| Internet-Draft | Integrated OAM | March 2021 |
| Mirsky, et al. | Expires 30 September 2021 | [Page] |
This document describes the Integrated Operation, Administration, and Maintenance (IntOAM) protocol. IntOAM is based on the lightweight capabilities of Bidirectional Forwarding Detection defined in RFC 5880 Bidirectional Forwarding Detection, and the RFC 6374 Packet Loss and Delay Measurement for MPLS Networks to measure performance metrics like packet loss and packet delay. Also, a method to perform lightweight on-demand authentication is defined in this specification.¶
This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.¶
Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.¶
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This Internet-Draft will expire on 30 September 2021.¶
Copyright (c) 2021 IETF Trust and the persons identified as the document authors. All rights reserved.¶
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.¶
[RFC5880] has provided the base specification of Bidirectional Forwarding Detection (BFD) as the light-weight mechanism to monitor a path continuity between two systems and detect a failure in the data-plane. Since its introduction, BFD has been broadly deployed. There were several attempts to introduce new capabilities in the protocol, some more successful than others. One of the obstacles to extending BFD capabilities may be seen in the compact format of the BFD control message. This document introduces the Integrated Operation, Administration, and Maintenance (IntOAM) protocol based on BFD's lightweight capabilities. It uses informational elements defined in [RFC6374] to measure various performance metrics, e.g., synthetic packet loss or packet delay. Combination of both Fault Management (FM) Performance Monitoring (PM) OAM functions in the IntOAM protocol is beneficial in some networks. For example, in a Deterministic Networking (DetNet) domain [RFC8655], it is easier to ensure that an IntOAM's test packet is fate-sharing with data packets rather than mapping several FM and PM OAM protocols to that DetNet data flow.¶
BFD: Bidirectional Forwarding Detection¶
G-ACh Generic Associated Channel¶
IntOAM Integrated OAM¶
HMAC Hashed Message Authentication Code¶
MTU Maximum Transmission Unit¶
PMTUD Path MTU Discovery¶
PMTUM Path MTU Monitoring¶
p2p: Point-to-Point¶
TLV Type, Length, Value¶
OAM Operations, Administration, and Maintenance¶
FM Fault Management¶
PM Performance Monitoring¶
DetNet Deterministic Networking¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| V | Diag |Sta|P|F|D|M| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Detect Mult | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| My Discriminator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Your Discriminator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Desired Min TX Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Required Min RX Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Required Min Echo RX Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ TLVs (variable) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where fields are defined as the following:¶
TLV is a variable-length field. Multiple TLVs MAY be placed in an IntOAM Control message. Additional TLVs may be enclosed within a given TLV, subject to the semantics of the (outer) TLV in question. If more than one TLV is to be included, the value of the Type field of the outmost outer TLV MUST be set to Multiple TLVs Used (TBA0), as assigned by IANA according to Section 6.1. Figure 2 displays the TLV format in an IntOAM protocol.¶
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Reserved | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Value ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where fields are defined as the following:¶
[Ed.note: Should the document reference Asynchronous and Demand modes in RFC 5880?]¶
A discriminator is defined in the IntOAM as an unsigned 32-bit long integer that identifies a particular IntOAM session. An IntOAM system MAY locally assign a discriminator for the given IntOAM session. Also, a discriminator MAY be distributed by the control plane or management plane.¶
In a point-to-point (p2p) IntOAM session, the value of the Your Discriminator field is used to demultiplex IntOAM sessions. An IntOAM system has to learn the value of discriminator that the remote IntOAM system associates with the IntOAM session between these two systems. The IntOAM system MAY use a three-way handshake mechanism to learn of discriminator of the remote system. Besides, the control or management plane MAY be used to associate discriminator values with the specific IntOAM session. In other scenarios, e.g., point-to-multipoint (p2mp) IntOAM session, the Your Discriminator's value could be left undefined for some nodes. In that case, such a node uses the My Discriminator field's value in combination with information that identifies the sender of the IntOAM Control message and the path identifier.¶
IntOAM has two operational modes that provide for proactive defect detection in a network- Asynchronous and Demand. An IntOAM implementation MUST be capable of operating in either of them. In the Asynchronous mode, an IntOAM system periodically transmits IntOAM Control messages. When an IntOAM system is in the Demand mode, it does not periodically transmit IntOAM Control messages. An IntOAM system in the Demand mode MAY transmit a Control message as a part of the Poll sequence. A system MAY be set into the Demand mode at any time during the IntOAM session.¶
The Echo function in IntOAM can be used in networks when an operator has ensured that the sender's test packet will first reach the intended target before being returned to the sender. The target node is not required to support IntOAM as the IntOAM packet is expected to be looped back by the data plane without the need to inspect the test packet itself. The IntOAM Control message and IntOAM TLVs MAY be used as the test packet by the IntOAM Echo function.¶
An IntOAM system, also referred to as a node in this document, that supports IntOAM first MUST discover the extent to which other nodes in the given session support the Integrated OAM. The node MUST send an IntOAM Control message initiating the Poll Sequence as defined in [RFC5880]. If the remote system fails to respond with the IntOAM Control message and the Final flag set, then the initiator node MUST conclude that the peer does not support the use of the IntOAM Control messages.¶
The first IntOAM Control message initiating the Poll Sequence SHOULD include the Capability TLV that lists capabilities that may be used at some time during the lifetime of the IntOAM session. Until the node negotiated the use of PM capabilities of the IntOAM, the node MUST NOT include any TLVs in the IntOAM Control message, other than the Capability TLV. The format of the Capability TLV is presented in Figure 3.¶
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Capability | Reserved | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| L | D | M | Unassigned |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Authentication ... | Padding ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where fields are defined as the following:¶
The remote IntOAM node that supports this specification MUST respond to the Capability TLV with the IntOAM Control message, includeding the Capability TLV listing capabilities the responder supports. The responder MUST set the Final flag in the IntOAM Control message.¶
IntOAM allows for the negotiation of time intervals at which an IntOAM system transmits and receives IntOAM Control packets. That equally applies to packets used for performance monitoring, whether it measures packet delay or packet loss, using TLVs defined in Section 5.4. An IntOAM system sets its timer values in an IntOAM Control packet that includes the Capabilities TLV. The negotiation process is similar to the one described in [RFC5880]. A local IntOAM system advertises its shortest interval for transmitting IntOAM packets to measure the indicated metrics and the shortest interval that is it capable of receiving PM IntOAM packets. Suppose a system does not support the given metric measurement, i.e., packet loss or packet delay. In that case, it MUST set the value of the Required Min RX Interval to zero when transmitting the IntOAM Control message with the Capability TLV. If an IntOAM system does not support one of the modes, periodic or on-demand, for the given performance metric, it MUST zero the appropriate bit in the field that describes the metric. The timer values apply to all PM modes that have their respective bits set in the Capacity TLV. If an operator wants to use a different time intervals for different performance metrics measurements, then separate Poll sequences with the Capabilities TLV included MAY be used. Thus IntOAM allows negotiating different time intervals for packet loss and packet delay measurements.¶
Padding TLV MAY be used to generate IntOAM Control messages of the desired length.¶
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Padding | Reserved | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Padding ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where fields are defined as the following:¶
Padding TLV MAY be used to generate IntOAM Control messages of different lengths. That capability is necessary to perform PMTUD, PMTUM, and measure synthetic packet loss and/or packet delay. When Padding TLV is used in combination with one of the performance measurement messages carried in Performance Metric TLVs as defined in Section 5.4, Padding TLV MUST follow the Performance Metric TLV.¶
Padding TLV MAY be used in PMTUM as part of periodically sent IntOAM Control messages. In this case, the number of consecutive messages that include Padding TLV MUST be not lesser than Detect Multiplier to ensure that the remote IntOAM peer will detect loss of messages with the Padding TLV. Also, Padding TLV MAY be present in an IntOAM Control message with the Poll flag set. If the remote IntOAM peer that supports this specification receives an IntOAM Control message with Padding TLV, it MUST include the Padding TLV with the Padding field of the same length as in the received packet and set the Final flag.¶
Diagnostic TLV MAY be used to characterize the result of the last requested operation.¶
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Diagnostic | Reserved | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Return Code | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where fields are defined as the following:¶
Loss measurement, delay measurement, and loss/delay measurement messages can be used in the IntOAM Control message to obtain respective one-way and round-trip metrics. All the messages are encapsulated as TLVs with Type values allocated by IANA, Section 6.¶
The sender MAY use the Performance Metric TLV (presented in Figure 6) to measure performance metrics and obtain the measurement report from the receiver.¶
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Perf. Metric | Reserved | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Loss Measurement Message, |
~ Delay Measurement Message, or ~
| Combined Loss/Delay Measurement Message |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where fields are defined as the following:¶
Performance Metric - one-octet field. Valid vaues are TBA3 through TBA5 allocated by IANA in Section 6 as follows:¶
To perform one-way loss and/or delay measurement, the IntOAM node MAY periodically transmit the IntOAM message with one of the TLVs listed above in Asynchronous mode. To perform synthetic loss measurement, the sender MUST monotonically increment the counter of transmitted test packets. When using Performance Metric TLV for synthetic measurement, an IntOAM Control message MAY also include Padding TLV. In that case, the Padding TLV MUST immediately follow Performance Metric TLV. Also, direct-mode loss measurement, as described in [RFC6374], is supported. Procedures to negotiate and manipulate transmission intervals defined in Sections 6.8.2 and 6.8.3 in [RFC5880] SHOULD be used to control the performance impact of using the IntOAM for performance measurement in the particular IntOAM session.¶
To measure the round-trip loss and/or delay metrics, an IntOAM node transmits the IntOAM Control message with the Performance Metric TLV with the Poll flag set. Before transmitting the IntOAM Control message with the Performance Metric TLV, the receiver MUST clear the Poll flag and set the Final flag.¶
Using IntOAM without any security measures, such as exchanging IntOAM Control messages without authentication, increases the risk of an attack, especially over multiple nodes. Thus, using IntOAM without security measures may cause false positive or false negative defect detection situations. In the former, an attacker may spoof IntOAM Control messages pretending to be a remote peer and can thus view the IntOAM session operation even though the real path had failed. In the latter, the attacker may spoof an altered IntOAM control message indicating that the IntOAM session is un-operational even though the path and the remote IntOAM peer operate normally.¶
BFD [RFC5880] allows for optional authentication protection of BFD Control messages to minimize the chances of attacks in a networking system. However, at least some of the supported authentication protocols do not provide sufficient protection in modern networks. Also, the current BFD technology requires authentication of each BFD Control message. Such an authentication requirement can put a computational burden on networking devices, especially in the Asynchronous mode, at least because authenticating each BFD Control message can require substantial computing resources to support packet exchange at high rates.¶
This specification defines a lightweight on-demand mode of authentication for an IntOAM session. The lightweight authentication is an optional mode. The mechanism includes negotiation (Section 5.5.1) and on-demand authentication (Section 5.5.2) phases. During the former, IntOAM peers advertise supported authentication capabilities and independently select the commonly supported mode of the authentication. In the authentication phase, each IntOAM system transmits, at certain events or periodically, authenticated IntOAM Control messages in Poll Sequence.¶
Figure 7 displays the format of the Authentication field that is part of the Capability Encoding:¶
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Len | AuthL | Authentication Mode ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where fields are defined as the following:¶
An IntOAM system uses Capability TLV, defined in Section 5.1, to discover the commonly supported mode of the Lightweight Authentication. The system sets the values in the Authentication field according to properly reflect its authentication capabilities. The IntOAM system transmits the IntOAM Control message with Capability TLV as the first in a Poll Sequence. The remote IntOAM system that supports this specification receives the IntOAM Control message with the advertised Lightweight Authentication modes and stores information locally. The system responds with the advertisement of its Lightweight Authentication capabilities in the IntOAM Control message with the Final flag set. Each IntOAM system uses local and received information about Lightweight Authentication capabilities to deduce the commonly supported modes and selects from that set to use the strongest authentication with the longest signature. If the common set is empty, i.e., none of supported by one IntOAM system authentication method is supported by another, an implementation MUST reflect this in its operational state and SHOULD notify an operator.¶
After IntOAM peers select an authentication mode for use in Lightweight Authentication each IntOAM system MUST use it to authenticate each IntOAM Control message transmitted as part of a Poll Sequence using Lightweight Authentication TLV presented in Figure 8.¶
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Authentication| Reserved | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ HMAC ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where fields are defined as the following:¶
The Lightweight Authentication TLV MUST be the last in an IntOAM Control message. Padding TLV (Section 5.2) MAY be used to align the length of the IntOAM Control message, excluding the Lightweight Authentication TLV, at multiple of 16 boundary.¶
The IntOAM system that receives the IntOAM Control message with the Lightweight Authentication TLV MUST first validate the .authentication by calculating the hash over the IntOAM Control message. If the validation succeeds, the receiver MUST transmit the IntOAM Control message with the Final flag set and the value of the Return code field in Diagnostic TLV set to None value (Table 5). If the validation of the lightweight authentication fails, then the IntOAM system MUST transmit the IntOAM Control message with the Final flag set and the value of the Return Code field of the Diagnostic TLV set to Lightweight Authentication failed value (Table 5). The IntOAM system MUST have a control policy that defines actions when the system receives the Lightweight Authentication failed return code.¶
IANA is requested to create the IntOAM TLV Type registry. All code points in the range 1 through 175 in this registry shall be allocated according to the "IETF Review" procedure specified in [RFC8126]. Code points in the range 176 through 239 in this registry shall be allocated according to the "First Come First Served" procedure specified in [RFC8126]. The remaining code points are allocated according to Table 1:¶
| Value | Description | Reference |
|---|---|---|
| 0 | Reserved | This document |
| 1- 175 | Unassigned | This document |
| 176 - 239 | Unassigned | This document |
| 240 - 251 | Experimental | This document |
| 252 - 254 | Private Use | This document |
| 255 | Reserved | This document |
This document defines the following new values in IntOAM Type registry:¶
| Value | Description | Reference |
|---|---|---|
| TBA0 | Multiple TLVs Used | This document |
| TBA1 | Padding | This document |
| TBA2 | Capability | This document |
| TBA3 | Loss Measurement | This document |
| TBA4 | Delay Measurement | This document |
| TBA5 | Combined Loss/Delay Measurement | This document |
| TBA6 | Diagnostic | This document |
| TBA8 | Lightweight Authentication | This document |
IANA is requested to create a Lightweight Authentication Modes registry. All code points in this registry shall be allocated according to the "IETF Review" procedure as specified in [RFC8126].¶
This document defines the following new values in the Lightweight Authentication Modes registry:¶
| Bit Position | Value | Description | Reference |
|---|---|---|---|
| 0 | 0x1 | Keyed SHA-1 | This document |
| 1 | 0x2 | Meticulous Keyed SHA-1 | This document |
| 2 | 0x4 | SHA-256 | This document |
IANA is requested to create the IntOAM Return Codes registry. All code points in the range 1 through 250 in this registry shall be allocated according to the "IETF Review" procedure as specified in [RFC8126]. The remaining code points are allocated according to Table 4:¶
| Value | Description | Reference |
|---|---|---|
| 0 | Reserved | This document |
| 1- 250 | Unassigned | IETF Review |
| 251-253 | Experimental | This document |
| 254 | Private Use | This document |
| 255 | Reserved | This document |
This document defines the following new values in IntOAM Return Codes registry:¶
| Value | Description | Reference |
|---|---|---|
| 0 | None | This document |
| 1 | One or more TLVs was not understood | This document |
| 2 | Lightweight Authentication failed | This document |
The same security considerations as those described in [RFC5880], [RFC6374], and [RFC8562]. apply to this document. Additionally, implementations that use distribution of discriminators over the control or management plane MUST use secure channels to protect systems from an infinite number of IntOAM sessions being created.¶
In some environments, an IntoOAM session can be instantiated using a bootstrapping mechanism supported by the control or management plane. As a result, the three-way handshaking mechanism between IntOAM systems is bypassed. That could cause the situation where one of the systems uses overaggressive transmission intervals that are not acceptable to the remote IntOAM system. As a result, IntOAM Control messages could be dropped, and the remote IntOAM system concludes the IntOAM session failed. The environment that does not use the three-way handshake mechanism to instantiate an IntOAM session MUST support means to balance resources used by the IntOAM.¶
TBD¶