]> Telefonica

oscar.gonzalezdedios@telefonica.com

Telefonica

samier.barguilgiraldo.ext@telefonica.com

Orange

mohamed.boucadair@orange.com

Huawei

bill.wu@huawei.com

Operations and Management netmod Internet-Draft RFC 8519 defines a YANG data model for Access Control Lists (ACLs). This document discusses a set of extensions that fix many of the limitations of the ACL model as initially defined in RFC 8519. The document also defines IANA-maintained modules for ICMP types and IPv6 extension headers. Discussion Venues Discussion of this document takes place on the Network Modeling Working Group mailing list (netmod@ietf.org), which is archived at . Source for this draft and an issue tracker can be found at .

Introduction defines Access Control Lists (ACLs) as a user-ordered set of filtering rules. The model targets the configuration of the filtering behavior of a device. However, the model structure, as defined in , suffers from a set of limitations. This document describes these limitations and proposes an enhanced ACL structure. The YANG module in this document is solely based on augmentations to the ACL YANG module defined in . The motivation of such enhanced ACL structure is discussed in detail in . When managing ACLs, it is common for network operators to group match elements in pre-defined sets. The consolidation into group matches allows for reducing the number of rules, especially in large scale networks. If, for example, it is needed to find a match against 100 IP addresses (or prefixes), a single rule will suffice rather than creating individual Access Control Entries (ACEs) for each IP address (or prefix). In doing so, implementations would optimize the performance of matching lists vs multiple rules matching. The enhanced ACL structure is also meant to facilitate the management of network operators. Instead of entering the IP address or port number literals, using user-named lists decouples the creation of the rule from the management of the sets. Hence, it is possible to remove/add entries to the list without redefining the (parent) ACL rule. In addition, the notion of Access Control List (ACL) and defined sets is generalized so that it is not device-specific as per . ACLs and defined sets may be defined at network / administrative domain level and associated to devices. This approach facilitates the reusability across multiple network elements. For example, managing the IP prefix sets from a network level makes it easier to maintain by the security groups. Network operators maintain sets of IP prefixes that are related to each other, e.g., deny-lists or accept-lists that are associated with those provided by a VPN customer. These lists are maintained and manipulated by security expert teams. Note that ACLs are used locally in devices but are triggered by other tools such as DDoS mitigation or BGP Flow Spec . Therefore, supporting means to easily map to the filtering rules conveyed in messages triggered by these tools is valuable from a network operation standpoint. The document also defines IANA-maintained modules for ICMP types and IPv6 extension headers. The design of the modules adheres to the recommendations in . The templates to generate the modules is available at , , and . Readers should refer to the IANA websites [REF_TBC], [REF_TBC2], and [REF_TBC3] to retrieve the latest version of the modules. The modules are provided in , , and for the users convenience, but these appendices will be removed from the final RFC.

Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here. The terminology for describing YANG modules is defined in . The meaning of the symbols in the tree diagrams is defined in . In addition to the terms defined in , this document makes use of the following term: Defined set: :Refers to reusable description of one or multiple information elements (e.g., IP address, IP prefix, port number, or ICMP type).

Overall Structure of The Enhanced ACL Module

Tree Structure shows the full enhanced ACL tree:

Enhanced ACL tree

Defined Sets The augmented ACL structure includes several containers to manage reusable sets of elements that can be matched in an ACL entry. Each set is uniquely identified by a name and can be called from the relevant entry. The following sets are defined:

• IPv4 prefix set:

  It contains a list of IPv4 prefixes. A match will be considered if the IP address (source or destination, depending on the ACL entry) is contained in any of the prefixes.

• IPv6 prefix set:

  It contains a list of IPv6 prefixes. A match will be considered if the IP address (source or destination, depending on the ACL entry) is contained in any of the prefixes.

• Port sets:

  It contains a list of port numbers to be used in TCP/UDP entries. The port numbers can be individual port numbers, a range of ports, and an operation.

• Protocol sets:

  It contains a list of protocol values. Each protocol can be identified either by a number (e.g., 17) or a name (e.g., UDP).

• ICMP sets:

  It contains a list of ICMPv4 or ICMPv6 types, each of them identified by a type value, optionally the code and the rest of the header.

• Aliases:

  An alias is defined by a combination of various parameters (e.g., IP prefix, protocol, port number, or VLAN). Sets of aliases can be defined and referred to in match criteria.

IPv6 Extension Headers The module can be used to manage ACLs that require matching against IPv6 extension headers. To that aim, a new IANA-maintained module is defined in in this document.

TCP Flags Handling The augmented ACL structure includes a new leaf 'flags-bitmask' to better handle flags. Clients that support both 'flags-bitmask' and 'flags' matching fields MUST NOT set these fields in the same request. shows an example of a request to install a filter to discard incoming TCP messages having all flags unset.

Example of an ACL to Deny TCP Null Attack Messages (Request Body)

Fragments Handling The augmented ACL structure includes a new leaf 'fragment' to better handle fragments. Clients that support both 'fragment' and 'flags' matching fields MUST NOT set these fields in the same request. shows the content of a POST request to allow the traffic destined to 198.51.100.0/24 and UDP port number 53, but to drop all fragmented packets. The following ACEs are defined (in this order):

• "drop-all-fragments" ACE: discards all fragments.
• "allow-dns-packets" ACE: accepts DNS packets destined to 198.51.100.0/24.

Example Illustrating Candidate Filtering of IPv4 Fragmented Packets (Message Body)

shows an example of the body of a POST request to allow the traffic destined to 2001:db8::/32 and UDP port number 53, but to drop all fragmented packets. The following ACEs are defined (in this order):

• "drop-all-fragments" ACE: discards all fragments (including atomic fragments). That is, IPv6 packets that include a Fragment header (44) are dropped.
• "allow-dns-packets" ACE: accepts DNS packets destined to 2001:db8::/32.

An Example Illustrating Filtering of IPv6 Fragmented Packets (Message Body)

Payload-based Filtering Some transport protocols use existing protocols (e.g., TCP or UDP) as substrate. The match criteria for such protocols may rely upon the 'protocol' under 'l3', TCP/UDP match criteria, part of the TCP/UDP payload, or a combination thereof. A new feature, called "match-on-payload", is defined in the document.

Match MPLS Headers The ACL model can be used to create rules to match MPLS fields on a packet. The MPLS headers defined in and contains the following fields:

• Traffic Class: 3 bits 'EXP' renamed to 'Traffic Class Field."
• Label Value: A 20-bit field that carries the actual value of the MPLS Label.
• TTL: An eight-bit field that is used to encode a time-to-live value.

The structure of the MPLS ACL subtree is shown in :

MPLS Header Match Subtree

VLAN Filter Being able to filter all packets that are bridged within a VLAN or that are routed into or out of a bridge domain is part of the VPN control requirements derived of the EVPN definition done in . So, all packets that are bridged within a VLAN or that are routed into or out of a VLAN can be captured, forwarded, translated or discarded based on the network policy applied. shows an ACL example to illustrate how to apply a VLAN range filter.

Example of VLAN Filter (Message Body)

ISID Filter Provider backbone bridging (PBB) was originally defined as Virtual Bridged Local Area Networks [IEEE802.1ah] standard. However, instead of multiplexing VLANs, PBB duplicates the MAC layer of the customer frame and separates it from the provider domain, by encapsulating it in a 24 bit instance service identifier (I-SID). This provides for more transparency between the customer network and the provider network. The I-component forms the customer or access facing interface or routing instance. The I-component is responsible for mapping customer Ethernet traffic to the appropriate I-SID. In the network is mandatory to configure the default service identifier. Being able to filter by I-component Service identifier is a feature of the EVNP-PBB configuration. shows an ACL example to illustrate the ISID range filtering.

Example ISID Filter (Message Body)

Additional Actions In order to support rate-limiting (see ), a new action called "rate-limit" is defined. shows an ACL example to rate-limit incoming SYNs during a SYN flood attack.

An Example of Rate-Limit Incoming TCP SYNs (Message Body).

Also, the model supports new actions to complement existing ones: Log ('log-action') and write a counter ('counter-action'). The current version of the module supports only local actions.

Enhanced ACL YANG Module This model imports types from , , and . = ../lower-port' { error-message "The upper-port number must be greater than or equal to the lower-port number."; } description "Upper port number of the port range."; } } leaf-list protocol { type uint8; description "Identifies the target protocol number. For example, 6 for TCP or 17 for UDP."; } leaf-list fqdn { type inet:domain-name; description "FQDN identifying the target."; } leaf-list uri { type inet:uri; description "URI identifying the target."; } } grouping icmpv4-header-fields { description "Collection of ICMPv4 header fields that can be used to set up a match filter."; leaf type { type iana-icmpv4-types:icmpv4-type; description "Also known as control messages."; reference "RFC 792: Internet Control Message Protocol."; } leaf code { type uint8; description "ICMP subtype."; reference "RFC 792: Internet Control Message Protocol."; } leaf rest-of-header { type binary; description "Unbounded in length, the contents vary based on the ICMP type and code."; reference "RFC 792: Internet Control Message Protocol"; } } grouping icmpv6-header-fields { description "Collection of ICMPv6 header fields that can be used to set up a match filter."; leaf type { type iana-icmpv6-types:icmpv6-type; description "Also known as control messages."; reference "RFC 4443: Internet Control Message Protocol (ICMPv6) for Internet Protocol Version 6 (IPv6) Specification."; } leaf code { type uint8; description "ICMP code."; reference "RFC 4443: Internet Control Message Protocol (ICMPv6) for Internet Protocol Version 6 (IPv6) Specification."; } leaf rest-of-header { type binary; description "Unbounded in length, the contents vary based on the ICMP type and code. Also referred to as 'Message Body' in ICMPv6."; reference "RFC 4443: Internet Control Message Protocol (ICMPv6) for Internet Protocol Version 6 (IPv6) Specification."; } } grouping acl-complementary-actions { description "Collection of complementary ACL actions."; container log-action { description "Container for defining log actions."; leaf log-type { type identityref { base acl-enh:log-types; } description "The type of log action to be performed."; } leaf log-id { when "../log-type = 'local-log'" { description "Name of the log file updated when type is 'local-log'."; } type string; description "The name of the counter action."; } } container counter-action { description "Container for defining counter actions."; leaf counter-type { type identityref { base acl-enh:counter-type; } description "The type of counter action to be performed."; } leaf-list counter-name { when "../counter-type = 'counter-name'" { description "Name for the counter or variable to update when counter-type is 'counter-name'."; } type string; description "List of possible variables or counter names to update based on match critieria."; } } } augment "/acl:acls/acl:acl/acl:aces/acl:ace" + "/acl:matches" { description "Adds a match type based on the payload."; choice payload { description "Matches based upon a prefix pattern."; container prefix-pattern { if-feature "match-on-payload"; description "Indicates the rule to perform the payload-based match."; uses payload; } } choice alias { description "Matches based upon aliases."; leaf-list alias-name { type alias-ref; description "Indicates one or more aliases."; } } choice mpls { container mpls-values { if-feature "match-on-mpls"; uses mpls-match-parameters-config; description "Provides the rule set that matches MPLS headers."; } description "Matches against MPLS headers, for example, label values"; } } augment "/acl:acls/acl:acl/acl:aces" + "/acl:ace/acl:matches/acl:l2" { description "Adds a match type based on MAC VLAN and ISID filters."; container vlan-filter { if-feature "match-on-vlan-filter"; description "Indicates how to handle MAC VLANs."; leaf frame-type { type string; description "Entering the frame type allows the filter to match a specific type of frame format"; } choice vlan-type { description "VLAN definition from range or operator."; case range { leaf lower-vlan { type uint16; must '. <= ../upper-vlan' { error-message "The lower-vlan must be less than or equal to the upper-vlan."; } mandatory true; description "Lower boundary for a vlan."; } leaf upper-vlan { type uint16; mandatory true; description "Upper boundary for a vlan."; } } case operator { leaf operator { type packet-fields:operator; default "eq"; description "Operator to be applied on the vlan below."; } leaf-list vlan { type uint16; description "VLAN number along with the operator on which to match."; } } } } container isid-filter { if-feature "match-on-isid-filter"; description "Indicates how to handle ISID filters. The I-component is responsible for mapping customer Ethernet traffic to the appropriate ISID."; choice isid-type { description "ISID definition from range or operator."; case range { leaf lower-isid { type uint16; must '. <= ../upper-isid' { error-message "The lower-isid must be less than or equal to the upper-isid."; } mandatory true; description "Lower boundary for a ISID."; } leaf upper-isid { type uint16; mandatory true; description "Upper boundary for a ISID."; } } case operator { leaf operator { type packet-fields:operator; default "eq"; description "Operator to be applied on the ISID below."; } leaf-list isid { type uint16; description "ISID number along with the operator on which to match."; } } } } } augment "/acl:acls/acl:acl/acl:aces" + "/acl:ace/acl:matches/acl:l3/acl:ipv4/acl:ipv4" { description "Handle non-initial and initial fragments for IPv4 packets."; container ipv4-fragment { description "Indicates how to handle IPv4 fragments."; uses fragment-fields; } leaf source-ipv4-prefix-list { type ipv4-prefix-set-ref; description "A reference to an IPv4 prefix list to match the source address."; } leaf destination-ipv4-prefix-list { type ipv4-prefix-set-ref; description "A reference to a prefix list to match the destination address."; } leaf next-header-set { type protocol-set-ref; description "A reference to a protocol set to match the next-header field."; } } augment "/acl:acls/acl:acl/acl:aces" + "/acl:ace/acl:matches/acl:l3/acl:ipv6/acl:ipv6" { description "Handles non-initial and initial fragments for IPv6 packets."; container ipv6-fragment { description "Indicates how to handle IPv6 fragments."; uses fragment-fields; } leaf source-ipv6-prefix-list { type ipv6-prefix-set-ref; description "A reference to a prefix list to match the source address."; } leaf destination-ipv6-prefix-list { type ipv6-prefix-set-ref; description "A reference to a prefix list to match the destination address."; } leaf protocol-set { type protocol-set-ref; description "A reference to a protocol set to match the protocol field."; } leaf extension-header { type iana-ipv6-ext-types:ipv6-extension-header-type; description "IPv6 extension header value."; } } augment "/acl:acls/acl:acl/acl:aces" + "/acl:ace/acl:matches/acl:l4/acl:tcp" { description "Handles TCP flags and port sets."; container flags-bitmask { description "Indicates how to handle TCP flags."; uses tcp-flags; } leaf source-tcp-port-set { type port-set-ref; description "A reference to a port set to match the source port."; } leaf destination-tcp-port-set { type port-set-ref; description "A reference to a port set to match the destination port."; } } augment "/acl:acls/acl:acl/acl:aces" + "/acl:ace/acl:matches/acl:l4/acl:udp" { description "Handle UDP port sets."; leaf source-udp-port-set { type port-set-ref; description "A reference to a port set to match the source port."; } leaf destination-udp-port-set { type port-set-ref; description "A reference to a port set to match the destination port."; } } augment "/acl:acls/acl:acl/acl:aces" + "/acl:ace/acl:matches/acl:l4/acl:icmp" { description "Handle ICMP type sets."; leaf icmpv4-set { type icmpv4-type-set-ref; description "A reference to an ICMPv4 type set to match the ICMPv4 type field."; } leaf icmpv6-set { type icmpv6-type-set-ref; description "A reference to an ICMPv6 type set to match the ICMPv6 type field."; } } augment "/acl:acls/acl:acl/acl:aces" + "/acl:ace/acl:actions" { description "Complementary actions including Rate-limit action."; uses acl-complementary-actions; leaf rate-limit { when "../acl:forwarding = 'acl:accept'" { description "Rate-limit valid only when accept action is used."; } type decimal64 { fraction-digits 2; } units "bytes per second"; description "Indicates a rate-limit for the matched traffic."; } } container defined-sets { description "Predefined sets of attributes used in policy match statements."; container ipv4-prefix-sets { description "Data definitions for a list of IPv4 or IPv6 prefixes which are matched as part of a policy."; list prefix-set { key "name"; description "List of the defined prefix sets."; leaf name { type string; description "Name of the prefix set -- this is used as a label to reference the set in match conditions."; } leaf description { type string; description "Defined Set description."; } leaf-list prefix { type inet:ipv4-prefix; description "List of IPv4 prefixes to be used in match conditions."; } } } container ipv6-prefix-sets { description "Data definitions for a list of IPv6 prefixes which are matched as part of a policy."; list prefix-set { key "name"; description "List of the defined prefix sets."; leaf name { type string; description "Name of the prefix set -- this is used as a label to reference the set in match conditions."; } leaf description { type string; description "A textual description of the prefix list."; } leaf-list prefix { type inet:ipv6-prefix; description "List of IPv6 prefixes to be used in match conditions."; } } } container port-sets { description "Data definitions for a list of ports which can be matched in policies."; list port-set { key "name"; description "List of port set definitions."; leaf name { type string; description "Name of the port set -- this is used as a label to reference the set in match conditions."; } list port { key "id"; description "Port numbers along with the operator on which to match."; leaf id { type string; description "Identifier of the list of port numbers."; } choice port { description "Choice of specifying the port number or referring to a group of port numbers."; container port-range-or-operator { description "Indicates a set of ports."; uses packet-fields:port-range-or-operator; } } } } } container protocol-sets { description "Data definitions for a list of protocols which can be matched in policies."; list protocol-set { key "name"; description "List of protocol set definitions."; leaf name { type string; description "Name of the protocols set -- this is used as a label to reference the set in match conditions."; } leaf-list protocol { type union { type uint8; type string; } description "Value of the protocol set."; //Check if we can reuse an IANA-maintained module } } } container icmpv4-type-sets { description "Data definitions for a list of ICMPv4 types which can be matched in policies."; list icmpv4-type-set { key "name"; description "List of ICMP type set definitions."; leaf name { type string; description "Name of the ICMPv4 type set -- this is used as a label to reference the set in match conditions."; } list types { key "type"; description "Includes a list of ICMPv4 types."; uses icmpv4-header-fields; } } } container icmpv6-type-sets { description "Data definitions for a list of ICMPv6 types which can be matched in policies."; list icmpv6-type-set { key "name"; description "List of ICMP type set definitions."; leaf name { type string; description "Name of the ICMPv6 type set -- this is used as a label to reference the set in match conditions."; } list types { key "type"; description "Includes a list of ICMPv6 types."; uses icmpv6-header-fields; } } } } container aliases { description "Top-levl container for aliases."; list alias { key "name"; description "List of aliases."; leaf name { type string; description "The name of the alias."; } uses alias; } } } ]]>

Security Considerations The YANG modules specified in this document define a schema for data that is designed to be accessed via network management protocol such as NETCONF or RESTCONF . The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) . The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS . The Network Configuration Access Control Model (NACM) provides the means to restrict access for particular NETCONF or RESTCONF users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content. There are a number of data nodes defined in this YANG module that are writable/creatable/deletable (i.e., config true, which is the default). These data nodes may be considered sensitive or vulnerable in some network environments. Write operations (e.g., edit-config) to these data nodes without proper protection can have a negative effect on network operations. These are the subtrees and data nodes and their sensitivity/vulnerability:

• TBC

Some of the readable data nodes in this YANG module may be considered sensitive or vulnerable in some network environments. It is thus important to control read access (e.g., via get, get-config, or notification) to these data nodes. These are the subtrees and data nodes and their sensitivity/vulnerability:

• TBC

IANA Considerations

URI Registrations This document requests IANA to register the following URIs in the "ns" subregistry within the "IETF XML Registry" :

YANG Module Name Registrations This document requests IANA to register the following YANG modules in the "YANG Module Names" subregistry within the "YANG Parameters" registry.

Considerations for IANA-Maintained Modules

ICMPv4 Types IANA Module IANA is requested to create and post the initial version of the "iana-icmpv4-types" YANG module by applying the XSLT stylesheet from to the XML version of . This document defines the initial version of the IANA-maintained "iana-icmpv4-types" YANG module. The most recent version of the YANG module is available from the "YANG Parameters" registry . IANA is requested to add this note to the registry :

• New values must not be directly added to the "iana-icmpv4-types" YANG module. They must instead be added to the "ICMP Type Numbers" registry .

When a value is added to the "ICMP Type Numbers" registry, a new "enum" statement must be added to the "iana-icmpv4-types" YANG module. The "enum" statement, and sub-statements thereof, should be defined:

"enum":

Replicates a name from the registry.

"value":

Contains the decimal value of the IANA-assigned value.

"status":

Is included only if a registration has been deprecated or obsoleted. IANA "deprecated" maps to YANG status "deprecated", and IANA "obsolete" maps to YANG status "obsolete".

"description":

Replicates the description from the registry.

"reference":

Replicates the reference(s) from the registry with the title of the document(s) added.

Unassigned or reserved values are not present in the module. When the "iana-icmpv4-types" YANG module is updated, a new "revision" statement with a unique revision date must be added in front of the existing revision statements. IANA is requested to add this note to "ICMP Type Numbers" : IANA is requested to updated the "Reference" in the "ICMP Type Numbers" registry as follows:

OLD:

NEW:

[This_Document]

ICMPv6 Types IANA Module IANA is requested to create and post the initial version of the "iana-icmpv6-types" YANG module by applying the XSLT stylesheet from to the XML version of . This document defines the initial version of the IANA-maintained "iana-icmpv6-types" YANG module. The most recent version of the YANG module is available from the "YANG Parameters" registry . IANA is requested to add this note to the registry :

• New values must not be directly added to the "iana-icmpv6-types" YANG module. They must instead be added to the "ICMPv6 "type" Numbers" registry .

When a value is added to the "ICMPv6 "type" Numbers" registry, a new "enum" statement must be added to the "iana-icmpv6-types" YANG module. The "enum" statement, and sub-statements thereof, should be defined:

"enum":

Replicates a name from the registry.

"value":

Contains the decimal value of the IANA-assigned value.

"status":

Is included only if a registration has been deprecated or obsoleted. IANA "deprecated" maps to YANG status "deprecated", and IANA "obsolete" maps to YANG status "obsolete".

"description":

Replicates the description from the registry.

"reference":

Replicates the reference(s) from the registry with the title of the document(s) added.

Unassigned or reserved values are not present in the module. When the "iana-icmpv6-types" YANG module is updated, a new "revision" statement with a unique revision date must be added in front of the existing revision statements. IANA is requested to add this note to "ICMPv6 "type" Numbers" : IANA is requested to updated the "Reference" in the "ICMPv6 "type" Numbers" registry as follows:

OLD:

NEW:

[This_Document]

IPv6 Extension Header Types IANA Module IANA is requested to create and post the initial version of the "iana-ipv6-ext-types" YANG module by applying the XSLT stylesheet from to the XML version of . This document defines the initial version of the IANA-maintained "iana-ipv6-ext-types" YANG module. The most recent version of the YANG module is available from the "YANG Parameters" registry . IANA is requested to add this note to the registry :

• New values must not be directly added to the "iana-ipv6-ext-types" YANG module. They must instead be added to the "IPv6 Extension Header Types" registry .

When a value is added to the "IPv6 Extension Header Types" registry, a new "enum" statement must be added to the "iana-ipv6-ext-types" YANG module. The "enum" statement, and sub-statements thereof, should be defined:

"enum":

Replicates a name from the registry.

"value":

Contains the decimal value of the IANA-assigned value.

"status":

Is included only if a registration has been deprecated or obsoleted. IANA "deprecated" maps to YANG status "deprecated", and IANA "obsolete" maps to YANG status "obsolete".

"description":

Replicates the description from the registry.

"reference":

Replicates the reference(s) from the registry with the title of the document(s) added.

Unassigned or reserved values are not present in the module. When the "iana-ipv6-ext-types" YANG module is updated, a new "revision" statement with a unique revision date must be added in front of the existing revision statements. IANA is requested to add this note to the "IPv6 Extension Header Types" registry : IANA is requested to updated the "Reference" in the "IPv6 Extension Header Types" registry as follows:

OLD:

NEW:

[This_Document]

References Normative References This document defines a data model for Access Control Lists (ACLs). An ACL is a user-ordered set of rules used to configure the forwarding behavior in a device. Each rule is used to find a match on a packet and define actions that will be performed on the packet. "Dissemination of Flow Specification Rules" (RFC 8955) provides a Border Gateway Protocol (BGP) extension for the propagation of traffic flow information for the purpose of rate limiting or filtering IPv4 protocol data packets. This document extends RFC 8955 with IPv6 functionality. It also updates RFC 8955 by changing the IANA Flow Spec Component Types registry. In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. YANG is a data modeling language used to model configuration data, state data, Remote Procedure Calls, and notifications for network management protocols. This document describes the syntax and semantics of version 1.1 of the YANG language. YANG version 1.1 is a maintenance release of the YANG language, addressing ambiguities and defects in the original specification. There are a small number of backward incompatibilities from YANG version 1. This document also specifies the YANG mappings to the Network Configuration Protocol (NETCONF). This document specifies the encoding to be used by an LSR in order to transmit labeled packets on Point-to-Point Protocol (PPP) data links, on LAN data links, and possibly on other data links as well. This document also specifies rules and procedures for processing the various fields of the label stack encoding. [STANDARDS-TRACK] The early Multiprotocol Label Switching (MPLS) documents defined the form of the MPLS label stack entry. This includes a three-bit field called the "EXP field". The exact use of this field was not defined by these documents, except to state that it was to be "reserved for experimental use". Although the intended use of the EXP field was as a "Class of Service" (CoS) field, it was not named a CoS field by these early documents because the use of such a CoS field was not considered to be sufficiently defined. Today a number of standards documents define its usage as a CoS field. To avoid misunderstanding about how this field may be used, it has become increasingly necessary to rename this field. This document changes the name of the field to the "Traffic Class field" ("TC field"). In doing so, it also updates documents that define the current use of the EXP field. [STANDARDS-TRACK] The widespread adoption of Ethernet L2VPN services and the advent of new applications for the technology (e.g., data center interconnect) have culminated in a new set of requirements that are not readily addressable by the current Virtual Private LAN Service (VPLS) solution. In particular, multihoming with all-active forwarding is not supported, and there's no existing solution to leverage Multipoint-to-Multipoint (MP2MP) Label Switched Paths (LSPs) for optimizing the delivery of multi-destination frames. Furthermore, the provisioning of VPLS, even in the context of BGP-based auto-discovery, requires network operators to specify various network parameters on top of the access configuration. This document specifies the requirements for an Ethernet VPN (EVPN) solution, which addresses the above issues. This document introduces a collection of common data types to be used with the YANG data modeling language. This document obsoletes RFC 6021. This document defines a collection of common data types using the YANG data modeling language. These derived common types are designed to be imported by other modules defined in the routing area. The Network Configuration Protocol (NETCONF) defined in this document provides mechanisms to install, manipulate, and delete the configuration of network devices. It uses an Extensible Markup Language (XML)-based data encoding for the configuration data as well as the protocol messages. The NETCONF protocol operations are realized as remote procedure calls (RPCs). This document obsoletes RFC 4741. [STANDARDS-TRACK] This document describes an HTTP-based protocol that provides a programmatic interface for accessing data defined in YANG, using the datastore concepts defined in the Network Configuration Protocol (NETCONF). This document describes a method for invoking and running the Network Configuration Protocol (NETCONF) within a Secure Shell (SSH) session as an SSH subsystem. This document obsoletes RFC 4742. [STANDARDS-TRACK] This document specifies version 1.3 of the Transport Layer Security (TLS) protocol. TLS allows client/server applications to communicate over the Internet in a way that is designed to prevent eavesdropping, tampering, and message forgery. This document updates RFCs 5705 and 6066, and obsoletes RFCs 5077, 5246, and 6961. This document also specifies new requirements for TLS 1.2 implementations. The standardization of network configuration interfaces for use with the Network Configuration Protocol (NETCONF) or the RESTCONF protocol requires a structured and secure operating environment that promotes human usability and multi-vendor interoperability. There is a need for standard mechanisms to restrict NETCONF or RESTCONF protocol access for particular users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content. This document defines such an access control model. This document obsoletes RFC 6536. This document describes an IANA maintained registry for IETF standards which use Extensible Markup Language (XML) related items such as Namespaces, Document Type Declarations (DTDs), Schemas, and Resource Description Framework (RDF) Schemas. YANG is a data modeling language used to model configuration and state data manipulated by the Network Configuration Protocol (NETCONF), NETCONF remote procedure calls, and NETCONF notifications. [STANDARDS-TRACK] Informative References n.d. n.d. n.d. n.d. This document specifies the Distributed Denial-of-Service Open Threat Signaling (DOTS) signal channel, a protocol for signaling the need for protection against Distributed Denial-of-Service (DDoS) attacks to a server capable of enabling network traffic mitigation on behalf of the requesting client. A companion document defines the DOTS data channel, a separate reliable communication layer for DOTS management and configuration purposes. This document obsoletes RFC 8782. This document defines a Border Gateway Protocol Network Layer Reachability Information (BGP NLRI) encoding format that can be used to distribute (intra-domain and inter-domain) traffic Flow Specifications for IPv4 unicast and IPv4 BGP/MPLS VPN services. This allows the routing system to propagate information regarding more specific components of the traffic aggregate defined by an IP destination prefix. It also specifies BGP Extended Community encoding formats, which can be used to propagate Traffic Filtering Actions along with the Flow Specification NLRI. Those Traffic Filtering Actions encode actions a routing system can take if the packet matches the Flow Specification. This document obsoletes both RFC 5575 and RFC 7674. Orange Huawei This memo provides guidelines for authors and reviewers of specifications containing YANG modules, including IANA-maintained modules. Recommendations and procedures are defined, which are intended to increase interoperability and usability of Network Configuration Protocol (NETCONF) and RESTCONF protocol implementations that utilize YANG modules. This document obsoletes RFC 8407. Also, this document updates RFC 8126 by providing additional guidelines for writing the IANA considerations for RFCs that specify IANA-maintained modules. This document captures the current syntax used in YANG module tree diagrams. The purpose of this document is to provide a single location for this definition. This syntax may be updated from time to time based on the evolution of the YANG language. This memo provides guidance for the IANA to use in assigning parameters for fields in the IPv4, IPv6, ICMP, UDP and TCP protocol headers. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. This document describes the format of a set of control messages used in ICMPv6 (Internet Control Message Protocol). ICMPv6 is the Internet Control Message Protocol for Internet Protocol version 6 (IPv6). [STANDARDS-TRACK] This document revises the IANA guidelines for allocating new Protocol field values in IPv4 header. It modifies the rules specified in RFC 2780 by removing the Expert Review option. The change will also affect the allocation of Next Header field values in IPv6. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. Various IPv6 extension headers have been standardised since the IPv6 standard was first published. This document updates RFC 2460 to clarify how intermediate nodes should deal with such extension headers and with any that are defined in the future. It also specifies how extension headers should be registered by IANA, with a corresponding minor update to RFC 2780.

ICMPv4 Types

XSLT Template to Generate The ICMPv4 Types IANA-Maintained Module

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Initial Version of the The ICMPv4 Types IANA-Maintained Module "; description "This YANG module translates IANA registry 'ICMP Type Numbers' to YANG derived types. Copyright (c) 2020 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 Revised BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info). This version of this YANG module was generated from the corresponding IANA registry using an XSLT stylesheet from the 'iana-yang' project (https://github.com/llhotka/iana-yang)."; reference "Internet Control Message Protocol (ICMP) Parameters (https://www.iana.org/assignments/icmp-parameters/)"; revision 2020-09-25 { description "Current revision as of the revision date specified in the XML representation of the registry page."; reference "https://www.iana.org/assignments/icmp-parameters/icmp-parameters.xml"; } /* Typedefs */ typedef icmpv4-type-name { type enumeration { enum EchoReply { value 0; description "Echo Reply"; reference "RFC 792"; } enum DestinationUnreachable { value 3; description "Destination Unreachable"; reference "RFC 792"; } enum SourceQuench { value 4; status deprecated; description "Source Quench (Deprecated)"; reference "- RFC 792 - RFC 6633"; } enum Redirect { value 5; description "Redirect"; reference "RFC 792"; } enum AlternateHostAddress { value 6; status deprecated; description "Alternate Host Address (Deprecated)"; reference "RFC 6918"; } enum Echo { value 8; description "Echo"; reference "RFC 792"; } enum RouterAdvertisement { value 9; description "Router Advertisement"; reference "RFC 1256"; } enum RouterSolicitation { value 10; description "Router Solicitation"; reference "RFC 1256"; } enum TimeExceeded { value 11; description "Time Exceeded"; reference "RFC 792"; } enum ParameterProblem { value 12; description "Parameter Problem"; reference "RFC 792"; } enum Timestamp { value 13; description "Timestamp"; reference "RFC 792"; } enum TimestampReply { value 14; description "Timestamp Reply"; reference "RFC 792"; } enum InformationRequest { value 15; status deprecated; description "Information Request (Deprecated)"; reference "- RFC 792 - RFC 6918"; } enum InformationReply { value 16; status deprecated; description "Information Reply (Deprecated)"; reference "- RFC 792 - RFC 6918"; } enum AddressMaskRequest { value 17; status deprecated; description "Address Mask Request (Deprecated)"; reference "- RFC 950 - RFC 6918"; } enum AddressMaskReply { value 18; status deprecated; description "Address Mask Reply (Deprecated)"; reference "- RFC 950 - RFC 6918"; } enum Traceroute { value 30; status deprecated; description "Traceroute (Deprecated)"; reference "- RFC 1393 - RFC 6918"; } enum DatagramConversionError { value 31; status deprecated; description "Datagram Conversion Error (Deprecated)"; reference "- RFC 1475 - RFC 6918"; } enum MobileHostRedirect { value 32; status deprecated; description "Mobile Host Redirect (Deprecated)"; reference "- David Johnson <> - RFC 6918"; } enum IPv6Where-Are-You { value 33; status deprecated; description "IPv6 Where-Are-You (Deprecated)"; reference "- Bill Simpson - RFC 6918"; } enum IPv6I-Am-Here { value 34; status deprecated; description "IPv6 I-Am-Here (Deprecated)"; reference "- Bill Simpson - RFC 6918"; } enum MobileRegistrationRequest { value 35; status deprecated; description "Mobile Registration Request (Deprecated)"; reference "- Bill Simpson - RFC 6918"; } enum MobileRegistrationReply { value 36; status deprecated; description "Mobile Registration Reply (Deprecated)"; reference "- Bill Simpson - RFC 6918"; } enum DomainNameRequest { value 37; status deprecated; description "Domain Name Request (Deprecated)"; reference "- RFC 1788 - RFC 6918"; } enum DomainNameReply { value 38; status deprecated; description "Domain Name Reply (Deprecated)"; reference "- RFC 1788 - RFC 6918"; } enum SKIP { value 39; status deprecated; description "SKIP (Deprecated)"; reference "- Tom Markson - RFC 6918"; } enum Photuris { value 40; description "Photuris"; reference "RFC 2521"; } enum ICMPmessagesutilizedbyexperimentalmobilityprotocolssuchasSeamoby { value 41; description "ICMP messages utilized by experimental mobility protocols such as Seamoby"; reference "RFC 4065"; } enum ExtendedEchoRequest { value 42; description "Extended Echo Request"; reference "RFC 8335"; } enum ExtendedEchoReply { value 43; description "Extended Echo Reply"; reference "RFC 8335"; } } description "This enumeration type defines mnemonic names and corresponding numeric values of ICMPv4 types."; reference "RFC 2708: IANA Allocation Guidelines For Values In the Internet Protocol and Related Headers"; } typedef icmpv4-type { type union { type uint8; type icmpv4-type-name; } description "This type allows reference to an ICMPv4 type using either the assigned mnemonic name or numeric value."; } } ]]>

ICMPv6 Types

XSLT Template to Generate The ICMPv6 Types IANA-Maintained Module

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Initial Version of the The ICMPv4 Types IANA-Maintained Module "; description "This YANG module translates IANA registry 'ICMPv6 \"type\" Numbers' to YANG derived types. Copyright (c) 2023 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 Revised BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info). This version of this YANG module was generated from the corresponding IANA registry using an XSLT stylesheet from the 'iana-yang' project (https://github.com/llhotka/iana-yang)."; reference "Internet Control Message Protocol version 6 (ICMPv6) Parameters (https://www.iana.org/assignments/icmpv6-parameters/)"; revision 2023-04-28 { description "Current revision as of the revision date specified in the XML representation of the registry page."; reference "https://www.iana.org/assignments/icmpv6-parameters/icmpv6-parameters.xml"; } /* Typedefs */ typedef icmpv6-type-name { type enumeration { enum DestinationUnreachable { value 1; description "Destination Unreachable."; reference "RFC 4443"; } enum PacketTooBig { value 2; description "Packet Too Big."; reference "RFC 4443"; } enum TimeExceeded { value 3; description "Time Exceeded."; reference "RFC 4443"; } enum ParameterProblem { value 4; description "Parameter Problem."; reference "RFC 4443"; } enum EchoRequest { value 128; description "Echo Request."; reference "RFC 4443"; } enum EchoReply { value 129; description "Echo Reply."; reference "RFC 4443"; } enum MulticastListenerQuery { value 130; description "Multicast Listener Query."; reference "RFC 2710"; } enum MulticastListenerReport { value 131; description "Multicast Listener Report."; reference "RFC 2710"; } enum MulticastListenerDone { value 132; description "Multicast Listener Done."; reference "RFC 2710"; } enum RouterSolicitation { value 133; description "Router Solicitation."; reference "RFC 4861"; } enum RouterAdvertisement { value 134; description "Router Advertisement."; reference "RFC 4861"; } enum NeighborSolicitation { value 135; description "Neighbor Solicitation."; reference "RFC 4861"; } enum NeighborAdvertisement { value 136; description "Neighbor Advertisement."; reference "RFC 4861"; } enum RedirectMessage { value 137; description "Redirect Message."; reference "RFC 4861"; } enum RouterRenumbering { value 138; description "Router Renumbering."; reference "RFC 2894"; } enum ICMPNodeInformationQuery { value 139; description "ICMP Node Information Query."; reference "RFC 4620"; } enum ICMPNodeInformationResponse { value 140; description "ICMP Node Information Response."; reference "RFC 4620"; } enum InverseNeighborDiscoverySolicitationMessage { value 141; description "Inverse Neighbor Discovery Solicitation Message."; reference "RFC 3122"; } enum InverseNeighborDiscoveryAdvertisementMessage { value 142; description "Inverse Neighbor Discovery Advertisement Message."; reference "RFC 3122"; } enum Version2MulticastListenerReport { value 143; description "Version 2 Multicast Listener Report."; reference "RFC 3810"; } enum HomeAgentAddressDiscoveryRequestMessage { value 144; description "Home Agent Address Discovery Request Message."; reference "RFC 6275"; } enum HomeAgentAddressDiscoveryReplyMessage { value 145; description "Home Agent Address Discovery Reply Message."; reference "RFC 6275"; } enum MobilePrefixSolicitation { value 146; description "Mobile Prefix Solicitation."; reference "RFC 6275"; } enum MobilePrefixAdvertisement { value 147; description "Mobile Prefix Advertisement."; reference "RFC 6275"; } enum CertificationPathSolicitationMessage { value 148; description "Certification Path Solicitation Message."; reference "RFC 3971"; } enum CertificationPathAdvertisementMessage { value 149; description "Certification Path Advertisement Message."; reference "RFC 3971"; } enum ICMPmessagesutilizedbyexperimentalmobilityprotocolssuchasSeamoby { value 150; description "ICMP messages utilized by experimental mobility protocols such as Seamoby."; reference "RFC 4065"; } enum MulticastRouterAdvertisement { value 151; description "Multicast Router Advertisement."; reference "RFC 4286"; } enum MulticastRouterSolicitation { value 152; description "Multicast Router Solicitation."; reference "RFC 4286"; } enum MulticastRouterTermination { value 153; description "Multicast Router Termination."; reference "RFC 4286"; } enum FMIPv6Messages { value 154; description "FMIPv6 Messages."; reference "RFC 5568"; } enum RPLControlMessage { value 155; description "RPL Control Message."; reference "RFC 6550"; } enum ILNPv6LocatorUpdateMessage { value 156; description "ILNPv6 Locator Update Message."; reference "RFC 6743"; } enum DuplicateAddressRequest { value 157; description "Duplicate Address Request."; reference "RFC 6775"; } enum DuplicateAddressConfirmation { value 158; description "Duplicate Address Confirmation."; reference "RFC 6775"; } enum MPLControlMessage { value 159; description "MPL Control Message."; reference "RFC 7731"; } enum ExtendedEchoRequest { value 160; description "Extended Echo Request."; reference "RFC 8335"; } enum ExtendedEchoReply { value 161; description "Extended Echo Reply."; reference "RFC 8335"; } } description "This enumeration type defines mnemonic names and corresponding numeric values of ICMPv6 types."; reference "RFC 2708: IANA Allocation Guidelines For Values In the Internet Protocol and Related Headers"; } typedef icmpv6-type { type union { type uint8; type icmpv6-type-name; } description "This type allows reference to an ICMPv6 type using either the assigned mnemonic name or numeric value."; } } ]]>

IPv6 Extension Header Types

XSLT Template to Generate The IPv6 Extension Header Types IANA-Maintained Module

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Initial Version of the The ICMPv4 Types IANA-Maintained Module "; description "This YANG module translates IANA registry 'IPv6 Extension Header Types' to YANG derived types. Copyright (c) 2023 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 Revised BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info). This version of this YANG module was generated from the corresponding IANA registry using an XSLT stylesheet from the 'iana-yang' project (https://github.com/llhotka/iana-yang)."; reference "Internet Protocol Version 6 (IPv6) Parameters (https://www.iana.org/assignments/ipv6-parameters/)"; revision 2023-09-29 { description "Current revision as of the revision date specified in the XML representation of the registry page."; reference "https://www.iana.org/assignments/ipv6-parameters/ipv6-parameters.xml"; } /* Typedefs */ typedef ipv6-extension-header-type-name { type enumeration { enum IPv6Hop-by-HopOption { value 0; description "IPv6 Hop-by-Hop Option"; reference "RFC 8200"; } enum RoutingHeaderforIPv6 { value 43; description "Routing Header for IPv6"; reference "- RFC 8200 - RFC 5095"; } enum FragmentHeaderforIPv6 { value 44; description "Fragment Header for IPv6"; reference "RFC 8200"; } enum EncapsulatingSecurityPayload { value 50; description "Encapsulating Security Payload"; reference "RFC 4303"; } enum AuthenticationHeader { value 51; description "Authentication Header"; reference "RFC 4302"; } enum DestinationOptionsforIPv6 { value 60; description "Destination Options for IPv6"; reference "RFC 8200"; } enum MobilityHeader { value 135; description "Mobility Header"; reference "RFC 6275"; } enum HostIdentityProtocol { value 139; description "Host Identity Protocol"; reference "RFC 7401"; } enum Shim6Protocol { value 140; description "Shim6 Protocol"; reference "RFC 5533"; } } description "This enumeration type defines mnemonic names and corresponding numeric values of IPv6 Extension header types."; reference "RFC 2708: IANA Allocation Guidelines For Values In the Internet Protocol and Related Headers"; } typedef ipv6-extension-header-type { type union { type uint8; type ipv6-extension-header-type-name; } description "This type allows reference to an IPv6 Extension header type using either the assigned mnemonic name or the numeric protocol number value."; } } ]]>

Problem Statement & Gap Analysis

Suboptimal Configuration: Lack of Support for Lists of Prefixes IP prefix-related data nodes, e.g., "destination-ipv4-network" or "destination-ipv6-network", do not support handling a list of IP prefixes, which may then lead to having to support large numbers of ACL entries in a configuration file. The same issue is encountered when ACLs have to be in place to mitigate DDoS attacks that involve a set of sources (e.g., ). The situation is even worse when both a list of sources and destination prefixes are involved in the filtering. shows an example of the required ACL configuration for filtering traffic from two prefixes.

Example Illustrating Sub-optimal Use of the ACL Model with a Prefix List (Message Body)

Such a configuration is suboptimal for both:

• Network controllers that need to manipulate large files. All or a subset for this configuration will need to be passed to the underlying network devices.
• Devices may receive such a configuration and thus will need to maintain it locally.

Manageability: Impossibility to Use Aliases or Defined Sets The same approach as the one discussed for IP prefixes can be generalized by introducing the concept of "aliases" or "defined sets". The defined sets are reusable definitions across several ACLs. Each category is modelled in YANG as a list of parameters related to the class it represents. The following sets can be considered:

• Prefix sets:

  Used to create lists of IPv4 or IPv6 prefixes.

• Protocol sets:

  Used to create a list of protocols.

• Port number sets:

  Used to create lists of TCP or UDP port values (or any other transport protocol that makes uses of port numbers). The identity of the protocols is identified by the protocol set, if present. Otherwise, a set applies to any protocol.

• ICMP sets:

  Uses to create lists of ICMP-based filters. This applies only when the protocol is set to ICMP or ICMPv6.

Aliases may also be considered to manage resources that are identified by a combination of various parameters (e.g., prefix, protocol, port number, FQDN, or VLAN IDs). Note that some aliases can be provided by decomposing them into separate sets.

Bind ACLs to Devices, Not Only Interfaces In the context of network management, an ACL may be enforced in many network locations. As such, the ACL module should allow for binding an ACL to multiple devices, not only (abstract) interfaces. The ACL name must, thus, be unique at the scale of the network, but the same name may be used in many devices when enforcing node-specific ACLs.

Partial or Lack of IPv4/IPv6 Fragment Handling does not support fragment handling for IPv6 but offers a partial support for IPv4 through the use of 'flags'. Nevertheless, the use of 'flags' is problematic since it does not allow a bitmask to be defined. For example, setting other bits not covered by the 'flags' filtering clause in a packet will allow that packet to get through (because it won't match the ACE). Defining a new IPv4/IPv6 matching field called 'fragment' is thus required to efficiently handle fragment-related filtering rules.

Suboptimal TCP Flags Handling supports including flags in the TCP match fields, however that structure does not support matching operations as those supported in BGP Flow Spec. Defining this field to be defined as a flag bitmask together with a set of operations is meant to efficiently handle TCP flags filtering rules.

Rate-Limit Action specifies that forwarding actions can be 'accept' (i.e., accept matching traffic), 'drop' (i.e., drop matching traffic without sending any ICMP error message), or 'reject' (i.e., drop matching traffic and send an ICMP error message to the source). However, there are situations where the matching traffic can be accepted, but with a rate-limit policy. This capability is not supported by .

Payload-based Filtering Some transport protocols use existing protocols (e.g., TCP or UDP) as substrate. The match criteria for such protocols may rely upon the 'protocol' under 'l3', TCP/UDP match criteria, part of the TCP/UDP payload, or a combination thereof. does not support matching based on the payload. Likewise, the current version of the ACL model does not support filtering of encapsulated traffic.

Reuse the ACLs Content Across Several Devices Having a global network view of the ACLs is highly valuable for service providers. An ACL could be defined and applied based on the network topology hierarchy. So, an ACL can be defined at the network level and, then, that same ACL can be used (or referenced to) in several devices (including termination points) within the same network. This network/device ACLs differentiation introduces several new requirements, e.g.:

• An ACL name can be used at both network and device levels.
• An ACL content updated at the network level should imply a transaction that updates the relevant content in all the nodes using this ACL.
• ACLs defined at the device level have a local meaning for the specific node.
• A device can be associated with a router, a VRF, a logical system, or a virtual node. ACLs can be applied in physical and logical infrastructure.

Match MPLS Headers The ACLs could be used to create rules to match MPLS fields on a packet. does not support such function.

Acknowledgements Many thanks to Jon Shallow and Miguel Cros for the review and comments to the document, including prior to publishing the document. Thanks to Qiufang Ma, Victor Lopez, and Joe Clarke for the comments and suggestions. The IANA-maintained models were generated using an XSLT stylesheet from the 'iana-yang' project (https://github.com/llhotka/iana-yang). This work is partially supported by the European Commission under Horizon 2020 Secured autonomic traffic management for a Tera of SDN flows (Teraflow) project (grant agreement number 101015857).