YANG Data Models for the DS-Lite
draft-ietf-softwire-dslite-yang-04

Abstract

This document defines a YANG data model 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 http://datatracker.ietf.org/drafts/current/.

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This Internet-Draft will expire on February 3, 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 (http://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.

Table of Contents

• 1. Introduction
• 1.1. Terminology
• 1.2. Tree Diagrams
• 2. DS-Lite YANG Data Models
• 3. DS-Lite AFTR YANG Module
• 4. DS-Lite B4 YANG Module
• 5. Security Considerations
• 6. IANA Considerations
• 7. Acknowledgements
• 8. References
• 8.1. Normative references
• 8.2. Informative references
• Authors' Addresses

1. Introduction

This document defines a data model for DS-Lite [RFC6333], using the YANG data modeling language [RFC6020]. Both the Address Family Transition Router (AFTR) and Basic Bridging BroadBand (B4) elements are covered by this specification.

DS-Lite deployment considerations are discussed in [RFC6908].

This document follows the guidelines of [RFC6087].

This document uses the common YANG types defined in [RFC6991].

1.1. Terminology

This document makes use of the terms defined in [RFC6333].

The terminology for describing YANG data models is defined in [RFC6020].

1.2. Tree Diagrams

The meaning of the symbols in these diagrams is as follows:

• Brackets "[" and "]" enclose list keys.
• Curly braces "{" and "}" contain names of optional features that make the corresponding node conditional.
• Abbreviations before data node names: "rw" means configuration (read-write), "ro" state data (read-only).
• Symbols after data node names: "?" means an optional node, "!" a container with presence, and "*" denotes a "list" or "leaf-list".
• Parentheses enclose choice and case nodes, and case nodes are also marked with a colon (":").
• Ellipsis ("...") stands for contents of subtrees that are not shown.

2. DS-Lite YANG Data Models

Figure 1 depicts the YANG data model for the AFTR, while Figure 2 shows the YANG data model for the B4 element.

The AFTR model supports enabling one or more instances of the AFTR function on a device; each instance is responsible for serving a group of B4s. The data model assumes that each AFTR instance can: be enable/disabled, be provisioned with dedicated configuration data, and maintain its own mapping table. The data model assumes that pools of IPv4 addresses can be provisioned to the AFTR. The AFTR module augments the NAT module in [I-D.sivakumar-yang-nat].

As such, this document assumes [RFC4787][RFC5382][RFC5508] are enabled by default. Also, the data model adheres to the recommendations in [RFC6888] and [RFC7857]. Further, the data model supports state migration as per [RFC7785].

PCP-related considerations are out of scope of the document. A YANG data model for PCP is documented in [I-D.boucadair-pcp-yang].

module: ietf-dslite-aftr
  augment /nat:nat-module/nat:nat-instances/nat:nat-instance:
    +--rw ipv6-address?                  inet:ipv6-address
    +--rw ipv4-address?                  inet:ipv4-address
    +--rw tunnel-mtu?                    uint16
    +--rw subscriber-mask?               uint8
    +--rw state-migrate?                 boolean
    +--rw max-softwire-per-subscriber?   uint8
    +--rw mss-clamping
    |  +--rw mss-clamping-enable?   boolean
    |  +--rw mss-value?             uint16
    +--rw v6-v4-dscp-preservation?       boolean
  augment /nat:nat-module/nat:nat-instances/nat:nat-instance/nat:mapping-table/nat:mapping-entry:
    +--rw b4-ip-address?      inet:ipv6-address
    +--rw v6-dscp?            uint8
    +--rw internal-v4-dscp?   uint8
    +--rw external-v4-dscp?   uint8

Figure 1: YANG Data Model for DS-Lite AFTR

module: ietf-dslite-b4
    +--rw dslite-b4
       +--rw enable?                boolean
       +--rw dslite-b4-instances
          +--rw dslite-b4-instance* [id]
             +--rw id                         uint32
             +--rw name?                      string
             +--rw aftr-ipv6-addr             inet:ipv6-address
             +--rw ipv4-address?              inet:ipv4-address
             +--rw tunnel-mtu?                uint16
             +--rw v6-v4-dscp-preservation    boolean

Figure 2: YANG Data Model for DS-Lite B4

3. DS-Lite AFTR YANG Module

<CODE BEGINS> file "ietf-dslite-aftr@2017-07-27.yang"

module ietf-dslite-aftr {
    namespace "urn:ietf:params:xml:ns:yang:ietf-dslite-aftr";
    prefix dslite-aftr;
    
    import ietf-inet-types { prefix inet; }
 
    import ietf-nat {
       prefix nat;
     }
    
    organization "Softwire Working Group";
    contact 
     "Mohamed Boucadair <mohamed.boucadair@orange.com>
      Christian Jacquenet <christian.jacquenet@orange.com>
      Senthil Sivakumar <ssenthil@cisco.com>";

   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
      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 2017-07-27 {
      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";
    }

    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 NAT module with AFTR parameters

augment "/nat:nat-module/nat:nat-instances/nat:nat-instance" {
   description 
        "Augments NAT module with AFTR parameters."; 
        
   leaf ipv6-address {
           type inet:ipv6-address;
           description 
             "IPv6 address of the dslite-aftr.";

           reference
              "RFC 6333."; 
        }
    
    leaf ipv4-address {
        type inet:ipv4-address;
        default "192.0.0.1";
        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 subscriber-mask {
        type uint8 {
            range "0 .. 128";
            }
        default "56";
        description 
            "The subscriber-mask is an integer that indicates
             the length of significant bits to be applied on 
             the source IPv6 address (internal side) to 
             unambiguously identify a CPE.
    
             Subscriber-mask is a system-wide configuration
             parameter that is used to enforce generic 
             per-subscriber policies (e.g., port-quota).
    
             The enforcement of these generic policies does not  
             require the configuration of every subscriber's prefix.
    
             Example: suppose the 2001:db8:100:100::/56 prefix is
             assigned to a DS-Lite enabled CPE. Suppose also that the
             2001:db8:100:100::1 is the IPv6 address used by the
             B4 that resides in that CPE. When the AFTR
             receives a packet from this client, 
             it applies the subscriber-mask (e.g., 56) on 
             the source IPv6 address to compute the associated prefix
             for this client (that is 2001:db8:100:100::/56).  Then, 
             the AFTR enforces policies based on that prefix 
             (2001:db8:100:100::/56), not on the exact 
             source IPv6 address";

        reference
          "RFC 7785."; 
    } 
  
    leaf state-migrate {
        type boolean;
        default true;
        description 
            "State migration is enabled by default.";

        reference
          "RFC 7785."; 
    } 
     
    leaf max-softwire-per-subscriber {
        type uint8;
        default 1;
        description 
         "Configures the maximum softwire 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
        of active softwires).";

        reference
          "Section 4 of RFC 7785."; 
    } 
      
    container mss-clamping {
        description 
          "MSS rewriting configuration.";

        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.";
        }
     }
   
    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 mapping entry:  Extended NAT44 mapping Entry

augment "/nat:nat-module/nat:nat-instances/nat:nat-instance/nat:mapping-table/nat:mapping-entry"{
   description
     "Augments the NAT mapping table with DS-Lite specifics.";

    leaf b4-ip-address {
        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."; 
   }
 }
}
<CODE ENDS>

4. DS-Lite B4 YANG Module

<CODE BEGINS> file "ietf-dslite-b4@2017-07-27.yang"

module ietf-dslite-b4 {
    namespace "urn:ietf:params:xml:ns:yang:ietf-dslite-b4";
    prefix dslite-b4;
    
    import ietf-inet-types { prefix inet; }
    
    organization "Softwire Working Group";
    contact 
     "Mohamed Boucadair <mohamed.boucadair@orange.com>
      Christian Jacquenet <christian.jacquenet@orange.com>
      Senthil Sivakumar <ssenthil@cisco.com>";

   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 2017-07-27 {
      description "Separate B4 from AFTR.";
       reference "-ietf-04";
    }

container dslite-b4 {

    description
     "dslite-b4";

    leaf enable {
        type boolean;
        description
         "Enable/disable dslite-b4 function.";
    }

    container dslite-b4-instances {
       description
         "dslite-b4 instances";

        list dslite-b4-instance {
            key "id";
              description
                "a dslite-b4 instance.";
                
           leaf id {
              type uint32;
              description 
                "dslite-b4 instance identifier.";
           }

           leaf name {
              type string;
              description 
                "A name associated with the dslite-b4 instance.";
           }

          leaf aftr-ipv6-addr {
              type inet:ipv6-address;
              mandatory true;
              description
                 "The AFTR's IPv6 address.";

              reference
                 "RFC 6333."; 
           }

    leaf 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
          [RFC6333].
          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 v6-v4-dscp-preservation {
        type boolean;
        mandatory true;
        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.";
    }
    }
  }
 }
}
<CODE ENDS>

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

         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.

         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

This document requests IANA to register the following URIs in the "IETF XML Registry" [RFC3688]: [RFC6020].

7. Acknowledgements

Thanks to Q. Wu for identifying a compiling error.

Many thanks to Ian Farrer for the review and comments.

8. References

8.1. Normative references

8.2. Informative references

Authors' Addresses