Network Working Group A. Takacs
Internet-Draft Ericsson
Intended status: Standards Track D. Fedyk
Expires: April 29, 2010 Alcatel-Lucent
J. He
Huawei
October 26, 2009
OAM Configuration Framework and Requirements for GMPLS RSVP-TE
draft-ietf-ccamp-oam-configuration-fwk-02
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Abstract
OAM is an integral part of transport connections, hence it is
required that OAM functions are activated/deactivated in sync with
connection commissioning/decommissioning; avoiding spurious alarms
and ensuring consistent operation. In certain technologies OAM
entities are inherently established once the connection is set up,
while other technologies require extra configuration to establish and
configure OAM entities. This document specifies extensions to
RSVP-TE to support the establishment and configuration of OAM
entities along with LSP signaling.
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Requirements Language
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
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. GMPLS RSVP-TE Extensions . . . . . . . . . . . . . . . . . . . 9
3.1. Operation overview . . . . . . . . . . . . . . . . . . . . 9
3.2. LSP Attributes flags . . . . . . . . . . . . . . . . . . . 10
3.3. OAM Configuration TLV . . . . . . . . . . . . . . . . . . 11
3.4. TCME Configuration TLV . . . . . . . . . . . . . . . . . . 13
3.5. NIME Configuration TLV . . . . . . . . . . . . . . . . . . 14
3.6. Monitoring Disabled - Admin_Status bit . . . . . . . . . . 15
3.7. OAM configuration errors . . . . . . . . . . . . . . . . . 15
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
5. Security Considerations . . . . . . . . . . . . . . . . . . . 18
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19
Appendix A. Discussion on alternatives . . . . . . . . . . . . . 20
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24
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1. Introduction
GMPLS is designed as an out-of-band control plane supporting dynamic
connection provisioning for any suitable data plane technology;
including spatial switching (e.g., incoming port or fiber to outgoing
port or fiber), wavelength-division multiplexing (e.g., DWDM), time-
division multiplexing (e.g., SONET/SDH, G.709), and lately Ethernet
Provider Backbone Bridging -- Traffic Engineering (PBB-TE) and MPLS
Transport Profile (MPLS-TP). In most of these technologies there are
Operations and Management (OAM) functions employed to monitor the
health and performance of the connections and to trigger data plane
(DP) recovery mechanisms. Similarly to connections, OAM functions
follow general principles but also have some technology specific
characteristics.
OAM is an integral part of transport connections, hence it is
required that OAM functions are activated/deactivated in sync with
connection commissioning/decommissioning; avoiding spurious alarms
and ensuring consistent operation. In certain technologies OAM
entities are inherently established once the connection is set up,
while other technologies require extra configuration to establish and
configure OAM entities. In some situations the use of OAM functions,
like those of Fault- (FM) and Performance Management (PM), may be
optional confirming to actual network management policies. Hence the
network operator must be able to choose which kind of OAM functions
to apply to specific connections and with what parameters the
selected OAM functions should be configured and operated. To achieve
this objective OAM entities and specific functions must be
selectively configurable.
In general, it is required that the management plane and control
plane connection establishment mechanisms are synchronized with OAM
establishment and activation. In particular, if the GMPLS control
plane is employed it is desirable to bind OAM setup and configuration
to connection establishment signaling to avoid two separate
management/configuration steps (connection setup followed by OAM
configuration) which increases delay, processing and more importantly
may be prune to misconfiguration errors. Once OAM entities are setup
and configured pro-active as well as on-demand OAM functions can be
activated via the management plane. On the other hand, it should be
possible to activate/deactivate pro-active OAM functions via the
GMPLS control plane as well.
This document describes requirements on OAM configuration and control
via RSVP-TE, and specifies extensions to the RSVP-TE protocol
providing a framework to configure and control OAM entities along
with capability to carry technology specific information. Extensions
can be grouped into generic elements that are applicable to any OAM
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solution and technology specific elements that provide additional
configuration parameters only needed for a specific OAM technology.
This document specifies the technology agnostic elements which alone
can be used to establish and control OAM entities in the case no
technology specific information is needed, and specifies the way
additional technology specific OAM parameters are provided.
The mechanisms described in this document provide an additional
option for bootstrapping OAM that is not intended to replace or
deprecate the use of other technology specific OAM bootstrapping
techniques; e.g., LSP Ping [RFC4379] for MPLS networks. The
procedures specified in this document are intended only for use in
environments where RSVP-TE signaling is already in use to set up the
LSPs that are to be monitored using OAM.
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2. Requirements
MPLS OAM requirements are described in [RFC4377]. It provides
requirements to create consistent OAM functionality for MPLS
networks. GMPLS OAM requirements are described in [GMPLS-OAM]. The
GMPLS OAM requirements are based on the MPLS OAM requirements
[RFC4377], in addition it also considers the existing OAM techniques
in non-packet networks.
The following list is an excerpt of MPLS OAM requirements documented
in [RFC4377]. Only a few requirements are discussed that bear a
direct relevance to the discussion set forth in this document.
o It is desired to support the automation of LSP defect detection.
It is especially important in cases where large numbers of LSPs
might be tested.
o In particular some LSPs may require automated ingress-LSR to
egress-LSR testing functionality, while others may not.
o Mechanisms are required to coordinate network responses to
defects. Such mechanisms may include alarm suppression,
translating defect signals at technology boundaries, and
synchronizing defect detection times by setting appropriately
bounded detection timeframes.
MPLS-TP defines a profile of MPLS targeted at transport applications
[MPLS-TP-FWK]. This profile specifies the specific MPLS
characteristics and extensions required to meet transport
requirements, including providing additional OAM, survivability and
other maintenance functions not currently supported by MPLS.
Specific OAM requirements for MPLS-TP are specified in
[MPLS-TP-OAM-REQ]. MPLS-TP poses requirements on the control plane
to configure and control OAM entities.
o The use of OAM functions SHOULD be optional for the operator. A
network operator SHOULD be able to choose which OAM functions to
use and which Maintenance Entity to apply them to.
o The MPLS-TP control plane MUST support the configuration and
modification of OAM maintenance points as well as the activation/
deactivation of OAM when the transport path is established or
modified. OAM functions SHOULD be configurable as part of
connectivity (LSP or PW) management.
Ethernet Connectivity Fault Management (CFM) defines an adjunct
connectivity monitoring OAM flow to check the liveliness of Ethernet
networks [IEEE-CFM]. With PBB-TE [IEEE-PBBTE] Ethernet networks will
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support explicitly-routed Ethernet connections. CFM can be used to
track the liveliness of PBB-TE connections and detect data plane
failures. In IETF the GMPLS controlled Ethernet Label Switching
(GELS) [GELS-Framework] work is extending the GMPLS control plane to
support the establishment of point-to-point PBB-TE data plane
connections. Without control plane support separate management
commands would be needed to configure and start CFM.
GMPLS based OAM configuration and control should be general to be
applicable to a wide range of data plane technologies and OAM
solution. There are three typical data plane technologies used for
transport application, which are wavelength based such as WSON, TDM
based such as SDH/SONET, packet based such as MPLS-TP [MPLS-TP-FWK]
and Ethernet PBB-TE [IEEE-PBBTE]. In all these data planes, the
operator MUST be able to configure and control the following OAM
functions.
o It MUST be possible to explicitly request the setup of OAM
entities for the signaled LSP and provide specific information for
the setup if this is required by the technology.
o Control of alarms is important to avoid false alarm indications
and reporting to the management system. It MUST be possible to
enable/disable alarms generated by OAM functions. In some cases
selective alarm control may be desirable when, for instance, the
operator is only concerned about critical alarms thus the non-
service affecting alarms should be inhibited.
o When periodic messages are used for liveliness check (continuity
check) of LSPs it MUST be possible to set the frequency of
messages allowing proper configuration for fulfilling the
requirements of the service and/or meeting the detection time
boundaries posed by possible congruent connectivity check
operations of higher layer applications. For a network operator
to be able to balance the trade-off in fast failure detection and
overhead it is beneficial to configure the frequency of continuity
check messages on a per LSP basis.
o Pro-active Performance Monitoring (PM) functions are continuously
collecting information about specific characteristics of the
connection. For consistent measurement of Service Level
Agreements (SLAs) it may be required that measurement points agree
on a common probing rate to avoid measurement problems.
o The extensions must allow the operator to use only a minimal set
of OAM configuration and control features if the data plane
technology, the OAM solution or network management policy allows.
The extensions must be reusable as much as reasonably possible.
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That is generic OAM parameters and data plane or OAM technology
specific parameters must be separated.
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3. GMPLS RSVP-TE Extensions
3.1. Operation overview
In general, two types of Maintenance Poits (MPs) can be
distinguished: Maintenance End Points (MEPs) and Maintenance
Intermediate Points (MIPs). MEPs are capable of initiating and
terminating OAM messages for Fault Management (FM) and Performance
Monitoring (PM). MIPs on the other hand are located at transit nodes
of an LSP and are capable of reacting to some OAM messages but
otherwise do not initiate messages. Maintenance Entity (ME) refers
to an association of MEPs and MIPs that are provisioned to monitor an
LSP. The ME association is achieved by configuring MPs of an ME with
the same unique ME Assocication ID (MA ID). Each MEP must have
unique identification (MEP ID) within a Maintenance Entity.
When an LSP is signaled forwarding association is established between
endpoints and transit nodes via label bindings. This association
creates a context for the OAM entities monitoring the LSP. On top of
this association OAM entities may be configured with an MA ID and MEP
IDs. The MA ID may be used to detect misconfiguration errors and
leaking OAM traffic. While the MEP ID can be used to demultiplex and
identify the originating MEP of OAM messages. Since MIPs do not
originate OAM packets, on top of the configuration of Maintenance
Entity associations, no specific configuration is required for them.
Along the LSP several Tandem Connections may be provisioned and
associated to the end-to-end connection. These Tandem Connections
may implement their own OAM monitoring entities. The Tandem
Connection Maintenance Entities (TCMEs) provide the same monitoring
capabilities for a segment of a connection as what is possible on an
end-to-end basis. As the endpoints of a TCME may be (and usually
are) intermediate nodes of an end-to-end LSP, the placement of TCME
ingress and egress endpoints must be explicitly identified.
Altough provisioned together with the end-to-end connection, each
TCME defines a new context for the OAM entities, which is independent
from the end-to-end connection. The MA ID and MEP IDs for a TCME are
within this new context.
When an LSP is signaled Non-Intrusive Maintenance Elements (NIME) may
be deployed along the path. These elements differ from the MIPs as
they implemetn egress MEP functions: they not only process OAM
messages but they can also trigger consequent actions, for instance,
initiate segment protection switching. The NIMEs belong to the OAM
entity context of the end-to-end LSP and, thus, the same MA ID is
applied. As the NIMEs are placed at intermediate nodes, their
placement must be explicitly indicated.
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In addition to the MA and MEP identification parameters pro-active
OAM functions (e.g., Continuity Check (CC), Performance Monitoring)
may have specific parameters requiring configuration as well. In
particular, the frequency of periodic CC packets and the measurement
interval for loss and delay measurements may need to be configured.
MEP
+-------------+
|OAM Functions|
| FM | PM |
+------+------+
| MEP ID |
+-------------+
| MA ID |
+-------------+
+-------------+
| connection |
+-------------+
In some cases all the above parameters may be either derived form
some exiting information or pre-configured default values can be
used. In the simplest case the control plane needs to provide
information whether or not a MA with MPs need to be setup for the
signaled LSP. If OAM entities are created signaling must provide
means to activate/deactivate OAM message flows and associated alarms.
MA and MEP IDs as well as configuration of OAM functions are
technology specific, i.e., vary depending on the data plane
technology and the chosen OAM solution. In addition, for any given
data plane technology a set of OAM solutions may be applicable. The
OAM configuration framework allows selecting a specific OAM solution
to be used for the signaled LSP and provides technology specific TLVs
to carry further detailed configuration information.
3.2. LSP Attributes flags
In RSVP-TE the Flags field of the SESSION_ATTRIBUTE object is used to
indicate options and attributes of the LSP. The Flags field has 8
bits and hence is limited to differentiate only 8 options. [RFC4420]
defines new objects for RSVP-TE messages to allow the signaling of
arbitrary attribute parameters making RSVP-TE easily extensible to
support new applications. Furthermore, [RFC4420] allows options and
attributes that do not need to be acted on by all Label Switched
Routers (LSRs) along the path of the LSP. In particular, these
options and attributes may apply only to key LSRs on the path such as
the ingress LSR and egress LSR. Options and attributes can be
signaled transparently, and only examined at those points that need
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to act on them. The LSP_ATTRIBUTES and the LSP_REQUIRED_ATTRIBUTES
objects are defined in [RFC4420] to provide means to signal LSP
attributes and options in the form of TLVs. Options and attributes
signaled in the LSP_ATTRIBUTES object can be passed transparently
through LSRs not supporting a particular option or attribute, while
the contents of the LSP_REQUIRED_ATTRIBUTES object must be examined
and processed by each LSR. One TLV is defined in [RFC4420]: the
Attributes Flags TLV.
One bit (10 IANA to assign): "OAM MEP entities desired" is allocated
in the LSP Attributes Flags TLV. If the "OAM MEP entities desired"
bit is set it is indicating that the establishment of OAM MEP
entities are required at the endpoints of the signaled LSP. If the
establishment of MEPs is not supported an error must be generated:
"OAM Problem/MEP establishment not supported".
If the "OAM MEP entities desired" bit is set and additional
parameters are needed to configure the OAM entities an OAM
Configuration TLV may be included in the LSP_ATTRIBUTES object.
One bit (11 IANA to assign): "OAM MIP entities desired" is allocated
in the LSP Attributes Flags TLV. If the "OAM MIP entities desired"
bit is set it is indicating that the establishment of OAM MIP
entities are required at the transit nodes of the signaled LSP. This
bit can only be set if the "OAM MEP entities desired" bit is set. If
the establishment of MIPs is not supported an error must be
generated: "OAM Problem/MIP establishment not supported".
One bit (12 IANA to assign): "Alarm indication desired" is allocated
in the LSP Attributes Flags TLV. If the "Alarm indication desired"
bit is set it is indicating that the OAM entities of the signaled LSP
should be notified of lower layer failures. In the case of
hierarchical LSPs this will create an association between the
underlying (server) LSP's OAM entities and the currently signaled
(client) LSP's OAM entities.
3.3. OAM Configuration TLV
This TLV specifies which OAM technology/method should be used for the
LSP. The OAM Configuration TLV is carried in the LSP_ATTRIBUTES
object in Path messages.
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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 (2) (IANA) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OAM Type | Reserved | OAM Function |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ sub-TLVs ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: indicates a new type: the OAM Configuration TLV (2) (IANA to
assign).
OAM Type: specifies the technology specific OAM method. If the
requested OAM method is not supported an error must be generated:
"OAM Problem/Unsupported OAM Type".
This document defines no types. The receiving node based on the OAM
Type will check if a corresponding technology specific OAM
configuration sub-TLV is included. If different technology specific
OAM configuration sub-TLV is included than what was specified in the
OAM Type an error must be generated: "OAM Problem/OAM Type Mismatch".
OAM Type Description
------------ --------------------
0-255 Reserved
There is a hierarchy in between the OAM configuration elements.
First, the "OAM MEP (and MIP) entities desired" flag needs to be set,
if it is set an "OAM Configuration TLV" may be included in the
LSP_ATTRIBUTES object, if this TLV is present based on the OAM Type a
technology specific OAM configuration sub-TLV may be present. If
this hierarchy is broken (e.g., "OAM MEP entities desired" flag is
not set but an OAM Configuration TLV is present an error must be
generated: "OAM Problem/Configuration Error".
OAM Function Flags: specifies pro-active OAM functions (e.g.,
connectivity monitoring, loss and delay measurement) that should be
established and configured. If the selected OAM Function(s) is(are)
not supported an error must be generated: "OAM Problem/Unsupported
OAM Function".
This document defines the following flags.
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OAM Function Flag Description
--------------------- ---------------------------
0 Connectivity Monitoring
1 Performance Monitoring/Loss
2 Performance Monitoring/Delay
3.4. TCME Configuration TLV
Two TCME Configuration TLVs together specify a Tandem Connection
Monitoring entity: they designate the TCM ingress and TCM egress
MEPs, respectively. TCME Configuration TLVs are carried in
HOP_ATTRIBUTES subobjects [HOP_ATTR] in the ERO, the corresponding
node in the ERO identifies where TCME MEP is placed. Both TCME
Configuration TLVs of the same TCME must specify the same OAM
technology and method.
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 (2) (IANA) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OAM Type |H|M| Level | OAM Functions |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SUB TLVs |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: indicates a new type: the TCME Configuration TLV (2) (IANA to
assign).
OAM Type: specifies the technology specific OAM method. The OAM Type
values defined for OAM Configuration TLV are applied here. If the
requested OAM method is not supported an error must be generated:
"OAM Problem/Unsupported OAM Type".
One bit (Flag H) is allocated to indicate which endpoint of a TCME is
encoded by the TCME Configuration TLV. Setting this flag indicates
the ingress endpoints while clearing it indicates the egress one.
One bit (Flag M) "TCME MIP entities desired" is allocated. This flag
indicates if OAM MIP entities monitoring the TCME are required. If
this function is not supported an error must be generated: "OAM
Problem/TCME MIP establishment not supported".
Level provides a key for the ingress node to determine the egress of
the same TCME. Therefore, the same Level values must be set to the
ingress and egress endpoints of the same TCME. Overlapping
(including nesting) TCM entities must use different Level values, but
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two entries not having common segments may use the same Level value.
Value 0 is reserved and must not be used to identify a TCM entity.
Futher technology specific constraints of the Level value may be
defined by accompying documents.
OAM Function Flags: specifies pro-active OAM functions (e.g.,
connectivity monitoring, loss and delay measurement) that should be
established and configured. Same flags are applied as for OAM
Configuration TLV.
Both TLVs may contain technology sub-TLVs and the encoded sub-TLVs
are relevant to the referred monitoring endpoint. The TCM ingress
may update the OAM configuration of the egress point by changing
already defined sub-TLVs or by adding new sub-TLVs.
If the node, where TCME endpoint is to be configured, does not
support that feature, must generate an error: "OAM Problem/TCM not
supported".
Since a TCME Configuration TLV pair encodes a TCME, the ingress node
must check if a proper TCME Configuration TLV encoding the egress MEP
is included in the ERO. If no such TLV (i.e., the same Level value
is set and flag H is cleared) is found an error must be generated:
"OAM Problem/TCM Egress is not properly configured".
The above check ensures that a TCM egress will not be configured
without peering TCM ingress. Therefore, there is no need TCME
ingress checking procedure at the TCME egress.
3.5. NIME Configuration TLV
Inserting a NIME Configuration TLV into a HOP_ATTRIBUTES object
[HOP_ATTR] indicates that a non-intrusive monitoring element is to be
configured. Futhermore, it encodes what OAM technology and method
should be used at that entity.
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 (3) (IANA) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OAM Type |D|U| Level | OAM Functions |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SUB TLVs |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Type: indicates a new type: the NIM OAM Configuration TLV (3) (IANA
to assign).
OAM Type: specifies the technology specify OAM method. If the
requested OAM method is not supported an error must be generated:
"OAM Problem/Unsupported OAM Type". The same OAM type values to be
used as for OAM Configuration TLV.
Level value indicates which OAM flow of the connection is monitored:
the end-to-end OAM flow (Level = 0) or TCM entity associated to the
connection (Level > 0).
Two bits (Flags D,U) indicates the direction of the monitored entity.
The downstream traffic is monitored if flag D is set, while setting
flag U means monitoring the upstream direction. Both directions are
monitored if both flags are set. When both flags are cleared or the
flag U is set but the LSP is not bidirectional an error must be
generated: "OAM Problem/Invalid NIM direction defined".
OAM Function Flags: specifies pro-active OAM functions (e.g.,
connectivity monitoring, loss and delay measurement) that should be
established and configured. Same procedures and flags applied as for
OAM Configuration TLV.
3.6. Monitoring Disabled - Admin_Status bit
Administrative Status Information is carried in the ADMIN_STATUS
Object. The Administrative Status Information is described in
[RFC3471], the ADMIN_STATUS Object is specified for RSVP-TE in
[RFC3473].
One bit is allocated for the administrative control of OAM
monitoring. In addition to the Reflect (R) bit, 7 bits are currently
occupied (assigned by IANA or temporarily blocked by work in progress
Internet drafts). As the 24th bit (IANA to assign) this draft
introduces the Monitoring Disabled (M) bit. When this bit is set the
monitoring and OAM triggered alarms of the LSP are disabled (e.g., no
continuity check messages are sent, no AIS is generated).
3.7. OAM configuration errors
To handle OAM configuration errors a new Error Code (IANA to assign)
"OAM Problem" is introduced. To refer to specific problems a set of
Error Values is defined.
If a node does not support the establishment of OAM MEP or MIP
entities it must use the error value (IANA to assign): "MEP
establishment not supported" or "MIP establishment not supported"
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respectively in the PathErr message.
If a node does not support a specific OAM technology/solution it must
use the error value (IANA to assign): "Unsupported OAM Type" in the
PathErr message.
If a different technology specific OAM configuration TLV is included
than what was specified in the OAM Type an error must be generated
with error value:"OAM Type Mismatch" in the PathErr message.
There is a hierarchy in between the OAM configuration elements. If
this hierarchy is broken an the error value: "OAM Problem/
Configuration Error" must be used in the PathErr message.
If a node does not support a specific OAM Function it must use the
error value (IANA to assign): "Unsupported OAM Function" in the
PathErr message.
If an intermediate node is configured as a TCM ingress node, but no
egress node for the same TCM entity is encoded in the ERO it must use
"OAM Problem/TCM Egress is not properly configured" error value in
the PathErr message
If the node, where TCME endpoint is to be configured, does not
support that feature, must generate an error: "OAM Problem/TCM not
supported".
If the technology does not support deploying MIPs monitoring a TCME
an error must be generated by the TCME ingress: "OAM Problem/TCME MIP
establishment not supported".
If an intermediate node is configured as a non-intrusive monitoring
node, but direction flags encode an invalid direction (both flags are
set to 0 or flag "U" is set in the case of an unidirectional LSP) the
node must issue a PathErr message with "OAM Problem/invalid NIM
direction defined".
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4. IANA Considerations
One bit (Monitoring Disabled (M)) needs to be allocated in the
ADMIN_STATUS Object.
One bit ("OAM entities desired") needs to be allocated in the LSP
Attributes Flag Registry.
This document specifies one new TLVs to be carried in the
LSP_ATTRIBUTES and LSP_REQUIRED_ATTRIBUTES objects in Path messages:
OAM Configuration TLV.
One new Error Code: "OAM Problem" and three new values: "MEP
establishment not supported", "MIP establishment not supported",
"Unsupported OAM Type" and "Unsupported OAM Function" needs to be
assigned.
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5. Security Considerations
The signaling of OAM related parameters and the automatic
establishment of OAM entities introduces additional security
considerations to those discussed in [RFC3473]. In particular, a
network element could be overloaded, if an attacker would request
liveliness monitoring, with frequent periodic messages, for a high
number of LSPs, targeting a single network element.
Security aspects will be covered in more detailed in subsequent
versions of this document.
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6. Acknowledgements
The authors would like to thank Francesco Fondelli, Adrian Farrel,
Loa Andersson, Eric Gray and Dimitri Papadimitriou for their useful
comments.
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Appendix A. Discussion on alternatives
This appendix summarizes the discussions after IETF-71 about the way
OAM configuration information should be carried in RSVP-TE.
The first question is how the requirement for OAM establishment is
signaled and how the operation of OAM is controlled. There is a
straightforward way to achieve these using existing objects and
fields:
o Use one or more OAM flags in the LSP Attributes Flag TLV within
the LSP_ATTRIBUTES/LSP_REQUIRED_ATTRIBUTES object to signal that
OAM entities for the LSP need to be established. If for any
reason this cannot be done a notification is sent or an error is
raised.
o Once the LSP with the desired OAM entities is established OAM
operation may be controlled using one or more flags in the
ADMIN_STATUS object. For instance, the generation of connectivity
monitoring messages can be disabled/enabled by setting/clearing a
flag in the ADMIN_STATUS object.
However, there are two alternatives when it comes to signaling the
actual configuration parameters of OAM entities.
o Extension of the LSP_ATTRIBUTES object with new TLVs.
o Definition of a new RSVP-TE object to carry OAM information.
In the first case, a new OAM configuration TLV is defined in the
LSP_ATTRIBUTES object. This TLV would provide the detailed
information needed for LSPs with a set OAM flag in the LSP Attributes
Flag TLV. The rationale for this approach is that in addition to
setting flags the LSP_ATTRIBUTES object may carry complementary
information for all or some of the flags set. Furthermore, as top
level RSVP-TE objects may become scarce resources, it seems to be
beneficial not to allocate new RSVP-TE objects for the purpose of
providing detailed information for new LSP Attribute Flags.
Currently there is only one TLV, the Attributes Flag TLV, defined in
the LSP_ATTRIBUTES object. Defining a new TLV associated with one of
the flags would make a precedence and possibly be a guideline for
similar future extensions.
The other alternative would be to allocate a dedicated object for OAM
configuration information. The rationale for this is that the
complex information that may be required for OAM configuration would
unnecessarily add complexity to LSP_ATTRIBUTES/
LSP_REQUIRED_ATTRIBUTES objects and their processing mechanisms.
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Furthermore, traditionally RSVP uses dedicated objects (*_SPECs) to
carry configuration information of data plane entities, thus a new
object like an "OAM_SPEC" may be a better fit to existing protocol
elements.
The authors of this document favor the first alternative (adding new
TLVs to LSP_ATTRIBTES/LSP_REQUIRED_ATTRIBUTES. However, which
alternative to select for standardization is up for the working group
to decide. In any case, the information to be carried would be the
same or very similar for both alternatives.
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7. References
[GELS-Framework]
"GMPLS Ethernet Label Switching Architecture and
Framework", Internet Draft, work in progress.
[GMPLS-OAM]
"OAM Requirements for Generalized Multi-Protocol Label
Switching (GMPLS) Networks", Internet Draft, work in
progress.
[HOP_ATTR]
Kern, A. and A. Takacs, "Encoding of Attributes of LSP
hops using RSVP-TE", Internet-draft Work in progress,
October 2009.
[IEEE-CFM]
"IEEE 802.1ag, Draft Standard for Connectivity Fault
Management", work in progress.
[IEEE-PBBTE]
"IEEE 802.1Qay Draft Standard for Provider Backbone
Bridging Traffic Engineering", work in progress.
[MPLS-TP-FWK]
"A Framework for MPLS in Transport Networks", Internet
Draft, work in progress.
[MPLS-TP-OAM-REQ]
"Requirements for OAM in MPLS Transport Networks",
Internet Draft, work in progress.
[RFC3469] "Framework for Multi-Protocol Label Switching (MPLS)-based
Recovery", RFC 3469, February 2003.
[RFC3471] "Generalized Multi-Protocol Label Switching (GMPLS)
Signaling Functional Description", RFC 3471, January 2003.
[RFC3473] "Generalized Multi-Protocol Label Switching (GMPLS)
Signaling Resource ReserVation Protocol-Traffic
Engineering (RSVP-TE) Extensions", RFC 3473, January 2003.
[RFC4377] "Operations and Management (OAM) Requirements for Multi-
Protocol Label Switched (MPLS) Networks", RFC 4377,
February 2006.
[RFC4420] "Encoding of Attributes for Multiprotocol Label Switching
(MPLS) Label Switched Path (LSP) Establishment Using
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Resource ReserVation Protocol-Traffic Engineering
(RSVP-TE)", RFC 4420, February 2006.
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Authors' Addresses
Attila Takacs
Ericsson
Laborc u. 1.
Budapest, 1037
Hungary
Email: attila.takacs@ericsson.com
Don Fedyk
Alcatel-Lucent
Groton, MA 01450
USA
Email: donald.fedyk@alcatel-lucent.com
Jia He
Huawei
Email: hejia@huawei.com
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