--- 1/draft-ietf-isis-mpls-elc-12.txt 2020-05-28 06:13:15.688750299 -0700 +++ 2/draft-ietf-isis-mpls-elc-13.txt 2020-05-28 06:13:15.712750910 -0700 @@ -1,57 +1,57 @@ -Network Working Group X. Xu +LSR Working Group X. Xu Internet-Draft Alibaba Inc Intended status: Standards Track S. Kini -Expires: October 30, 2020 +Expires: November 29, 2020 P. Psenak C. Filsfils S. Litkowski Cisco Systems, Inc. M. Bocci Nokia - April 28, 2020 + May 28, 2020 Signaling Entropy Label Capability and Entropy Readable Label Depth Using IS-IS - draft-ietf-isis-mpls-elc-12 + draft-ietf-isis-mpls-elc-13 Abstract Multiprotocol Label Switching (MPLS) has defined a mechanism to load- balance traffic flows using Entropy Labels (EL). An ingress Label Switching Router (LSR) cannot insert ELs for packets going into a given Label Switched Path (LSP) unless an egress LSR has indicated via signaling that it has the capability to process ELs, referred to - as the Entropy Label Capability (ELC), on that tunnel. In addition, - it would be useful for ingress LSRs to know each LSR's capability for + as the Entropy Label Capability (ELC), on that LSP. In addition, it + would be useful for ingress LSRs to know each LSR's capability for reading the maximum label stack depth and performing EL-based load- balancing, referred to as Entropy Readable Label Depth (ERLD). This document defines a mechanism to signal these two capabilities using - IS-IS. + IS-IS and BGP-LS. 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 October 30, 2020. + This Internet-Draft will expire on November 29, 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 publication of this document. Please review these documents @@ -80,105 +80,101 @@ 1. Introduction [RFC6790] describes a method to load-balance Multiprotocol Label Switching (MPLS) traffic flows using Entropy Labels (EL). It also introduces the concept of Entropy Label Capability (ELC) and defines the signaling of this capability via MPLS signaling protocols. Recently, mechanisms have been defined to signal labels via link- state Interior Gateway Protocols (IGP) such as IS-IS [RFC8667]. This draft defines a mechanism to signal the ELC using IS-IS. - In cases where LSPs are used (e.g., SR-MPLS [RFC8660], it would be - useful for ingress LSRs to know each intermediate LSR's capability of - reading the maximum label stack depth and performing EL-based load- - balancing. This capability, referred to as Entropy Readable Label - Depth (ERLD) as defined in [RFC8662] may be used by ingress LSRs to - determine the position of the EL label in the stack, and whether it's - necessary to insert multiple ELs at different positions in the label - stack. + In cases where Segment Routing (SR) is used with the MPLS Data Plane + (e.g., SR-MPLS [RFC8660]), it would be useful for ingress LSRs to + know each intermediate LSR's capability of reading the maximum label + stack depth and performing EL-based load-balancing. This capability, + referred to as Entropy Readable Label Depth (ERLD) as defined in + [RFC8662], may be used by ingress LSRs to determine the position of + the EL label in the stack, and whether it's necessary to insert + multiple ELs at different positions in the label stack. This + document defines a mechanism to signal the ERLD using IS-IS. 2. Terminology This memo makes use of the terms defined in [RFC6790], and [RFC8662]. 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. 3. Advertising ELC Using IS-IS Even though ELC is a property of the node, in some cases it is advantageous to associate and advertise the ELC with a prefix. In a multi-area network, routers may not know the identity of the prefix originator in a remote area, or may not know the capabilities of such - originator. Similarly in a multi-domain network, the identity of the - prefix originator and its capabilities may not be known to the + originator. Similarly, in a multi-domain network, the identity of + the prefix originator and its capabilities may not be known to the ingress LSR. Bit 3 in the Prefix Attribute Flags [RFC7794] is used as the ELC Flag (E-flag), as shown in Figure 1. If a router has multiple interfaces, the router MUST NOT announce the ELC for any local host prefixes unless all of its interfaces are capable of processing ELs. If a router supports ELs on all of its interfaces, it SHOULD set the ELC for every local host prefix it advertises in IS-IS. 0 1 2 3 4 5 6 7... +-+-+-+-+-+-+-+-+... |X|R|N|E| ... +-+-+-+-+-+-+-+-+... Figure 1: Prefix Attribute Flags E-flag: ELC Flag (Bit 3) - Set for local host prefix of the originating node if it supports ELC on all interfaces. - When a router propagates a prefix between ISIS levels ([RFC5302], it - MUST preserve the ELC signaling for this prefix. + The ELC signaling MUST be preserved when a router propagates a prefix + between ISIS levels [RFC5302]. When redistributing a prefix between two IS-IS protocol instances or redistributing from another protocol to an IS-IS protocol instance, a - router SHOULD preserve the ELC signaling for that prefix. The exact - mechanism used to exchange ELC between protocol instances running on - an Autonomous System Boundary Router (ASBR) is outside of the scope - of this document. + router SHOULD preserve the ELC signaling for that prefix if it + exists. The exact mechanism used to exchange ELC between protocol + instances running on an Autonomous System Boundary Router is outside + of the scope of this document. 4. Advertising ERLD Using IS-IS - A new MSD-type [RFC8491], called ERLD-MSD is defined to advertise the - ERLD [RFC8662] of a given router. A MSD-Type code 2 has been + A new MSD-Type [RFC8491], called ERLD-MSD, is defined to advertise + the ERLD [RFC8662] of a given router. A MSD-Type code 2 has been assigned by IANA for ERLD-MSD. The MSD-Value field is set to the ERLD in the range between 0 to 255. The scope of the advertisement depends on the application. If a router has multiple interfaces with different capabilities of reading the maximum label stack depth, the - router MUST advertise the smallest one. + router MUST advertise the smallest value found across all its + interfaces. The absence of ERLD-MSD advertisements indicates only that the advertising node does not support advertisement of this capability. The considerations for advertising the ERLD are specified in [RFC8662]. - 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 - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | MSD-Type=TBD2 | ERLD | - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - Figure 2: ERLD MSD-Type Format - If the ERLD-MSD Type is received in the Link MSD Sub-TLV, it MUST be ignored. 5. Signaling ELC and ERLD in BGP-LS The IS-IS extensions defined in this document can be advertised via - BGP-LS [RFC7752] using existing BGP-LS TLVs. + BGP-LS (Distribution of Link-State and TE Information Using BGP) + [RFC7752] using existing BGP-LS TLVs. The ELC is advertised using the Prefix Attribute Flags TLV as defined in [I-D.ietf-idr-bgp-ls-segment-routing-ext]. The ERLD-MSD is advertised using the Node MSD TLV as defined in [I-D.ietf-idr-bgp-ls-segment-routing-msd]. 6. IANA Considerations Early allocation has been done by IANA for this document as follows: @@ -195,25 +191,25 @@ 7. Security Considerations This document specifies the ability to advertise additional node capabilities using IS-IS and BGP-LS. As such, the security considerations as described in [RFC7981], [RFC7752], [RFC7794], [RFC8491], [RFC8662], [I-D.ietf-idr-bgp-ls-segment-routing-ext] and [I-D.ietf-idr-bgp-ls-segment-routing-msd] are applicable to this document. Incorrectly setting the E flag during origination, propagation or - redistribution may lead to black-holing of the traffic on the egress - node. + redistribution may lead to poor or no load-balancing of the MPLS + traffic or black-holing of the MPLS traffic on the egress node. Incorrectly setting of the ERLD value may lead to poor or no load- - balancing of the traffic. + balancing of the MPLS traffic. 8. Contributors The following people contributed to the content of this document and should be considered as co-authors: Gunter Van de Velde (editor) Nokia Antwerp BE @@ -246,22 +242,22 @@ [I-D.ietf-idr-bgp-ls-segment-routing-ext] Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H., and M. Chen, "BGP Link-State extensions for Segment Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-16 (work in progress), June 2019. [I-D.ietf-idr-bgp-ls-segment-routing-msd] Tantsura, J., Chunduri, U., Talaulikar, K., Mirsky, G., and N. Triantafillis, "Signaling MSD (Maximum SID Depth) using Border Gateway Protocol - Link State", draft-ietf- - idr-bgp-ls-segment-routing-msd-17 (work in progress), - April 2020. + idr-bgp-ls-segment-routing-msd-18 (work in progress), May + 2020. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC5302] Li, T., Smit, H., and T. Przygienda, "Domain-Wide Prefix Distribution with Two-Level IS-IS", RFC 5302, DOI 10.17487/RFC5302, October 2008, .