Path Computation Element Communication Protocol (PCEP) Extensions to Enable IFIT
draft-chen-pce-pcep-ifit-05
PCE H. Yuan
Internet-Draft UnionPay
Intended status: Standards Track T. Zhou
Expires: July 14, 2022 W. Li
G. Fioccola
Y. Wang
Huawei
January 10, 2022
Path Computation Element Communication Protocol (PCEP) Extensions to
Enable IFIT
draft-chen-pce-pcep-ifit-05
Abstract
This document defines PCEP extensions to distribute In-situ Flow
Information Telemetry (IFIT) information. So that IFIT behavior can
be enabled automatically when the path is instantiated. In-situ Flow
Information Telemetry (IFIT) refers to network OAM data plane on-path
telemetry techniques, in particular the most popular are In-situ OAM
(IOAM) and Alternate Marking. The IFIT attributes here described can
be generalized for all path types but the application to Segment
Routing (SR) is considered in this document. This document extends
PCEP to carry the IFIT attributes under the stateful PCE model.
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 in BCP 14 [RFC2119]
[RFC8174] when, and only when, they appear in all capitals, as shown
here.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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material or to cite them other than as "work in progress."
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This Internet-Draft will expire on July 14, 2022.
Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. PCEP Extensions for IFIT Attributes . . . . . . . . . . . . . 4
2.1. IFIT for SR Policies . . . . . . . . . . . . . . . . . . 5
3. IFIT capability advertisement TLV . . . . . . . . . . . . . . 5
4. IFIT Attributes TLV . . . . . . . . . . . . . . . . . . . . . 7
4.1. IOAM Sub-TLVs . . . . . . . . . . . . . . . . . . . . . . 8
4.1.1. IOAM Pre-allocated Trace Option Sub-TLV . . . . . . . 9
4.1.2. IOAM Incremental Trace Option Sub-TLV . . . . . . . . 10
4.1.3. IOAM Directly Export Option Sub-TLV . . . . . . . . . 10
4.1.4. IOAM Edge-to-Edge Option Sub-TLV . . . . . . . . . . 11
4.2. Enhanced Alternate Marking Sub-TLV . . . . . . . . . . . 12
5. PCEP Messages . . . . . . . . . . . . . . . . . . . . . . . . 13
5.1. The PCInitiate Message . . . . . . . . . . . . . . . . . 13
5.2. The PCUpd Message . . . . . . . . . . . . . . . . . . . . 14
5.3. The PCRpt Message . . . . . . . . . . . . . . . . . . . . 14
6. Example of application to SR Policy . . . . . . . . . . . . . 14
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
8. Security Considerations . . . . . . . . . . . . . . . . . . . 17
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 18
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
11.1. Normative References . . . . . . . . . . . . . . . . . . 18
11.2. Informative References . . . . . . . . . . . . . . . . . 20
Appendix A. . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
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1. Introduction
In-situ Flow Information Telemetry (IFIT) refers to network OAM
(Operations, Administration, and Maintenance) data plane on-path
telemetry techniques, including In-situ OAM (IOAM)
[I-D.ietf-ippm-ioam-data] and Alternate Marking [RFC8321]. It can
provide flow information on the entire forwarding path on a per-
packet basis in real time.
An automatic network requires the Service Level Agreement (SLA)
monitoring on the deployed service. So that the system can quickly
detect the SLA violation or the performance degradation, hence to
change the service deployment.
This document defines extensions to PCEP to distribute paths carrying
IFIT information. So that IFIT behavior can be enabled automatically
when the path is instantiated.
RFC 5440 [RFC5440] describes the Path Computation Element Protocol
(PCEP) as a communication mechanism between a Path Computation Client
(PCC) and a Path Computation Element (PCE), or between a PCE and a
PCE.
RFC 8231 [RFC8231] specifies extensions to PCEP to enable stateful
control and it describes two modes of operation: passive stateful PCE
and active stateful PCE. Further, RFC 8281 [RFC8281] describes the
setup, maintenance, and teardown of PCE-initiated LSPs for the
stateful PCE model.
When a PCE is used to initiate paths using PCEP, it is important that
the head end of the path also understands the IFIT behavior that is
intended for the path. When PCEP is in use for path initiation it
makes sense for that same protocol to be used to also carry the IFIT
attributes that describe the IOAM or Alternate Marking procedure that
needs to be applied to the data that flow those paths.
The PCEP extension defined in this document allows to signal the IFIT
capabilities. In this way IFIT methods are automatically activated
and running. The flexibility and dynamicity of the IFIT applications
are given by the use of additional functions on the controller and on
the network nodes, but this is out of scope here.
IFIT is a solution focusing on network domains according to [RFC8799]
that introduces the concept of specific domain solutions. A network
domain consists of a set of network devices or entities within a
single administration. As mentioned in [RFC8799], for a number of
reasons, such as policies, options supported, style of network
management and security requirements, it is suggested to limit
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applications including the emerging IFIT techniques to a controlled
domain. Hence, the IFIT methods MUST be typically deployed in such
controlled domains.
The Use Case of Segment Routing (SR) is also discussed considering
that IFIT methods are becoming mature for Segment Routing over the
MPLS data plane (SR-MPLS) and Segment Routing over IPv6 data plane
(SRv6). SR policy [I-D.ietf-spring-segment-routing-policy] is a set
of candidate SR paths consisting of one or more segment lists and
necessary path attributes. It enables instantiation of an ordered
list of segments with a specific intent for traffic steering. The
PCEP extension defined in this document also enables SR policy with
native IFIT, that can facilitate the closed loop control and enable
the automation of SR service.
It is to be noted the companion document [I-D.qin-idr-sr-policy-ifit]
that proposes the BGP extension to enable IFIT methods for SR policy.
2. PCEP Extensions for IFIT Attributes
This document is to add IFIT attribute TLVs as PCEP Extensions. The
following sections will describe the requirement and usage of
different IFIT modes, and define the corresponding TLV encoding in
PCEP.
The IFIT attributes here described can be generalized and included as
TLVs carried inside the LSPA (LSP Attributes) object in order to be
applied for all path types, as long as they support the relevant data
plane telemetry method. IFIT Attributes TLVs are optional and can be
taken into account by the PCE during path computation and by the PCC
during path setup. In general, the LSPA object can be carried within
a PCInitiate message, a PCUpd message, or a PCRpt message in the
stateful PCE model.
In this document it is considered the case of SR Policy since IOAM
and Alternate Marking are more mature especially for Segment Routing
(SR) and for IPv6.
It is to be noted that, if it is needed to apply different IFIT
methods for each Segment List, the IFIT attributes can be added into
the PATH-ATTRIB object, instead of the LSPA object, according to
[I-D.koldychev-pce-multipath] that defines PCEP Extensions for
Signaling Multipath Information.
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2.1. IFIT for SR Policies
RFC 8664 [RFC8664] and [I-D.ietf-pce-segment-routing-ipv6] specify
extensions to the Path Computation Element Communication Protocol
(PCEP) that allow a stateful PCE to compute and initiate Traffic-
Engineering (TE) paths, as well as a Path Computation Client (PCC) to
request a path subject to certain constraints and optimization
criteria in SR networks both for SR-MPLS and SRv6.
IFIT attibutes, here defined as TLVs for the LSPA object, complement
both RFC 8664 [RFC8664], [I-D.ietf-pce-segment-routing-ipv6] and
[I-D.ietf-pce-segment-routing-policy-cp].
3. IFIT capability advertisement TLV
During the PCEP initialization phase, PCEP speakers (PCE or PCC)
SHOULD advertise their support of IFIT methods (e.g. IOAM and
Alternate Marking).
A PCEP speaker includes the IFIT-CAPABILITY TLVs in the OPEN object
to advertise its support for PCEP IFIT extensions. The presence of
the IFIT-CAPABILITY TLV in the OPEN object indicates that the IFIT
methods are supported.
RFC 8664 [RFC8664] and [I-D.ietf-pce-segment-routing-ipv6] define a
new Path Setup Type (PST) for SR and also define the SR-PCE-
CAPABILITY sub-TLV. This document defined a new IFIT-CAPABILITY TLV,
that is an optional TLV for use in the OPEN Object for IFIT
attributes via PCEP capability advertisement.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |P|I|D|E|M|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Fig. 1 IFIT-CAPABILITY TLV Format
Where:
Type: to be assigned by IANA.
Length: 4.
Flags: The following flags are defined in this document:
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P: IOAM Pre-allocated Trace Option Type-enabled flag
[I-D.ietf-ippm-ioam-data]. If set to 1 by a PCC, the P flag
indicates that the PCC allows instantiation of the IOAM Pre-
allocated Trace feature by a PCE. If set to 1 by a PCE, the P
flag indicates that the PCE supports the IOAM Pre-allocated Trace
feature instantiation. The P flag MUST be set by both PCC and PCE
in order to support the IOAM Pre-allocated Trace instantiation
I: IOAM Incremental Trace Option Type-enabled flag
[I-D.ietf-ippm-ioam-data]. If set to 1 by a PCC, the I flag
indicates that the PCC allows instantiation of the IOAM
Incremental Trace feature by a PCE. If set to 1 by a PCE, the I
flag indicates that the PCE supports the relative IOAM Incremental
Trace feature instantiation. The I flag MUST be set by both PCC
and PCE in order to support the IOAM Incremental Trace feature
instantiation
D: IOAM DEX Option Type-enabled flag
[I-D.ietf-ippm-ioam-direct-export]. If set to 1 by a PCC, the D
flag indicates that the PCC allows instantiation of the relative
IOAM DEX feature by a PCE. If set to 1 by a PCE, the D flag
indicates that the PCE supports the relative IOAM DEX feature
instantiation. The D flag MUST be set by both PCC and PCE in
order to support the IOAM DEX feature instantiation
E: IOAM E2E Option Type-enabled flag [I-D.ietf-ippm-ioam-data].
If set to 1 by a PCC, the E flag indicates that the PCC allows
instantiation of the relative IOAM E2E feature by a PCE. If set
to 1 by a PCE, the E flag indicates that the PCE supports the
relative IOAM E2E feature instantiation. The E flag MUST be set
by both PCC and PCE in order to support the IOAM E2E feature
instantiation
M: Alternate Marking enabled flag RFC 8321 [RFC8321]. If set to 1
by a PCC, the M flag indicates that the PCC allows instantiation
of the relative Alternate Marking feature by a PCE. If set to 1
by a PCE, the M flag indicates that the PCE supports the relative
Alternate Marking feature instantiation. The M flag MUST be set
by both PCC and PCE in order to support the Alternate Marking
feature instantiation
Unassigned bits are considered reserved. They MUST be set to 0 on
transmission and MUST be ignored on receipt.
Advertisement of the IFIT-CAPABILITY TLV implies support of IFIT
methods (IOAM and/or Alternate Marking) as well as the objects, TLVs,
and procedures defined in this document. It is worth mentioning that
IOAM and Alternate Marking can be activated one at a time or can
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coexist; so it is possible to have only IOAM or only Alternate
Marking enabled but they are recognized in general as IFIT
capability.
The IFIT Capability Advertisement can imply the following cases:
o The PCEP protocol extensions for IFIT MUST NOT be used if one or
both PCEP speakers have not included the IFIT-CAPABILITY TLV in
their respective OPEN message.
o A PCEP speaker that does not recognize the extensions defined in
this document would simply ignore the TLVs as per RFC 5440
[RFC5440].
o If a PCEP speaker supports the extensions defined in this document
but did not advertise this capability, then upon receipt of IFIT-
ATTRIBUTES TLV in the LSP Attributes (LSPA) object, it SHOULD
generate a PCErr with Error-Type 19 (Invalid Operation) with the
relative Error-value "IFIT capability not advertised" and ignore
the IFIT-ATTRIBUTES TLV.
4. IFIT Attributes TLV
The IFIT-ATTRIBUTES TLV provides the configurable knobs of the IFIT
feature, and it can be included as an optional TLV in the LSPA object
(as described in RFC 5440 [RFC5440]).
For a PCE-initiated LSP RFC 8281 [RFC8281], this TLV is included in
the LSPA object with the PCInitiate message. For the PCC-initiated
delegated LSPs, this TLV is carried in the Path Computation State
Report (PCRpt) message in the LSPA object. This TLV is also carried
in the LSPA object with the Path Computation Update Request (PCUpd)
message to direct the PCC (LSP head-end) to make updates to IFIT
attributes.
The TLV is encoded in all PCEP messages for the LSP if IFIT feature
is enabled. The absence of the TLV indicates the PCEP speaker wishes
to disable the feature. This TLV includes multiple IFIT-ATTRIBUTES
sub-TLVs. The IFIT-ATTRIBUTES sub-TLVs are included if there is a
change since the last information sent in the PCEP message. The
default values for missing sub-TLVs apply for the first PCEP message
for the LSP.
The format of the IFIT-ATTRIBUTES TLV is shown in the following
figure:
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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 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// sub-TLVs //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Fig. 2 IFIT-ATTRIBUTES TLV Format
Where:
Type: to be assigned by IANA.
Length: The Length field defines the length of the value portion in
bytes as per RFC 5440 [RFC5440].
Value: This comprises one or more sub-TLVs.
The following sub-TLVs are defined in this document:
Type Len Name
-----------------------------------------------------
1 8 IOAM Pre-allocated Trace Option
2 8 IOAM Incremental Trace Option
3 12 IOAM Directly Export Option
4 4 IOAM Edge-to-Edge Option
5 4 Enhanced Alternate Marking
Fig. 3 Sub-TLV Types of the IFIT-ATTRIBUTES TLV
4.1. IOAM Sub-TLVs
In-situ Operations, Administration, and Maintenance (IOAM)
[I-D.ietf-ippm-ioam-data] records operational and telemetry
information in the packet while the packet traverses a path between
two points in the network. In terms of the classification given in
RFC 7799 [RFC7799] IOAM could be categorized as Hybrid Type 1. IOAM
mechanisms can be leveraged where active OAM do not apply or do not
offer the desired results.
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For the SR use case, when SR policy enables IOAM, the IOAM header
will be inserted into every packet of the traffic that is steered
into the SR paths. Since this document aims to define the control
plane, it is to be noted that a relevant document for the data plane
is [I-D.ietf-ippm-ioam-ipv6-options] for Segment Routing over IPv6
data plane (SRv6).
4.1.1. IOAM Pre-allocated Trace Option Sub-TLV
The IOAM tracing data is expected to be collected at every node that
a packet traverses to ensure visibility into the entire path a packet
takes within an IOAM domain. The preallocated tracing option will
create pre-allocated space for each node to populate its information.
The format of IOAM pre-allocated trace option Sub-TLV is defined as
follows:
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 | Length=8 |
+---------------------------------------------------------------+
| Namespace ID | Rsvd1 |
+-------------------------------+-----------------------+-------+
| IOAM Trace Type | Flags | Rsvd2 |
+----------------------------------------------+--------+-------+
Fig. 4 IOAM Pre-allocated Trace Option Sub-TLV
Where:
Type: 1 (to be assigned by IANA).
Length: 8. It is the total length of the value field not including
Type and Length fields.
Namespace ID: A 16-bit identifier of an IOAM-Namespace. The
definition is the same as described in section 4.4 of
[I-D.ietf-ippm-ioam-data].
IOAM Trace Type: A 24-bit identifier which specifies which data types
are used in the node data list. The definition is the same as
described in section 4.4 of [I-D.ietf-ippm-ioam-data].
Flags: A 4-bit field. The definition is the same as described in
[I-D.ietf-ippm-ioam-flags] and section 4.4 of
[I-D.ietf-ippm-ioam-data].
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Rsvd1: A 16-bit field reserved for further usage. It MUST be zero
and ignored on receipt.
Rsvd2: A 4-bit field reserved for further usage. It MUST be zero and
ignored on receipt.
4.1.2. IOAM Incremental Trace Option Sub-TLV
The incremental tracing option contains a variable node data fields
where each node allocates and pushes its node data immediately
following the option header.
The format of IOAM incremental trace option Sub-TLV is defined as
follows:
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 | Length=8 |
+---------------------------------------------------------------+
| Namespace ID | Rsvd1 |
+-------------------------------+-----------------------+-------+
| IOAM Trace Type | Flags | Rsvd2 |
+----------------------------------------------+--------+-------+
Fig. 5 IOAM Incremental Trace Option Sub-TLV
Where:
Type: 2 (to be assigned by IANA).
Length: 8. It is the total length of the value field not including
Type and Length fields.
All the other fields definition is the same as the pre-allocated
trace option Sub-TLV in the previous section.
4.1.3. IOAM Directly Export Option Sub-TLV
IOAM directly export option is used as a trigger for IOAM data to be
directly exported to a collector without being pushed into in-flight
data packets.
The format of IOAM directly export option Sub-TLV is defined as
follows:
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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=3 | Length=12 |
+---------------------------------------------------------------+
| Namespace ID | Flags |
+-------------------------------+---------------+---------------+
| IOAM Trace Type | Rsvd |
+-----------------------------------------------+---------------+
| Flow ID |
+---------------------------------------------------------------+
Fig. 6 IOAM Directly Export Option Sub-TLV
Where:
Type: 3 (to be assigned by IANA).
Length: 12. It is the total length of the value field not including
Type and Length fields.
Namespace ID: A 16-bit identifier of an IOAM-Namespace. The
definition is the same as described in section 4.4 of
[I-D.ietf-ippm-ioam-data].
IOAM Trace Type: A 24-bit identifier which specifies which data types
are used in the node data list. The definition is the same as
described in section 4.4 of [I-D.ietf-ippm-ioam-data].
Flags: A 16-bit field. The definition is the same as described in
section 3.2 of [I-D.ietf-ippm-ioam-direct-export].
Flow ID: A 32-bit flow identifier. The definition is the same as
described in section 3.2 of [I-D.ietf-ippm-ioam-direct-export].
Rsvd: A 4-bit field reserved for further usage. It MUST be zero and
ignored on receipt.
4.1.4. IOAM Edge-to-Edge Option Sub-TLV
The IOAM edge to edge option is to carry data that is added by the
IOAM encapsulating node and interpreted by IOAM decapsulating node.
The format of IOAM edge-to-edge option Sub-TLV is defined as follows:
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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=4 | Length=4 |
+---------------------------------------------------------------+
| Namespace ID | IOAM E2E Type |
+-------------------------------+-------------------------------+
Fig. 7 IOAM Edge-to-Edge Option Sub-TLV
Where:
Type: 4 (to be assigned by IANA).
Length: 4. It is the total length of the value field not including
Type and Length fields.
Namespace ID: A 16-bit identifier of an IOAM-Namespace. The
definition is the same as described in section 4.6 of
[I-D.ietf-ippm-ioam-data].
IOAM E2E Type: A 16-bit identifier which specifies which data types
are used in the E2E option data. The definition is the same as
described in section 4.6 of [I-D.ietf-ippm-ioam-data].
4.2. Enhanced Alternate Marking Sub-TLV
The Alternate Marking [RFC8321]technique is an hybrid performance
measurement method, per RFC 7799 [RFC7799] classification of
measurement methods. Because this method is based on marking
consecutive batches of packets. It can be used to measure packet
loss, latency, and jitter on live traffic.
For the SR use case, since this document aims to define the control
plane, it is to be noted that a relevant document for the data plane
is [I-D.ietf-6man-ipv6-alt-mark] for Segment Routing over IPv6 data
plane (SRv6).
The format of Enhanced Alternate Marking (EAM) Sub-TLV is defined as
follows:
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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=5 | Length=4 |
+-------------------------------+-------+---------------+-------+
| FlowMonID | Period |H|E| R |
+---------------------------------------+---------------+-------+
Fig. 8 Enhanced Alternate Marking Sub-TLV
Where:
Type: 5 (to be assigned by IANA).
Length: 4. It is the total length of the value field not including
Type and Length fields.
FlowMonID: A 20-bit identifier to uniquely identify a monitored flow
within the measurement domain. The definition is the same as
described in section 5.3 of [I-D.ietf-6man-ipv6-alt-mark]. It is to
be noted that PCE also needs to maintain the uniqueness of FlowMonID
as described in [I-D.ietf-6man-ipv6-alt-mark].
Period: Time interval between two alternate marking period. The unit
is second.
H: A flag indicating that the measurement is Hop-By-Hop.
E: A flag indicating that the measurement is end to end.
R: A 2-bit field reserved for further usage. It MUST be zero and
ignored on receipt.
5. PCEP Messages
5.1. The PCInitiate Message
A PCInitiate message is a PCEP message sent by a PCE to a PCC to
trigger LSP instantiation or deletion RFC 8281 [RFC8281].
For the PCE-initiated LSP with the IFIT feature enabled, IFIT-
ATTRIBUTES TLV MUST be included in the LSPA object with the
PCInitiate message.
The Routing Backus-Naur Form (RBNF) definition of the PCInitiate
message RFC 8281 [RFC8281] is unchanged by this document.
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5.2. The PCUpd Message
A PCUpd message is a PCEP message sent by a PCE to a PCC to update
the LSP parameters RFC 8231 [RFC8231].
For PCE-initiated LSPs with the IFIT feature enabled, the IFIT-
ATTRIBUTES TLV MUST be included in the LSPA object with the PCUpd
message. The PCE can send this TLV to direct the PCC to change the
IFIT parameters.
The RBNF definition of the PCUpd message RFC 8231 [RFC8231] is
unchanged by this document.
5.3. The PCRpt Message
The PCRpt message RFC 8231 [RFC8231] is a PCEP message sent by a PCC
to a PCE to report the status of one or more LSPs.
For PCE-initiated LSPs RFC 8281 [RFC8281], the PCC creates the LSP
using the attributes communicated by the PCE and the local values for
the unspecified parameters. After the successful instantiation of
the LSP, the PCC automatically delegates the LSP to the PCE and
generates a PCRpt message to provide the status report for the LSP.
The RBNF definition of the PCRpt message RFC 8231 [RFC8231] is
unchanged by this document.
For both PCE-initiated and PCC-initiated LSPs, when the LSP is
instantiated the IFIT methods are applied as specified for the
corresponding data plane. [I-D.ietf-ippm-ioam-ipv6-options] and
[I-D.ietf-6man-ipv6-alt-mark] are the relevant documents for Segment
Routing over IPv6 data plane (SRv6).
6. Example of application to SR Policy
A PCC or PCE sets the IFIT-CAPABILITY TLV in the Open message during
the PCEP initialization phase to indicate that it supports the IFIT
procedures.
[I-D.ietf-pce-segment-routing-policy-cp] defines the PCEP extension
to support Segment Routing Policy Candidate Paths and in this regard
the SRPAG Association object is introduced.
The Examples of PCC Initiated SR Policy with single or multiple
candidate-paths and PCE Initiated SR Policy with single or multiple
candidate-paths are reported in
[I-D.ietf-pce-segment-routing-policy-cp].
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In case of PCC Initiated SR Policy, PCC sends PCReq message to the
PCE, encoding the SRPAG ASSOCIATION object and IFIT-ATTRIBUTES TLV
via the LSPA object. This is valid for both single and multiple
candidate-paths. Finally PCE returns the path in PCRep message, and
echoes back the SRPAG object that were used in the computation and
IFIT LSPA TLVs too. Additionally, PCC sends PCRpt message to the
PCE, including the LSP object and the SRPAG ASSOCIATION object and
IFIT-ATTRIBUTES TLV via the LSPA object. Then PCE computes path and
finally PCE updates the SR policy candidate path's ERO using PCUpd
message considering the IFIT LSPA TLVs too.
In case of PCE Initiated SR Policy, PCE sends PCInitiate message,
containing the SRPAG Association object and IFIT-ATTRIBUTES TLV via
the LSPA object. This is valid for both single and multiple
candidate-paths. Then PCC uses the color, endpoint and preference
from the SRPAG object to create a new candidate path considering the
IFIT LSPA TLVs too. Finally PCC sends a PCRpt message back to the
PCE to report the newly created Candidate Path. The PCRpt message
contains the SRPAG Association object and IFIT-ATTRIBUTES
information.
The procedure of enabling/disabling IFIT is simple, indeed the PCE
can update the IFIT-ATTRIBUTES of the LSP by sending subsequent Path
Computation Update Request (PCUpd) messages. PCE can update the
IFIT-ATTRIBUTES of the LSP by sending Path Computation State Report
(PCRpt) messages.
7. IANA Considerations
This document defines the new IFIT-CAPABILITY TLV and IFIT-ATTRIBUTES
TLV. IANA is requested to make the assignment from the "PCEP TLV
Type Indicators" subregistry of the "Path Computation Element
Protocol (PCEP) Numbers" registry as follows:
Value Description Reference
-------------------------------------------------------------
TBD1 IFIT-CAPABILITY This document
TBD2 IFIT-ATTRIBUTES This document
This document specifies the IFIT-CAPABILITY TLV Flags field. IANA is
requested to create a registry to manage the value of the IFIT-
CAPABILITY TLV's Flags field within the "Path Computation Element
Protocol (PCEP) Numbers" registry.
New values are to be assigned by Standards Action RFC 8126 [RFC8126].
Each bit should be tracked with the following qualities:
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* Bit number (count from 0 as the most significant bit)
* Flag Name
* Reference
IANA is requested to set 5 new bits in the IFIT-CAPABILITY TLV Flags
Field registry, as follows:
Bit no. Flag Name Reference
---------------------------------------------------------------------
27 P: IOAM Pre-allocated Trace Option flag This document
28 I: IOAM Incremental Trace Option flag This document
29 D: IOAM Directly Export Option flag This document
30 E: IOAM Edge-to-Edge Option This document
31 M: Alternate Marking Flag This document
This document also specifies the IFIT-ATTRIBUTES sub-TLVs. IANA is
requested to create an "IFIT-ATTRIBUTES Sub-TLV Types" subregistry
within the "Path Computation Element Protocol (PCEP) Numbers"
registry.
IANA is requested to set the Registration Procedure for this registry
to read as follows:
Range Registration Procedure
------------------------------------------
0-65503 IETF Review
65504-65535 Experimental Use
This document defines the following types:
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Type Description Reference
---------------------------------------------------------------
0 Reserved This document
1 IOAM Pre-allocated Trace Option This document
2 IOAM Incremental Trace Option This document
3 IOAM Directly Export Option This document
4 IOAM Edge-to-Edge Option This document
5 Enhanced Alternate Marking This document
6-65503 Unassigned This document
65504-65535 Experimental Use This document
This document defines a new Error-value for PCErr message of Error-
Type 19 (Invalid Operation). IANA is requested to allocate a new
Error-value within the "PCEP-ERROR Object Error Types and Values"
subregistry of the "Path Computation Element Protocol (PCEP) Numbers"
registry as follows:
Error-Type Meaning Error-value Reference
---------------------------------------------------------------
19 Invalid TBD3: IFIT This document
Operation capability not
advertised
8. Security Considerations
This document defines the new IFIT-CAPABILITY TLV and IFIT Attributes
TLVs, which do not add any substantial new security concerns beyond
those already discussed in RFC 8231 [RFC8231] and RFC 8281 [RFC8281]
for stateful PCE operations. As per RFC 8231 [RFC8231], it is
RECOMMENDED that these PCEP extensions only be activated on
authenticated and encrypted sessions across PCEs and PCCs belonging
to the same administrative authority, using Transport Layer Security
(TLS) RFC 8253 [RFC8253], as per the recommendations and best current
practices in BCP 195 RFC 7525 [RFC7525] (unless explicitly set aside
in RFC 8253 [RFC8253]).
Implementation of IFIT methods (IOAM and Alternate Marking) are
mindful of security and privacy concerns, as explained in
[I-D.ietf-ippm-ioam-data] and RFC 8321 [RFC8321]. Anyway incorrect
IFIT parameters in the IFIT-ATTRIBUTES sub-TLVs SHOULD not have an
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adverse effect on the LSP as well as on the network, since it affects
only the operation of the telemetry methodology.
IFIT data MUST be propagated in a limited domain in order to avoid
malicious attacks and solutions to ensure this requirement are
respectively discussed in [I-D.ietf-ippm-ioam-data] and
[I-D.ietf-6man-ipv6-alt-mark].
IFIT methods (IOAM and Alternate Marking) are applied within a
controlled domain where the network nodes are locally administered.
A limited administrative domain provides the network administrator
with the means to select, monitor and control the access to the
network, making it a trusted domain also for the PCEP extensions
defined in this document.
9. Contributors
The following people provided relevant contributions to this
document:
Huanan Chen, independent, -
Dhruv Doody, Huawei Technologies, dhruv.ietf@gmail.com
10. Acknowledgements
The authors of this document would like to thank Huaimo Chen for the
comments and review of this document.
11. References
11.1. Normative References
[I-D.ietf-6man-ipv6-alt-mark]
Fioccola, G., Zhou, T., Cociglio, M., Qin, F., and R.
Pang, "IPv6 Application of the Alternate Marking Method",
draft-ietf-6man-ipv6-alt-mark-12 (work in progress),
October 2021.
[I-D.ietf-ippm-ioam-data]
Brockners, F., Bhandari, S., and T. Mizrahi, "Data Fields
for In-situ OAM", draft-ietf-ippm-ioam-data-17 (work in
progress), December 2021.
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[I-D.ietf-ippm-ioam-direct-export]
Song, H., Gafni, B., Zhou, T., Li, Z., Brockners, F.,
Bhandari, S., Sivakolundu, R., and T. Mizrahi, "In-situ
OAM Direct Exporting", draft-ietf-ippm-ioam-direct-
export-07 (work in progress), October 2021.
[I-D.ietf-ippm-ioam-flags]
Mizrahi, T., Brockners, F., Bhandari, S., Sivakolundu, R.,
Pignataro, C., Kfir, A., Gafni, B., Spiegel, M., and J.
Lemon, "In-situ OAM Loopback and Active Flags", draft-
ietf-ippm-ioam-flags-07 (work in progress), October 2021.
[I-D.ietf-ippm-ioam-ipv6-options]
Bhandari, S. and F. Brockners, "In-situ OAM IPv6 Options",
draft-ietf-ippm-ioam-ipv6-options-06 (work in progress),
July 2021.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009,
<https://www.rfc-editor.org/info/rfc5440>.
[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <https://www.rfc-editor.org/info/rfc7525>.
[RFC7799] Morton, A., "Active and Passive Metrics and Methods (with
Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799,
May 2016, <https://www.rfc-editor.org/info/rfc7799>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
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[RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path
Computation Element Communication Protocol (PCEP)
Extensions for Stateful PCE", RFC 8231,
DOI 10.17487/RFC8231, September 2017,
<https://www.rfc-editor.org/info/rfc8231>.
[RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody,
"PCEPS: Usage of TLS to Provide a Secure Transport for the
Path Computation Element Communication Protocol (PCEP)",
RFC 8253, DOI 10.17487/RFC8253, October 2017,
<https://www.rfc-editor.org/info/rfc8253>.
[RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path
Computation Element Communication Protocol (PCEP)
Extensions for PCE-Initiated LSP Setup in a Stateful PCE
Model", RFC 8281, DOI 10.17487/RFC8281, December 2017,
<https://www.rfc-editor.org/info/rfc8281>.
[RFC8321] Fioccola, G., Ed., Capello, A., Cociglio, M., Castaldelli,
L., Chen, M., Zheng, L., Mirsky, G., and T. Mizrahi,
"Alternate-Marking Method for Passive and Hybrid
Performance Monitoring", RFC 8321, DOI 10.17487/RFC8321,
January 2018, <https://www.rfc-editor.org/info/rfc8321>.
[RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
and J. Hardwick, "Path Computation Element Communication
Protocol (PCEP) Extensions for Segment Routing", RFC 8664,
DOI 10.17487/RFC8664, December 2019,
<https://www.rfc-editor.org/info/rfc8664>.
[RFC8799] Carpenter, B. and B. Liu, "Limited Domains and Internet
Protocols", RFC 8799, DOI 10.17487/RFC8799, July 2020,
<https://www.rfc-editor.org/info/rfc8799>.
11.2. Informative References
[I-D.ietf-pce-segment-routing-ipv6]
Li, C., Negi, M., Sivabalan, S., Koldychev, M.,
Kaladharan, P., and Y. Zhu, "PCEP Extensions for Segment
Routing leveraging the IPv6 data plane", draft-ietf-pce-
segment-routing-ipv6-10 (work in progress), November 2021.
[I-D.ietf-pce-segment-routing-policy-cp]
Koldychev, M., Sivabalan, S., Barth, C., Peng, S., and H.
Bidgoli, "PCEP extension to support Segment Routing Policy
Candidate Paths", draft-ietf-pce-segment-routing-policy-
cp-06 (work in progress), October 2021.
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[I-D.ietf-spring-segment-routing-policy]
Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and
P. Mattes, "Segment Routing Policy Architecture", draft-
ietf-spring-segment-routing-policy-14 (work in progress),
October 2021.
[I-D.koldychev-pce-multipath]
Koldychev, M., Sivabalan, S., Saad, T., Beeram, V. P.,
Bidgoli, H., Yadav, B., and S. Peng, "PCEP Extensions for
Signaling Multipath Information", draft-koldychev-pce-
multipath-05 (work in progress), February 2021.
[I-D.qin-idr-sr-policy-ifit]
Qin, F., Yuan, H., Zhou, T., Fioccola, G., and Y. Wang,
"BGP SR Policy Extensions to Enable IFIT", draft-qin-idr-
sr-policy-ifit-04 (work in progress), October 2020.
Appendix A.
Authors' Addresses
Hang Yuan
UnionPay
1899 Gu-Tang Rd., Pudong
Shanghai
China
Email: yuanhang@unionpay.com
Tianran Zhou
Huawei
156 Beiqing Rd., Haidian District
Beijing
China
Email: zhoutianran@huawei.com
Weidong Li
Huawei
156 Beiqing Rd., Haidian District
Beijing
China
Email: poly.li@huawei.com
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Giuseppe Fioccola
Huawei
Riesstrasse, 25
Munich
Germany
Email: giuseppe.fioccola@huawei.com
Yali Wang
Huawei
156 Beiqing Rd., Haidian District
Beijing
China
Email: wangyali11@huawei.com
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