| < draft-hu-spring-segment-routing-proxy-forwarding-18.txt | draft-hu-spring-segment-routing-proxy-forwarding-19.txt > | |||
|---|---|---|---|---|
| Network Working Group Z. Hu | Network Working Group Z. Hu | |||
| Internet-Draft Huawei Technologies | Internet-Draft Huawei Technologies | |||
| Intended status: Standards Track H. Chen | Intended status: Standards Track H. Chen | |||
| Expires: 1 September 2022 Futurewei | Expires: 13 October 2022 Futurewei | |||
| J. Yao | J. Yao | |||
| Huawei Technologies | Huawei Technologies | |||
| C. Bowers | C. Bowers | |||
| Juniper Networks | Juniper Networks | |||
| Y. Zhu | Y. Zhu | |||
| China Telecom | China Telecom | |||
| Y. Liu | Y. Liu | |||
| China Mobile | China Mobile | |||
| 28 February 2022 | 11 April 2022 | |||
| SR-TE Path Midpoint Restoration | SR-TE Path Midpoint Restoration | |||
| draft-hu-spring-segment-routing-proxy-forwarding-18 | draft-hu-spring-segment-routing-proxy-forwarding-19 | |||
| Abstract | Abstract | |||
| Segment Routing Traffic Engineering (SR-TE) supports explicit paths | Segment Routing Traffic Engineering (SR-TE) supports explicit paths | |||
| using segment lists containing adjacency-SIDs, node-SIDs and binding- | using segment lists containing adjacency-SIDs, node-SIDs and binding- | |||
| SIDs. The current SR FRR such as TI-LFA provides fast re-route | SIDs. The current SR FRR such as TI-LFA provides fast re-route | |||
| protection for the failure of a node along a SR-TE path by the direct | protection for the failure of a node along a SR-TE path by the direct | |||
| neighbor or say point of local repair (PLR) to the failure. However, | neighbor or say point of local repair (PLR) to the failure. However, | |||
| once the IGP converges, the SR FRR is no longer sufficient to forward | once the IGP converges, the SR FRR is no longer sufficient to forward | |||
| traffic of the path around the failure, since the non-neighbors of | traffic of the path around the failure, since the non-neighbors of | |||
| skipping to change at page 2, line 15 ¶ | skipping to change at page 2, line 15 ¶ | |||
| Internet-Drafts are working documents of the Internet Engineering | Internet-Drafts are working documents of the Internet Engineering | |||
| Task Force (IETF). Note that other groups may also distribute | Task Force (IETF). Note that other groups may also distribute | |||
| working documents as Internet-Drafts. The list of current Internet- | working documents as Internet-Drafts. The list of current Internet- | |||
| Drafts is at https://datatracker.ietf.org/drafts/current/. | Drafts is at https://datatracker.ietf.org/drafts/current/. | |||
| Internet-Drafts are draft documents valid for a maximum of six months | Internet-Drafts are draft documents valid for a maximum of six months | |||
| and may be updated, replaced, or obsoleted by other documents at any | and may be updated, replaced, or obsoleted by other documents at any | |||
| time. It is inappropriate to use Internet-Drafts as reference | time. It is inappropriate to use Internet-Drafts as reference | |||
| 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 1 September 2022. | This Internet-Draft will expire on 13 October 2022. | |||
| Copyright Notice | Copyright Notice | |||
| Copyright (c) 2022 IETF Trust and the persons identified as the | Copyright (c) 2022 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 (https://trustee.ietf.org/ | Provisions Relating to IETF Documents (https://trustee.ietf.org/ | |||
| license-info) in effect on the date of publication of this document. | license-info) in effect on the date of publication of this document. | |||
| Please review these documents carefully, as they describe your rights | Please review these documents carefully, as they describe your rights | |||
| and restrictions with respect to this document. Code Components | and restrictions with respect to this document. Code Components | |||
| extracted from this document must include Revised BSD License text as | extracted from this document must include Revised BSD License text as | |||
| described in Section 4.e of the Trust Legal Provisions and are | described in Section 4.e of the Trust Legal Provisions and are | |||
| provided without warranty as described in the Revised BSD License. | provided without warranty as described in the Revised BSD License. | |||
| Table of Contents | Table of Contents | |||
| 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 | 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 | |||
| 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 | 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 | |||
| 2. Proxy Forwarding . . . . . . . . . . . . . . . . . . . . . . 4 | 2. Proxy Forwarding . . . . . . . . . . . . . . . . . . . . . . 4 | |||
| 3. Protocol Extensions for Proxy Forwarding . . . . . . . . . . 4 | 3. Protocol Extensions/Re-uses for Proxy Forwarding . . . . . . 4 | |||
| 3.1. Advertising Proxy Forwarding . . . . . . . . . . . . . . 4 | 3.1. Advertising Binding Segment . . . . . . . . . . . . . . . 4 | |||
| 3.2. Advertising Binding Segment . . . . . . . . . . . . . . . 5 | 3.2. Advertising Proxy Forwarding . . . . . . . . . . . . . . 5 | |||
| 4. Proxy Forwarding Example . . . . . . . . . . . . . . . . . . 6 | 4. Proxy Forwarding Example . . . . . . . . . . . . . . . . . . 6 | |||
| 4.1. Advertising Proxy Forwarding . . . . . . . . . . . . . . 8 | 4.1. Advertising Proxy Forwarding . . . . . . . . . . . . . . 8 | |||
| 4.2. Building Proxy Forwarding Table . . . . . . . . . . . . . 8 | 4.2. Building Proxy Forwarding Table . . . . . . . . . . . . . 8 | |||
| 4.3. Proxy Forwarding for Binding Segment . . . . . . . . . . 9 | 4.3. Proxy Forwarding for Binding Segment . . . . . . . . . . 9 | |||
| 5. Security Considerations . . . . . . . . . . . . . . . . . . . 10 | 5. Security Considerations . . . . . . . . . . . . . . . . . . . 10 | |||
| 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 | 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 | |||
| 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 | 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 | |||
| 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 | 7.1. Normative References . . . . . . . . . . . . . . . . . . 10 | |||
| 8.1. Normative References . . . . . . . . . . . . . . . . . . 10 | 7.2. Informative References . . . . . . . . . . . . . . . . . 11 | |||
| 8.2. Informative References . . . . . . . . . . . . . . . . . 11 | ||||
| Appendix A. Proxy Forwarding for Adjacency and Node Segment . . 11 | Appendix A. Proxy Forwarding for Adjacency and Node Segment . . 11 | |||
| A.1. Next Segment is an Adjacency Segment . . . . . . . . . . 11 | A.1. Next Segment is an Adjacency Segment . . . . . . . . . . 11 | |||
| A.2. Next Segment is a Node Segment . . . . . . . . . . . . . 12 | A.2. Next Segment is a Node Segment . . . . . . . . . . . . . 12 | |||
| Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 | Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 | |||
| 1. Introduction | 1. Introduction | |||
| Segment Routing Traffic Engineering (SR-TE) is a technology that | Segment Routing Traffic Engineering (SR-TE) is a technology that | |||
| implements traffic engineering using a segment list. SR-TE supports | implements traffic engineering using a segment list. SR-TE supports | |||
| the creation of explicit paths using adjacency-SIDs, node-SIDs, | the creation of explicit paths using adjacency-SIDs, node-SIDs, | |||
| skipping to change at page 4, line 22 ¶ | skipping to change at page 4, line 22 ¶ | |||
| capability from the neighbors of a failed node will send traffic | capability from the neighbors of a failed node will send traffic | |||
| using the node-SID of the failed node to the nearest Proxy Forwarder | using the node-SID of the failed node to the nearest Proxy Forwarder | |||
| after the IGP converges on the event of the failure. | after the IGP converges on the event of the failure. | |||
| Once the affected traffic reaches a Proxy Forwarder, it sends the | Once the affected traffic reaches a Proxy Forwarder, it sends the | |||
| traffic on the post-failure shortest path to the node immediately | traffic on the post-failure shortest path to the node immediately | |||
| following the failed node in the segment list. | following the failed node in the segment list. | |||
| For a binding segment of a possible failed node, the node advertises | For a binding segment of a possible failed node, the node advertises | |||
| the information about the binding segment, including the binding SID | the information about the binding segment, including the binding SID | |||
| and the list of SIDs associated with the binding SID, to its direct | and the list of SIDs/segments associated with the binding SID, to its | |||
| neighbors only. Note that the information is not advertised in the | direct neighbors only. Note that the information is not advertised | |||
| network domain. | in the network domain. | |||
| After the node fails and the IGP converges on the failure, the | After the node fails and the IGP converges on the failure, the | |||
| traffic with the binding SID of the failed node will reach its | traffic with the binding SID of the failed node will reach its | |||
| neighbor having SR Proxy Forwarding capability. Once receiving the | neighbor having SR Proxy Forwarding capability. Once receiving the | |||
| traffic, the neighbor swaps the binding SID with the list of SIDs | traffic, the neighbor swaps the binding SID with the list of SIDs/ | |||
| associated with the binding SID and sends the traffic along the post- | segments associated with the binding SID and sends the traffic along | |||
| failure shortest path to the first node in the segment list. | the post-failure shortest path to the first node in the segment list. | |||
| 3. Protocol Extensions for Proxy Forwarding | 3. Protocol Extensions/Re-uses for Proxy Forwarding | |||
| This section describes the semantic of protocol extensions/re-use for | This section describes the semantic of protocol extensions/re-uses | |||
| advertising the SR proxy forwarding capability of a node in a network | for advertising the information about each binding segment (including | |||
| domain and the information about each binding segment (including its | its binding SID and the list of SIDs/segments associated with the | |||
| binding SID and the list of SIDs associated) of a node to its direct | binding SID) of a node to its direct neighbors and the SR proxy | |||
| forwarding capability of a node in a network domain. | ||||
| 3.1. Advertising Binding Segment | ||||
| For a binding segment (or binding for short) on a node A, which | ||||
| consists of a binding SID and a list of SIDs/segments, node A | ||||
| advertises an LS containing the binding (i.e., the binding SID and | ||||
| the list of the SIDs/segments) in a binding segment TLV. The LS is | ||||
| advertised only to each of the node A's neighboring nodes. For | ||||
| OSPFv2, the LS is a opaque LSA of LS type 9 (i.e., a link local scope | ||||
| LSA). For IS-IS, the TLV is advertised in Circuit Scoped Link State | ||||
| PDUs (CS-LSP) [RFC7356]. | ||||
| Alternatively, when a protocol (such as PCE or BGP running on a | ||||
| controller) supports sending a binding on a node A to A, this | ||||
| protocol may be extended to send the binding with node A to A's | ||||
| neighbors if the controller knows the neighbors and there are | ||||
| protocol (PCE or BGP) sessions between the controller and the | ||||
| neighbors. | neighbors. | |||
| 3.1. Advertising Proxy Forwarding | Note: how to send bindings of node A to A's neighbors via which | |||
| protocol is out of the scope of this document. | ||||
| 3.2. Advertising Proxy Forwarding | ||||
| When a node P is able to do SR proxy forwarding for its neighboring | When a node P is able to do SR proxy forwarding for its neighboring | |||
| nodes for protecting the failures of these nodes, P advertises its SR | nodes for protecting the failures of these nodes, P advertises its SR | |||
| proxy forwarding capability for these nodes. The mirror SID | proxy forwarding capability for these nodes. The mirror SID | |||
| [RFC8402][RFC8667] for a node N (Neighbor of P) advertised by P | [RFC8402] for a node N (Neighbor of P) advertised by P using IS-IS | |||
| indicates the capability of P for N. | extensions [RFC8667] indicates the capability of P for N. | |||
| For a node X in the network, it learns the prefix/node SID of node N, | For a node X in the network, it learns the prefix/node SID of node N, | |||
| which is originated and advertised by node N. It creates a proxy | which is originated and advertised by node N. It creates a proxy | |||
| prefix/node SID of node N for node P if node P is capable of doing SR | prefix/node SID of node N for node P if node P is capable of doing SR | |||
| proxy forwarding for node N. The proxy prefix/node SID of node N for | proxy forwarding for node N. The proxy prefix/node SID of node N for | |||
| node P is a copy of the prefix/node SID of node N originated by node | node P is a copy of the prefix/node SID of node N originated by node | |||
| N, but stored under (or say, associated with) node P. The route to | N, but stored under (or say, associated with) node P. The route to | |||
| the proxy prefix/node SID is through proxy forwarding capable nodes. | the proxy prefix/node SID is through proxy forwarding capable nodes. | |||
| In normal operations, node X prefers to use the prefix/node SID of | In normal operations, node X prefers to use the prefix/node SID of | |||
| skipping to change at page 5, line 23 ¶ | skipping to change at page 5, line 46 ¶ | |||
| traffic towards its final destination without going through node N. | traffic towards its final destination without going through node N. | |||
| Note that the behaviors of normal IP forwarding and routing | Note that the behaviors of normal IP forwarding and routing | |||
| convergences in a network are not changed at all by the SR proxy | convergences in a network are not changed at all by the SR proxy | |||
| forwarding. For example, the next hop used by BGP is an IP address | forwarding. For example, the next hop used by BGP is an IP address | |||
| (or prefix). The IGP and BGP converge in normal ways for changes in | (or prefix). The IGP and BGP converge in normal ways for changes in | |||
| the network. The packet with its IP destination to this next hop is | the network. The packet with its IP destination to this next hop is | |||
| forwarded according to the IP forwarding table (FIB) derived from IGP | forwarded according to the IP forwarding table (FIB) derived from IGP | |||
| and BGP routes. | and BGP routes. | |||
| Alternatively, P advertises its capability in its LS. For OSPF, P | Similar to IS-IS [RFC8667], OSPF should be extended for advertising | |||
| advertises its information opaque LSA with one bit (called PF bit) | mirror SID to indicate the capability. Note that OSPF extensions is | |||
| set to one indicating that P has the capability for all its | out of the scope of this document. | |||
| neighbors. For IS-IS, P advertises its LSP with PF bit. | ||||
| If node P can not do a SR proxy forwarding for all its neighboring | ||||
| nodes, but for some of them, then it advertises the node SID of each | ||||
| of the nodes as a proxy node SID, indicating that it is able to do | ||||
| proxy forwarding for the node SID. | ||||
| 3.2. Advertising Binding Segment | ||||
| For a binding segment (or binding for short) on a node A, which | ||||
| consists of a binding SID and a list of segments, node A advertises | ||||
| an LS containing the binding (i.e., the binding SID and the list of | ||||
| the segments) in a binding segment TLV. The LS is advertised only to | ||||
| each of the node A's neighboring nodes. For OSPFv2, the LS is a | ||||
| opaque LSA of LS type 9 (i.e., a link local scope LSA). For IS-IS, | ||||
| the TLV is advertised in Circuit Scoped Link State PDUs (CS-LSP) | ||||
| [RFC7356]. | ||||
| Alternatively, when a protocol (such as PCE or BGP running on a | ||||
| controller) supports sending a binding on a node A to A, this | ||||
| protocol may be extended to send the binding with node A to A's | ||||
| neighbors if the controller knows the neighbors and there are | ||||
| protocol (PCE or BGP) sessions between the controller and the | ||||
| neighbors. | ||||
| 4. Proxy Forwarding Example | 4. Proxy Forwarding Example | |||
| This section illustrates the proxy forwarding for a binding SID | This section illustrates the proxy forwarding for a binding SID | |||
| through an example. The proxy forwarding for a node SID and an | through an example. The proxy forwarding for a node SID and an | |||
| adjacency SID can refer to | adjacency SID can refer to | |||
| [I-D.ietf-spring-segment-protection-sr-te-paths] or Appendix. | [I-D.ietf-spring-segment-protection-sr-te-paths] or Appendix. | |||
| Figure 1 is an example network topology used to illustrate the proxy | Figure 1 is an example network topology used to illustrate the proxy | |||
| forwarding mechanism for a binding SID. Each node N has SRGB = | forwarding mechanism for a binding SID. Each node N has SRGB = | |||
| [N000-N999]. RT1 is an ingress node of SR domain. RT3 is a failure | [N000-N999]. RT1 is an ingress node of SR domain. RT3 is a failure | |||
| skipping to change at page 10, line 21 ¶ | skipping to change at page 10, line 21 ¶ | |||
| two types of behaviors in data plane when a node in a network fails. | two types of behaviors in data plane when a node in a network fails. | |||
| One is that for a node, which is a upstream (except for the direct | One is that for a node, which is a upstream (except for the direct | |||
| upstream) node of the failed node along a SR-TE path, it continues to | upstream) node of the failed node along a SR-TE path, it continues to | |||
| send the traffic to the failed node along the SR-TE path for an | send the traffic to the failed node along the SR-TE path for an | |||
| extended period of time. The other is that for a node, which is the | extended period of time. The other is that for a node, which is the | |||
| direct upstream node of the failed node, it fast re-routes the | direct upstream node of the failed node, it fast re-routes the | |||
| traffic around the failed node to the direct downstream node of the | traffic around the failed node to the direct downstream node of the | |||
| failed node along the SR-TE path. These behaviors are internal to a | failed node along the SR-TE path. These behaviors are internal to a | |||
| network and should not cause extra security issues. | network and should not cause extra security issues. | |||
| 6. IANA Considerations | 6. Acknowledgements | |||
| 7. Acknowledgements | ||||
| The authors would like to thank Peter Psenak, Acee Lindem, Les | The authors would like to thank Peter Psenak, Acee Lindem, Les | |||
| Ginsberg, Bruno Decraene and Jeff Tantsura for their comments to this | Ginsberg, Bruno Decraene and Jeff Tantsura for their comments to this | |||
| work. | work. | |||
| 8. References | 7. References | |||
| 8.1. Normative References | 7.1. Normative References | |||
| [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate | [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate | |||
| 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>. | |||
| [RFC7356] Ginsberg, L., Previdi, S., and Y. Yang, "IS-IS Flooding | [RFC7356] Ginsberg, L., Previdi, S., and Y. Yang, "IS-IS Flooding | |||
| Scope Link State PDUs (LSPs)", RFC 7356, | Scope Link State PDUs (LSPs)", RFC 7356, | |||
| DOI 10.17487/RFC7356, September 2014, | DOI 10.17487/RFC7356, September 2014, | |||
| <https://www.rfc-editor.org/info/rfc7356>. | <https://www.rfc-editor.org/info/rfc7356>. | |||
| skipping to change at page 11, line 11 ¶ | skipping to change at page 11, line 11 ¶ | |||
| Decraene, B., Litkowski, S., and R. Shakir, "Segment | Decraene, B., Litkowski, S., and R. Shakir, "Segment | |||
| Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, | Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, | |||
| July 2018, <https://www.rfc-editor.org/info/rfc8402>. | July 2018, <https://www.rfc-editor.org/info/rfc8402>. | |||
| [RFC8667] Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C., | [RFC8667] Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C., | |||
| Bashandy, A., Gredler, H., and B. Decraene, "IS-IS | Bashandy, A., Gredler, H., and B. Decraene, "IS-IS | |||
| Extensions for Segment Routing", RFC 8667, | Extensions for Segment Routing", RFC 8667, | |||
| DOI 10.17487/RFC8667, December 2019, | DOI 10.17487/RFC8667, December 2019, | |||
| <https://www.rfc-editor.org/info/rfc8667>. | <https://www.rfc-editor.org/info/rfc8667>. | |||
| 8.2. Informative References | 7.2. Informative References | |||
| [I-D.ietf-rtgwg-segment-routing-ti-lfa] | [I-D.ietf-rtgwg-segment-routing-ti-lfa] | |||
| Litkowski, S., Bashandy, A., Filsfils, C., Francois, P., | Litkowski, S., Bashandy, A., Filsfils, C., Francois, P., | |||
| Decraene, B., and D. Voyer, "Topology Independent Fast | Decraene, B., and D. Voyer, "Topology Independent Fast | |||
| Reroute using Segment Routing", Work in Progress, | Reroute using Segment Routing", Work in Progress, | |||
| Internet-Draft, draft-ietf-rtgwg-segment-routing-ti-lfa- | Internet-Draft, draft-ietf-rtgwg-segment-routing-ti-lfa- | |||
| 08, 21 January 2022, <https://www.ietf.org/archive/id/ | 08, 21 January 2022, <https://www.ietf.org/archive/id/ | |||
| draft-ietf-rtgwg-segment-routing-ti-lfa-08.txt>. | draft-ietf-rtgwg-segment-routing-ti-lfa-08.txt>. | |||
| [I-D.ietf-spring-segment-protection-sr-te-paths] | [I-D.ietf-spring-segment-protection-sr-te-paths] | |||
| Hegde, S., Bowers, C., Litkowski, S., Xu, X., and F. Xu, | Hegde, S., Bowers, C., Litkowski, S., Xu, X., and F. Xu, | |||
| "Segment Protection for SR-TE Paths", Work in Progress, | "Segment Protection for SR-TE Paths", Work in Progress, | |||
| Internet-Draft, draft-ietf-spring-segment-protection-sr- | Internet-Draft, draft-ietf-spring-segment-protection-sr- | |||
| te-paths-02, 21 January 2022, | te-paths-03, 7 March 2022, | |||
| <https://www.ietf.org/archive/id/draft-ietf-spring- | <https://www.ietf.org/archive/id/draft-ietf-spring- | |||
| segment-protection-sr-te-paths-02.txt>. | segment-protection-sr-te-paths-03.txt>. | |||
| [I-D.ietf-spring-segment-routing-policy] | [I-D.ietf-spring-segment-routing-policy] | |||
| Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and | Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and | |||
| P. Mattes, "Segment Routing Policy Architecture", Work in | P. Mattes, "Segment Routing Policy Architecture", Work in | |||
| Progress, Internet-Draft, draft-ietf-spring-segment- | Progress, Internet-Draft, draft-ietf-spring-segment- | |||
| routing-policy-18, 17 February 2022, | routing-policy-22, 22 March 2022, | |||
| <https://www.ietf.org/archive/id/draft-ietf-spring- | <https://www.ietf.org/archive/id/draft-ietf-spring- | |||
| segment-routing-policy-18.txt>. | segment-routing-policy-22.txt>. | |||
| Appendix A. Proxy Forwarding for Adjacency and Node Segment | Appendix A. Proxy Forwarding for Adjacency and Node Segment | |||
| This Section shows through example how a proxy node forward traffic | This Section shows through example how a proxy node forward traffic | |||
| to the destination node when a node fails and the next segment of | to the destination node when a node fails and the next segment of | |||
| label stack is an adjacency-SID or node-SID. | label stack is an adjacency-SID or node-SID. | |||
| A.1. Next Segment is an Adjacency Segment | A.1. Next Segment is an Adjacency Segment | |||
| As shown in Figure 1, Label Stack 3 {10012, 20023, 30034, 40045} uses | As shown in Figure 1, Label Stack 3 {10012, 20023, 30034, 40045} uses | |||
| End of changes. 21 change blocks. | ||||
| 63 lines changed or deleted | 57 lines changed or added | |||
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