PCEP extensions for Circuit Style Policies
draft-sidor-pce-circuit-style-pcep-extensions-00
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
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|---|---|---|---|
| Authors | Samuel Sidor , Zafar Ali , Praveen Maheshwari | ||
| Last updated | 2022-03-07 | ||
| Replaced by | draft-ietf-pce-circuit-style-pcep-extensions | ||
| RFC stream | (None) | ||
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| Consensus boilerplate | Unknown | ||
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draft-sidor-pce-circuit-style-pcep-extensions-00
PCE Working Group S. Sidor
Internet-Draft Z. Ali
Intended status: Standards Track Cisco Systems, Inc.
Expires: 5 September 2022 P. Maheshwari
Airtel India
4 March 2022
PCEP extensions for Circuit Style Policies
draft-sidor-pce-circuit-style-pcep-extensions-00
Abstract
This document proposes a set of extensions for Path Computation
Element Communication Protocol (PCEP) for Circuit Style Policies -
Segment-Routing Policy designed to satisfy requirements for
connection-oriented transport services. New TLV is introduced to
control path recomputation triggers and new flag to add ability to
request path with strict hops only.
Requirements Language
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.
Status of This Memo
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/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 5 September 2022.
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Copyright Notice
Copyright (c) 2022 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
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Overview of Extensions to PCEP . . . . . . . . . . . . . . . 3
3.1. LSP-EXTENDED-FLAG TLV . . . . . . . . . . . . . . . . . . 3
3.2. RECOMPUTATION-TRIGGERS TLV . . . . . . . . . . . . . . . 4
4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Strict path enforcement . . . . . . . . . . . . . . . . . 5
4.2. Path computation triggers . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6.1. LSP-EXTENDED-FLAG TLV . . . . . . . . . . . . . . . . . . 6
6.2. RECOMPUTATION-TRIGGERS TLV . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.1. Normative References . . . . . . . . . . . . . . . . . . 6
7.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
Usage of Segment-routing and PCEP in connection-oriented transport
services require path persistancy and hop-by-hop behavior for PCE
computed paths.
Circuit-Style Policy introduced in [I-D.schmutzer-pce-cs-sr-policy]
requires PCEP extensions, which are covered in this document.
This document:
* Introduces possibility to request strict path from the PCE by
extending LSP-EXTENDED-FLAG TLV
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* Adding new TLV for encoding blocked path recomputation triggers to
the PCE is introduced, to be carried inside the LSP object, which
is defined in [RFC8231].
* Clarifies usage of existing O-flag from RP object in Segment-
routing
PCEP extensions described in this document are applicable to RSVP-TE
and SR-TE.
2. Terminology
The following terminologies are used in this document:
ERO: Explicit Route Object
IGP: Interior Gateway Protocol
LSP: Label Switched Path.
LSPA: Label Switched Path Attributes.
OTN: Optical Transport Network.
PCC: Path Computation Client
PCE: Path Computation Element
PCEP: Path Computation Element Protocol.
SDH: Synchronous Digital Hierarchy
SID: Segment Identifier
SONET: Synchronous Optical Network
SR: Segment Routing.
SR-TE: Segment Routing Traffic Engineering.
3. Overview of Extensions to PCEP
3.1. LSP-EXTENDED-FLAG TLV
O-flag is proposed in the LSP-EXTENDED-FLAG TLV, which was introduced
in 5.1.2 of [I-D.ietf-pce-lsp-extended-flags] and extended with
E-flag in [I-D.peng-pce-entropy-label-position]
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The format of the LSP-EXTENDED-FLAG is 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=TBD1 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |O|E|
// LSP Extended Flags //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: LSP-EXTENDED-FLAG TLV Format
Type (16 bits): the value is TBD1 by IANA.
Length (16 bits): multiple of 4 octets.
O (Strict-Path): If set to 1, this indicates to the PCE that a path
exclusively made of strict hops is required. Strict hop definition
can be found in Section 4.1
3.2. RECOMPUTATION-TRIGGERS TLV
This document defines new TLV for the LSP Object for encoding
information about blocked path recomputation triggers.
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 = TBD2 | Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Flags |T|P|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type (16 bits): the value is TBD2 by IANA.
Length (16 bits): 4 octets
Reserved: MUST be set to zero by the sender and MUST be ignored by
the receiver.
Flags: This document defines the following flag bits. The other
bits MUST be set to zero by the sender and MUST be ignored by the
receiver.
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* T (Topology-change): If set to 1, the PCE MUST NOT trigger
recomputation as a result of received updated topology
information.
* P (Periodic-timer): If set to 1, the PCE MUST NOT trigger
recomputation based on any periodic timer.
4. Operation
4.1. Strict path enforcement
PCC MAY set the O flag in LSP-EXTENDED-FLAG TLV in PCRpt message to
the PCE to indicate that a path exclusively made of strict hops is
required.
O flag cleared or LSP-EXTENDED-FLAG TLV not included indicates that a
loose path is acceptable.
In PCUpdate or PCInitiate messages, when the O bit is set, this
indicates that strict path is provided.
The flag is applicable only for stateful messages. Existing O flag
in RP object MAY be used to indicate similar behavior in PCReq and
PCRep messages as described in as described in Section 7.4.1 of
[RFC5440].
If O flag is set to 1 for both stateful and stateless messages for SR
paths introduced in [RFC8664], the PCE MUST use Adjacency SIDs only.
4.2. Path computation triggers
PCC MAY set flags in RECOMPUTATION-TRIGGERS-TLV to block specific
triggers. If TLV is not included or all flags are set to 0, then the
PCE MAY use any event to start path computation.
Disabled recomputation triggered by topology event is not blocking
path computation started based PCRpt or based on updated state of
associated LSP.
If trigger blocked by specific flag is not supported or allowed on
the PCE, then PCE MAY ignore received flag value. The PCE SHOULD
reflect blocked triggers in PCUpdate message.
TLV MAY be included in PCInitiate and PCUpdate messages to indicate,
which triggers will be disabled on the PCE. PCC should reflect flag
values in PCRpt messages to forward requirement to other PCEs in the
network.
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5. Security Considerations
No additional security measure is required.
6. IANA Considerations
6.1. LSP-EXTENDED-FLAG TLV
[I-D.ietf-pce-lsp-extended-flags] defines the LSP-EXTENDED-FLAG TLV.
IANA is requested to make the following assignment from the "LSP-
EXTENDED-FLAG TLV Flag Field" registry:
+======+======================+===============+
| Bit | Description | Reference |
+======+======================+===============+
| TBD1 | Strict-Path Flag (O) | This document |
+------+----------------------+---------------+
Table 1
6.2. RECOMPUTATION-TRIGGERS TLV
IANA is requested to make the assignment of a new value for the
existing "PCEP TLV Type Indicators" registry as follows:
+==========+============================+===============+
| TLV Type | TLV Name | Reference |
+==========+============================+===============+
| TBD2 | RECOMPUTATION-TRIGGERS TLV | This document |
+----------+----------------------------+---------------+
Table 2
7. References
7.1. Normative References
[I-D.ietf-pce-lsp-extended-flags]
Xiong, Q., "LSP Object Flag Extension of Stateful PCE",
Work in Progress, Internet-Draft, draft-ietf-pce-lsp-
extended-flags-01, 18 October 2021,
<https://www.ietf.org/archive/id/draft-ietf-pce-lsp-
extended-flags-01.txt>.
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[I-D.peng-pce-entropy-label-position]
Xiong, Q., Peng, S., and F. Qin, "PCEP Extension for SR-
MPLS Entropy Label Position", Work in Progress, Internet-
Draft, draft-peng-pce-entropy-label-position-07, 2 March
2022, <https://www.ietf.org/archive/id/draft-peng-pce-
entropy-label-position-07.txt>.
[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>.
[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>.
[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>.
[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>.
7.2. Informative References
[I-D.schmutzer-pce-cs-sr-policy]
Schmutzer, C., Filsfils, C., Ali, Z., and F. Clad,
"Circuit Style Segment Routing Policies", Work in
Progress, Internet-Draft, draft-schmutzer-pce-cs-sr-
policy-00, 30 September 2021,
<https://www.ietf.org/archive/id/draft-schmutzer-pce-cs-
sr-policy-00.txt>.
Authors' Addresses
Samuel Sidor
Cisco Systems, Inc.
Eurovea Central 3.
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Pribinova 10
811 09 Bratislava
Slovakia
Email: ssidor@cisco.com
Zafar Ali
Cisco Systems, Inc.
Email: zali@cisco.com
Praveen Maheshwari
Airtel India
Email: Praveen.Maheshwari@airtel.com
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