| Internet-Draft | BGP-LS for Advertising SAV Rules | April 2025 |
| Tong, et al. | Expires 25 October 2025 | [Page] |
This document describes the protocol extensions of BGP Link-State to collect source address validation (SAV) rules generated by different protocols/mechanisms, to facilitate multi-sourced SAV rules monitoring and management.¶
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Source Address Validation (SAV) can efficiently prevent source address spoofing-based attacks. SAV rules, which indicate the valid/invalid incoming interfaces of a specific source IP address or source IP prefix, are installed on routers for checking the source addresses of received packets.¶
SAV rules can be generated by static configuration, management tools, or based on different routing protocols such as OSPFv2, OSPFv3, IS-IS, BGP, or their extensions [I-D.ietf-savnet-intra-domain-architecture][I-D.ietf-savnet-inter-domain-architecture]. Due to the requirements of application scenarios, a router may use more than one tool at the same time to obtain SAV rules. Therefore, the rules on the router will be multi-sourced, which complicates management. What is more challenging is that there may exist conflicts among these multi-sourced rules and the rules can be dynamic.¶
To facilitate SAV rules monitoring and management, this document proposes to extend BGP-LS ([RFC9552]) for advertising SAV rules on routers to a centralized server. The centralized server can effectively collect multi-sourced SAV rules from routers. For the purpose of advertising SAV rules within BGP-LS advertisements, two new NLRIs called SAV Rule NLRIs are proposed for IPv4 and IPv6, respectively.¶
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 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
The "Link-State NLRI" defined in [RFC9552] is extended to carry the SAV rule information. The format of "Link-State NLRI" is defined in [RFC9552] as follows:¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NLRI Type | Total NLRI Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Link-State NLRI (variable) //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This document defines two new NLRI Types known as SAV Rule NLRIs (values are TBD) for the advertisement of SAV rule Information.¶
This document defines SAV Rule NLRI Types with their common format as shown in the following figure:¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+
| Protocol-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier |
+ (8 octets) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Local Node Descriptors TLVs (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// SAV Rule Descriptors TLVs (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields are defined as follows:¶
Protocol-ID: Specifies the source of SAV rules in this NLRI. Protocol-ID values defined in [RFC9552][RFC9086] can be reused.¶
Local Node Descriptors TLV: Contains Node Descriptors for the nodes storing SAV rules. This is a mandatory TLV in SAV Rule NLRIs. The Type is 256. The length of this TLV is variable. The value contains one or more Node Descriptor sub-TLVs defined in [RFC9552].¶
SAV Rule Descriptors TLVs: There can be one or more SAV Rule Descriptors TLVs for carrying SAV rules.¶
The SAV Rule Descriptor field is a set of TLV triplets. SAV Rule Descriptors TLVs identify a set of SAV rules having the same set of valid interfaces as defined in [I-D.ietf-savnet-general-sav-capabilities]. The following TLVs are valid as SAV Rule Descriptors in the SAV Rule NLRI:¶
+-------------+---------------------+----------+
| TLV Code | Description | Length |
| Point | | |
+-------------+---------------------+----------+
| TBD | Interface Name | variable |
| TBD | Interface Group | 4 |
| TBD | SAV Prefix | variable |
+-------------+---------------------+----------+
An Interface Name TLV is used to identify one valid interface of the source prefixes carried in SAV Prefix TLVs. The format of Interface Name TLV is as follows:¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Interface Name (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
There can be zero, one or more Interface Name TLVs in the SAV Rule Descriptor field.¶
An Interface Group TLV is to identify a group of valid interfaces of the source prefixes carried in SAV Prefix TLVs. The format of Interface Group TLV is as follows:¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Interface Group (4 octets) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Interface Group value can have either a local meaning or a global meaning. On the one hand, it can be a local interface property on the target routers, and the meaning of it depends on the configurations of network administrator [I-D.ietf-idr-flowspec-interfaceset]. On the other hand, a global meaning Group Identifier field carries an AS number, which represents all the interfaces connected to the neighboring AS with the AS number. [I-D.geng-idr-flowspec-sav]¶
Interface Group value can also be an Interface ID for identifying a specific interface.¶
There can be zero, one or more Interface Group TLVs in the SAV Rule Descriptor field. Interface Group TLVs can be used together with Interface Name TLVs.¶
When there is neither an Interface Name TLV nor an Interface Group TLV, the source prefixes carried in SAV Prefix TLVs are considered valid for all the interfaces on the router.¶
A SAV Prefix TLV carries one IP address prefix (IPv4 or IPv6). The format of SAV Prefix TLV is as follows:¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Length | IP Prefix (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
There can be one or more SAV Prefix TLVs in the SAV Rule Descriptor field. The IPv4 SAV Prefix TLVs will only appear in the IPv4 SAV Rule NLRI, and The IPv6 SAV Prefix TLVs are only for the IPv6 SAV Rule NLRI¶
There can be more than one SAV mechanisms based on the same source (identified by Protocol-ID). In order to distinguish the different sources of rules in a more fine-grained manner, the Type field needs to be allocated for multiple values, and each value identifies a specific SAV mechanism based on the same source identified by Protocol-ID.¶
The BGP-LS Attribute, an optional and non-transitive BGP Attribute, is used to carry the validation mode information of SAV rules {I-D.ietf-savnet-general-sav-capabilities}. The following SAV Mode Attribute TLV is defined for the BGP-LS Attribute associated with a SAV Rule NLRI:¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |M | Reserved | +-+-+-+-+-+-+-+-+
The SAV Mode TLV carries a Mode Flag (M flag is shown in the figure and occupies two bits) describing the validation mode attribute.¶
When M flag is set to 00, the mode is Mode 1: interface-based source prefix allowlist. The NLRI carries the source prefixes and interfaces. Only the carried prefixes are valid on the carried interfaces, and any other prefixes are invalid on these interfaces.¶
When M flag is set to 01, the mode is Mode 2: interface-based source prefix blocklist. The NLRI carries the source prefixes and interfaces. Only the carried prefixes are invalid on the carried interfaces, and any other prefixes are valid on these interfaces.¶
When M flag is set to 10, the mode is Mode 3: prefix-based interface allowlist. The NLRI carries the source prefixes and interfaces. Only the carried interfaces are valid for the carried prefixes, and any other interfaces are invalid for those prefixes. Any other prefixes will not be validated.¶
When M flag is set to 11, the mode is Mode 4: prefix-based interface blocklist. The NLRI carries the source prefixes and interfaces. Only the carried interfaces are invalid for the carried prefixes, and any other interfaces are valid for those prefixes. Any other prefixes will not be validated.¶
SAV actions in this document adopt the traffic filtering actions defined in [RFC8955] and [RFC8956].¶
Traffic filtering actions defined in [RFC 8955] include traffic-rate-bytes, traffic-rate-packets, traffic-action, rt-redirect, and traffic-marking, which are applicable to IPv4 and IPv6. Rt-redirect-ipv6 is a new traffic filtering action defined in [RFC 8956], which is applicable to IPv6. The encapsulation formats of SAV actions are consistent with the encapsulation formats defined in [RFC 8955] and [RFC 8956].¶
A SAV rule may match multiple SAV actions, and there may be conflicts among these SAV actions. Section 7.7 of [RFC 8955] describes the conflicts among Traffic filtering actions.¶
In this section, we provide examples of how to configure SAV rule NLRI for the four validation modes. The SAV rule NLRI can carry zero, one, or multiple interfaces/interface groups and one or more prefixes.¶
In this mode, only the prefixes carried in the SAV rule NLRI are considered valid on the specified interface. All other prefixes arriving at this interface are considered invalid.¶
Example:¶
In this mode, the prefixes carried in the SAV rule NLRI are considered invalid on the specified interface. All other prefixes arriving at this interface are considered valid.¶
Example:¶
In this mode, for a specific source prefix, only the interfaces carried in the SAV rule NLRI are considered valid. Packets with this source prefix arriving at other interfaces are invalid. Other prefixes are not checked.¶
Example:¶
In this mode, for a specific source prefix, the interfaces carried in the SAV rule NLRI are considered invalid. Packets with this source prefix arriving at other interfaces are valid. Other prefixes are not checked.¶
Example:¶
The BGP-LS advertisements for the SAV Rule NLRI type are generally originated by the node running SAV mechanisms/protocols.¶
The Existing BGP operational and management procedures apply to this document. No new procedures are defined in this document. The considerations as specified in [RFC9552] apply to this document.¶
This section describes the code point allocation by IANA for this document.¶
This document requests assigning code-points from the registry for SAV Rule NLRIs:¶
+------+---------------------------+ | Type | NLRI Type | +------+---------------------------+ | TBD | IPv4 SAV Rule NLRI | | TBD | IPv6 SAV Rule NLRI | +------+---------------------------+¶
This document requests assigning code-points from the registry for BGP-LS SAV Rule Descriptors TLVs based on Figure 3.¶
This document requests assigning a code-point from the registry for the BGP-LS SAV Mode attribute TLV.¶
Procedures and protocol extensions defined in this document do not affect the base BGP security model. See [RFC6952] for details. The security considerations of the base BGP-LS specification as described in [RFC9552] also apply.¶