draft-ietf-isis-mpls-elc-08.txt   draft-ietf-isis-mpls-elc-09.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: March 6, 2020 Expires: April 6, 2020
P. Psenak P. Psenak
C. Filsfils C. Filsfils
Cisco
S. Litkowski S. Litkowski
Orange Cisco
September 3, 2019 October 4, 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-08 draft-ietf-isis-mpls-elc-09
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 to process ELs, referred to via signaling that it has the capability to process ELs, referred to
as Entropy Label Capability (ELC), on that tunnel. In addition, it as Entropy Label Capability (ELC), on that tunnel. In addition, it
would be useful for ingress LSRs to know each LSR's capability for would be useful for ingress LSRs to know each LSR's capability for
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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.
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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 ELC Using IS-IS . . . . . . . . . . . . . . . . . 3
4. Advertising ELC Using IS-IS . . . . . . . . . . . . . . . . . 3 4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 5. Advertising ERLD Using IS-IS . . . . . . . . . . . . . . . . 4
6. BGP-LS Extension . . . . . . . . . . . . . . . . . . . . . . 4 6. Signaling ELC and ERLD in BGP-LS . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
8. Security Considerations . . . . . . . . . . . . . . . . . . . 5 8. Security Considerations . . . . . . . . . . . . . . . . . . . 5
9. Normative References . . . . . . . . . . . . . . . . . . . . 5 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 9.1. Normative References . . . . . . . . . . . . . . . . . . 5
9.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
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
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useful for ingress LSRs to know each intermediate LSR's capability of useful for ingress LSRs to know each intermediate LSR's capability of
reading the maximum label stack depth and performing EL-based load- reading the maximum label stack depth and performing EL-based load-
balancing. This capability, referred to as Entropy Readable Label balancing. This capability, referred to as Entropy Readable Label
Depth (ERLD) as defined in [I-D.ietf-mpls-spring-entropy-label] may Depth (ERLD) as defined in [I-D.ietf-mpls-spring-entropy-label] may
be used by ingress LSRs to determine the position of the EL label in 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 the stack, and whether it's necessary to insert multiple ELs at
different positions in the label stack. different positions in the label stack.
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], [RFC4971] and
[I-D.ietf-mpls-spring-entropy-label].
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 ELC Using IS-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
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
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
router has multiple line-cards with different capabilities of reading
the maximum label stack depth, the router MUST advertise the smallest
one.
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
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 a remote area, or may not know the capabilities of such originator in a remote area, or may not know the capabilities of such
originator. Similarly in a multi-domain network, the identity of the originator. Similarly in a multi-domain network, the identity 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"
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originator in a remote area, or may not know the capabilities of such originator in a remote area, or may not know the capabilities of such
originator. Similarly in a multi-domain network, the identity of the originator. Similarly in a multi-domain network, the identity 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 line-cards 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 line-cards, 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
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| ...
+-+-+-+-+-+-+-+-+... +-+-+-+-+-+-+-+-+...
Figure 1: Prefix Attribute Flags
E-flag: ELC Flag (Bit 3)
Set for local host prefix of the originating node
if it supports ELC.
When a router leaks a prefix between two levels (upwards or
downwards), it MUST preserve the ELC signaling for this prefix.
When redistributing a prefix between two IS-IS protocol instances or When redistributing a prefix between two IS-IS protocol instances or
redistributing 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 signaling for that prefix. The exact router SHOULD preserve the ELC signaling for that prefix. The exact
mechanism used to exchange ELC between protocol instances running on mechanism used to exchange ELC between protocol instances running 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 4. 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. BGP-LS Extension 5. Advertising ERLD Using IS-IS
A new MSD-type of the Node MSD ((Maximum SID Depth) sub-TLV
[RFC8491], called ERLD is 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-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 scope of the advertisement depends on
the application. If a router has multiple line-cards with different
capabilities of reading the maximum label stack depth, the router
MUST advertise the smallest one.
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
When the ERLD MSD-Type is received in the Link MSD Sub-TLV, it MUST
be ignored.
6. Signaling ELC and ERLD in BGP-LS
The IS-IS extensions defined in this document can be advertised via The IS-IS extensions defined in this document can be advertised via
BGP-LS [RFC7752] using existing BGP-LS TLVs. BGP-LS [RFC7752] using existing BGP-LS TLVs.
The ELC Flag included in the Prefix Attribute Flags sub-TLV, as The ELC Flag included in the Prefix Attribute Flags sub-TLV, as
defined in Section 4, is advertised using the Prefix Attribute Flags defined in Section 3, is advertised using the Prefix Attribute Flags
TLV (TLV 1170) of the BGP-LS IPv4/IPv6 Prefix NLRI Attribute as TLV (TLV 1170) of the BGP-LS IPv4/IPv6 Prefix NLRI Attribute as
defined in section 2.3.2 of defined in section 2.3.2 of
[I-D.ietf-idr-bgp-ls-segment-routing-ext]. [I-D.ietf-idr-bgp-ls-segment-routing-ext].
The ERLD MSD-type introduced for IS-IS in Section 3 is advertised The ERLD MSD-type introduced for IS-IS in Section 5 is advertised
using the Node MSD TLV (TLV 266) of the BGP-LS Node NLRI Attribute as 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]. defined in section 3 of [I-D.ietf-idr-bgp-ls-segment-routing-msd].
7. IANA Considerations 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.
8. Security Considerations 8. Security Considerations
The security considerations as described in [RFC4971] nd The security considerations as described in [RFC4971] nd
[I-D.ietf-mpls-spring-entropy-label] are applicable to this document. [I-D.ietf-mpls-spring-entropy-label] are applicable to this document.
Incorrectly setting the E flag (ELC capable) (during origination, Incorrectly setting the E flag (ELC capable) (during origination,
leaking or redistribution) may lead to black-holing of the traffic on leaking or redistribution) may lead to black-holing of the traffic on
the egress node. the egress node.
9. Normative References Incorrectly setting of the ERLD value may lead to poor load-balancing
of the traffic.
9. References
9.1. Normative References
[I-D.ietf-idr-bgp-ls-segment-routing-ext] [I-D.ietf-idr-bgp-ls-segment-routing-ext]
Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H., Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H.,
and M. Chen, "BGP Link-State extensions for Segment and M. Chen, "BGP Link-State extensions for Segment
Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-16 Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-16
(work in progress), June 2019. (work in progress), June 2019.
[I-D.ietf-isis-segment-routing-extensions] [I-D.ietf-idr-bgp-ls-segment-routing-msd]
Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A., Tantsura, J., Chunduri, U., Talaulikar, K., Mirsky, G.,
Gredler, H., and B. Decraene, "IS-IS Extensions for and N. Triantafillis, "Signaling MSD (Maximum SID Depth)
Segment Routing", draft-ietf-isis-segment-routing- using Border Gateway Protocol Link-State", draft-ietf-idr-
extensions-25 (work in progress), May 2019. bgp-ls-segment-routing-msd-08 (work in progress),
September 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 6, line 30 skipping to change at page 6, line 47
[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>.
9.2. Informative References
[I-D.ietf-isis-segment-routing-extensions]
Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A.,
Gredler, H., and B. Decraene, "IS-IS Extensions for
Segment Routing", draft-ietf-isis-segment-routing-
extensions-25 (work in progress), May 2019.
Authors' Addresses Authors' Addresses
Xiaohu Xu Xiaohu Xu
Alibaba Inc Alibaba Inc
Email: xiaohu.xxh@alibaba-inc.com Email: xiaohu.xxh@alibaba-inc.com
Sriganesh Kini Sriganesh Kini
Email: sriganeshkini@gmail.com Email: sriganeshkini@gmail.com
skipping to change at page 7, line 4 skipping to change at page 7, line 31
Peter Psenak Peter Psenak
Cisco Cisco
Email: ppsenak@cisco.com Email: ppsenak@cisco.com
Clarence Filsfils Clarence Filsfils
Cisco Cisco
Email: cfilsfil@cisco.com Email: cfilsfil@cisco.com
Stephane Litkowski Stephane Litkowski
Orange Cisco
Email: stephane.litkowski@orange.com Email: sslitkows@cisco.com
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