BGP Extension for SR-MPLS Entropy Label Position
draft-zhou-idr-bgp-srmpls-elp-00
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IDR Working Group J. Zhou
Internet-Draft Shaofu. Peng
Intended status: Standards Track ZTE Corp.
Expires: August 21, 2020 Feb 18, 2020
BGP Extension for SR-MPLS Entropy Label Position
draft-zhou-idr-bgp-srmpls-elp-00
Abstract
This document proposed an extension for BGP to configure the entropy
label position for SR-MPLS networks.
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
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and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 21, 2020.
Copyright Notice
Copyright (c) 2020 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
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Zhou & Peng Expires August 21, 2020 [Page 1]
Internet-DraBGP Extension for SR-MPLS Entropy Label Position Feb 2020
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. BGP Extensions of Segment Flags . . . . . . . . . . . . . . . 2
3. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
5. Normative References . . . . . . . . . . . . . . . . . . . . 3
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 3
1. Introduction
Entropy Label(EL)[RFC6790] is a technology that can be used for load-
balancing in Segment Routing (SR) MPLS.
[I-D.ietf-mpls-spring-entropy-label] discusses in detail the factors
to be considered when inserting EL in SR, analyzes the possible
insertion positions of entropy labels, and gives a specific algorithm
for calculating the position of entropy labels.
An MPLS label stack can contain multiple ELs, so multiple EL
insertion positions may be calculated. When calculating the
position, it is necessary to consider the Maximum SID Depth(MSD)
capability of the head node and Entropy Readable Label Depth(ERLD)
capability of the intermediate node in combination with the
algorithm. The position calculation of EL is usually completed by
the controller, which is issued by the controller to the head node.
[I-D.ietf-idr-segment-routing-te-policy] defines the specific process
of how the controller in the SR network passes the path calculation
result of the SR-TE policy to the head node of the network through
BGP.
In this document, the EL position information is transmitted by
extending the flags of Segment List Sub-TLV in the BGP.
2. BGP Extensions of Segment Flags
The Segment Flags is defined in Section 2.4.3.2.12 of
[I-D.ietf-idr-segment-routing-te-policy].
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|V|A|E| |
+-+-+-+-+-+-+-+-+
E-Flag: This flag indicates that presence of <ELI, EL> label pairs
are inserted after this segment. It is applicable to all Segment
Types.
Zhou & Peng Expires August 21, 2020 [Page 2]
Internet-DraBGP Extension for SR-MPLS Entropy Label Position Feb 2020
3. Operations
Supposed the head end had received a SR-TE path from the controller
with multiple Segment List Sub-TLVs, for example, <S1, S2, S3, S4,
S5, S6>, especially S3 and S6 with E-flag. It indicates that two
<ELI, EL> pairs SHOULD be inserted into the label stack of the SR-TE
forwarding entry, respectively 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>.
4. IANA Considerations
This document requests bit 2 for Entropy Label Flag.
Bit Description Reference
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