. Both timestamp TLVs MAY be
used simultaneously.
Note, ALARM_SPEC objects SHOULD NOT be added to the Path and Resv
states of LSPs that are in "alarm communication inhibited" state.
ALARM_SPEC objects MAY be added to the state of LSPs that are in an
"administratively down" state. These states are indicated by the I
and A bits of the Admin_Status object; see Section 3.2.
To remove local alarm information, a node simply removes the matching
locally generated ALARM_SPEC objects from the outgoing Path and Resv
messages. A node MAY modify a locally generated ALARM_SPEC object.
Normal refresh and trigger message processing applies to Path or Resv
messages that contain ALARM_SPEC objects. Note that changes in
ALARM_SPEC objects from one message to the next may include a
modification in the contents of a specific ALARM_SPEC object, or a
change in the number of ALARM_SPEC objects present. All changes in
ALARM_SPEC objects SHOULD be processed as trigger messages.
Failure to follow the above directives, in particular the ones
labeled "SHOULD" and "SHOULD NOT", may result in the alarm
information not being properly or fully communicated.
3.1.3. Error Codes and Values
The Error Codes and Values used in ALARM_SPEC objects are the same as
those used in ERROR_SPEC objects. New Error Code values for use with
both ERROR_SPEC and ALARM_SPEC objects may be assigned to support
alarm types defined by other standards.
In this document we define one new Error Code. The Error Code uses
the value 31 and is referred to as "Alarms". The values used in the
Error Values field when the Error Code is "Alarms" are the same as
the values defined in the IANAItuProbableCause Textual Convention of
IANA-ITU-ALARM-TC-MIB in the Alarm MIB [RFC3877]. Note that these
values are managed by IANA; see http://www.iana.org.
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RFC 4783 GMPLS - Communication of Alarm Information December 2006
3.1.4. Backwards Compatibility
The support of ALARM_SPEC objects is OPTIONAL. Non-supporting nodes
will (according to the rules defined in [RFC2205]) pass the objects
through the node unmodified, because the ALARM_SPEC object has a
C-Num of the form 11bbbbbb.
This allows alarm information to be collected and examined in a
network built from a collection of nodes some of which support the
communication of alarm information, and some of which do not.
3.2. Controlling Alarm Communication
Alarm information communication is controlled via Administrative
Status Information as carried in the Admin_Status object. A new bit
is defined, called the I bit, that indicates when alarm communication
is to be inhibited. The definition of this bit does not modify the
procedures defined in Section 7 of [RFC3473].
3.2.1. Updated Admin_Status Object
The format of the Admin_Status object is updated to include the I
bit:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class-Num(196)| C-Type (1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R| Reserved |I| |T|A|D|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Inhibit Alarm Communication (I): 1 bit
When set, indicates that alarm communication is disabled for
the LSP and that nodes SHOULD NOT add local alarm information.
See Section 7.1 of [RFC3473] for the definition of the remaining
bits.
3.2.2. Procedures
The I bit may be set and cleared using the procedures defined in
Sections 7.2 and 7.3 of [RFC3473]. A node that receives (or
generates) an Admin_Status object with the A or I bits set (1),
SHOULD remove all locally generated alarm information from the
matching LSP's outgoing Path and Resv messages. When a node receives
(or generates) an Admin_Status object with the A and I bits clear (0)
and there is local alarm information present, it SHOULD add the local
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RFC 4783 GMPLS - Communication of Alarm Information December 2006
alarm information to the matching LSP's outgoing Path and Resv
messages.
The processing of non-locally generated ALARM_SPEC objects MUST NOT
be impacted by the contents of the Admin_Status object; that is,
received ALARM_SPEC objects MUST be forwarded unchanged regardless of
the received or transmitted settings of the I and A bits. Note that,
per [RFC3473], the absence of the Admin_Status object is equivalent
to receiving an object containing values all set to zero (0).
I bit related processing behavior MAY be overridden locally based on
configuration.
When generating Notify messages for LSPs with the I bit set, the TLVs
described in this document MAY be added to the ERROR_SPEC object sent
in the Notify message.
3.3. Message Formats
This section presents the RSVP message-related formats as modified by
this document. The formats specified in [RFC3473] served as the
basis of these formats. The objects are listed in suggested
ordering.
The format of a Path message is as follows:
::= [ ]
[ [ | ] ... ]
[ ]
[ ]
[ ]
[ ... ]
[ ]
[ ]
[ ]
[ ... ]
[ ... ]
is not modified by this document.
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RFC 4783 GMPLS - Communication of Alarm Information December 2006
The format of a Resv message is as follows:
::= [ ]
[ [ | ] ... ]
[ ]
[ ] [ ]
[ ]
[ ]
[ ... ]
[ ... ]
