PCEP Extension for SR-MPLS Entropy Label Position
draft-peng-pce-entropy-label-position-01
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 | Shaofu Peng , Quan Xiong | ||
| Last updated | 2019-09-12 | ||
| Replaced by | draft-ietf-pce-entropy-label-position | ||
| RFC stream | (None) | ||
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draft-peng-pce-entropy-label-position-01
PCE S. Peng
Internet-Draft Q. Xiong
Intended status: Standards Track ZTE Corporation
Expires: March 14, 2020 September 11, 2019
PCEP Extension for SR-MPLS Entropy Label Position
draft-peng-pce-entropy-label-position-01
Abstract
This document proposes a set of extensions for PCEP to configure the
entropy label position for SR-MPLS networks.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on March 14, 2020.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
3. PCEP Extensions . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. The OPEN Object . . . . . . . . . . . . . . . . . . . . . 4
3.2. The LSP Object . . . . . . . . . . . . . . . . . . . . . 4
3.2.1. The LSP-EXTENDED-FLAG TLV . . . . . . . . . . . . . . 5
3.3. The ERO Object . . . . . . . . . . . . . . . . . . . . . 5
4. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7.1. New SR PCE Capability Flag Registry . . . . . . . . . . . 6
7.2. New LSP Flag Registry . . . . . . . . . . . . . . . . . . 6
7.3. New SR-ERO Flag Registry . . . . . . . . . . . . . . . . 7
8. Normative References . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
[RFC5440] describes the Path Computation Element Protocol (PCEP)
which is used between a Path Computation Element (PCE) and a Path
Computation Client (PCC) (or other PCE) to enable computation of
Multi-protocol Label Switching (MPLS) for Traffic Engineering Label
Switched Path (TE LSP). PCEP Extensions for the Stateful PCE Model
[RFC8231] describes a set of extensions to PCEP to enable active
control of MPLS-TE and Generalized MPLS (GMPLS) tunnels. [RFC8281]
describes the setup and teardown of PCE-initiated LSPs under the
active stateful PCE model, without the need for local configuration
on the PCC, thus allowing for dynamic centralized control of a
network.
Segment Routing (SR) leverages the source routing paradigm. Segment
Routing can be instantiated on MPLS data plane which is referred to
as SR-MPLS [I-D.ietf-spring-segment-routing-mpls]. SR-MPLS leverages
the MPLS label stack to construct the SR path. PCEP Extensions for
Segment Routing [I-D.ietf-pce-segment-routing] specifies extensions
to the PCEP that allow a stateful PCE to compute and initiate TE
paths, as well as a PCC to request a path subject to certain
constraint(s) and optimization criteria in SR networks.
Entropy label (EL) [RFC6790] is a technique used in the MPLS data
plane to provide entropy for load-balancing. Entropy Label Indicator
(ELI) can be immediately preceding an EL in the MPLS label stack.
The idea behind the EL is that the ingress router computes a hash
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based on several fields from a given packet and places the result in
an additional label, named "entropy label". Then, this entropy label
can be used as part of the hash keys used by an LSR. Using the
entropy label as part of the hash keys reduces the need for deep
packet inspection in the LSR while keeping a good level of entropy in
the load-balancing. When the entropy label is used, the keys used in
the hashing functions are still a local configuration matter and an
LSR may use solely the entropy label or a combination of multiple
fields from the incoming packet.
[I-D.ietf-mpls-spring-entropy-label] proposes to use entropy labels
for SR-MPLS networks. The Entropy Readable Label Depth (ERLD) is
defined as the number of labels which means that the router will
perform load-balancing using the ELI/EL. An appropriate algorithm
would consider the following goals:
o a limited number of <ELI, EL> pairs should be inserted deeper in
the label-stack.
o the inserted position should be whithin the ERLD of most transit
nodes.
o a minimum number of <ELI, EL> to satisfy the above criteria.
In some cases, It is required for the controller (e.g. PCE) to
perform the TE path computation as well as the Entropy Label Position
(ELP), because the contoller has the ERLD information of all nodes,
especially for inter-domain scenarios. This document proposes a set
of extensions for PCEP to configure the ELP information for SR-MPLS
networks.
2. Conventions used in this document
2.1. Terminology
The terminology is defined as [RFC5440], [RFC6790],
[I-D.ietf-pce-segment-routing] and
[I-D.ietf-mpls-spring-entropy-label].
2.2. 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.
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3. PCEP Extensions
3.1. The OPEN Object
As defined in [I-D.ietf-pce-segment-routing], PCEP speakers use SR
PCE Capability sub-TLV to exchange information about their SR
capability when PST=1 in the PST List of the PATH-SETUP-TYPE-
CAPABILITY TLV carried in Open object. This document defined a new
flag (E-flag) for SR PCE Capability sub-TLV as shown in Figure 1.
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=TBD11 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Flags |E|N|X| MSD |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: E-flag in SR-PCE-CAPABILITY sub-TLV
E (ELP Configuration is supported) : A PCC or PCE sets this flag bit
to 1 carried in Open message to indicate that it supports the SR path
with ELP configuration.
3.2. The LSP Object
The LSP Object is defined in Section 7.3 of [RFC8231]. This document
defiend a new flag (E-flag) for the LSP Object as Figure 2 shown:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PLSP-ID | Flag|E|C| O |A|R|S|D|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// TLVs //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: E-flag in LSP Object
E (Request for ELP Configuration) : If the bit is set to 1, it
indicates that the PCC requests PCE to compute the SR path with ELP
information. A PCE would also set this bit to 1 to indicate that the
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ELP information is included by PCE and encoded in the PCRep, PCUpd or
PCInitiate message.
3.2.1. The LSP-EXTENDED-FLAG TLV
As defined in [RFC8231], the length of LSP Object Flag field is 12
bits and it defined the value from bit 5 to bit 11. The bits from 1
to 3 are defined in [RFC8623], the bit value 4 is used in [RFC8281].
So all bits of the flag has been used and this document proposes to
define a new LSP-EXTENDED-FLAG TLV for LSP object to extend the
length of the flag as the Figure 3 shown.
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=TBD | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extended Flag |E|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: LSP-EXTENDED-FLAG TLV Format
The bit E has the same defination with section 3.2 and the other bits
of the Extended flag can be used for other drafts in the future.
3.3. The ERO Object
SR-ERO subobject is used for SR-TE path which consists of one or more
SIDs as defined in [I-D.ietf-pce-segment-routing]. This document
defiend a new flag (E-flag) for the SR-ERO subobject as Figure 3
shown:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type=36 | Length | NT | Flags |E|F|S|C|M|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// NAI (variable, optional) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: E-flag in SR-ERO subobject
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E (ELP Configuration) : If this flag is set, it means that the
position after this SR-ERO subobject is the position to insert <ELI,
EL>, otherwise it cannot insert <ELI, EL> after this segment.
4. Operations
The SR path is initiated by PCE or PCC with PCReq, PCInitiated or
PCUpd messages and the E bit is set to 1 in LSP object to request the
ELP configuration. The SR-TE path being recieved by PCC with SR-ERO
segment list, for example, <S1, S2, S3, S4, S5, S6>, especially S3
and S6 with E-flag set. It indicates that two <ELI, EL> pairs MUST
be inserted into the label stack of the SR-TE forwarding entry,
repectively after the label for S3 and label for S6. With EL
information, the label stack for SR-MPLS would be <label1, label2,
label3, ELI, EL, label4, label5, label6, ELI, EL>.
5. Security Considerations
TBA
6. Acknowledgements
TBA
7. IANA Considerations
7.1. New SR PCE Capability Flag Registry
SR PCE Capability TLV is defined in [I-D.ietf-pce-segment-routing],
and the registry to manage the Flag field of the SR PCE Capability
TLV is requested in [I-D.ietf-pce-segment-routing]. IANA is
requested to make allocations from the registry, as follows:
+--------+-------------------------------------+------------------+
| Value | Name | Reference |
+--------+-------------------------------------+------------------+
| TBD11 | ELP Configuration is supported (E) | [this document] |
+--------+-------------------------------------+------------------+
Table 1
7.2. New LSP Flag Registry
[RFC8231] defines the LSP object; per that RFC, IANA created a
registry to manage the value of the LSP object's Flag field. IANA is
requested to make allocations from the registry, as follows:
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+--------+------------------------------------+------------------+
| Value | Name | Reference |
+--------+------------------------------------+------------------+
| TBD | Request for ELP Configuration (E) | [this document] |
| TBD | LSP-EXTENDED-FLAG TLV | [this document] |
+--------+------------------------------------+------------------+
Table 2
7.3. New SR-ERO Flag Registry
SR-ERO subobject is defined in [I-D.ietf-pce-segment-routing], and
the registry to manage the Flag field of SR-ERO is requested in
[I-D.ietf-pce-segment-routing]. IANA is requested to make
allocations from the registry, as follows:
+--------+------------------------+------------------+
| Value | Name | Reference |
+--------+------------------------+------------------+
| 36 | ELP Configuration (E) | [this document] |
+--------+------------------------+------------------+
Table 3
8. Normative References
[I-D.ietf-mpls-spring-entropy-label]
Kini, S., Kompella, K., Sivabalan, S., Litkowski, S.,
Shakir, R., and J. Tantsura, "Entropy label for SPRING
tunnels", draft-ietf-mpls-spring-entropy-label-12 (work in
progress), July 2018.
[I-D.ietf-pce-segment-routing]
Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
and J. Hardwick, "PCEP Extensions for Segment Routing",
draft-ietf-pce-segment-routing-16 (work in progress),
March 2019.
[I-D.ietf-spring-segment-routing-mpls]
Bashandy, A., Filsfils, C., Previdi, S., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing with MPLS
data plane", draft-ietf-spring-segment-routing-mpls-22
(work in progress), May 2019.
[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>.
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[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>.
[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
RFC 6790, DOI 10.17487/RFC6790, November 2012,
<https://www.rfc-editor.org/info/rfc6790>.
[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>.
[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>.
[RFC8623] Palle, U., Dhody, D., Tanaka, Y., and V. Beeram, "Stateful
Path Computation Element (PCE) Protocol Extensions for
Usage with Point-to-Multipoint TE Label Switched Paths
(LSPs)", RFC 8623, DOI 10.17487/RFC8623, June 2019,
<https://www.rfc-editor.org/info/rfc8623>.
Authors' Addresses
Shaofu Peng
ZTE Corporation
No.50 Software Avenue
Nanjing, Jiangsu 210012
China
Email: peng.shaofu@zte.com.cn
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Quan Xiong
ZTE Corporation
No.6 Huashi Park Rd
Wuhan, Hubei 430223
China
Email: xiong.quan@zte.com.cn
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