A YANG Data Model for IPv4-in-IPv6 Softwires

The IETF Softwire Working Group has developed several IPv4-in-IPv6 Softwire mechanisms to address various deployment contexts and constraints. As a companion to the architectural specification documents, this document focuses on the provisioning of A+P softwire functional elements: Border Routers (BRs) and Customer Premises Equipment (CEs). This document defines a YANG data model that can be used to configure and manage A+P Softwire elements using the NETCONF protocol . DS-Lite YANG data model is defined in . The Softwire YANG model is structured into two sub-models: Lightweight 4over6 MAP-E and MAP-T (combined due to their common configuration parameters). Two root containers are defined: Container "softwire-config" holds the collection of YANG definitions common to all Softwire element configuration. Container "softwire-state" holds YANG definitions for the operational state of the Softwire elements. A NETCONF notify module is also included. This approach has been taken so that the model can be easily extended to support additional Softwire mechanisms, if required.

The reader should be familiar with the concepts and terms defined in , , , and the YANG data modelling language .

The meaning of the symbols in these diagrams are as follows: Brackets "[" and "]" enclose list keys. Braces "{" and "}" enclose feature content. Parentheses "(" and ")" enclose choice and case nodes, and case nodes are also marked with a colon (":"). Symbols after data node names: "?" means an optional node, and "*" denotes a list and leaf-list. Abbreviations before data node names: "rw" means configuration data (read-write), and "ro" means state data (read-only).

The model does not include CPE NAT-specific provisioning parameters that may be used for IPv4 address sharing other than the external IP address and port set which a softwire client may use for NAT44. NAT-specific considerations are out of scope of this document. A YANG model for the configuration and management of NAT gateways is described in .

The following sections of the document are structured with the root of the Softwire YANG model (common to all mechanisms) described first. Subsequent sections describe the models relevant to the different softwire mechanisms. All functions are listed, but the YANG models use the "feature" statement to distinguish among the different softwire mechanisms. This document defines a new module named "ietf-softwire" for Softwire data models such that this module auments "ietf-ipv6-unicast-routing" module that is defined in .

Lightweight 4over6 (binding) includes two elements: lwAFTR (BR) and lwB4 (CE). The lwAFTR holds configuration for IPv4-IPv6 address bindings which are used for the forwarding of traffic originating from lwB4s. The lwB4 is configured with the relevant parameters for establishing the IPv4-in-IPv6 tunnel including an IPv6 address for the lwAFTR and the IPv4 configuration for NAT44.

MAP-E and MAP-T elements are provisioned with the MAP rules necessary for defining MAP domains and forwarding rules. For MAP-T CEs, an additional "ipv6-prefix" parameter is also included. Note that when referring to MAP-E/T (algorithm), the CE and BR shares the same model for configuration and management.

describes the high level softwire YANG data model and the way tree is organized is common to all of the different softwire mechanisms listed in :

defines the softwire data model for lw4o6 (softwire binding mode) which includes lwAFTR (BR) and lwB4 (CE):

The data model assumes that each CE/BR instance can: be enable/disabled, be provisioned with a dedicated configuration data, and maintain its own binding table. Additional information on some of the important lwAFTR nodes is provided below: binding-table-versioning: optionally used to add a incremental version number and/or timestamp to the binding table. This can be used for logging/data retention purposes. The version number is incremented and a new timestamp value written whenever a change is made to the contents of the binding table or a new binding table list is created. binding-entry: used to define the binding relationship between 3-tuples, which contains the lwB4's IPv6 address/prefix, the allocated IPv4 address and restricted port-set. For detail information, please refer to . tunnel-payload-mtu: used to set the IPv4 MTU for the lw4o6 tunnel. tunnel-path-mru: used to set the maximum lw4o6 IPv6 encapsulating packet size that can be received. psid-offset: used to set the number of offset bits. psid-len: defines the number of ports that will be allocated for the softwire. psid: used to identify the set of ports allocated for a specific softwire. tunnel-num-threshold: used to set the maximum number of tunnels that can be created on the lw4o6 device simultaneously. active-tunnel-num (ro): used to present the number of tunnels currently provisioned on the device. active (ro): used to show the status of particular binding-entry. Additional information on some of the important lwB4 nodes is provided below: b4-ipv6-addr-format: indicates the format of lwB4 IPv6 address. If set to true, it indicates that the IPv6 source address of the lwB4 is constructed according to the description in Section 6 of ; if set to false, the lwB4 can use any /128 address from the assigned IPv6 prefix. binding-ipv6info: used to set the IPv6 address type which is combined in a binding entry, for a complete address or a prefix.

defines the softwire data model for MAP-E and MAP-T:

Additional information on some of the important MAP-E and MAP-T nodes is provided below: algo-versioning: optionally used to add a incremental version number and/or timestamp to the algorithm. This can be used for logging/data retention purposes. The version number is incremented and a new timestamp value written whenever a change is made to the algorithm or a new instance is created. forwarding: specifies whether the rule can be used as a Forward Mapping Rule (FMR). If not set, this rule is a Basic Mapping Rule (BMR) only and must not be used for forwarding. See Section 4.1 of . ea-len: used to set the length of the Embedded-Address (EA), which defined in the mapping rule for a MAP domain. dmr-ipv6-prefix: defines the Default Mapping Rule (DMR) for MAP-T. This parameter is optional when configuring a MAP-T BR. stat-count (ro): use to show the numbers of packets and bytes information of specific device respectively.

This section describes the tree structure for notifications. These notifications pertain to the configuration and monitoring portions of the specific Softwire mechanisms. The logic is that the softwire instance notifies the NETCONF client with the index for a mapping entry and the NETCONF client retrieves the related information from the operational datastore of that instance.

/softwire-state/binding/br/.../id | +--ro invalid-entry* -> /softwire-config/binding/br/.../binding-table/binding-entry/binding-ipv6info | +--ro added-entry* inet:ipv6-address | +--ro modified-entry* -> /softwire-config/binding/br/.../binding-table/binding-entry/binding-ipv6info +---n softwire-binding-ce-event {binding,ce}? | +--ro ce-binding-ipv6-addr-change inet:ipv6-address +---n softwire-algorithm-instance-event {algorithm}? +--ro algo-id -> /softwire-config/algorithm/.../id +--ro invalid-entry* -> /softwire-config/algorithm/.../id +--ro added-entry* -> /softwire-config/algorithm/.../id +--ro modified-entry* -> /softwire-config/algorithm/.../id ]]> Additional information on some of the important notification nodes is listed below: invalid-entry, added-entry, modified-entry: used to notify the client that a specific binding entry or MAP rule is expired or invalidated, added, or modified. ce-binding-ipv6-addr-change: used to notify that the lwB4's binding-ipv6-address has been changed or the value of the 'b4-ipv6-addr-format' is "False".

This module imports typedefs from .

file "ietf-softwire@2016-06-04.yang" module ietf-softwire { namespace "urn:ietf:params:xml:ns:yang:ietf-softwire"; prefix "softwire"; import ietf-inet-types {prefix inet; } import ietf-yang-types {prefix yang; } organization "Softwire Working Group"; contact " Qi Sun Hao Wang Yong Cui Ian Sladjana Zoric Mohamed Boucadair Rajiv "; description "This document defines a YANG data model for the configuration and management of A+P Softwire Border Routers (BRs) and Customer Premises Equipment (CEs). It covers Lightweight 4over6, MAP-E and MAP-T mechanisms. Copyright (c) 2016 IETF Trust and the persons identified as authors of the code. All rights reserved. This version of this YANG module is part of RFC XXX; see the RFC itself for full legal notices."; revision 2016-06-04 { description "Version-05: Combined MAP-E/MAP-T into a single tree. Added binding table/alogorthm versioning"; reference "-05"; } revision 2015-09-30 { description "Version-04: Fix YANG syntax; Add flags to map-rule; Remove the map-rule-type element. "; reference "-04"; } revision 2015-04-07 { description "Version-03: Integrate lw4over6; Updata state nodes; Correct grammar errors; Reuse groupings; Update descriptions. Simplify the model."; reference "-03"; } revision 2015-02-10 { description "Version-02: Add notifications."; reference "-02"; } revision 2015-02-06 { description "Version-01: Correct grammar errors; Reuse groupings; Update descriptions."; reference "-01"; } revision 2015-02-02 { description "Initial revision."; reference "-00"; } /* * Features */ feature binding { description "Lightweight 4over6 (binding) is an IPv4-over-IPv6 tunnelling transition mechanism. Lightweight 4over6 is a solution designed specifically for complete independence between IPv6 subnet prefix (and /128 IPv6 address) and IPv4 address with or without IPv4 address sharing. This is accomplished by maintaining state for each softwire (per-subscriber state) in the central lwAFTR and a hub-and-spoke forwarding architecture. In order to delegate the NAPT function and achieve IPv4 address sharing, port-restricted IPv4 addresses needs to be allocated to CEs. Besides lw4o6, this feature also covers MAP in 1:1 mode (offset=0, PSID explicit)"; reference "RFC7596"; } feature br { if-feature binding; description "The AFTR for Lightweight 4over6, so-called lwAFTR (BR). This feature indicates that a instance functions as a lwAFTR (BR). A lwAFTR (BR) is an IPv4-in-IPv6 tunnel concentrator that maintains per-subscriber IPv4-IPv6 address binding."; } feature ce { if-feature binding; description "The B4 for Lightweight 4over6, so-called lwB4 (CE). This feature indicates that a instance functions as a lwB4 (CE). A lwB4 (ce) is an IPv4-in-IPv6 tunnel initiator. It is dual-stack capable node, either a directly connected end-host or a CE. It sources IPv4 connections using the configured port-set and the public IPv4 address."; } feature algorithm { description "MAP-E is an IPv6 transition mechanism for transporting IPv4 packets across an IPv6 network using IP encapsulation. MAP-E allows for a reduction of the amount of centralized state using rules to express IPv4/IPv6 address mappings. This introduces an algorithmic relationship between the IPv6 subnet and IPv4 address. The Mapping of Address and Port - Translation (MAP-T) architecture is a double stateless NAT64 based solution. It uses the stateless algorithmic address & transport layer port mapping scheme defined in MAP-E. The MAP-T solution differs from MAP-E in the use of IPv4-IPv6 translation, rather than encapsulation, as the form of IPv6 domain transport. This feature indicates the instance functions as a MAP-E or MAP-T instance."; reference "RFC7597 & RFC7599"; } /* * Grouping */ grouping port-set { description "Use the PSID algorithm to represent a range of transport layer ports."; leaf psid-offset { type uint8 { range 0..16; } mandatory true; description "The number of offset bits. In Lightweight 4over6, the default value is 0 for assigning one contiguous port range. In MAP-E/T, the default value is 6, which excludes system ports by default and assigns distributed port ranges. If the this parameter is larger than 0, the value of offset MUST be greater than 0."; } leaf psid-len { type uint8 { range 0..15; } mandatory true; description "The length of PSID, representing the sharing ratio for an IPv4 address."; } leaf psid { type uint16; mandatory true; description "Port Set Identifier (PSID) value, which identifies a set of ports algorithmically."; } } grouping binding-entry { description "The lwAFTR maintains an address binding table that contains the binding between the lwB4's IPv6 address, the allocated IPv4 address and restricted port-set."; leaf binding-ipv6info { type union { type inet:ipv6-address; type inet:ipv6-prefix; } mandatory true; description "The IPv6 information for a binding entry. If it's an IPv6 prefix, it indicates that the IPv6 source address of the lwB4 is constructed according to the description in RFC7596; if it's an IPv6 address, it means the lwB4 uses any /128 address from the assigned IPv6 prefix. "; } leaf binding-ipv4-addr { type inet:ipv4-address; mandatory true; description "The IPv4 address assigned to the lwB4, which is used as the IPv4 external address for lwB4 local NAPT44."; } container port-set { description "For Lightweight 4over6, the default value of offset should be 0, to configure one contiguous port range."; uses port-set { refine psid-offset { default "0"; } } } leaf br-ipv6-addr { type inet:ipv6-address; mandatory true; description "The IPv6 address for lwaftr."; } leaf lifetime { type uint32; units seconds; description "The lifetime for the binding entry"; } } /* grouping nat-table { description "Grouping 'nat-table' is not extended. The current mechanism is focusing on the provisioning of external IP address and port set; other NAT-specific considerations are out of scope."; } */ grouping traffic-stat { description "Traffic statistics"; leaf sentPacket { type yang:zero-based-counter64; description "Number of packets sent."; } leaf sentByte { type yang:zero-based-counter64; description "Traffic sent, in bytes"; } leaf rcvdPacket { type yang:zero-based-counter64; description "Number of packets received."; } leaf rcvdByte { type yang:zero-based-counter64; description "Traffic received, in bytes"; } leaf droppedPacket { type yang:zero-based-counter64; description "Number of packets dropped."; } leaf droppedByte { type yang:zero-based-counter64; description "Traffic dropped, in bytes"; } } /* * Configuration Data Nodes */ container softwire-config { description "The configuration data for Softwire instances. And the shared data describes the softwire data model which is common to all of the different softwire mechanisms, such as description."; leaf description { type string; description "A textual description of Softwire."; } container binding { if-feature binding; description "lw4over6 (binding) configuration."; container br { if-feature br; description "Indicate this instance supports the lwAFTR (BR) function. The instances advertise the BR feature through the capability exchange mechanism when a NETCONF session is established."; leaf enable { type boolean; description "Enable/disable the lwAFTR (BR) function."; } container br-instances { description "A set of BRs to be configured."; list br-instance { key "id"; description "A set of lwAFTRs to be configured."; container binding-table-version { description "binding table's version"; leaf binding-table-version{ type uint64; description "Incremental version number to the binding table"; } leaf binding-table-date { type yang:date-and-time; description "Timestamp to the binding table"; } } leaf id { type uint32; mandatory true; description "An instance identifier."; } leaf name { type string; description "The name for the lwaftr."; } leaf softwire-num-threshold { type uint32; mandatory true; description "The maximum number of tunnels that can be created on the lwAFTR."; } leaf tunnel-payload-mtu { type uint16; mandatory true; description "The payload MTU for Lightweight 4over6 tunnel."; } leaf tunnel-path-mru { type uint16; mandatory true; description "The path MRU for Lightweight 4over6 tunnel."; } container binding-table { description "binding table"; list binding-entry { key "binding-ipv6info"; description "binding entry"; uses binding-entry; } } } } } container ce { if-feature ce; description "Indicate this instance supports the lwB4 (CE) function. The instances advertise the CE feature through the capability exchange mechanism when a NETCONF session is established."; leaf enable { type boolean; description "Enable/disable the lwB4 (CE) function."; } container ce-instances { description "A set of CEs to be configured."; list ce-instance { key "binding-ipv6info"; description "instances for CE"; leaf name { type string; description "The CE's name."; } leaf tunnel-payload-mtu { type uint16; mandatory true; description "The payload MTU for Lightweight 4over6 tunnel."; } leaf tunnel-path-mru { type uint16; mandatory true; description "The path MRU for Lightweight 4over6 tunnel."; } leaf b4-ipv6-addr-format { type boolean; mandatory true; description "The format of lwB4 (CE) IPv6 address. If set to true, it indicates that the IPv6 source address of the lwB4 is constructed according to the description in [RFC7596]; if set to false, the lwB4 (CE) can use any /128 address from the assigned IPv6 prefix."; } uses binding-entry; } } } } container algorithm { if-feature algorithm; description "Indicate the instances support the MAP-E and MAP-T function. The instances advertise the map-e feature through the capability exchange mechanism when a NETCONF session is established."; leaf enable { type boolean; description "Enable/disable the MAP-E or MAP-T function."; } container algo-instances { description "A set of MAP-E or MAP-T instances to be configured, applying to BRs and CEs. A MAP-E/T instance defines a MAP domain comprising one or more MAP-CE and MAP-BR"; list algo-instance { key "id"; description "instance for MAP-E/MAP-T"; container algo-versioning { description "algorithm's version"; leaf algo-version { type uint64; description "Incremental version number to the algorithm"; } leaf algo-date { type yang:date-and-time; description "Timestamp to the algorithm"; } } leaf id { type uint32; mandatory true; description "Algorithm Instance ID"; } leaf name { type string; description "The name for the instance."; } leaf data-plane { type enumeration { enum "encapsulation" { description "encapsulation for MAP-E"; } enum "translation" { description "translation for MAP-T"; } } description "Encapsulation is for MAP-E while translation is for MAP-T"; } leaf ea-len { type uint8; mandatory true; description "Embedded Address (EA) bits are the IPv4 EA-bits in the IPv6 address identify an IPv4 prefix/address (or part thereof) or a shared IPv4 address (or part thereof) and a port-set identifier. The length of the EA-bits is defined as part of a MAP rule for a MAP domain."; } leaf rule-ipv6-prefix { type inet:ipv6-prefix; mandatory true; description "The Rule IPv6 prefix defined in the mapping rule."; } leaf rule-ipv4-prefix { type inet:ipv4-prefix; mandatory true; description "The Rule IPv4 prefix defined in the mapping rule."; } leaf forwarding { type boolean; mandatory true; description "This parameter specifies whether the rule may be used for forwarding (FMR). If set, this rule is used as an FMR; if not set, this rule is a BMR only and must not be used for forwarding."; } leaf psid-offset { type uint8 { range 0..16; } mandatory true; description "The number of offset bits. In Lightweight 4over6, the default value is 0 for assigning one contiguous port range. In MAP-E/T, the default value is 6, which excludes system ports by default and assigns distributed port ranges. If the this parameter is larger than 0, the value of offset MUST be greater than 0."; } leaf psid-len { type uint8 { range 0..15; } mandatory true; description "The length of PSID, representing the sharing ratio for an IPv4 address."; } leaf tunnel-payload-mtu { type uint16; description "The payload MTU for MAP-E tunnel."; } leaf tunnel-path-mru { type uint16; description "The path MRU for MAP-E tunnel."; } leaf br-ipv6-addr { type inet:ipv6-address; mandatory true; description "The IPv6 address of the MAP-E BR."; } leaf dmr-ipv6-prefix { type inet:ipv6-prefix; description "The IPv6 prefix of the MAP-T BR. "; } } } } } /* * Operational state Data Nodes */ container softwire-state { config false; description "The operational state data for Softwire instances. "; leaf description { type string; description "A textual description of the softwire instances."; } container binding { if-feature binding; description "lw4over6 (binding) state."; container br { if-feature br; config false; description "Indicate this instance supports the lwAFTR (BR) function. The instances advertise the lwaftr (BR) feature through the capability exchange mechanism when a NETCONF session is established."; container br-instances { description "A set of BRs."; list br-instance { key "id"; description "instances for BR"; leaf id { type uint32; mandatory true; description "id"; } leaf name { type string; description "The name for this lwaftr."; } uses traffic-stat; leaf active-softwire-num { type uint32; description "The number of currently active tunnels on the lw4over6 (binding) instance."; } container binding-table { description "id"; list binding-entry { key "binding-ipv6info"; description "An identifier of the binding entry."; leaf binding-ipv6info { type union { type inet:ipv6-address; type inet:ipv6-prefix; } mandatory true; description "The IPv6 information used to identify a binding entry. "; } leaf active { type boolean; description "Status of a specific tunnel."; } } } } } } container ce { if-feature ce; config false; description "Indicate this instance supports the lwB4 (CE) function. The instances advertise the lwb4 (CE) feature through the capability exchange mechanism when a NETCONF session is established."; container ce-instances { description "Status of the configured CEs."; list ce-instance { key "binding-ipv6info"; description "a lwB4 (CE) instance."; leaf name { type string; description "The CE's name."; } leaf binding-ipv6info { type union { type inet:ipv6-address; type inet:ipv6-prefix; } mandatory true; description "The IPv6 information used to identify a binding entry. "; } uses traffic-stat; } } } } container algorithm { if-feature algorithm; config false; description "Indicate the instances support the MAP-E and MAP-T function. The instances advertise the map-e/map-t feature through the capability exchange mechanism when a NETCONF session is established."; container algo-instances { description "Status of MAP-E instance(s)."; list algo-instance { key "id"; description "Instances for algorithm"; leaf id { type uint32; mandatory true; description "id"; } leaf name { type string; description "The map-e instance name."; } uses traffic-stat; } } } } /* * Notifications */ notification softwire-br-event { if-feature binding; if-feature br; description "Notification for BR."; leaf br-id { type leafref { path "/softwire-state/binding/br/br-instances/" + "br-instance/id"; } description "..."; } leaf-list invalid-entry { type leafref { path "/softwire-config/binding/br/br-instances/" + "br-instance[id=current()/../br-id]/" + "binding-table/binding-entry/binding-ipv6info"; } description "Notify the client that a specific binding entry has been expired/invalid. The binding-ipv6info identifies an entry."; } leaf-list added-entry { type inet:ipv6-address; description "Notify the client that a binding entry has been added. The ipv6 address of that entry is the index. The client get other information from the lwaftr about the entry indexed by that ipv6 address. "; } leaf-list modified-entry { type leafref { path "/softwire-config/binding/br/br-instances/" + "br-instance[id=current()/../br-id]/" + "binding-table/binding-entry/binding-ipv6info"; } description "..."; } } notification softwire-ce-event { if-feature binding; if-feature ce; description "CE notification"; leaf ce-binding-ipv6-addr-change { type inet:ipv6-address; mandatory true; description "The source tunnel IPv6 address of the lwB4. If 'b4-ipv6-addr-format' is false, or the lwb4's binding-ipv6-address changes for any reason, it SHOULD notify the NETCONF client."; } } notification softwire-algorithm-instance-event { if-feature algorithm; description "Notifications for MAP-E or MAP-T."; leaf algo-id { type leafref { path "/softwire-config/algorithm/algo-instances/algo-instance/id"; } mandatory true; description "MAP-E or MAP-T event."; } leaf-list invalid-entry-id { type leafref { path "/softwire-config/algorithm/algo-instances/algo-instance/id"; } description "Invalid entry event."; } leaf-list added-entry { type leafref { path "/softwire-config/algorithm/algo-instances/algo-instance/id"; } description "Added entry."; } leaf-list modified-entry { type leafref { path "/softwire-config/algorithm/algo-instances/algo-instance/id"; } description "Modified entry."; } } } ]]>



    
      The lwAFTR maintains an address binding table which contains the
      following 3-tuples:

      
          IPv6 Address for a single lwB4

          Public IPv4 Address

          Restricted port-set
        

      The entry has two functions: the IPv6 encapsulation of inbound IPv4
      packets destined to the lwB4 and the validation of outbound IPv4-in-IPv6
      packets received from the lwB4 for de-capsulation.

      Let's consider an example to add an entry that maintains the
      relationship between 3-tuples of lwB4 (2001:db8::1), '192.0.2.1' and
      '1234' in the binding table of the lwAFTR (2001:db8::2). Here is the
      example binding-table configuration xml:

      
        

  
    
      
    
  
    
      
        
          2001:db8::2
          
            
              192.0.2.1
              
                1234
              
              2001:db8::1
              1
            
          
        
      
    
  

        ]]>
      
    

    
      The YANG module defined in this memo is designed to be accessed via
      the NETCONF protocol . The lowest NETCONF
      layer is the secure transport layer and the mandatory to implement
      secure transport is SSH . The NETCONF
      access control model  provides the means
      to restrict access for particular NETCONF users to a pre-configured
      subset of all available NETCONF protocol operations and content.

      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.
    

    
      This document requests IANA to register the following URI in the
      "IETF XML Registry" .
          
        

      This document requests IANA to register the following YANG module in
      the "YANG Module Names" registry .
          
        
    

    
      The authors would like to thank Lishan Li, Bert Wijnen, Giles Heron,
      and Ole Troan for their contributions to this work.