draft-ietf-isis-mpls-elc-07.txt   draft-ietf-isis-mpls-elc-08.txt 
Network Working Group X. Xu Network Working Group X. Xu
Internet-Draft Alibaba Inc Internet-Draft Alibaba Inc
Intended status: Standards Track S. Kini Intended status: Standards Track S. Kini
Expires: November 15, 2019 Expires: March 6, 2020
P. Psenak P. Psenak
C. Filsfils C. Filsfils
Cisco Cisco
S. Litkowski S. Litkowski
Orange Orange
May 14, 2019 September 3, 2019
Signaling Entropy Label Capability and Entropy Readable Label Depth Signaling Entropy Label Capability and Entropy Readable Label Depth
Using IS-IS Using IS-IS
draft-ietf-isis-mpls-elc-07 draft-ietf-isis-mpls-elc-08
Abstract Abstract
Multiprotocol Label Switching (MPLS) has defined a mechanism to load- Multiprotocol Label Switching (MPLS) has defined a mechanism to load-
balance traffic flows using Entropy Labels (EL). An ingress Label balance traffic flows using Entropy Labels (EL). An ingress Label
Switching Router (LSR) cannot insert ELs for packets going into a Switching Router (LSR) cannot insert ELs for packets going into a
given Label Switched Path (LSP) unless an egress LSR has indicated given Label Switched Path (LSP) unless an egress LSR has indicated
via signaling that it has the capability of processing ELs, referred via signaling that it has the capability to process ELs, referred to
to as Entropy Label Capability (ELC), on that tunnel. In addition, as Entropy Label Capability (ELC), on that tunnel. In addition, it
it would be useful for ingress LSRs to know each LSR's capability of would be useful for ingress LSRs to know each LSR's capability for
reading the maximum label stack depth and performing EL-based load- reading the maximum label stack depth and performing EL-based load-
balancing, referred to as Entropy Readable Label Depth (ERLD). This balancing, referred to as Entropy Readable Label Depth (ERLD). This
document defines a mechanism to signal these two capabilities using document defines a mechanism to signal these two capabilities using
IS-IS. These mechanisms are particularly useful, where label IS-IS. These mechanisms are particularly useful, where label
advertisements are done via protocols like IS-IS. advertisements are done via protocols like IS-IS.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 15, 2019. This Internet-Draft will expire on March 6, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Advertising ERLD Using IS-IS . . . . . . . . . . . . . . . . 3 3. Advertising ERLD Using IS-IS . . . . . . . . . . . . . . . . 3
4. Advertising ELC Using IS-IS . . . . . . . . . . . . . . . . . 3 4. Advertising ELC Using IS-IS . . . . . . . . . . . . . . . . . 3
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 6. BGP-LS Extension . . . . . . . . . . . . . . . . . . . . . . 4
7. Security Considerations . . . . . . . . . . . . . . . . . . . 4 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
8. Normative References . . . . . . . . . . . . . . . . . . . . 4 8. Security Considerations . . . . . . . . . . . . . . . . . . . 5
9. Normative References . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction 1. Introduction
[RFC6790] describes a method to load-balance Multiprotocol Label [RFC6790] describes a method to load-balance Multiprotocol Label
Switching (MPLS) traffic flows using Entropy Labels (EL). "The Use Switching (MPLS) traffic flows using Entropy Labels (EL). "The Use
of Entropy Labels in MPLS Forwarding" [RFC6790] introduces the of Entropy Labels in MPLS Forwarding" [RFC6790] introduces the
concept of Entropy Label Capability (ELC) and defines the signalings concept of Entropy Label Capability (ELC) and defines the signalings
of this capability via MPLS signaling protocols. Recently, of this capability via MPLS signaling protocols. Recently,
mechanisms have been defined to signal labels via link-state Interior mechanisms have been defined to signal labels via link-state Interior
Gateway Protocols (IGP) such as IS-IS Gateway Protocols (IGP) such as IS-IS
[I-D.ietf-isis-segment-routing-extensions]. In such scenario, the [I-D.ietf-isis-segment-routing-extensions]. In such scenarios, the
defined signaling mechanisms are inadequate. This draft defines a defined signaling mechanisms are inadequate. This draft defines a
mechanism to signal the ELC using IS-IS. This mechanism is useful mechanism to signal the ELC using IS-IS. This mechanism is useful
when the label advertisement is also done via IS-IS. when the label advertisement is also done via IS-IS.
In addition, in the cases where stacked LSPs are used for whatever In addition, in the cases where LSPs are used for whatever reasons
reasons (e.g., SR-MPLS [I-D.ietf-spring-segment-routing-mpls]), it (e.g., SR-MPLS [I-D.ietf-spring-segment-routing-mpls]), it would be
would be useful for ingress LSRs to know each intermediate LSR's useful for ingress LSRs to know each intermediate LSR's capability of
capability of reading the maximum label stack depth and performing reading the maximum label stack depth and performing EL-based load-
EL-based load-balancing. This capability, referred to as Entropy balancing. This capability, referred to as Entropy Readable Label
Readable Label Depth (ERLD) as defined in Depth (ERLD) as defined in [I-D.ietf-mpls-spring-entropy-label] may
[I-D.ietf-mpls-spring-entropy-label] may be used by ingress LSRs to be used by ingress LSRs to determine the position of the EL label in
determine whether it's necessary to insert an EL for a given LSP in the stack, and whether it's necessary to insert multiple ELs at
the case where there has already been at least one EL in the label different positions in the label stack.
stack [I-D.ietf-mpls-spring-entropy-label].
2. Terminology 2. Terminology
This memo makes use of the terms defined in [RFC6790] and [RFC4971]. This memo makes use of the terms defined in [RFC6790] and [RFC4971].
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
3. Advertising ERLD Using IS-IS 3. Advertising ERLD Using IS-IS
A new MSD-type of the Node MSD sub-TLV [RFC8491], called ERLD is A new MSD-type of the Node MSD sub-TLV [RFC8491], called ERLD is
defined to advertise the ERLD of a given router. As shown in defined to advertise the ERLD of a given router. As shown in
Figure 2, it is formatted as described in [RFC8491] with a new MSD- Figure 2, it is formatted as described in [RFC8491] with a new MSD-
Type code to be assigned by IANA (the type code of 2 is desired) and Type code to be assigned by IANA (the type code of 2 is desired) and
the Value field is set to the ERLD in the range between 0 to 255. the 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 The scope of the advertisement depends on the application. If a
router has multiple linecards with different capabilities of reading router has multiple line-cards with different capabilities of reading
the maximum label stack depth, the router MUST advertise the smallest the maximum label stack depth, the router MUST advertise the smallest
one. one.
0 1 2 3 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 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 | | MSD-Type=TBD2 | ERLD |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: ERLD MSD-Type Format Figure 2: ERLD MSD-Type Format
4. Advertising ELC Using IS-IS 4. Advertising ELC Using IS-IS
Even though ELC is a property of the node, in some cases it 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 advantageous to associate and advertise the ELC with a prefix. In a
multi-area network, routers may not know the identity of the prefix multi-area network, routers may not know the identity of the prefix
originator in the remote area, or may not know the capabilities of originator in a remote area, or may not know the capabilities of such
such originator. Similarly in a multi-domain network, the identity originator. Similarly in a multi-domain network, the identity of the
of the prefix originator and its capabilities may not be known to the prefix originator and its capabilities may not be known to the
ingress LSR. ingress LSR.
One bit of the "Bit Values for Prefix Attribute Flags Sub-TLV" One bit of the "Bit Values for Prefix Attribute Flags Sub-TLV"
registry defined in [RFC7794] (Bit 3 is desired) is to be assigned by registry defined in [RFC7794] (Bit 3 is desired) is to be assigned by
the IANA for the ELC. If a router has multiple line cards, the the IANA for the ELC. If a router has multiple line cards, the
router MUST NOT announce the ELC for any prefixes that are locally router MUST NOT announce the ELC for any prefixes that are locally
attached unless all of its linecards are capable of processing ELs. attached unless all of its line-cards are capable of processing ELs.
If a router supports ELs on all of its linecards, it SHOULD set the If a router supports ELs on all of its line-cards, it SHOULD set the
ELC for every local host prefix it advertises in IS-IS. ELC for every local host prefix it advertises in IS-IS.
When a router leaks a prefix between two levels (upwards or When a router leaks a prefix between two levels (upwards or
downwards), it MUST preserve the ELC signalling for this prefix. downwards), it MUST preserve the ELC signaling for this prefix.
0 1 2 3 4 5 6 7... 0 1 2 3 4 5 6 7...
+-+-+-+-+-+-+-+-+... +-+-+-+-+-+-+-+-+...
|X|R|N|E| ... |X|R|N|E| ...
+-+-+-+-+-+-+-+-+... +-+-+-+-+-+-+-+-+...
When redistributing a prefix between two IS-IS protocol instances or When redistributing a prefix between two IS-IS protocol instances or
redistributed from another protocol to an IS-IS protocol instance, a redistributing from another protocol to an IS-IS protocol instance, a
router SHOULD preserve the ELC signalling for that prefix. The exact router SHOULD preserve the ELC signaling for that prefix. The exact
mechanism on how to exchange ELC between protocol instances running mechanism used to exchange ELC between protocol instances running on
on an ASBR is outside of the scope of this document and is an ASBR is outside of the scope of this document and is
implementation specific. implementation specific.
5. Acknowledgements 5. Acknowledgements
The authors would like to thank Yimin Shen, George Swallow, Acee The authors would like to thank Yimin Shen, George Swallow, Acee
Lindem, Les Ginsberg, Ketan Talaulikar, Jeff Tantsura, Bruno Decraene Lindem, Les Ginsberg, Ketan Talaulikar, Jeff Tantsura, Bruno Decraene
Carlos Pignataro, Wim Hendrickx, and Gunter Van De Velde for their Carlos Pignataro, Wim Hendrickx, and Gunter Van De Velde for their
valuable comments. valuable comments.
6. IANA Considerations 6. BGP-LS Extension
The IS-IS extensions defined in this document can be advertised via
BGP-LS [RFC7752] using existing BGP-LS TLVs.
The ELC Flag included in the Prefix Attribute Flags sub-TLV, as
defined in Section 4, is advertised using the Prefix Attribute Flags
TLV (TLV 1170) of the BGP-LS IPv4/IPv6 Prefix NLRI Attribute as
defined in section 2.3.2 of
[I-D.ietf-idr-bgp-ls-segment-routing-ext].
The ERLD MSD-type introduced for IS-IS in Section 3 is advertised
using the Node MSD TLV (TLV 266) of the BGP-LS Node NLRI Attribute as
defined in section 3 of [I-D.ietf-idr-bgp-ls-segment-routing-ext].
7. IANA Considerations
IANA is requested to allocate the E-bit (bit position 3 is desired) IANA is requested to allocate the E-bit (bit position 3 is desired)
from the "Bit Values for Prefix Attribute Flags Sub-TLV" registry. from the "Bit Values for Prefix Attribute Flags Sub-TLV" registry.
IANA is requested to allocate a MSD type (the type code of 2 is IANA is requested to allocate a MSD type (the type code of 2 is
desired) from the "IGP MSD Types" registry for ERLD. desired) from the "IGP MSD Types" registry for ERLD.
7. Security Considerations 8. Security Considerations
The security considerations as described in [RFC4971] are applicable The security considerations as described in [RFC4971] nd
to this document. This document does not introduce any new security [I-D.ietf-mpls-spring-entropy-label] are applicable to this document.
risks.
8. Normative References Incorrectly setting the E flag (ELC capable) (during origination,
leaking or redistribution) may lead to black-holing of the traffic on
the egress node.
9. Normative References
[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-isis-segment-routing-extensions] [I-D.ietf-isis-segment-routing-extensions]
Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A., Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A.,
Gredler, H., and B. Decraene, "IS-IS Extensions for Gredler, H., and B. Decraene, "IS-IS Extensions for
Segment Routing", draft-ietf-isis-segment-routing- Segment Routing", draft-ietf-isis-segment-routing-
extensions-24 (work in progress), April 2019. extensions-25 (work in progress), May 2019.
[I-D.ietf-mpls-spring-entropy-label] [I-D.ietf-mpls-spring-entropy-label]
Kini, S., Kompella, K., Sivabalan, S., Litkowski, S., Kini, S., Kompella, K., Sivabalan, S., Litkowski, S.,
Shakir, R., and J. Tantsura, "Entropy label for SPRING Shakir, R., and J. Tantsura, "Entropy label for SPRING
tunnels", draft-ietf-mpls-spring-entropy-label-12 (work in tunnels", draft-ietf-mpls-spring-entropy-label-12 (work in
progress), July 2018. progress), July 2018.
[I-D.ietf-spring-segment-routing-mpls] [I-D.ietf-spring-segment-routing-mpls]
Bashandy, A., Filsfils, C., Previdi, S., Decraene, B., Bashandy, A., Filsfils, C., Previdi, S., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing with MPLS Litkowski, S., and R. Shakir, "Segment Routing with MPLS
skipping to change at page 5, line 28 skipping to change at page 6, line 5
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC4971] Vasseur, JP., Ed., Shen, N., Ed., and R. Aggarwal, Ed., [RFC4971] Vasseur, JP., Ed., Shen, N., Ed., and R. Aggarwal, Ed.,
"Intermediate System to Intermediate System (IS-IS) "Intermediate System to Intermediate System (IS-IS)
Extensions for Advertising Router Information", RFC 4971, Extensions for Advertising Router Information", RFC 4971,
DOI 10.17487/RFC4971, July 2007, DOI 10.17487/RFC4971, July 2007,
<https://www.rfc-editor.org/info/rfc4971>. <https://www.rfc-editor.org/info/rfc4971>.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, DOI 10.17487/RFC5305, October
2008, <https://www.rfc-editor.org/info/rfc5305>.
[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and [RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
L. Yong, "The Use of Entropy Labels in MPLS Forwarding", L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
RFC 6790, DOI 10.17487/RFC6790, November 2012, RFC 6790, DOI 10.17487/RFC6790, November 2012,
<https://www.rfc-editor.org/info/rfc6790>. <https://www.rfc-editor.org/info/rfc6790>.
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016,
<https://www.rfc-editor.org/info/rfc7752>.
[RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and [RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and
U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4 U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4
and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794, and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794,
March 2016, <https://www.rfc-editor.org/info/rfc7794>. March 2016, <https://www.rfc-editor.org/info/rfc7794>.
[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 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8491] Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg, [RFC8491] Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg,
"Signaling Maximum SID Depth (MSD) Using IS-IS", RFC 8491, "Signaling Maximum SID Depth (MSD) Using IS-IS", RFC 8491,
DOI 10.17487/RFC8491, November 2018, DOI 10.17487/RFC8491, November 2018,
<https://www.rfc-editor.org/info/rfc8491>. <https://www.rfc-editor.org/info/rfc8491>.
Authors' Addresses Authors' Addresses
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