| Internet-Draft | BGP-LS for Advertising SAV Rules | October 2024 |
| Tong, et al. | Expires 24 April 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 rule 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.li-savnet-intra-domain-architecture][I-D.wu-savnet-inter-domain-architecture]. Due to the requirements of application scenarios, a router may use more than one tool at the same time to get the 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 of these multi-sourced rules and the rules can be dynamic.¶
To facilitate SAV rule 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 Type" 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 TLV (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// SAV Rule Descriptors TLVs (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields are defined as follows:¶
Protocol-ID: Protocol-ID field specifies the source of the SAV rules in this NLRI. Protocol-ID values defined in RFC9552 [RFC9086] can be reused.¶
Local Node Descriptors TLV: It contains Node Descriptors for the node 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 carring SAV rules.¶
The SAV Rule Descriptor field is a set of TLV triplets. SAV Rule Descriptors TLVs identify a set of SAV rule having the same set of valid interfaces as defined in [I-D.huang-savnet-sav-table]. 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 |
+-------------+---------------------+----------+
A Interface Name TLV is 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.¶
A 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 local meaning or 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 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.huang-savnet-sav-table]. 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 shown in the figure) describing the validation mode attribute.¶
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.¶