Network Working Group M. Boucadair Internet-Draft C. Jacquenet Intended status: Standards Track Orange Expires: April 12, 2018 S. Sivakumar Cisco Systems October 9, 2017 YANG Data Modules for the DS-Lite draft-ietf-softwire-dslite-yang-07 Abstract This document defines YANG modules for the DS-Lite Address Family Transition Router (AFTR) and Basic Bridging BroadBand (B4) elements . 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 April 12, 2018. Copyright Notice Copyright (c) 2017 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 carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Boucadair, et al. Expires April 12, 2018 [Page 1] Internet-Draft DS-Lite YANG October 2017 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 2. DS-Lite YANG Modules: An Overview . . . . . . . . . . . . . . 4 3. DS-Lite AFTR YANG Module . . . . . . . . . . . . . . . . . . 7 4. DS-Lite B4 YANG Module . . . . . . . . . . . . . . . . . . . 13 5. Security Considerations . . . . . . . . . . . . . . . . . . . 16 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 8.1. Normative references . . . . . . . . . . . . . . . . . . 17 8.2. Informative references . . . . . . . . . . . . . . . . . 18 Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 20 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21 1. Introduction This document defines data models for DS-Lite [RFC6333], using the YANG data modeling language [RFC7950]. Both the Address Family Transition Router (AFTR) and Basic Bridging BroadBand (B4) elements are covered by this specification. As a reminder, Figure 1 illustrates an overview of the DS-Lite architecture that involves AFTR and B4 elements. Boucadair, et al. Expires April 12, 2018 [Page 2] Internet-Draft DS-Lite YANG October 2017 +-----------+ | Host | +-----+-----+ |10.0.0.1 | | |10.0.0.2 +---------|---------+ | | | | Home router | |+--------+--------+| || B4 || |+--------+--------+| +--------|||--------+ |||2001:db8:0:1::1 ||| |||<-IPv4-in-IPv6 softwire ||| -------|||------- / ||| \ | ISP core network | \ ||| / -------|||------- ||| |||2001:db8:0:2::1 +--------|||--------+ | AFTR | |+--------+--------+| || Concentrator || |+--------+--------+| | |NAT| | | +-+-+ | +---------|---------+ |192.0.2.1 | --------|-------- / | \ | Internet | \ | / --------|-------- | |198.51.100.1 +-----+-----+ | IPv4 Host | +-----------+ Figure 1: DS-Lite Base Architecture Boucadair, et al. Expires April 12, 2018 [Page 3] Internet-Draft DS-Lite YANG October 2017 DS-Lite deployment considerations are discussed in [RFC6908]. This document follows the guidelines of [RFC6087], uses the common YANG types defined in [RFC6991], and adopts Network Management Datastore Architecture (NMDA). 1.1. Terminology This document makes use of the terms defined in Section 3 of [RFC6333]. The terminology for describing YANG data modules is defined in [RFC7950]. The meaning of the symbols in tree diagrams is defined in [I-D.ietf-netmod-yang-tree-diagrams]. 2. DS-Lite YANG Modules: An Overview As shown in Figure 1: o The AFTR element is a combination of an IPv4-in-IPv6 encapsualtion/decapsulation function and a NAT function. o The B4 element is an IPv4-in-IPv6 encapsulation function. Therefore, the AFTR YANG module is designed to augment both the Interfaces YANG module [RFC7223] and the NAT YANG module [I-D.ietf-opsawg-nat-yang] with DS-Lite specific features. The B4 YANG module augments the interfaces YANG module. Concretely, the AFTR YANG module (Figure 2) augments the Interfaces YANG module with the following: o An IPv6 address used by the AFTR for sending and receiving IPv4- in-IPv6 packets (aftr-ipv6-address). o An IPv4 address that is used by the AFTR for troubleshooting purposes (aftr-ipv4-address): According to [RFC6333], that address can be used to report ICMP problems and will appear in traceroute outputs. o The tunnel MTU to avoid fragmentation (tunnel-mtu): Since using an IPv4-in-IPv6 encapsulation to carry IPv4 traffic over IPv6 reduces the effective MTU of the datagram, operators should be able to increase the MTU size by at least 40 bytes to accommodate both the IPv6 encapsulation header and the IPv4 datagram without fragmenting the IPv6 packet (Section 2.2 of [RFC6908]). Boucadair, et al. Expires April 12, 2018 [Page 4] Internet-Draft DS-Lite YANG October 2017 o A policy to limit the number of DS-Lite softwires per subscriber (max-softwire-per-subscriber): This policy aims to prevent a misbehaving subscriber from mounting several DS-Lite softwires that would consume additional AFTR resources (e.g., get more external ports if the quota were enforced on a per-softwire basis, consume extra processing due to a large number of active softwires) [RFC7785]. o A DSCP marking policy to be followed when encapsulating/ decapsulating packets (v6-v4-dscp-preservation): Section 2.10 of [RFC6908] discusses the uniform model which assumes that implementations of this model copy the DSCP value to the outer IP header at encapsulation and copy the outer header's DSCP value to the inner IP header at decapsulation. Operators should configure the AFTR so that it copies the DSCP value in the IPv4 header to the Traffic Class field in the IPv6 header, and vice versa. In addition, the AFTR YANG module augments the NAT YANG module (nat- policy, in particular) with the following: o A policy to instruct the AFTR whether a state can be automatically migrated (state-migrate): This policy avoids stale mappings at the AFTR and minimizes the risk of service disruption for subscribers. According to [RFC7785], the AFTR should migrate existing state to be bound to the new IPv6 address in the event a new IPv6 address is assigned to the B4 element. This operation ensures that traffic destined to the previous B4's IPv6 address will be redirected to the newer B4's IPv6 address. o An instruction to rewrite the TCP Maximum Segment Size (MSS) option (mss-clamping) to avoid TCP fragmentation. Given that the NAT44 table of the AFTR element is extended to include the source IPv6 address of incoming packets, the AFTR YANG module augments the NAT mapping-entry with the following: o b4-ipv6-address which is used to record the source IPv6 address of a packet received from a B4 element. This IPv6 address is required to disambiguate between the overlapping IPv4 address space of customers. o The value of the Traffic Class field in the IPv6 header as received from a B4 element (v6-dscp): This information is used to preserve DSCP marking when encapsulating/decapsulationg at the AFTR. Boucadair, et al. Expires April 12, 2018 [Page 5] Internet-Draft DS-Lite YANG October 2017 o The IPv4 DSCP marking of the IPv4 packet received from a B4 element (internal-v4-dscp): This information can be used by the AFTR fro enforcing the poi o The IPv4 DSCP marking as set by the AFTR in its external interface (external-v4-dscp): An AFTR can be instructed to preserve the same marking or to set it to another value when forwarding an IPv4 packet upstream. module: ietf-dslite-aftr augment /if:interfaces/if:interface: +--rw aftr-ipv6-address? inet:ipv6-address +--rw aftr-ipv4-address? inet:ipv4-address +--rw tunnel-mtu? uint16 +--rw max-softwire-per-subscriber? uint8 +--rw v6-v4-dscp-preservation? boolean augment /nat:nat-module/nat:nat-instances/nat:nat-instance/nat:nat-policy: +--rw state-migrate? boolean +--rw mss-clamping +--rw mss-clamping-enable? boolean +--rw mss-value? uint16 augment /nat:nat-module/nat:nat-instances/nat:nat-instance/nat:mapping-table/nat:mapping-entry: +--rw b4-ipv6-address? inet:ipv6-address +--rw v6-dscp? uint8 +--rw internal-v4-dscp? uint8 +--rw external-v4-dscp? uint8 Figure 2: YANG Module for DS-Lite AFTR Examples to illustrate the use of this module are provided in Appendix A. The B4 YANG module (Figure 3) augments the Interfaces YANG module with the following: o An IPv6 address used by a B4 element for sending and receiving IPv4-in-IPv6 packets (b4-ipv6-address). o The IPv6 address of the AFTR to use by a B4 element (aftr- ipv6-addr). o An IPv4 address that is used by a B4 element for troubleshooting purposes (b4-ipv4-address). o The tunnel MTU at the B4 side to avoid fragmentation (tunnel-mtu). Boucadair, et al. Expires April 12, 2018 [Page 6] Internet-Draft DS-Lite YANG October 2017 o An instruction whether DSCP marking is to preserved when encapsulating an IPv4 packet in an IPv6 packet (v6-v4-dscp- preservation). module: ietf-dslite-b4 augment /if:interfaces/if:interface: +--rw b4-ipv6-address? inet:ipv6-address +--rw aftr-ipv6-addr? inet:ipv6-address +--rw b4-ipv4-address? inet:ipv4-address +--rw tunnel-mtu? uint16 +--rw v6-v4-dscp-preservation? boolean Figure 3: YANG Module for DS-Lite B4 PCP-related considerations are out of scope of the document. A YANG module for PCP is documented in [I-D.boucadair-pcp-yang]. 3. DS-Lite AFTR YANG Module file "ietf-dslite-aftr@2017-10-09.yang" module ietf-dslite-aftr { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-dslite-aftr"; prefix dslite-aftr; import ietf-inet-types { prefix inet; } import ietf-interfaces { prefix if; } import iana-if-type { prefix ianaift; } import ietf-nat {prefix nat;} organization "Softwire Working Group"; contact "Mohamed Boucadair Christian Jacquenet Senthil Sivakumar "; description "This module is a YANG module for DS-Lite AFTR implementations. Copyright (c) 2017 IETF Trust and the persons identified as authors of the code. All rights reserved. Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Simplified BSD License Boucadair, et al. Expires April 12, 2018 [Page 7] Internet-Draft DS-Lite YANG October 2017 set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info). This version of this YANG module is part of RFC XXXX; see the RFC itself for full legal notices."; revision 2017-10-09 { description "Early yangdoctors review."; reference "-ietf-07"; } revision 2017-08-10 { description "The module augments also the Interface module."; reference "-ietf-04"; } revision 2017-07-27 { description "Redesign the module as an augment of the NAT YANG module."; reference "-ietf-04"; } revision 2017-07-03 { description "Fix some minor points."; reference "-ietf-03"; } revision 2017-01-03 { description "Fixed a compilation error: https://github.com/mbj4668/pyang/issues/296."; reference "-ietf-02"; } revision 2016-11-14 { description "Integrates the comments from Ian: add B4 module, add an MSS leaf, add more details about logging protocols, and other edits."; reference "-ietf-01"; } revision 2016-07-27 { description "-00 IETF version."; reference "-ietf-00"; } revision 2016-06-13 { description "Update the module."; reference "-04"; Boucadair, et al. Expires April 12, 2018 [Page 8] Internet-Draft DS-Lite YANG October 2017 } revision 2015-12-16 { description "Fix an error."; reference "-03"; } revision 2015-09-01 { description "Add port threshold notifications."; reference "-02"; } revision 2015-08-31 { description "Fix a timeout issue."; reference "-01"; } revision 2015-08-17 { description "First spec."; reference "-00"; } // Augment Interface module with DS-Lite Softwire augment "/if:interfaces/if:interface" { when "if:type = 'ianaift:tunnel'"; description "Augments Interface module with AFTR parameters. IANA interface types are maintained at this registery: https://www.iana.org/assignments/ianaiftype-mib/ianaiftype-mib. tunnel (131), -- Encapsulation interface"; leaf aftr-ipv6-address { type inet:ipv6-address; description "IPv6 address of the DS-Lite AFTR."; reference "RFC 6333."; } leaf aftr-ipv4-address { type inet:ipv4-address; default "192.0.0.1"; Boucadair, et al. Expires April 12, 2018 [Page 9] Internet-Draft DS-Lite YANG October 2017 description "IPv4 address of the DS-Lite AFTR. 192.0.0.1 is reserved for the AFTR element. This address can be used to report ICMP problems and will appear in traceroute outputs."; reference "RFC 6333."; } leaf tunnel-mtu { type uint16; description "Configures a tunnel MTU. [RFC6908] specifies that since fragmentation and reassembly is not optimal, the operator should do everything possible to eliminate the need for it. If the operator uses simple IPv4-in-IPv6 softwire, it is recommended that the MTU size of the IPv6 network between the B4 and the AFTR accounts for the additional overhead (40 bytes)."; reference "RFC 6908."; } leaf max-softwire-per-subscriber { type uint8; default 1; description "Configures the maximum softwires per subscriber feature. A subscriber is uniquely identified by means of subscriber-mask. This policy aims to prevent a misbehaving subscriber from mounting several DS-Lite softwires that would consume additional AFTR resources (e.g., get more external ports if the quota were enforced on a per-softwire basis, consume extra processing due to a large number Boucadair, et al. Expires April 12, 2018 [Page 10] Internet-Draft DS-Lite YANG October 2017 of active softwires)."; reference "Section 4 of RFC 7785."; } leaf v6-v4-dscp-preservation { type boolean; description "Copies the DSCP value from the IPv6 header and vice versa. According to Section 2.10 of [RFC6908], operators should use this model by provisioning the network such that the AFTR copies the DSCP value in the IPv4 header to the Traffic Class field in the IPv6 header, after the encapsulation for the downstream traffic."; reference "Section 2.10 of RFC 6908."; } } // Augment NAT module with AFTR parameters augment "/nat:nat-module/nat:nat-instances/"+ "nat:nat-instance/nat:nat-policy" { when "../nat:nat-capabilities/nat:nat-flavor = 'nat:nat44'"; description "Augments the NAT44 module with AFTR parameters."; leaf state-migrate { type boolean; default true; description "State migration is enabled by default. In the event a new IPv6 address is assigned to the B4 element, the AFTR should migrate existing state to be bound to the new IPv6 address. This operation ensures that traffic destined to the previous B4's IPv6 address will be redirected to the newer B4's IPv6 address. The destination IPv6 address for tunneling Boucadair, et al. Expires April 12, 2018 [Page 11] Internet-Draft DS-Lite YANG October 2017 return traffic from the AFTR should be the last seen as the B4's IPv6 source address from the CPE. The AFTR uses the subscriber-mask to determine whether two IPv6 addresses belong to the same CPE (e.g., if the subscriber-mask is set to 56, the AFTR concludes that 2001:db8:100:100::1 and 2001:db8:100:100::2 belong to the same CPE assigned with 2001:db8:100:100::/56)."; reference "RFC 7785."; } container mss-clamping { description "MSS rewriting configuration to avoid IPv6 fragmentation."; leaf mss-clamping-enable { type boolean; description "Enable/disable MSS rewriting feature."; } leaf mss-value { type uint16; units "octets"; description "Sets the MSS value to be used for MSS rewriting."; } } } // Augment NAT mapping entry: Extended NAT44 mapping Entry augment "/nat:nat-module/nat:nat-instances/nat:nat-instance/"+ "nat:mapping-table/nat:mapping-entry"{ when "../../nat:nat-capabilities/nat:nat-flavor = 'nat:nat44'"; description "Augments the NAT44 mapping table with DS-Lite specifics."; leaf b4-ipv6-address { Boucadair, et al. Expires April 12, 2018 [Page 12] Internet-Draft DS-Lite YANG October 2017 type inet:ipv6-address; description "Corresponds to the IPv6 address used by the B4 element."; reference "RFC 6333."; } leaf v6-dscp { type uint8; description "DSCP value used at the softwire level (i.e., IPv6 header)."; } leaf internal-v4-dscp { type uint8; description "DSCP value of the encapsulated IPv4 packet."; } leaf external-v4-dscp { type uint8; description "DSCP value of the translated IPv4 packet as marked by the AFTR."; } } } 4. DS-Lite B4 YANG Module file "ietf-dslite-b4@2017-10-09.yang" module ietf-dslite-b4 { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-dslite-b4"; prefix dslite-b4; import ietf-inet-types { prefix inet; } import ietf-interfaces { prefix if; } import iana-if-type { prefix ianaift; } Boucadair, et al. Expires April 12, 2018 [Page 13] Internet-Draft DS-Lite YANG October 2017 organization "Softwire Working Group"; contact "Mohamed Boucadair Christian Jacquenet Senthil Sivakumar "; description "This module is a YANG module for DS-Lite B4 implementations. Copyright (c) 2017 IETF Trust and the persons identified as authors of the code. All rights reserved. Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Simplified BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info). This version of this YANG module is part of RFC XXXX; see the RFC itself for full legal notices."; revision 2017-10-09 { description "Early yangdoctors review."; reference "-ietf-07"; } revision 2017-08-10 { description "Augment the interfaces YANG module."; reference "-ietf-05"; } revision 2017-07-27 { description "Separate B4 from AFTR."; reference "-ietf-04"; } // Augment Interface module with DS-Lite Softwire augment "/if:interfaces/if:interface" { when "if:type = 'ianaift:tunnel'"; description "Augments Interface module with B4 parameters. IANA interface types are maintained at this registry: https://www.iana.org/assignments/ianaiftype-mib/ianaiftype-mib. tunnel (131), -- Encapsulation interface"; Boucadair, et al. Expires April 12, 2018 [Page 14] Internet-Draft DS-Lite YANG October 2017 leaf b4-ipv6-address { type inet:ipv6-address; description "The IPv6 address used by the B4 element."; reference "RFC 6333."; } leaf aftr-ipv6-addr { type inet:ipv6-address; description "The AFTR's IPv6 address."; reference "RFC 6333."; } leaf b4-ipv4-address { type inet:ipv4-address; default "192.0.0.2"; description "IPv4 address of the DS-Lite B4. 192.0.0.0/29 is reserved for the B4 element. This address can be used to report ICMP problems and will appear in traceroute outputs."; reference "RFC 6333."; } leaf tunnel-mtu { type uint16; description "Configures a tunnel MTU. [RFC6908] specifies that since fragmentation and reassembly is not optimal, the operator should do everything possible to eliminate the need for it. If the operator uses simple IPv4-in-IPv6 softwire, it is recommended that the MTU size of the IPv6 network between the B4 and the AFTR Boucadair, et al. Expires April 12, 2018 [Page 15] Internet-Draft DS-Lite YANG October 2017 accounts for the additional overhead (40 bytes)."; reference "RFC 6908."; } leaf v6-v4-dscp-preservation { type boolean; description "Copies the DSCP value from the IPv6 header and vice versa. Operators should use this model by provisioning the network such that the AFTR copies the DSCP value in the IPv4 header to the Traffic Class field in the IPv6 header, after the encapsulation for the downstream traffic."; reference "Section 2.10 of RFC 6908."; } } } 5. Security Considerations The YANG module defined in this memo is designed to be accessed via the NETCONF protocol [RFC6241]. The lowest NETCONF layer is the secure transport layer and the support of SSH is mandatory to implement secure transport [RFC6242]. The NETCONF access control model [RFC6536] provides means to restrict access for particular NETCONF users to a pre-configured subset of all available NETCONF protocol operations and contents. All data nodes defined in the YANG module which can be created, modified and deleted (i.e., config true, which is the default). These data nodes are considered sensitive. Write operations (e.g., edit-config) applied to these data nodes without proper protection can negatively affect network operations. 6. IANA Considerations This document requests IANA to register the following URIs in the "IETF XML Registry" [RFC3688]: Boucadair, et al. Expires April 12, 2018 [Page 16] Internet-Draft DS-Lite YANG October 2017 URI: urn:ietf:params:xml:ns:yang:ietf-dslite-aftr Registrant Contact: The IESG. XML: N/A; the requested URI is an XML namespace. URI: urn:ietf:params:xml:ns:yang:ietf-dslite-b4 Registrant Contact: The IESG. XML: N/A; the requested URI is an XML namespace. This document requests IANA to register the following YANG modules in the "YANG Module Names" registry [RFC7950]. name: ietf-dslite-aftr namespace: urn:ietf:params:xml:ns:yang:ietf-dslite-aftr prefix: dslite-aftr reference: RFC XXXX name: ietf-dslite-b4 namespace: urn:ietf:params:xml:ns:yang:ietf-dslite-b4 prefix: dslite-b4 reference: RFC XXXX 7. Acknowledgements Thanks to Q. Wu for identifying a compiling error. Mahesh Jethanandani provided an eraly ynagdoctors review; many thanks to him. Many thanks to Ian Farrer for the review and comments 8. References 8.1. Normative references [I-D.ietf-opsawg-nat-yang] Boucadair, M., Sivakumar, S., Jacquenet, C., Vinapamula, S., and Q. Wu, "A YANG Data Model for Network Address Translation (NAT) and Network Prefix Translation (NPT)", draft-ietf-opsawg-nat-yang-05 (work in progress), October 2017. [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004, . Boucadair, et al. Expires April 12, 2018 [Page 17] Internet-Draft DS-Lite YANG October 2017 [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., and A. Bierman, Ed., "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, . [RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011, . [RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual- Stack Lite Broadband Deployments Following IPv4 Exhaustion", RFC 6333, DOI 10.17487/RFC6333, August 2011, . [RFC6536] Bierman, A. and M. Bjorklund, "Network Configuration Protocol (NETCONF) Access Control Model", RFC 6536, DOI 10.17487/RFC6536, March 2012, . [RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types", RFC 6991, DOI 10.17487/RFC6991, July 2013, . [RFC7223] Bjorklund, M., "A YANG Data Model for Interface Management", RFC 7223, DOI 10.17487/RFC7223, May 2014, . [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016, . 8.2. Informative references [I-D.boucadair-pcp-yang] Boucadair, M., Jacquenet, C., Sivakumar, S., and S. Vinapamula, "YANG Data Models for the Port Control Protocol (PCP)", draft-boucadair-pcp-yang-04 (work in progress), May 2017. [I-D.ietf-netmod-yang-tree-diagrams] Bjorklund, M. and L. Berger, "YANG Tree Diagrams", draft- ietf-netmod-yang-tree-diagrams-01 (work in progress), June 2017. [RFC6087] Bierman, A., "Guidelines for Authors and Reviewers of YANG Data Model Documents", RFC 6087, DOI 10.17487/RFC6087, January 2011, . Boucadair, et al. Expires April 12, 2018 [Page 18] Internet-Draft DS-Lite YANG October 2017 [RFC6908] Lee, Y., Maglione, R., Williams, C., Jacquenet, C., and M. Boucadair, "Deployment Considerations for Dual-Stack Lite", RFC 6908, DOI 10.17487/RFC6908, March 2013, . [RFC7785] Vinapamula, S. and M. Boucadair, "Recommendations for Prefix Binding in the Context of Softwire Dual-Stack Lite", RFC 7785, DOI 10.17487/RFC7785, February 2016, . Boucadair, et al. Expires April 12, 2018 [Page 19] Internet-Draft DS-Lite YANG October 2017 Appendix A. Examples The following example shows an AFTR that is reachable at 2001:db8::2. Also, this XML snippet indicates that the AFTR is provided with an IPv4 address (192.0.0.1) to be used for troubleshooting purposes such as reporting problems to B4s. Moreover, the AFTR is instructed to limit the number of softwires per subscriber to '1'. myAFTR ianaift:tunnel true 2001:db8::2 192.0.0.1 1 The following shows an XML excerpt depicting a dynamic UDP mapping entry maintained by a DS-Lite AFTR. In reference to this example, the UDP packet received with a source IPv6 address (2001:db8::1), a source IPv4 address (192.0.2.1) and source port number (1568) is translated into a UDP packet having a source IPv4 address (198.51.100.1) and source port (15000). The lifetime of this mapping is 300 seconds. Boucadair, et al. Expires April 12, 2018 [Page 20] Internet-Draft DS-Lite YANG October 2017 15 dynamic-explicit 17 2001:db8::1 192.0.2.1 1568 198.51.100.1 15000 300 Authors' Addresses Mohamed Boucadair Orange Rennes 35000 France EMail: mohamed.boucadair@orange.com Christian Jacquenet Orange Rennes 35000 France EMail: christian.jacquenet@orange.com Boucadair, et al. Expires April 12, 2018 [Page 21] Internet-Draft DS-Lite YANG October 2017 Senthil Sivakumar Cisco Systems 7100-8 Kit Creek Road Research Triangle Park, North Carolina 27709 USA Phone: +1 919 392 5158 EMail: ssenthil@cisco.com Boucadair, et al. Expires April 12, 2018 [Page 22]