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This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79.
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This document defines a method for the configuration of MPLS Transport Profile (MPLS-TP) Operations, Administration and Maintenance (OAM) functionalities through extensions to RSVP-TE.
1.
Introduction
1.1.
Contributing Authors
1.2.
Requirements Language
1.3.
Background
2.
Overview of BFD OAM operation
3.
RSVP-TE Extensions
3.1.
Operation overview
3.2.
OAM Configuration TLV
3.3.
BFD CC OAM Configuration TLV
3.3.1.
Local Discriminator sub-TLV
3.3.2.
Suggested TX interval
3.4.
BFD CC&CV OAM Configuration TLV
3.4.1.
Source unique MEP-ID sub-TLV
4.
IANA Considerations
5.
BFD OAM configuration errors
6.
Security Considerations
7.
References
7.1.
Normative References
7.2.
Informative References
Appendix A.
Additional Stuff
§
Authors' Addresses
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This document defines a method for the configuration of MPLS Transport Profile (MPLS-TP) Operations, Administration and Maintenance (OAM) functionalities through extensions to RSVP-TE.
The procedures included describe Bidirectional Forwarding Detection (BFD) configuration for Continuity Check (CC) and Connection Verification (CV). Updated versions of this document will describe the configuration of the remaining MPLS-TP OAM functionalities.
The future updates of this document are meant to proceed consequently to the upcoming MPLS-TP documents defining the MPLS-TP specific OAM functionalities and with [MPLS-TP-IDENTIF] which specifies identifiers for MPLS-TP objects.
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The editors gratefully acknowledge the precious contributions of Lou Berger, Annamaria Fulignoli, Andras Kern, David Jocha, David Sinicrope, Attila Takacs and Benoit Tremblay.
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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 RFC 2119 (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.) [RFC2119].
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MPLS Transport Profile (MPLS-TP), describes a profile of MPLS that enables operational models typical in transport networks, while providing additional OAM, survivability and other maintenance functions not currently supported by MPLS.
For the cases where a control plane is used with MPLS-TP, the GMPLS control plane, RSVP-TE [RFC3471] and/or OSPF-TE [RFC3630] ISIS-TE [5307] has been chosen to support the establishment of MPLS-TP LSPs.
[MPLS-TP-OAM-REQ] defines the requirements by which the OAM functionality of MPLS-TP should abide.
The MPLS-TP design team provided recommendations regarding the functionalities that should be covered by the existing toolsets and which extensions or new tools will be needed in order to provide full coverage of the OAM functionalities for MPLS-TP. A detailed overview of the adopted OAM tools will be documented in [MPLS-TP OAM Analysis].
This document provides extensions to RSVP-TE in order to accommodate the MPLS-TP CC (Continuity Check) and CV (Connectivity Verification) MPLS-TP OAM functionalities. Further revisions of this document will describe RSVP-TE extensions for the other MPLS-TP OAM functionalities as needed.
Bidirectional Forwarding Detection (BFD), as described in [BFD], defines a protocol that provides low-overhead, short-duration detection of failures in the path between two forwarding engines, including the interfaces, data link(s), and to the extent possible the forwarding engines themselves. BFD can be used to track the liveliness of MPLS-TP point-to-point and p2mp connections and detect data plane failures. This version of the draft is focused on unidirectional and bidirectional p2p connection.
BFD has been chosen to cover MPLS-TP CC functionality.
An extended version of BFD, as described in [BFD-CV], has been chosen to accomplish both MPLS-TP CC and CV.
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BFD is a simple hello protocol that in many respects is similar to the detection components of well-known routing protocols. A pair of system transmits BFD packets periodically over each path between the two systems, and if a system stops receiving BFD packets for long enough, some component in that particular bidirectional path to the neighboring system is assumed to have failed. Systems may also negotiate to not send periodic BFD packets in order to reduce overhead.
A path is only declared to be operational when two-way communication has been established between systems, though this does not preclude the use of unidirectional links.
[BFD] sect. 3 states that a separate BFD session is created for each communications path and data protocol in use between two systems.
Each system estimates how quickly it can send and receive BFD packets in order to come to an agreement with its neighbor about how rapidly detection of failure will take place. These estimates can be modified in real time in order to adapt to unusual situations. This design also allows for fast systems on a shared medium with a slow system to be able to more rapidly detect failures between the fast systems while allowing the slow system to participate to the best of its ability.
The ability of each system to control the BFD packet transmission rate in both directions provides a mechanism for congestion control, particularly when BFD is used across multiple network hops.
As recommended in [BFD-CV], the BFD tool needs to be extended for the CV functionality by the addition of a unique identifier in order to meet the requirements. The document in [BFD-CV] specifies the BFD extension and behavior to meet the requirements for MPLS-TP proactive Continuity Check and Connectivity Verification functionality and the RDI functionality as defined in [MPLS-TP-OAM-REQ].
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Below, extension to RSVP-TE for setting up BFD or BFD extended version are defined in order to configure MPLS-TP CC and CV OAM functionalities during the LSP setup.
The terms "ingress LER" and "egress LER" will not refer in this document to any direction in the forwarding plane, but only to the LER triggering the LSP setup (ingress LER) and the one triggering the response to it (egress LER).
During the LSP signaling, the Control Plane instance in the ingress and the egress LER announces the BFD OAM Configuration TLV (inside the LSP_ATTRIBUTES object carried by the Path and Resv message respectively), which includes the "Local Discriminator" sub-TLV. During the BFD session the ingress LER will use as "MyDiscriminator" the value announced in the "Local Discriminator"(Path message) and as "YourDiscriminator" the value received in the "Local Discriminator" (Resv message).
The system initiating the signaling MUST advertise the interval value at which it requires BFD control packets both in transmission and reception. If the receiving system can not support this value, a new value can be signaled back in the Resv message, with the constraint that the new value MUST be comprised between the Maximum and Minimum values indicated by the ingress. If the egress system can not support any value in the indicated range, it will reply with an error.
In the case BFD extended version should be configured, the unique MEP ID parameter MUST be included along with the Discriminator and timing values as described in the following sections.
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Below is reported the "OAM Configuration TLV", defined in [OAM-CONF-FWK]. It 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.
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 the OAM Configuration TLV (2) (IANA to assign).
OAM Type: one octect that specifies the technology specific OAM Type. If the requested OAM Type is not supported an error must be generated: "OAM Problem/Unsupported OAM Type".
In this document a new OAM Type - OAM Type 2 - is defined: MPLS-TP OAM.
| OAM Type | Description |
|---|---|
| 0 | Reserved |
| 1 | Ethernet OAM |
| 2 | MPLS-TP OAM |
| 3-256 | Reserved |
The receiving node when the BFD OAM Type is requested should look for the corresponding technology specific BFD OAM configuration TLV.
OAM Function Flags: a two octect field that specifies pro-active OAM functions 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".
The Flag 0 was already in use for "Connectivity Monitoring" and it will be used in this document to establish MPLS-TP Continuity Check (CC) functionality. A new Flag 3 is defined here and will be used to establish MPLS-TP Continuity Check and Connectivity Verification (CC & CV) functionality. Control Plane control of on Demand functions are for further studies.
The following table summarizes the Flags usage.
| OAM Type | Description |
|---|---|
| 0 | Continuity Check (CC) |
| 1 | Reserved |
| 2 | Reserved |
| 3 | Continuity Check and Connectivity Verification (CC&CV) |
| 4-16 | Reserved |
The receiving LER when the MPLS-TP OAM Type is requested should check which Flags are set and look for the corresponding technology specific configuration TLV.
- "BFD CC OAM Configuration TLV" which MUST be used if Flag = 0 for configuring BFD for setting up the proactive MPLS-TP CC OAM tool (TLV type = 4, IANA to define);
- "BFD CC&CV OAM Configuration TLV" which MUST be used if Flag = 3 for configuring BFD for setting up the proactive MPLS-TP CC&CV OAM tool (TLV type = 5, IANA to define).
In case the receiving LER does not support the CC&CV functionality, an error "OAM Problem/Unsupported BFD functionality" must be generated when receiving the BFD CC&CV OAM Configuration TLV.
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The BFD CC OAM Configuration TLV (depicted below) is defined for BFD OAM specific configuration parameters. The BFD CC OAM Configuration TLV is carried as a sub-TLV of the "OAM Configuration TLV" in the LSP_ATTRIBUTES object both in Path and Resv messages.
This new TLV accommodates generic BFD OAM information and carries sub-TLVs.
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 (4) (IANA) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Vers.|R| Reserved (set to all 0s) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ sub TLVs ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: indicates a new type, the "BFD CC OAM Configuration TLV" (4) (IANA to define).
Length: indicates the total length including sub-TLVs.
Version: identifies the BFD protocol version. If a node does not support a specific BFD version an error must be generated: “OAM Problem/Unsupported OAM Version ”
R Flag: Role Flag. If set, the receiving node is required to act with an Active Role as described in [BFD] sect. 6.1. When the BFD OAM Configuration TLV is carried in the Resv message, the flag is not taken into consideration by the receiving node.
The BFD CC OAM Configuration TLV MUST include the following sub-TLVs in the Path message:
- "Local Discriminator" sub-TLV;
- "Suggested TX interval" sub-TLV.
The BFD CC OAM Configuration TLV MUST include the following sub-TLVs in the Resv message:
- "Local Discriminator" sub-TLV;
- "Suggested TX interval" sub-TLV if a different timing value needs to be used.
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The Local Discriminator sub-TLV is depicted below.
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 (1) (IANA) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Discriminator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: indicates a new type, the Local Discriminator sub TLV (1) (IANA to define).
Length: indicates the total length of the TLV including padding as defined in [BFD].
Local Discriminator: A unique, nonzero discriminator value generated by the transmitting system and referring to itself, used to demultiplex multiple BFD sessions between the same pair of systems. This Discriminator will be signaled both by the ingress LSR and the egress LSR in the Path and Resv message respectively.
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The Suggested TX interval sub-TLV is depicted below.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Req. TX int. Type (2) (IANA) | Length = 24 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Acceptable Min. Asynchronous TX interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Suggested Asynchronous TX interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Acceptable Max. Asynchronous TX interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Required Echo TX Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Detect. Mult | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: indicates a new type, the Suggested TX interval sub TLV (3) (IANA to define).
Length: indicates the total length of the TLV including padding, it is set to 24 (octects).
Suggested Asynchronous TX interval: the interval, in microseconds, that the system initiating the signaling want to have when both transmitting and receiving BFD Control packets, less any jitter applied. The value zero is reserved. If the receiving system can not support this value, a new value can be signaled back in the Resv message, with the constraint that the new value will be not higher than "Acceptable Max. Asynchronous TX interval" and not lower than "Acceptable Min. Asynchronous TX interval".
Acceptable Min. Asynchronous TX interval: the maximum TX interval, in microseconds, that the system initiating the signaling can support. In case the receiving system sends back this TLV for proposing a different "Suggested Asynchronous TX interval", the "Acceptable Min. Asynchronous TX interval" will not be taken into consideration by the system which initiated the signaling.
Acceptable Max. Asynchronous TX interval: the minimum TX interval, in microseconds, that the system initiating the signaling can support. In case the receiving system sends back this TLV for proposing a different "Suggested Asynchronous TX interval", the "Acceptable Max. Asynchronous TX interval" will not be taken into consideration by the system which initiated the signaling.
Required Echo TX Interval: the minimum interval, in microseconds, between received BFD Echo packets that this system is capable of supporting, less any jitter applied by the sender as described in [BFD] sect. 6.8.9. This value is also an indication for the receiving system of the minimum interval between transmitted BFD Echo packets. If this value is zero, the transmitting system does not support the receipt of BFD Echo packets. If the receiving system can not support this value an error MUST be generated "Unsupported BFD TX rate interval"
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The BFD CC&CV OAM Configuration TLV (depicted below) is defined for BFD OAM specific configuration parameters. The BFD CC&CV OAM Configuration TLV is carried as a sub-TLV of the "OAM Configuration TLV" in the LSP_ATTRIBUTES object both in Path and Resv messages.
This new TLV accommodates generic BFD OAM information and carries sub-TLVs.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BFD CC&CV Type (5) (IANA) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Vers.|R| Reserved (set to all 0s) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ sub TLVs ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: indicates a new type, the BFD CC&CV OAM Configuration TLV (5) (IANA to define).
Length: indicates the TLV total length (in octects) including sub-TLVs.
Version: identifies the BFD protocol version. If a node does not support a specific BFD version an error must be generated: "OAM Problem/Unsupported OAM Version"
R Flag: Role Flag. If set, the receiving node is required to act with an Active Role as described in [BFD] sect. 6.1. When the BFD OAM Configuration TLV is carried in the Resv message, the flag it not taken into consideration by the receiving node.
The BFD CC&CV OAM Configuration TLV MUST include the following sub-TLVs in the Path message:
- "Local Discriminator" sub-TLV;
- "Suggested TX interval" sub-TLV;
- "Source unique MEP-ID" sub-TLV.
The BFD CC&CV OAM Configuration TLV MUST include the following sub-TLVs in the Resv message:
- "Local Discriminator" sub-TLV;
- "Suggested TX interval" sub-TLV if a different timing value needs to be used;
- "Source unique MEP-ID" sub-TLV.
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The MPLS Generic Associated Channel specification (see[RFC5586] sect. 3) describes the ACH TLV structure that can be used to provide additional context information to the G-ACh packet.
In this section it is showed how the "Source unique MEP-ID" sub-TLV in the BFD CC&CV OAM Configuration TLV can be used to configure the TLV Objects in the ACH TLV for providing the MEP Identifier information and the ME Identifier information as required by[MPLS-TP-OAM-FWK].
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Source unique MEP-ID Type (3)(IANA)| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Source unique MEP-ID ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Length: indicates the TLV total length (in octects) including sub-TLVs.
Source unique MEP-ID: the unique MEP Identifier of the source of the BFD packet. Please refer to [MPLS-TP-IDENTIF] for a detailed explanation of the field composition and to possible changes of the field definition. As the writing time, the "Source unique MEP-ID" is defined to be the Network_IF_ID. The Network_IF_ID is also defined in [MPLS-TP-IDENTIF], section 4.
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This document specifies the following new TLV types.
sub-TLVs types to be carried in the OAM Configuration TLV in LSP_ATTRIBUTES:
- "BFD CC OAM Configuration" sub-TLV type: 4
- "BFD CC&CV OAM Configuration" sub-TLV type (to be carried in the OAM Configuration TLV in LSP_ATTRIBUTES): 5
sub-TLV types to be carried in the BFD OAM Configuration sub-TLV:
- "Local Discriminator" sub-TLV type: 1
- "Suggested TX interval" sub-TLV type: 2
- "Source unique MEP-ID" sub-TLV type: 3
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In addition to error values specified in [OAM-CONF-FWK] and [ETH-OAM] this document defines the following values for the "OAM Problem" Error Code:
- "OAM Problem/Unsupported BFD functionality"
- "OAM Problem/Unsupported BFD TX rate interval"
- "OAM Problem/Unsupported MEP ID Format"
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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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| [ETH-OAM] | Takacs, A., Gero, B., Fedyk, D., Mohan, D., and D. Long, “GMPLS RSVP-TE Extensions for Ethernet OAM,” 2009. |
| [LSP Ping] | Kompella, K. and G. Swallow, “Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures,” 2006. |
| [MPLS-TP OAM Analysis] | Sprecher, N., Nadeau, T., van Helvoort, H., and Weingarten, “MPLS-TP OAM Analysis,” 2006. |
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This becomes an Appendix.
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| Elisa Bellagamba (editor) | |
| Ericsson | |
| Farogatan 6 | |
| Kista, 164 40 | |
| Sweden | |
| Phone: | +46 761440785 |
| Email: | elisa.bellagamba@ericsson.com |
| Loa Andersson (editor) | |
| Ericsson | |
| Farogatan 6 | |
| Kista, 164 40 | |
| Sweden | |
| Phone: | |
| Email: | loa.andersson@ericsson.com |
| Pontus Skoldstrom | |
| Acreo AB | |
| Electrum 236 | |
| Kista, 164 40 | |
| Sweden | |
| Phone: | +46 8 6327731 |
| Email: | pontus.skoldstrom@acreo.se |