draft-ietf-mpls-tp-fault-06.txt   draft-ietf-mpls-tp-fault-07.txt 
MPLS Working Group G. Swallow, Ed. MPLS Working Group G. Swallow, Ed.
Internet-Draft Cisco Systems, Inc. Internet-Draft Cisco Systems, Inc.
Intended status: Standards Track A. Fulignoli, Ed. Intended status: Standards Track A. Fulignoli, Ed.
Expires: February 16, 2012 Ericsson Expires: March 5, 2012 Ericsson
M. Vigoureux, Ed. M. Vigoureux, Ed.
Alcatel-Lucent Alcatel-Lucent
S. Boutros S. Boutros
Cisco Systems, Inc. Cisco Systems, Inc.
D. Ward D. Ward
Juniper Networks, Inc. Juniper Networks, Inc.
August 15, 2011 September 2, 2011
MPLS Fault Management OAM MPLS Fault Management OAM
draft-ietf-mpls-tp-fault-06 draft-ietf-mpls-tp-fault-07
Abstract Abstract
This draft specifies OAM messages to indicate service disruptive This document specifies Operations, Administration, and Maintenance
conditions for MPLS based Transport Network Label Switched Paths messages to indicate service disruptive conditions for MPLS based
(LSPs). The notification mechanism employs a generic method for a Transport Network Label Switched Paths. The notification mechanism
service disruptive condition to be communicated to a Maintenance End employs a generic method for a service disruptive condition to be
Point (MEP). An MPLS Operation, Administration, and Maintenance communicated to a Maintenance Entity Group End Point. This document
(OAM) channel is defined along with messages to communicate various defines an MPLS OAM channel, along with messages to communicate
types of service disruptive conditions. various types of service disruptive conditions.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 16, 2012. This Internet-Draft will expire on March 5, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 20 skipping to change at page 2, line 20
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 4 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. MPLS Fault Management Messages . . . . . . . . . . . . . . . . 4 2. MPLS Fault Management Messages . . . . . . . . . . . . . . . . 5
2.1. MPLS Alarm Indication Signal . . . . . . . . . . . . . . . 5 2.1. MPLS Alarm Indication Signal . . . . . . . . . . . . . . . 5
2.1.1. MPLS Link Down Indication . . . . . . . . . . . . . . 5 2.1.1. MPLS Link Down Indication . . . . . . . . . . . . . . 6
2.2. MPLS Lock Report . . . . . . . . . . . . . . . . . . . . . 6 2.2. MPLS Lock Report . . . . . . . . . . . . . . . . . . . . . 6
2.3. Propagation of MPLS Fault Messages . . . . . . . . . . . . 6 2.3. Propagation of MPLS Fault Messages . . . . . . . . . . . . 7
3. MPLS Fault Management Channel . . . . . . . . . . . . . . . . 7 3. MPLS Fault Management Channel . . . . . . . . . . . . . . . . 7
4. MPLS Fault Management Message Format . . . . . . . . . . . . . 7 4. MPLS Fault Management Message Format . . . . . . . . . . . . . 7
4.1. Fault Management Message TLVs . . . . . . . . . . . . . . 9 4.1. Fault Management Message TLVs . . . . . . . . . . . . . . 9
4.1.1. Interface Identifier TLV . . . . . . . . . . . . . . . 9 4.1.1. Interface Identifier TLV . . . . . . . . . . . . . . . 10
4.1.2. Global Identifier . . . . . . . . . . . . . . . . . . 10 4.1.2. Global Identifier . . . . . . . . . . . . . . . . . . 10
5. Sending and Receiving Fault Management Messages . . . . . . . 10 5. Sending and Receiving Fault Management Messages . . . . . . . 11
5.1. Sending a Fault Management Message . . . . . . . . . . . . 10 5.1. Sending a Fault Management Message . . . . . . . . . . . . 11
5.2. Clearing a FM Indication . . . . . . . . . . . . . . . . . 11 5.2. Clearing a FM Indication . . . . . . . . . . . . . . . . . 11
5.3. Receiving a FM Indication . . . . . . . . . . . . . . . . 11 5.3. Receiving a FM Indication . . . . . . . . . . . . . . . . 11
6. Minimum Implementation Requirements . . . . . . . . . . . . . 11 6. Minimum Implementation Requirements . . . . . . . . . . . . . 12
7. Security Considerations . . . . . . . . . . . . . . . . . . . 12 7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
8.1. Pseudowire Associated Channel Type . . . . . . . . . . . . 13 8.1. Pseudowire Associated Channel Type . . . . . . . . . . . . 13
8.2. MPLS Fault OAM Message Type Registry . . . . . . . . . . . 13 8.2. MPLS Fault OAM Message Type Registry . . . . . . . . . . . 14
8.3. MPLS Fault OAM TLV Registry . . . . . . . . . . . . . . . 14 8.3. MPLS Fault OAM Flag Registry . . . . . . . . . . . . . . . 14
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 8.4. MPLS Fault OAM TLV Registry . . . . . . . . . . . . . . . 14
9.1. Normative References . . . . . . . . . . . . . . . . . . . 14 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
9.1. Normative References . . . . . . . . . . . . . . . . . . . 15
9.2. Informative References . . . . . . . . . . . . . . . . . . 15 9.2. Informative References . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction 1. Introduction
Proper operation of a transport network depends on the ability to
quickly identify faults and focus attention on the root cause of the
disruption. This document defines MPLS Fault Management Operations,
Administration, and Maintenance (OAM) messages. When a fault occurs
in a server (sub-)layer, Fault Management OAM messages are sent to
clients of that server so that alarms, which otherwise would be
generated by the subsequent disruption of the clients, may be
suppressed. This prevents a storm of alarms and allows operations to
focus on the actual faulty elements of the network.
In traditional transport networks, circuits such as T1 lines are In traditional transport networks, circuits such as T1 lines are
typically provisioned on multiple switches. When an event that typically provisioned on multiple switches. When an event that
causes disruption occurs on any link or node along the path of such a causes disruption occurs on any link or node along the path of such a
transport circuit, OAM indications are generated which may in turn transport circuit, OAM indications are generated. When received,
suppress alarms and/or activate a backup circuit. The MPLS based these indications may be used to suppress alarms and/or activate a
Transport Network provides mechanisms equivalent to traditional backup circuit. The MPLS based Transport Network provides mechanisms
transport circuits. Therefore a Fault Management (FM) capability equivalent to traditional transport circuits. Therefore a Fault
must be defined for MPLS. This capability is being defined to meet Management (FM) capability must be defined for MPLS. This document
the MPLS-TP requirements as defined in RFC 5654 [1], and the MPLS-TP defines FM capabilities to meet the MPLS-TP requirements as described
Operations, Administration and Maintenance Requirements as defined in in RFC 5654 [1], and the MPLS-TP Operations, Administration, and
RFC 5860 [2]. These mechanisms are intended to be applicable to Maintenance Requirements as described in RFC 5860 [2]. These
other aspects of MPLS as well. However, applicability to other types mechanisms are intended to be applicable to other aspects of MPLS as
of LSPs is beyond the scope of this document. well. However, applicability to other types of LSPs is beyond the
scope of this document.
Two broad classes of service disruptive conditions are identified. Two broad classes of service disruptive conditions are identified.
1. Fault: the situation in which the density of anomalies has 1. Fault: The inability of a function to perform a required action.
reached a level where the ability to perform a required function This does not include an inability due to preventive maintenance,
has been interrupted. lack of external resources, or planned actions.
2. Lock: an administrative status in which it is expected that only 2. Lock: an administrative status in which it is expected that only
test traffic, if any, and OAM (dedicated to the LSP) can be sent test traffic, if any, and OAM (dedicated to the LSP) can be sent
on an LSP. on an LSP.
Within the Fault class, a further category, Defect is identified. A Within this document a further term is defined, server-(sub-)layer-
defect is the inability of a function to perform a required action. failure, or more briefly server-failure. A server-failure occurs
A defect is a persistent fault. when a fault condition or conditions have persisted long enough to
consider the required service function to have terminated. In the
case of a protected server, this would mean that both the working and
and any protection facilities have suffered faults of the required
duration.
This document specifies an MPLS OAM channel called an "MPLS-OAM Fault This document specifies an MPLS OAM channel called an "MPLS-OAM Fault
Management (FM)" channel. A single message format and a set of Management (FM)" channel. A single message format and a set of
procedures are defined to communicate service disruptive conditions procedures are defined to communicate service disruptive conditions
from the location where they occur to the endpoints of LSPs which are from the location where they occur to the endpoints of LSPs which are
affected by those conditions. Multiple message types and flags are affected by those conditions. Multiple message types and flags are
used to indicate and qualify the particular condition. used to indicate and qualify the particular condition.
Corresponding to the two classes of service disruptive conditions Corresponding to the two classes of service disruptive conditions
listed above, two messages are defined to communicate the type of listed above, two messages are defined to communicate the type of
condition. These are known as: condition. These are known as:
Alarm Indication Signal (AIS) Alarm Indication Signal (AIS)
Lock Report (LKR) Lock Report (LKR)
1.1. Terminology 1.1. Terminology
ACH: Associated Channel Header ACH: Associated Channel Header
ACh: Associated Channel
CC: Continuity Check CC: Continuity Check
FM: Fault Management FM: Fault Management
GAL: Generic Associated Channel Label GAL: Generic Associated Channel Label
LOC: Loss of Continuity LOC: Loss of Continuity
LSP: Label Switched Path LSP: Label Switched Path
LSR: Label Switching Router
MEP: Maintenance Entity Group End Point MEP: Maintenance Entity Group End Point
MPLS: Multi-Protocol Label Switching MPLS: Multi-Protocol Label Switching
MPLS-TP: MPLS Transport Profile MPLS-TP: MPLS Transport Profile
MS-PW: Multi-Segment Pseudowire MS-PW: Multi-Segment Pseudowire
OAM: Operations, Administration and Maintenance OAM: Operations, Administration, and Maintenance
PHP: Penultimate Hop Pop PHP: Penultimate Hop Pop
PW: Pseudowire PW: Pseudowire
S-PE: PW Switching Provider Edge
TLV: Type, Length, Value TLV: Type, Length, Value
1.2. Requirements Language 1.2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [3]. document are to be interpreted as described in RFC 2119 [3].
2. MPLS Fault Management Messages 2. MPLS Fault Management Messages
This document defines messages to indicate service disruptive This document defines two messages to indicate service disruptive
conditions. Two messages are defined, Alarm Indication Signal, and conditions, Alarm Indication Signal, and Lock Report. The semantics
Lock Report. The semantics of the individual messages are described of the individual messages are described in subsections below. Fault
in subsections below. Fault OAM messages are applicable to LSPs used OAM messages are applicable to LSPs used in the MPLS Transport
in the MPLS Transport Profile. Such LSPs are bound to specific Profile. Such LSPs are bound to specific server layers based upon
server layers based upon static configuration or signaling in a static configuration or signaling in a client/server relationship.
client/server relationship.
Fault Management messages are carried in-band of the client LSP or Fault Management messages are carried in-band of the client LSP or
MS-PW by using the Associated Channel Header (ACH). For LSPs other MS-PW by using the Associated Channel Header (ACH). For LSPs other
than PWs, the ACH is identified by the Generic Associated Channel than PWs, the ACH is identified by the Generic Associated Channel
Label (GAL) as defined in RFC5586 [4]. To facilitate recognition and Label (GAL) as defined in RFC5586 [4]. To facilitate recognition and
delivery of Fault Management messages, the Fault Management Channel delivery of Fault Management messages, the Fault Management Channel
is identified by a unique ACH codepoint. is identified by a unique Associated Channel (ACh) codepoint.
Fault OAM messages are generated by server MEPs at intermediate nodes Fault OAM messages are generated by intermediate nodes where a client
where a client LSP is switched. When a server (sub-)layer, (e.g. a LSP is switched. When a server (sub-)layer, (e.g. a link or
link or bidirectional LSP) used by the client LSP fails, the bidirectional LSP) used by the client LSP fails, the intermediate
intermediate node sends Fault Management messages downstream towards node sends Fault Management messages downstream towards the endpoint
the endpoint of the LSP. Strictly speaking, when a server MEP of the LSP. The messages are sent to the client MEPs by inserting
detects a service disruptive condition, Fault Management messages are them into the affected client LSPs in the direction downstream of the
generated by the convergence server-to-client adaptation function. fault location. These messages are sent periodically until the
The messages are sent to the client MEPs by inserting them into the condition is cleared.
affected client LSPs in the direction downstream of the fault
location. These messages are sent periodically until the condition
is cleared.
2.1. MPLS Alarm Indication Signal 2.1. MPLS Alarm Indication Signal
The MPLS Alarm Indication Signal (AIS) message is generated in The MPLS Alarm Indication Signal (AIS) message is generated in
response to detecting faults in the server (sub-)layer. The AIS response to detecting faults in the server (sub-)layer. The AIS
message SHOULD be sent as soon as the condition is detected. For message SHOULD be sent as soon as the condition is detected, but MAY
example, an AIS message may be sent during a protection switching be delayed owing to processing in an implementation, and MAY be
event and would cease being sent (or cease being forwarded by the suppressed if protection is achieved very rapidly. For example, an
protection switch selector) if the protection switch was successful AIS message may be sent during a protection switching event and would
in restoring the link. cease being sent (or cease being forwarded by the protection switch
selector) if the protection switch was successful in restoring the
link. However, an implementation may instead wait to see if the
protection switch is successful prior to sending any AIS messages.
The primary purpose of the AIS message is to suppress alarms in the The primary purpose of the AIS message is to suppress alarms in the
layer network above the level at which the fault occurs. When the layer network above the level at which the fault occurs. When the
Link Down Indication is set, the AIS message MAY be used to trigger Link Down Indication is set, the AIS message MAY be used to trigger
recovery mechanisms. recovery mechanisms.
2.1.1. MPLS Link Down Indication 2.1.1. MPLS Link Down Indication
The Link Down Indication (LDI) is communicated by setting the L-flag The Link Down Indication (LDI) is communicated by setting the L-flag
to 1. The L-flag is set in the AIS message in response to detecting to 1. A node sets the L-flag in the AIS message in response to
a defect in the server layer. The L-flag MUST NOT be set until the detecting a failure in the server layer. A node MUST NOT set the
fault has been determined to be a defect. The L-flag MUST be set if L-flag until the fault has been determined to be a server-failure. A
the fault has been determined to be a defect. For example during a node MUST set the L-flag if the fault has been determined to be a
protection switching event the L-flag is not set. However if the server-failure. For example during a server layer protection
switching event, a node MUST NOT set the L-flag. However if the
protection switch was unsuccessful in restoring the link within the protection switch was unsuccessful in restoring the link within the
expected repair time, the L-flag MUST be set. expected repair time, the node MUST set the L-flag.
The setting of the L-flag can be predetermined based on the The setting of the L-flag can be predetermined based on the
protection state. For example, if a server layer is protected and protection state. For example, if a server layer is protected and
both the working and protection paths are available, both the active both the working and protection paths are available, the node should
and standby server MEPs should be programmed to send AIS with the send AIS with the L-flag clear upon detecting a fault condition. If
L-flag clear upon detecting a fault condition. If the server layer the server layer is unprotected or the server layer is protected but
is unprotected or the server layer is protected but only the active only the active path is available, the node should send AIS with the
path is available, the active server MEP should be programmed to send L-flag set upon detecting a loss of continuity (LOC) condition. Note
AIS with the L-flag set upon detecting a LOC condition. Note again again that the L-flag is not set until a server-failure has been
that the L-flag is not until a defect has been declared. Thus if declared. Thus if there is any hold-off timer associated with the
there is any hold-off timer associated with the LOC, then the L-flag LOC, then the L-flag is not set until that timer has expired.
is not set until that timer has expired.
The receipt of an AIS message with the L-flag set MAY be treated as The receipt of an AIS message with the L-flag set MAY be treated as
the equivalent of loss of continuity (LOC) at the client layer. The the equivalent of LOC at the client layer. The choice of treatment
choice of treatment is related to the rate at which the Continuity is related to the rate at which the Continuity Check (CC) function is
Check (CC) function is running. In a normal transport environment, running. In a normal transport environment, CC is run at a high rate
CC is run at a high rate in order to detect a failure within 10s of in order to detect a failure within 10s of milliseconds. In such an
milliseconds. In such an environment, the L-flag MAY be ignored and environment, the L-flag MAY be ignored and the AIS message is used
the AIS message is used solely for alarm suppression. solely for alarm suppression.
In more general MPLS environments the CC function may be running at a In more general MPLS environments the CC function may be running at a
much slower rate. In this environment, the Link Down Indication much slower rate. In this environment, the Link Down Indication
enables faster switch-over upon a failure occurring along the client enables faster switch-over upon a failure occurring along the client
LSP. LSP.
2.2. MPLS Lock Report 2.2. MPLS Lock Report
The MPLS Lock Report (LKR) message is generated when a server The MPLS Lock Report (LKR) message is generated when a server
(sub-)layer entity has been administratively locked. Its purpose is (sub-)layer entity has been administratively locked. Its purpose is
skipping to change at page 6, line 46 skipping to change at page 7, line 8
carry client traffic. The purpose of the LKR message is to suppress carry client traffic. The purpose of the LKR message is to suppress
alarms in the layer network above the level at which the alarms in the layer network above the level at which the
administrative lock occurs and to allow the clients to differentiate administrative lock occurs and to allow the clients to differentiate
the lock condition from a fault condition. While the primary purpose the lock condition from a fault condition. While the primary purpose
of the LKR message is to suppress alarms, similar to AIS with the LDI of the LKR message is to suppress alarms, similar to AIS with the LDI
(L-flag set), the receipt of an LKR message MAY be treated as the (L-flag set), the receipt of an LKR message MAY be treated as the
equivalent of loss of continuity at the client layer. equivalent of loss of continuity at the client layer.
2.3. Propagation of MPLS Fault Messages 2.3. Propagation of MPLS Fault Messages
If the CC function is disabled, a MEP SHOULD generate AIS messages MPLS-TP allows for a hierarchy of LSPs. When the client MEP of an
toward any client when either the AIS or LKR indication is raised. LSP which is also acting as a server layer receives FM indications,
Note that the L-flag is not automatically propagated. The rules of the following rules apply. If the CC function is disabled for the
Section 2.1.1 apply. In particular, the L-flag is not set until a server LSP, a node SHOULD generate AIS messages toward any clients
defect has been declared. when either the AIS or LKR indication is raised. Note that the
L-flag is not automatically propagated. The rules of Section 2.1.1
apply. In particular, the L-flag is not set until a server-failure
has been declared.
3. MPLS Fault Management Channel 3. MPLS Fault Management Channel
The MPLS Fault Management channel is identified by the ACH as defined The MPLS Fault Management channel is identified by the ACH as defined
in RFC 5586 [4] with the Channel Type set to the MPLS Fault in RFC 5586 [4] with the Associated Channel Type set to the MPLS
Management (FM) code point = 0xHH. [HH to be assigned by IANA from Fault Management (FM) code point = 0xHHHH. [HHHH to be assigned by
the PW Associated Channel Type registry. Note: An early codepoint IANA from the PW Associated Channel Type registry.] The FM Channel
allocation has made: 0x0058 Fault OAM (TEMPORARY - expires does not use ACh TLVs and MUST NOT include the ACh TLV header. The
2012-07-20)] The FM Channel does not use ACH TLVs and MUST NOT ACH with the FM ACh code point is shown below.
include the ACH TLV header. The FM ACH Channel is shown below.
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|Version| Reserved | 0xHH Fault Management Channel | |0 0 0 1|Version| Reserved | 0xHHHH FM Channel |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ~ | ~
~ MPLS Fault Management Message ~ ~ MPLS Fault Management Message ~
~ | ~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: ACH Indication of the MPLS Fault Management Channel Figure 1: ACH Indication of the MPLS Fault Management Channel
The first three fields are defined in RFC 5586 [4]. The first three fields are defined in RFC 5586 [4].
The Fault Management Channel is 0xHH (to be assigned by IANA). The Fault Management Channel is 0xHHHH (to be assigned by IANA).
4. MPLS Fault Management Message Format 4. MPLS Fault Management Message Format
The format of the Fault Management message is shown below. The format of the Fault Management message is shown below.
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Vers | Resvd | Msg Type | Flags | Refresh Timer | | Vers | Resvd | Msg Type | Flags | Refresh Timer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 8, line 22 skipping to change at page 8, line 37
The Message Type indicates the type of condition as listed in the The Message Type indicates the type of condition as listed in the
table below. table below.
Msg Type Description Msg Type Description
-------- ----------------------------- -------- -----------------------------
0x0 Reserved 0x0 Reserved
0x1 Alarm Indication Signal (AIS) 0x1 Alarm Indication Signal (AIS)
0x2 Lock Report (LKR) 0x2 Lock Report (LKR)
Refresh Timer
The maximum time between successive FM messages specified in
seconds. The range is 1 to 20. The value 0 is not permitted.
Total TLV Length
The total TLV length is the total of all included TLVs.
Flags Flags
Two flags are defined. The reserved flags in this field MUST be Two flags are defined. The reserved flags in this field MUST be
set to zero on transmission and ignored on receipt. set to zero on transmission and ignored on receipt.
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
| Reserved |L|R| | Reserved |L|R|
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
Figure 3: Flags Figure 3: Flags
L-flag L-flag
Link Down Indication. The L-flag only has significance in the Link Down Indication. The L-flag only has significance in the
AIS message. For the LKR message the L-flag MUST be set to AIS message. For the LKR message the L-flag MUST be set to
zero and ignored on receipt. See Section 2.1.1 for details on zero and ignored on receipt. See Section 2.1.1 for details on
setting this bit. setting this bit.
R-flag R-flag
The R-flag is normally set to zero. A setting of one indicates The R-flag is clear to indicate the presence of an FM condition
the removal of a previously sent FM condition. and is to one to indicate the removal of a previously sent FM
condition.
Refresh Timer
The maximum time between successive FM messages specified in
seconds. The range is 1 to 20. The value 0 is not permitted.
Total TLV Length
The total length in bytes of all included TLVs.
4.1. Fault Management Message TLVs 4.1. Fault Management Message TLVs
TLVs are used in Fault Management messages to carry information that TLVs are used in Fault Management messages to carry information that
may not pertain to all messages as well as to allow for may not pertain to all messages as well as to allow for
extensibility. The TLVs currently defined are the IF_ID, and the extensibility. The TLVs currently defined are the IF_ID, and the
Global_ID. Global_ID.
TLVs (Type-Length-Value tuples) have the following format: TLVs (Type-Length-Value tuples) have the following format:
skipping to change at page 11, line 11 skipping to change at page 11, line 29
MAY be included. MAY be included.
The message is then sent. Assuming the condition persists, the The message is then sent. Assuming the condition persists, the
message MUST be retransmitted two more times at an interval of one message MUST be retransmitted two more times at an interval of one
second. Further retransmissions are made according to the value of second. Further retransmissions are made according to the value of
the refresh timer. Retransmissions continue until the condition is the refresh timer. Retransmissions continue until the condition is
cleared. cleared.
5.2. Clearing a FM Indication 5.2. Clearing a FM Indication
Ceasing to send FM messages will clear the indication after 3.5 times When a fault is cleared, a node MUST cease sending the associated FM
the refresh timer. To clear an indication more quickly, the messages. Ceasing to send FM messages will clear the indication
following procedure is used. The R-flag of the FM message is set to after 3.5 times the refresh timer. To clear an indication more
one. Other fields of the FM message SHOULD NOT be modified. The quickly, the following procedure is used. The R-flag of the FM
message is sent immediately and then retransmitted two more times at message is set to one. Other fields of the FM message SHOULD NOT be
an interval of one second. modified. The message is sent immediately and then retransmitted two
more times at an interval of one second. Note, however if another
fault occurs, the node MUST cease these retransmissions and a
generate new FM messages for the new fault.
5.3. Receiving a FM Indication 5.3. Receiving a FM Indication
When a FM message is received, a MEP examines it to ensure that it is When a FM message is received, a MEP examines it to ensure that it is
well formed. If the message type is reserved or unknown, the message well formed. If the message type is reserved or unknown, the message
is ignored. is ignored. If the version number is unknown, the message is
ignored.
If the R-flag is set to zero, the MEP checks to see if a condition If the R-flag is set to zero, the MEP checks to see if a condition
matching the message type and IF_ID exists. If it does not, the matching the message type exists. If it does not, the condition
condition to the message type is entered. An expiration-timer is set specific to the message type is entered. An expiration-timer is set
to 3.5 times the refresh timer. If the message type and IF_ID match to 3.5 times the refresh timer. If the message type matches an
an existing condition, message is considered a refresh and the existing condition, the message is considered a refresh and the
expiration-timer is reset. expiration-timer is reset. In both cases, if an IF_ID tlv is
present, it is recorded.
If the R-flag is set to one, the MEP checks to see if a condition If the R-flag is set to one, the MEP checks to see if a condition
matching the message type and IF_ID exists. If it does, that matching the message type and IF_ID exists. If it does, that
condition is cleared. Otherwise the message is ignored. condition is cleared. Otherwise the message is ignored.
If the expiration-time expires, the condition is cleared. If the expiration-time expires, the condition is cleared.
6. Minimum Implementation Requirements 6. Minimum Implementation Requirements
At a minimum an implementation MUST support the following: At a minimum an implementation MUST support the following:
1. Sending AIS and LKR messages at a rate of 1 per second. 1. Sending AIS and LKR messages at a rate of 1 per second.
2. Support of setting the L-flag to indicated a defect. 2. Support of setting the L-flag to indicate a server-failure.
3. Receiving AIS and LKR messages with any allowed Refresh Timer 3. Receiving AIS and LKR messages with any allowed Refresh Timer
value. value.
The following items are optional to implement. The following items are OPTIONAL to implement.
1. Sending AIS and LKR message with other values of the Refresh 1. Sending AIS and LKR message with values of the Refresh Timer
Timer other than 1 second. other than 1 second.
2. Support of receiving the L-flag. 2. Support of receiving the L-flag.
3. Support of setting the R-flag to a value other than zero. 3. Support of setting the R-flag to a value other than zero.
4. Support of receiving the R-flag. 4. Support of receiving the R-flag.
5. All TLVs. 5. All TLVs.
7. Security Considerations 7. Security Considerations
MPLS-TP is a subset of MPLS and so builds upon many of the aspects of MPLS-TP is a subset of MPLS and so builds upon many of the aspects of
the security model of MPLS. MPLS networks make the assumption that the security model of MPLS. MPLS networks make the assumption that
it is very hard to inject traffic into a network, and equally hard to it is very hard to inject traffic into a network, and equally hard to
cause traffic to be directed outside the network. The control plane cause traffic to be directed outside the network. The control plane
protocols utilize hop-by-hop security, and assume a "chain-of-trust" protocols utilize hop-by-hop security, and assume a "chain-of-trust"
model such that end-to-end control plane security is not used. For model such that end-to-end control plane security is not used. For
more information on the generic aspects of MPLS security, see RFC more information on the generic aspects of MPLS security, see RFC
5920 [6]. 5920 [8].
This document describes a protocol carried in the G-ACh RFC 5586 [4], This document describes a protocol carried in the G-ACh RFC 5586 [4],
and so is dependent on the security of the G-ACh, itself. The G-ACh and so is dependent on the security of the G-ACh, itself. The G-ACh
is a generalization of the Associated Channel defined in RFC 4385 is a generalization of the Associated Channel defined in RFC 4385
[7]. Thus, this document relies heavily on the security mechanisms [6]. Thus, this document relies heavily on the security mechanisms
provided for the Associated Channel and described in those two provided for the Associated Channel and described in those two
documents. documents.
A specific concern for the G-ACh is that is can be used to provide a A specific concern for the G-ACh is that is can be used to provide a
covert channel. This problem is wider than the scope of this covert channel. This problem is wider than the scope of this
document and does not need to be addressed here, but it should be document and does not need to be addressed here, but it should be
noted that the channel provides end-to-end connectivity and SHOULD noted that the channel provides end-to-end connectivity and SHOULD
NOT be policed by transit nodes. Thus, there is no simple way of NOT be policed by transit nodes. Thus, there is no simple way of
preventing any traffic being carried between in the G-ACh consenting preventing any traffic being carried in the G-ACh between consenting
nodes. nodes.
A good discussion of the data plane security of an associated channel A good discussion of the data plane security of an associated channel
may be found in RFC 5085 [9]. That document also describes some may be found in RFC 5085 [9]. That document also describes some
mitigation techniques. mitigation techniques.
It should be noted that the G-ACh is essentially connection-oriented It should be noted that the G-ACh is essentially connection-oriented
so injection or modification of control messages specified in this so injection or modification of control messages specified in this
document require the subversion of a transit node. Such subversion document requires the subversion of a transit node. Such subversion
is generally considered hard in MPLS networks, and impossible to is generally considered hard in MPLS networks, and impossible to
protect against at the protocol level. Management level techniques protect against at the protocol level. Management level techniques
are more appropriate. are more appropriate.
Spurious fault OAM messages form a vector for a denial of service Spurious fault OAM messages form a vector for a denial of service
attack. However, since these messages are carried in a control attack. However, since these messages are carried in a control
channel, except of one case discussed below, one would have to gain channel, except for one case discussed below, one would have to gain
access to a node providing the service in order to effect such an access to a node providing the service in order to effect such an
attack. Since transport networks are usually operated as a walled attack. Since transport networks are usually operated as a walled
garden, such threats are less likely. garden, such threats are less likely.
If external MPLS traffic is mapped to an LSP via a PHP forwarding If external MPLS traffic is mapped to an LSP via a PHP forwarding
operation, it is possible to insert a GAL label followed by a fault operation, it is possible to insert a GAL followed by a fault OAM
OAM message. In such a situation an operator SHOULD filter any fault message. In such a situation an operator SHOULD protect against this
OAM messages with the GAL label at the top of the label stack. attack by filtering any fault OAM messages with the GAL at the top of
the label stack.
8. IANA Considerations 8. IANA Considerations
8.1. Pseudowire Associated Channel Type 8.1. Pseudowire Associated Channel Type
Fault OAM requires a unique Associated Channel Type which are Fault OAM requires a unique Associated Channel Type which are
assigned by IANA from the Pseudowire Associated Channel Types assigned by IANA from the Pseudowire Associated Channel Types
Registry. Registry.
Registry: Registry:
Value Description TLV Follows Reference Value Description TLV Follows Reference
----------- ----------------------- ----------- --------- ----------- ----------------------- ----------- ---------
0xHHHH Fault OAM No (This Document) 0xHHHH Fault OAM No (This Document)
[Note: An early codepoint allocation was made: 0x0058 Fault OAM
(TEMPORARY - expires 2012-07-20)]
8.2. MPLS Fault OAM Message Type Registry 8.2. MPLS Fault OAM Message Type Registry
This sections details the MPLS Fault OAM TLV Registry, a new name This section details the MPLS Fault OAM Message Type Registry, a new
spaces to be managed by IANA. The Type space is divided into name space to be managed by IANA. The Type space is divided into
assignment ranges; the following terms are used in describing the assignment ranges; the following terms are used in describing the
procedures by which IANA allocates values: "Standards Action" (as procedures by which IANA allocates values: "Standards Action" (as
defined in RFC 5226 [8]) and "Private Use". defined in RFC 5226 [7]) and "Experimental Use".
MPLS Fault OAM Message Types take values in the range 0-255. MPLS Fault OAM Message Types take values in the range 0-255.
Assignments in the range 0-251 are via Standards Action; values in Assignments in the range 0-251 are via Standards Action; values in
the range 251-255 are for Private Use, and MUST NOT be allocated. the range 252-255 are for Experimental Use, and MUST NOT be
allocated.
Message Types defined in this document are: Message Types defined in this document are:
Msg Type Description Msg Type Description
-------- ----------------------------- -------- -----------------------------
0x0 Reserved 0x0 Reserved (not available for allocation)
0x1 Alarm Indication Signal (AIS) 0x1 Alarm Indication Signal (AIS)
0x2 Lock Report (LKR) 0x2 Lock Report (LKR)
8.3. MPLS Fault OAM TLV Registry 8.3. MPLS Fault OAM Flag Registry
This section details the MPLS Fault OAM Flag Registry, a new name
space to be managed by IANA. The Flag space ranges from 0-7. All
flags are allocated by "Standards Action".
Flags defined in this document are:
Bit Hex Value Description
--- --------- -----------
0-5 Unassigned
6 0x2 L-Flag
7 0x1 R-Flag
8.4. MPLS Fault OAM TLV Registry
This sections details the MPLS Fault OAM TLV Registry, a new name This sections details the MPLS Fault OAM TLV Registry, a new name
spaces to be managed by IANA. The Type space is divided into spaces to be managed by IANA. The Type space is divided into
assignment ranges; the following terms are used in describing the assignment ranges; the following terms are used in describing the
procedures by which IANA allocates values: "Standards Action" (as procedures by which IANA allocates values: "Standards Action" (as
defined in RFC 5226 [8]), "Specification Required" and "Private Use". defined in RFC 5226 [7]), "Specification Required" and "Private Use".
MPLS Fault OAM TLVs which take values in the range 0-255. MPLS Fault OAM TLVs which take values in the range 0-255.
Assignments in the range 0-191 are via Standards Action; assignments Assignments in the range 0-191 are via Standards Action; assignments
in the range 192-248 are made via "Specification Required"; values in in the range 192-247 are made via "Specification Required"; values in
the range 248-255 are for Private Use, and MUST NOT be allocated. the range 248-255 are for Experimental Use, and MUST NOT be
allocated.
TLVs defined in this document are: TLVs defined in this document are:
Value TLV Name Value TLV Name
----- ------- ----- -------
0 Reserved 0 Reserved (not available for allocation)
1 Interface Identifier TLV 1 Interface Identifier TLV
2 Global Identifier 2 Global Identifier
9. References 9. References
9.1. Normative References 9.1. Normative References
[1] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N., and S. [1] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N., and S.
Ueno, "Requirements of an MPLS Transport Profile", RFC 5654, Ueno, "Requirements of an MPLS Transport Profile", RFC 5654,
September 2009. September 2009.
skipping to change at page 14, line 47 skipping to change at page 15, line 37
[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement [3] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[4] Bocci, M., Vigoureux, M., and S. Bryant, "MPLS Generic [4] Bocci, M., Vigoureux, M., and S. Bryant, "MPLS Generic
Associated Channel", RFC 5586, June 2009. Associated Channel", RFC 5586, June 2009.
[5] Bocci, M., Swallow, G., and E. Gray, "MPLS-TP Identifiers", [5] Bocci, M., Swallow, G., and E. Gray, "MPLS-TP Identifiers",
draft-ietf-mpls-tp-identifiers-07 (work in progress), July 2011. draft-ietf-mpls-tp-identifiers-07 (work in progress), July 2011.
[6] Fang, L., "Security Framework for MPLS and GMPLS Networks", [6] Bryant, S., Swallow, G., Martini, L., and D. McPherson,
RFC 5920, July 2010.
[7] Bryant, S., Swallow, G., Martini, L., and D. McPherson,
"Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use
over an MPLS PSN", RFC 4385, February 2006. over an MPLS PSN", RFC 4385, February 2006.
[8] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA [7] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. Considerations Section in RFCs", BCP 26, RFC 5226, May 2008.
9.2. Informative References 9.2. Informative References
[8] Fang, L., "Security Framework for MPLS and GMPLS Networks",
RFC 5920, July 2010.
[9] Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit [9] Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit
Connectivity Verification (VCCV): A Control Channel for Connectivity Verification (VCCV): A Control Channel for
Pseudowires", RFC 5085, December 2007. Pseudowires", RFC 5085, December 2007.
Authors' Addresses Authors' Addresses
George Swallow (editor) George Swallow (editor)
Cisco Systems, Inc. Cisco Systems, Inc.
300 Beaver Brook Road 300 Beaver Brook Road
Boxborough, Massachusetts 01719 Boxborough, Massachusetts 01719
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