IDR Working Group C. Loibl Internet-Draft Next Layer Communications Obsoletes: 5575,7674 (if approved) S. Hares Intended status: Standards Track Huawei Expires:December 20, 2019May 7, 2020 R. Raszuk Bloomberg LP D. McPherson Verisign M. Bacher T-Mobile AustriaJune 18,November 4, 2019 Dissemination of Flow Specification Rulesdraft-ietf-idr-rfc5575bis-17draft-ietf-idr-rfc5575bis-18 Abstract This document obsoletes both RFC5575 and RFC7674. This document defines a Border Gateway Protocol Network Layer Reachability Information (BGP NLRI) encodingformatformat, that can be used to distribute traffic Flow Specifications. This allows the routing system to propagate information regarding more specific components of the traffic aggregate defined by an IP destination prefix. It also specifiesIPv4 traffic Flow Specifications via aBGPNLRI which carries trafficExtended Community encoding formats, that can be used to propagate Traffic Filtering Actions along with the Flow Specificationfilter, and an Extended community value which encodesNLRI. Those Traffic Filtering Actions encode actions a routing system can take if the packet matches thetraffic flow filters. The flow filters and the actions are processed in a fixed order. Other drafts specify IPv6, MPLS addresses, L2VPN addresses, and NV03 encapsulationFlow Specification. Additionally, it defines two applications ofIP addresses. This document obsoletes RFC5575 and RFC7674that encoding format: one that can be used tocorrect unclear specifications in the flow filters. Applications which use the bgp Flow Specification are: 1) application whichautomate inter-domain coordination of traffic filtering, such as what is required in order to mitigate (distributed)denial-of- service attacks; 2) applications which controldenial-of-service attacks, and a second application to provide traffic filtering in the context of a BGP/MPLS VPNservice, and 3)service. Other applicationswith(ie. centralized control of traffic in a SDN or NFVcontext. Some deployments of these three applications can be handled by the strict ordering of the BGP NLRI traffic flow filters,context) are also possible. Other drafts specify IPv6, MPLS addresses, L2VPN addresses, andthe strict actions encoded in the extended communityNV03 encapsulation of IP addresses as Flow Specificationactions.extensions. The information is carried via the BGP, thereby reusing protocol algorithms, operational experience, and administrative processes such as inter-provider peering agreements. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire onDecember 20, 2019.May 7, 2020. Copyright Notice Copyright (c) 2019 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Definitions of Terms Used in This Memo . . . . . . . . . . . 5 3. Flow Specifications . . . . . . . . . . . . . . . . . . . . .65 4. Dissemination of IPv4 FLow Specification Information . . . .76 4.1. Length Encoding . . . . . . . . . . . . . . . . . . . . . 7 4.2. NLRI Value Encoding . . . . . . . . . . . . . . . . . . .87 4.2.1.Type 1 - Destination PrefixOperators . . . . . . . . . . . . .8 4.2.2. Type 2 - Source Prefix. . . . . . . . . 7 4.2.2. Components . . . . . .8 4.2.3. Type 3 - IP Protocol. . . . . . . . . . . . . . . 9 4.3. Examples of Encodings .8 4.2.4. Type 4 - Port. . . . . . . . . . . . . . . . . 13 5. Traffic Filtering . . .10 4.2.5. Type 5 - Destination Port. . . . . . . . . . . . . .10 4.2.6. Type 6 - Source Port. . . . . 16 5.1. Ordering of Flow Specifications . . . . . . . . . . .10 4.2.7. Type 7 - ICMP type. . 17 6. Validation Procedure . . . . . . . . . . . . . . .11 4.2.8. Type 8 - ICMP code. . . . . 18 7. Traffic Filtering Actions . . . . . . . . . . . .11 4.2.9. Type 9 - TCP flags. . . . . . 19 7.1. Traffic Rate in Bytes (traffic-rate-bytes) sub-type 0x06 20 7.2. Traffic Rate in Packets (traffic-rate-packets) sub-type TBD . . . . . . . . . . .11 4.2.10. Type 10 - Packet length. . . . . . . . . . . . . . .12 4.2.11. Type 11 - DSCP (Diffserv Code Point). 21 7.3. Traffic-action (traffic-action) sub-type 0x07 . . . . . . 21 7.4. RT Redirect (rt-redirect) sub-type 0x08 .12 4.2.12. Type 12 - Fragment. . . . . . . . 22 7.5. Traffic Marking (traffic-marking) sub-type 0x09 . . . . . 22 7.6. Interaction with other Filtering Mechanisms in Routers . 23 7.7. Considerations on Traffic Filtering Action Interference . 23 8. Dissemination of Traffic Filtering in BGP/MPLS VPN Networks . 24 9. Traffic Monitoring .12 4.3. Examples of Encodings. . . . . . . . . . . . . . . . . .13 5. Traffic Filtering. . 25 10. Error-Handling . . . . . . . . . . . . . . . . . . . .14 5.1. Ordering of Traffic Filtering Rules. . . 25 11. Future NLRI Extensions . . . . . . . .15 6. Validation Procedure. . . . . . . . . . . 25 12. IANA Considerations . . . . . . . . .17 7. Traffic Filtering Actions. . . . . . . . . . . . 26 12.1. AFI/SAFI Definitions . . . . . .18 7.1. Traffic Rate in Bytes (traffic-rate-bytes) sub-type 0x06 19 7.2. Traffic Rate in Packets (traffic-rate-packets) sub-type TBD. . . . . . . . . . . . 26 12.2. Flow Component Definitions . . . . . . . . . . . . . . .20 7.3. Traffic-action (traffic-action) sub-type 0x0726 12.3. Extended Community Flow Specification Actions . . . . . 27 13. Security Considerations .20 7.4. RT Redirect (rt-redirect) sub-type 0x08. . . . . . . . .21 7.5. Traffic Marking (traffic-marking) sub-type 0x09. . . . .21 7.6. Considerations on Traffic Action Interference. . . . 30 14. Contributors . .21 8. Dissemination of Traffic Filtering in BGP/MPLS VPN Networks.22 8.1. Validation Procedures for BGP/MPLS VPNs. . . . . . . . .23 8.2. Traffic Actions Rules. . . . . . . . . . . . 31 15. Acknowledgements . . . . . .23 9. Limitations of Previous Traffic Filtering Efforts. . . . . .23 9.1. Limitations in Previous DDoS Traffic Filtering Efforts.23 9.2. Limitations in Previous BGP/MPLS Traffic Filtering Efforts. . . . . . . . . 31 16. References . . . . . . . . . . . . . . . .24 10. Traffic Monitoring. . . . . . . . . 32 16.1. Normative References . . . . . . . . . . . .24 11. Error-Handling and Future NLRI Extensions . . . . . . . . . . 24 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 12.1. AFI/SAFI Definitions . . . . . . . . . . . . . . . . . . 25 12.2. Flow Component Definitions . . . . . . . . . . . . . . . 25 12.3. Extended Community Flow Specification Actions . . . . . 26 13. Security Considerations . . . . . . . . . . . . . . . . . . . 29 14. Operational Security Considerations . . . . . .. . . . . .. 30 15. Original authors . . . . . . . . . . . . . . . . . . . . . . 30 16. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 30 17. References . . . . . . . . . . . . . . . . . . . . . . . . . 30 17.1. Normative32 16.2. Informative References . . . . . . . . . . . . . . . . .. 30 17.2. Informative References . . . .33 16.3. URIs . . . . . . . . . . . . .32 17.3. URIs. . . . . . . . . . . . . 34 Appendix A. Python code: flow_rule_cmp . . . . . . . . . . . . .3234 AppendixA.B. Comparison with RFC 5575 . . . . . . . . . . . . . .3236 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . .3337 1. Introduction This document obsoletes both "Dissemination of Flow Specification Rules" [RFC5575] and "Clarification of the Flowspec Redirect Extended Community"[RFC7674]. Modern IP routers contain both the capability to forward traffic according to IP prefixes as well as to classify, shape, rate limit, filter, or redirect packets based on administratively defined policies. These traffic policy mechanisms allow therouteroperator to define match rules that operate on multiple fields of the packet header. Actions such as the ones described above can be associated with each rule. The n-tuple consisting of the matching criteria defines an aggregate traffic Flow Specification. The matching criteria can include elements such as source and destination address prefixes, IP protocol, and transport protocol port numbers.ThisSection 4 of this document defines a general procedure to encodeflow specification rulesFlow Specification for aggregated traffic flows so that they can be distributed as a BGP [RFC4271] NLRI. Additionally,we defineSection 7 of this document defines the required Traffic Filtering Actions BGP Extended Communities and mechanisms toutilize this definition to the problem of immediate concern to the authors:use BGP for intra- and inter-provider distribution of traffic filtering rules to filter (distributed) denial-of-service (DoS) attacks. By expanding routing information with Flow Specifications, the routing system can take advantage of the ACL (Access Control List) or firewall capabilities in the router's forwarding path. FlowspecificationsSpecifications can be seen as more specific routing entries to a unicast prefix and are expected to depend upon the existing unicast data information. A Flow Specification received from an external autonomous system will need to be validated against unicast routing before beingaccepted.accepted (Section 6). The flow specification received from an internal BGP peer within the same autonomous system (per [RFC4271]) is assumed to have been validated prior to transmission within the iBGP mesh of an autonomous system. If the aggregate traffic flow defined by the unicast destination prefix is forwarded to a given BGP peer, then the local system can install more specificflow rulesFlow Specifications that may result in different forwarding behavior, as requested by this system.The key technology components required to address the class of problems targeted by this document are: 1. Efficient point-to-multipoint distribution of control plane information. 2. Inter-domain capabilities and routing policy support. 3. Tight integration with unicast routing, for verification purposes. Items 1 and 2 have already been addressed using BGP for other types of control plane information. Close integration with BGP also makes it feasible to specify a mechanism to automatically verify flow information against unicast routing. These factors are behind the choice of BGP as the carrier of Flow Specification information. As with previous extensions to BGP, this specification makes it possible to add additional information to Internet routers. These are limited in terms of the maximum number of data elements they can hold as well as the number of events they are able to process in a given unit of time. The authors believe that, as with previous extensions, service providers will be careful to keep information levels below the maximum capacity of their devices. Experience with previous BGP extensions has also shown that the maximum capacity of BGP speakers has been gradually increased according to expected loads. For example Internet unicast routing as well as other BGP applications increased their maximum capacity as they gain popularity.From an operational perspective, the utilization of BGP as the carrier for this information allows a network service provider to reuse both internal route distribution infrastructure (e.g., route reflector or confederation design) and existing external relationships (e.g., inter-domain BGP sessions to a customer network). While it is certainly possible to address this problem using other mechanisms, this solution has been utilized in deployments because of the substantial advantage of being an incremental addition to already deployed mechanisms. In current deployments, the information distributed bythe flow-specthis extension is originated both manually as well as automatically. The latter by systems that are able to detect malicious traffic flows. When automated systems are used, care should be taken to ensure their correctness as well asto limitthenumber and advertisement ratelimitations offlow routes.the systems that receive and process the advertised Flow Specifications (see also Section 13). This specification defines required protocol extensions to address most common applications of IPv4 unicast and VPNv4 unicast filtering. The same mechanism can be reused and new match criteria added to address similar filtering needs for other BGP address families such as IPv6 families[I-D.ietf-idr-flow-spec-v6],[I-D.ietf-idr-flow-spec-v6]. 2. Definitions of Terms Used in This MemoNLRIAFI - Address Family Identifier. AS - Autonomous System. Loc-RIB - The Loc-RIB contains the routes that have been selected by the local BGP speaker's Decision Process. NLRI - Network Layer Reachability Information. PE - Provider Edge router. RIB - Routing Information Base.Loc-RIB - Local RIB. ASSAFI -Autonomous System.Subsequent Address Family Identifier. VRF - Virtual Routing and Forwarding instance.PE - Provider Edge routerThe 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. 3. Flow Specifications A Flow Specification is an n-tuple consisting of several matching criteria that can be applied to IP traffic. A given IP packet is said to match the definedflowFlow Specification if it matches all the specified criteria. This n-tuple is encoded into a BGP NLRI defined below. A givenflowFlow Specification may be associated with a set of attributes, depending on the particular application; such attributes may or may not include reachability information (i.e., NEXT_HOP). Well-known or AS-specific community attributes can be used to encode a set of predetermined actions. A particular application is identified by a specific (Address Family Identifier, Subsequent Address Family Identifier (AFI, SAFI)) pair [RFC4760] and corresponds to a distinct set of RIBs. Those RIBs should be treated independently from each other in order to assure non-interference between distinct applications. BGP itself treats the NLRI asana key to an entry in its databases. Entries that are placed in the Loc-RIB are then associated with a given set of semantics, which is application dependent. This is consistent with existing BGP applications. For instance, IP unicast routing (AFI=1, SAFI=1) and IP multicast reverse-path information (AFI=1, SAFI=2) are handled by BGP without any particular semantics being associated with them until installed in the Loc-RIB. Standard BGP policy mechanisms, such as UPDATE filtering by NLRI prefix as well as community matching and manipulation,MUSTmust apply to the Flow Specification defined NLRI-type, especially in an inter- domain environment. Network operators can also control propagation of such routing updates by enabling or disabling the exchange of a particular (AFI, SAFI) pair on a given BGP peering session. 4. Dissemination of IPv4 FLow Specification InformationWe defineThis document defines a"Flow Specification"Flow Specification NLRI type (Figure 1) that may include several components such as destination prefix, source prefix, protocol, ports, and others (see Section 4.2 below). This NLRI information is encoded using MP_REACH_NLRI and MP_UNREACH_NLRI attributes as defined in [RFC4760]. Whenever the corresponding application does not requireNext-HopNext Hop information, this shall be encoded as a 0-octet length Next Hop in the MP_REACH_NLRI attributeand(if a non 0-octet Next Hop is present it should be ignored onreceipt.receipt). The NLRI field of the MP_REACH_NLRI and MP_UNREACH_NLRI is encoded as a 1- or 2-octet NLRI length field followed by a variable-length NLRI value. The NLRI length is expressed in octets.+------------------------------++-------------------------------+ | length (0xnn or0xfn nn)0xfnnn) |+------------------------------++-------------------------------+ | NLRI value (variable) |+------------------------------++-------------------------------+ Figure 1:Flow-specFlow Specification NLRI for IPv4 Implementations wishing to exchange Flow SpecificationrulesMUST use BGP's Capability Advertisement facility to exchange the Multiprotocol Extension Capability Code (Code 1) as defined in [RFC4760]. The (AFI, SAFI) pair carried in the Multiprotocol Extension Capability MUST be (AFI=1, SAFI=133) for IPv4 Flow Specification, and (AFI=1, SAFI=134) for VPNv4 Flow Specification. 4.1. Length Encoding o If the NLRI lengthvalueis smaller than 240 (0xf0hex),hex) octets, the length field can be encoded as a single octet. o Otherwise, it is encoded as an extended-length 2-octet value in which the most significant nibble of the first byte is all ones. InfigureFigure 1 above, values less-than 240 are encoded using two hex digits (0xnn). Values above 239 are encoded using 3 hex digits (0xfnnn). The highest value that can be represented with this encoding is 4095.TheFor example the length value241of 239 is encoded as 0xef (single octet) while 240 is encoded as0xf0f1.0xf0f0 (2-octet). 4.2. NLRI Value Encoding The Flow SpecificationNLRI-typeNLRI value consists ofseverala list of optionalsubcomponents.components and is encoded as follows: Encoding: <[component]+> A specific packet is considered to match theflow specificationFlow Specification when it matches the intersection (AND) of all the components present in thespecification. The encoding of each of the NLRI components begins with a type field (1 octet) followed by a variable length parameter. Section 4.2.1 to Section 4.2.12 define component types and parameter encodings for the IPv4 IP layer and transport layer headers. IPv6 NLRI component types are described in [I-D.ietf-idr-flow-spec-v6].FlowSpecification componentsSpecification. Components must follow strict type ordering by increasing numerical order. A given component type may (exactly once) or may not be present in thespecification.Flow Specification. If present, it MUST precede any component of higher numeric type value. All combinations ofcomponent typescomponents within a singleNLRIFlow Specification areallowed, even if the combination makes no sense from a semantical perspective. If a given component type within a prefix in unknown, the prefix in questionallowed. However, some combinations cannot match any packets (ie. "ICMP Type AND Port" will never match any packets), and thus SHOULD NOT beused for traffic filtering purposespropagated by BGP. 4.2.1. Operators Most of thereceiver. Since a Flow Specification has the semanticscomponents described below make use ofa logical ANDcomparison operators. Which ofall components, if a componentthe two operators is used isFALSE,defined bydefinition it cannot be applied. However, forthepurposes of BGP route propagation, this prefix should still be transmitted since BGP route distribution is independent on NLRI semantics. 4.2.1. Type 1 - Destination Prefix Encoding: <type (1 octet), prefix length (1 octet), prefix> Defines: the destination prefix to match. Prefixescomponents in Section 4.2.2. The operators are encoded asin BGP UPDATE messages, a length in bits is followed by enough octets to contain the prefix information. 4.2.2. Type 2 - Source Prefix Encoding: <type (1 octet), prefix-length (1 octet), prefix> Defines the source prefix to match. 4.2.3. Type 3 - IP Protocol Encoding:<type (1 octet), [op, value]+> Containsaset of {operator, value} pairs that are used to match the IP protocol value byte in IP packets. Thesingle octet. 4.2.1.1. Numeric Operator (numeric_op) This operatorbyteis encodedas:as shown in Figure 2. 0 1 2 3 4 5 6 7 +---+---+---+---+---+---+---+---+ | e | a | len | 0 |lt |gt |eq | +---+---+---+---+---+---+---+---+ Figure 2: NumericoperatorOperator (numeric_op) e - end-of-listbit.bit: Set in the last {op, value} pair in the list. a - ANDbit.bit: If unset, the previous term is logically ORed with the current one. If set, the operation is a logical AND. In the first operator byte of a sequence it SHOULD be encoded as unset and and MUST be treated as always unset on decoding. The AND operator has higher priority than OR for the purposes of evaluating logical expressions. len - length: The length of the value field for this operator given as (1 << len). This encodes 1(00) -(len=00), 2 (len=01), 4 (len=10), 8(11)(len=11) bytes.Type 3 flow component values SHOULD be encoded as single byte (len = 00).0 - SHOULD be set to 0 on NLRI encoding, and MUST be ignored during decoding lt - less than comparison between data and value. gt - greater than comparison between data and value. eq - equality between data and value. The bits lt, gt, and eq can be combined to produce common relational operators such as "less or equal", "greater or equal", and "not equalto".to" as shown in Table 1. +----+----+----+----------------------------------+ | lt | gt | eq | Resulting operation | +----+----+----+----------------------------------+ | 0 | 0 | 0 | false (independent of the value) | | 0 | 0 | 1 | == (equal) | | 0 | 1 | 0 | > (greater than) | | 0 | 1 | 1 | >= (greater than or equal) | | 1 | 0 | 0 | < (less than) | | 1 | 0 | 1 | <= (less than or equal) | | 1 | 1 | 0 | != (not equal value) | | 1 | 1 | 1 | true (independent of the value) | +----+----+----+----------------------------------+ Table 1: Comparison operation combinations4.2.4. Type 4 - Port Encoding:<type (1 octet), [op, value]+> Defines a list of {operator, value} pairs that matches source OR destination TCP/UDP ports.4.2.1.2. Bitmask Operator (bitmask_op) Thislistoperator is encodedusingas shown in Figure 3. 0 1 2 3 4 5 6 7 +---+---+---+---+---+---+---+---+ | e | a | len | 0 | 0 |not| m | +---+---+---+---+---+---+---+---+ Figure 3: Bitmask Operator (bitmask_op) e, a, len - Most significant nibble: (end-of-list bit, AND bit, and length field), as defined in thenumeric operatorNumeric Operator formatdefinedin Section4.2.3. Values SHOULD be encoded4.2.1.1. not - NOT bit: If set, logical negation of operation. m - Match bit: If set, this is a bitwise match operation defined as1- or 2-byte quantities. Port, source port, and destination port components evaluate"(data AND value) == value"; if unset, (data AND value) evaluates toFALSETRUE ifthe IP protocol fieldany of thepacket has abits in the valueother than TCP or UDP, ifmask are set in thepacket is fragmenteddata 0 - all 0 bits: SHOULD be set to 0 on NLRI encoding, andthis is notMUST be ignored during decoding 4.2.2. Components The encoding of each of thefirst fragment, or ifcomponents begins with a type field (1 octet) followed by a variable length parameter. The following sections define component types and parameter encodings for thesystemIPv4 IP layer and transport layer headers. IPv6 NLRI component types are described inunable to locate[I-D.ietf-idr-flow-spec-v6]. 4.2.2.1. Type 1 - Destination Prefix Encoding: <type (1 octet), length (1 octet), prefix (variable)> Defines thetransport header. Different implementations may or may not be abledestination prefix todecode the transport headermatch. The length and prefix fields are encoded as in BGP UPDATE messages [RFC4271] 4.2.2.2. Type 2 - Source Prefix Encoding: <type (1 octet), length (1 octet), prefix (variable)> Defines thepresence of IP options or Encapsulating Security Payload (ESP) NULL [RFC4303] encryption. 4.2.5.source prefix to match. The length and prefix fields are encoded as in BGP UPDATE messages [RFC4271] 4.2.2.3. Type53 -Destination Port Encoding:<typeIP Protocol Encoding: <type (1 octet),[op,[numeric_op, value]+>DefinesContains a list of{operator,{numeric_op, value} pairs that are used to match thedestination port of a TCP or UDP packet.IP protocol value byte in IP packet header (see [RFC0791] Section 3.1). Thislist is encoded usingcomponent uses thenumeric operator format definedNumeric Operator (numeric_op) described in Section4.2.3. Values4.2.1.1. Type 3 component values SHOULD be encoded as1- or 2-byte quantities. 4.2.6.single byte (numeric_op len=00). 4.2.2.4. Type64 -SourcePortEncoding:<typeEncoding: <type (1 octet),[op,[numeric_op, value]+> Defines a list of{operator,{numeric_op, value} pairsused to matchthat matches source OR destination TCP/UDP ports (see [RFC0793] Section 3.1 and [RFC0768] Section "Format"). This component matches if either the destination port OR the source port of aTCP or UDP packet.IP packet matches the value. Thislist is encoded usingcomponent uses thenumeric operator format definedNumeric Operator (numeric_op) described in Section4.2.3. Values4.2.1.1. Type 4 component values SHOULD be encoded as 1- or 2-bytequantities. 4.2.7.quantities (numeric_op len=00 or len=01). In case of the presence of the port (destination-port, source-port) component only TCP or UDP packets can match the entire Flow Specification. The port component, if present, never matches when the packet's IP protocol value is not 6 (TCP) or 17 (UDP), if the packet is fragmented and this is not the first fragment, or if the system is unable to locate the transport header. Different implementations may or may not be able to decode the transport header in the presence of IP options or Encapsulating Security Payload (ESP) NULL [RFC4303] encryption. 4.2.2.5. Type75 -ICMP type Encoding:<typeDestination Port Encoding: <type (1 octet),[op,[numeric_op, value]+> Defines a list of{operator,{numeric_op, value} pairs used to match thetype fielddestination port ofan ICMP packet.a TCP or UDP packet (see also [RFC0793] Section 3.1 and [RFC0768] Section "Format"). Thislist is encoded usingcomponent uses thenumeric operator format definedNumeric Operator (numeric_op) described in Section4.2.3. Values4.2.1.1. Type 5 component values SHOULD be encodedusing a single byte.as 1- or 2-byte quantities (numeric_op len=00 or len=01). TheICMP type specifiers evaluatelast paragraph of Section 4.2.2.4 also applies toFALSE whenever the protocol value is not ICMP. 4.2.8.this component. 4.2.2.6. Type86 -ICMP code Encoding:<typeSource Port Encoding: <type (1 octet),[op,[numeric_op, value]+> Defines a list of{operator,{numeric_op, value} pairs used to match thecode fieldsource port ofan ICMP packet.a TCP or UDP packet (see also [RFC0793] Section 3.1 and [RFC0768] Section "Format"). Thislist is encoded usingcomponent uses thenumeric operator format definedNumeric Operator (numeric_op) described in Section4.2.3. Values4.2.1.1. Type 6 component values SHOULD be encodedusing a single byte.as 1- or 2-byte quantities (numeric_op len=00 or len=01). TheICMP code specifiers evaluatelast paragraph of Section 4.2.2.4 also applies toFALSE whenever the protocol value is not ICMP. 4.2.9.this component. 4.2.2.7. Type97 -TCP flags Encoding:<typeICMP type Encoding: <type (1 octet),[op, bitmask]+> Bitmask values can be[numeric_op, value]+> Defines a list of {numeric_op, value} pairs used to match the type field of an ICMP packet (see also [RFC0792] Section "Message Formats"). This component uses the Numeric Operator (numeric_op) described in Section 4.2.1.1. Type 7 component values SHOULD be encoded as single byte (numeric_op len=00). In case of the presence of the ICMP type (code) component only ICMP packets can match the entire Flow Specification. The ICMP type (code) component, if present, never matches when the packet's IP protocol value is not 1 (ICMP), if the packet is fragmented and this is not the first fragment, or if the system is unable to locate the transport header. Different implementations may or may not be able to decode the transport header in the presence of IP options or Encapsulating Security Payload (ESP) NULL [RFC4303] encryption. 4.2.2.8. Type 8 - ICMP code Encoding: <type (1 octet), [numeric_op, value]+> Defines a list of {numeric_op, value} pairs used to match the code field of an ICMP packet (see also [RFC0792] Section "Message Formats"). This component uses the Numeric Operator (numeric_op) described in Section 4.2.1.1. Type 8 component values SHOULD be encoded as single byte (numeric_op len=00). The last paragraph of Section 4.2.2.7 also applies to this component. 4.2.2.9. Type 9 - TCP flags Encoding: <type (1 octet), [bitmask_op, bitmask]+> Defines a list of {bitmask_op, bitmask} pairs used to match TCP Control Bits (see also [RFC0793] Section 3.1). This component uses the Bitmask Operator (bitmask_op) described in Section 4.2.1.2. Type 9 component bitmasks MUST be encoded as 1- or 2-bytebitmask.bitmask (bitmask_op len=00 or len=01). When a single byte (bitmask_op len=00) is specified, it matches byte1314 of the TCP header[RFC0793],(see also [RFC0793] Section 3.1), which containsbits 8 though 15 ofthe4th 32-bit word.TCP Control Bits. When a 2-byte (bitmask_op len=01) encoding is used, it matches bytes12 and13 and 14 of the TCP header with the data offsetfield having a "don't care" value. This(leftmost 4 bits) always treated as 0. In case of the presence of the TCP flags componentevaluates to FALSE for packets that are notonly TCPpackets. This type uses the bitmask operator format, which differs frompackets can match thenumeric operator format inentire Flow Specification. The TCP flags component, if present, never matches when thelower nibble. 0 1 2 3 4 5packet's IP protocol value is not 67 +---+---+---+---+---+---+---+---+ | e | a | len | 0 | 0 |not| m | +---+---+---+---+---+---+---+---+ Bitmask operator e, a, len - Most significant nibble: (end-of-list bit, AND bit, and length field), as defined for in(TCP), if thenumeric operator format in Section 4.2.3. not - NOT bit. If set, logical negation of operation. m - Match bit. If set,packet is fragmented and this isa bitwise match operation defined as "(data AND value) == value";not the first fragment, or ifunset, (data AND value) evaluatesthe system is unable toTRUE if any oflocate thebits intransport header. Different implementations may or may not be able to decode thevalue mask are settransport header in thedata 0 - all 0 bits SHOULD be set to 0 on NLRI encoding, and MUST be ignored during decoding 4.2.10.presence of IP options or Encapsulating Security Payload (ESP) NULL [RFC4303] encryption. 4.2.2.10. Type 10 - Packet lengthEncoding:<typeEncoding: <type (1 octet),[op,[numeric_op, value]+> Defines a list of{operator,{numeric_op, value} pairs used to match on the total IP packet length (excluding Layer 2 but including IP header). Thislist is encoded usingcomponent uses thenumeric operator format definedNumeric Operator (numeric_op) described in Section4.2.3. Values4.2.1.1. Type 10 component values SHOULD be encodedusingas 1- or 2-bytequantities. 4.2.11.quantities (numeric_op len=00 or len=01). 4.2.2.11. Type 11 - DSCP (Diffserv Code Point)Encoding:<typeEncoding: <type (1 octet),[op,[numeric_op, value]+> Defines a list of{operator,{numeric_op, value} pairs used to match the 6-bit DSCP field[RFC2474].(see also [RFC2474]). Thislist is encoded usingcomponent uses thenumeric operator format definedNumeric Operator (numeric_op) described in Section4.2.3. Values SHOULD4.2.1.1. Type 11 component values MUST be encodedusing aas singlebyte.byte (numeric_op len=00). The six least significant bits contain the DSCP value. All other bits SHOULD beencodedtreated aszero and ignored on decoding. 4.2.12.0. 4.2.2.12. Type 12 - FragmentEncoding:<typeEncoding: <type (1 octet),[op,[bitmask_op, bitmask]+>Uses bitmask operator format defined in Section 4.2.9. 0 1 2 3 4 5 6 7 +---+---+---+---+---+---+---+---+ | 0 |Defines a list of {bitmask_op, bitmask} pairs used to match specific IP fragments. This component uses the Bitmask Operator (bitmask_op) described in Section 4.2.1.2. The Type 12 component bitmask MUST be encoded as single byte bitmask (bitmask_op len=00). 0 1 2 3 4 5 6 7 +---+---+---+---+---+---+---+---+ | 0 | 0 | 0 | 0 |LF |FF |IsF|DF | +---+---+---+---+---+---+---+---+ Figure 4: Fragment Bitmask Operand Bitmask values:Bit 7DF - Don't fragment - match if [RFC0791] IP Header Flags Bit-1 (DF)Bit 6is 1 IsF - Is a fragment(IsF) Bit 5- match if [RFC0791] IP Header Fragment Offset is not 0 FF - First fragment(FF) Bit 4- match if [RFC0791] IP Header Fragment Offset is 0 AND Flags Bit-2 (MF) is 1 LF - Last fragment(LF) Bit 0-3- match if [RFC0791] IP Header Fragment Offset is not 0 AND Flags Bit-2 (MF) is 0 0 - SHOULD be set to 0 on NLRI encoding, and MUST be ignored during decoding 4.3. Examples of Encodings 4.3.1. Example 1 An example of a Flow Specification NLRI encoding for: "all packets to10.0.1/24192.0.2.0/24 and TCP port 25".+------------------+----------+----------++--------+----------------+----------+----------+ | length | destination |protoprotocol | port |+------------------+----------+----------++--------+----------------+----------+----------+ |0x010x0b | 01 180ac0 000102 | 03 81 06 | 04 81 19 |+------------------+----------+----------+ Decode for protocol: +-------+----------+------------------------------++--------+----------------+----------+----------+ Decoded: +-------+------------+------------------------------+ | Value | | |+-------+----------+------------------------------++-------+------------+------------------------------+ | 0x0b | length | 11 octets (len<240 1-octet) | | 0x01 | type | Type 1 - Destination Prefix | | 0x18 | length | 24 bit | | 0xc0 | prefix | 192 | | 0x00 | prefix | 0 | | 0x02 | prefix | 2 | | 0x03 | type | Type 3 - IP Protocol | | 0x81 |operatornumeric_op | end-of-list, value size=1, = | | 0x06 | value | IP Protocol 6 = TCP | | 0x04 | type | Type 4 - Port | | 0x81 | numeric_op | end-of-list, value size=1, = | | 0x19 | value | 25 |+-------+----------+------------------------------++-------+------------+------------------------------+ This constitutes a NLRI with a NLRI length of 11 octets. 4.3.2. Example 2 An example of a Flow Specification NLRI encoding for: "all packets to10.1.1/24192.0.2.0/24 from192/8203.0.113.0/24 and port {range [137, 139] or 8080}".+------------------+----------+-------------------------++--------+----------------+----------------+-------------------------+ | length | destination | source | port |+------------------+----------+-------------------------++--------+----------------+----------------+-------------------------+ | 0x12 |0x01 18 0a 0101 18 c0 00 02 | 0208 c018 cb 00 71 | 04 03 89 45 8b 91 1f 90 |+------------------+----------+-------------------------+ Decode for port: +--------+----------+------------------------------++--------+----------------+----------------+-------------------------+ Decoded: +--------+------------+------------------------------+ | Value | | |+--------+----------+------------------------------++--------+------------+------------------------------+ |0x04 | type0x12 | length | 18 octets (len<240 1-octet) |0x03|operator0x01 |size=1, >=type | Type 1 - Destination Prefix |0x89|value0x18 |137length | 24 bit |0x45|operator0xc0 |"AND", value size=1, <=prefix | 192 |0x8b|value0x00 |139prefix | 0 |0x91|operator0x02 |end-of-list, value-size=2, =prefix | 2 |0x1f90|value0x02 |8080type |+--------+----------+------------------------------+ This constitutes anType 2 - Source Prefix | | 0x18 | length | 24 bit | | 0xcb | prefix | 203 | | 0x00 | prefix | 0 | | 0x71 | prefix | 113 | | 0x04 | type | Type 4 - Port | | 0x03 | numeric_op | value size=1, >= | | 0x89 | value | 137 | | 0x45 | numeric_op | "AND", value size=1, <= | | 0x8b | value | 139 | | 0x91 | numeric_op | end-of-list, value size=2, = | | 0x1f90 | value | 8080 | +--------+------------+------------------------------+ This constitutes a NLRI withana NLRI length of1618 octets. 4.3.3. Example 3 An example of a Flow Specification NLRI encoding for: "all packets to 192.0.2.1/32 and fragment { DF or FF } (matching packet with DF bit set or First Fragments) +--------+-------------------+----------+ | length | destination | fragment | +--------+-------------------+----------+ | 0x09 | 01 20 c0 00 02 01 | 0c 80 05 | +--------+-------------------+----------+ Decoded: +-------+------------+------------------------------+ | Value | | | +-------+------------+------------------------------+ | 0x09 | length | 9 octets (len<240 1-octet) | | 0x01 | type | Type 1 - Destination Prefix | | 0x20 | length | 32 bit | | 0xc0 | prefix | 192 | | 0x00 | prefix | 0 | | 0x02 | prefix | 2 | | 0x01 | prefix | 1 | | 0x0c | type | Type 12 - Fragment | | 0x80 | bitmask_op | end-of-list, value size=1 | | 0x05 | bitmask | DF=1, FF=1 | +-------+------------+------------------------------+ This constitutes a NLRI with a NLRI length of 9 octets. 5. Traffic Filtering Traffic filtering policies have been traditionally considered to be relatively static. Limitations ofthethese static mechanisms caused this new dynamic mechanism to be designed for the three new applications of trafficfiltering (preventionfiltering: o Prevention of traffic-based, denial-of-service (DOS)attacks, trafficattacks. o Traffic filtering in the context of BGP/MPLS VPNservice, and centralizedservice. o Centralized traffic control for SDN/NFVnetworks) requiresnetworks. These applications require coordination among service providersand/orand/ or coordination among the AS within a service provider.Section 9 has details on the limitation of previous mechanisms and why BGP Flow Specification provides a solution for to prevent DOS and aid BGP/MPLS VPN filtering rules. ThisThe Flow Specification NLRI definedabove to conveyin Section 4 conveys information about traffic filtering rules for traffic that should be discarded or handled in a manner specified by a set of pre-defined actions (which are defined in BGP Extended Communities). This mechanism is primarily designed to allow an upstream autonomous system to perform inbound filtering in their ingress routers of traffic that a given downstream AS wishes to drop. In order to achieve this goal, this draft specifies two application specific NLRI identifiers that provide traffic filters, and a set of actions encoding in BGP Extended Communities. The two application specific NLRI identifiers are: o IPv4 Flow Specification identifier (AFI=1, SAFI=133) along with specific semantic rules for IPv4 routes, and o VPNv4 Flow Specification identifier (AFI=1, SAFI=134) value, which can be used to propagate traffic filtering information in a BGP/ MPLS VPN environment.DistributionEncoding of theIPv4 Flow SpecificationNLRI is described in Section6, and distibution of BGP/MPLS traffic4 for IPv4 Flow Specificationis describedand in Section8.8 for VPNv4 Flow Specification. Thetrafficfiltering actions are described in Section 7. 5.1. Ordering ofTraffic Filtering Rules With traffic filtering rules, moreFlow Specifications More than oneruleFlow Specification may match a particular traffic flow. Thus, it is necessary to define the orderatin whichrulesFlow Specifications get matched and actions being applied to a particular traffic flow. This ordering functionmust beis such that itmustdoes not depend on the arrival order of the FlowSpecification's rulesSpecification via BGP andmust bethus is consistent in the network. The relative order of two FlowSpecification rulesSpecifications is determined by comparing their respective components. The algorithm starts by comparing the left-most components (lowest component type value) of therules.Flow Specifications. If the types differ, theruleFlow Specification with lowest numeric type value has higher precedence (and thus will match before) than theruleFlow Specification that doesn't contain that component type. If the component types are the same, then a type- specific comparison is performed (see below) if the types are equal the algorithm continues with the next component. For IP prefix values (IP destination or source prefix): If one of the two prefixesoverlap,to compare is a more specific prefix of theone withother, thelonger prefix-lengthmore specific prefix has higher precedence.If they do not overlapOtherwise the one with the lowest IP value has higher precedence. For all other component types, unless otherwise specified, the comparison is performed by comparing the component data as a binary string using the memcmp() function as defined bythe ISO C standard.[ISO_IEC_9899]. For strings with equal lengths the lowest string (memcmp) has higher precedence. For strings of different lengths, the common prefix is compared. If the common prefix is not equal the string with the lowest prefix has higher precedence. If the common prefix is equal, the longest string is considered to have higher precedence than the shorter one. The codebelowin Appendix A shows a Python3 implementation of the comparison algorithm. The full code was tested with Python 3.6.3 and can be obtained at https://github.com/stoffi92/flowspec-cmp [1].<CODE BEGINS> import itertools import ipaddress def flow_rule_cmp(a, b): for comp_a, comp_b in itertools.zip_longest(a.components, b.components): # If6. Validation Procedure Flow Specifications received from acomponent type does not existBGP peer that are accepted inone rule # this rule has lower precedence if not comp_a: return B_HAS_PRECEDENCE if not comp_b: return A_HAS_PRECEDENCE # higher precedence for lower component type if comp_a.component_type < comp_b.component_type: return A_HAS_PRECEDENCE if comp_a.component_type > comp_b.component_type: return B_HAS_PRECEDENCE # component typesthe respective Adj-RIB-In areequal -> type specific comparison if comp_a.component_typeused as input to the route selection process. Although the forwarding attributes of two routes for the same Flow Specification prefix may be the same, BGP is still required to perform its path selection algorithm in(IP_DESTINATION, IP_SOURCE): # assuming comp_a.value, comp_b.value of type ipaddress if comp_a.value.overlaps(comp_b.value): # longest prefixlen has precedence if comp_a.value.prefixlen > comp_b.value.prefixlen: return A_HAS_PRECEDENCE if comp_a.value.prefixlen < comp_b.value.prefixlen: return B_HAS_PRECEDENCE # components equal -> continue with next component elif comp_a.value > comp_b.value: return B_HAS_PRECEDENCE elif comp_a.value < comp_b.value: return A_HAS_PRECEDENCE else: # assuming comp_a.value, comp_b.value of type bytearray if len(comp_a.value) == len(comp_b.value): if comp_a.value > comp_b.value: return B_HAS_PRECEDENCE if comp_a.value < comp_b.value: return A_HAS_PRECEDENCE # components equal -> continue with next component else: common = min(len(comp_a.value), len(comp_b.value)) if comp_a.value[:common] > comp_b.value[:common]: return B_HAS_PRECEDENCE elif comp_a.value[:common] < comp_b.value[:common]: return A_HAS_PRECEDENCE # the first common bytes match elif len(comp_a.value) > len(comp_b.value): return A_HAS_PRECEDENCE else: return B_HAS_PRECEDENCE return EQUAL <CODE ENDS> 6. Validation Procedure Flow Specifications received from a BGP peer that are accepted in the respective Adj-RIB-In are used as input to the route selection process. Although the forwarding attributes of two routes for the same Flow Specification prefix may be the same, BGP is still required to perform its path selection algorithm in order to select the correct setorder to select the correct set of attributes to advertise. The first step of the BGP Route Selection procedure (Section 9.1.2 of [RFC4271] is to exclude from the selection procedure routes that are considered non-feasible. In the context of IP routing information, this step is used to validate that the NEXT_HOP attribute of a given route is resolvable. The concept can be extended, in the case of the Flow Specification NLRI, to allow other validation procedures.AThe validation process described below validates Flow Specifications against unicast routes received over the same AFI but the associated unicast routing information SAFI: Flow specification received over SAFI=133 will be validated against routes received over SAFI=1 Flow specification received over SAFI=134 will be validated against routes received over SAFI=128 By default a Flow Specification NLRImustMUST be validated such that it is considered feasible if and only if all of the below is true: a) A destination prefix component is embedded in the Flow Specification. b) The originator of the Flow Specification matches the originator of the best-match unicast route for the destination prefix embedded in the FlowSpecification.Specification (this is the unicast route with the longest possible prefix length covering the destination prefix embedded in the Flow Specification). c) There are no more specific unicast routes, when compared with the flow destination prefix, thathashave been received from a different neighboring AS than the best-match unicast route, which has been determined in rule b).RuleHowever, rule a) MAY be relaxed by explicit configuration, permitting Flow Specifications that include no destination prefix component. If such is the case, rules b) and c) are moot and MUST be disregarded. By originator of a BGP route, we mean either theBGPaddress of the originatorpath attribute, as used by route reflection,in the ORIGINATOR_ID Attribute [RFC4456], or thetransportsource IP address of the BGP peer, if this path attribute is not present. BGP implementations MUST also enforce that the AS_PATH attribute of a route received via the External Border Gateway Protocol (eBGP) contains the neighboring AS in the left-most position of the AS_PATH attribute. While this rule is optional in the BGP specification, it becomes necessary to enforce it for security reasons. The best-match unicast route may change over the time independently of the Flow Specification NLRI. Therefore, a revalidation of the Flow Specification NLRI MUST be performed whenever unicast routes change. Revalidation is defined as retesting that clause a and clause b above are true. Explanation: The underlying concept is that the neighboring AS that advertises the best unicast route for a destination is allowed to advertiseflow- specFlow Specification information that conveys a more or equally specific destination prefix. Thus, as long as there are no more specific unicast routes, received from a different neighboring AS, which would be affected by thatfiltering rule.Flow Specification. The neighboring AS is the immediate destination of the traffic described by the Flow Specification. If it requests these flows to be dropped, that request can be honored without concern that it represents a denial of service in itself. Supposedly, the traffic is being dropped by the downstream autonomous system, and there is no added value in carrying the traffic to it. 7. Traffic Filtering Actions Thisspecificationdocument defines a minimum set offiltering actionsTraffic Filtering Actions that it standardizes as BGP extended community values [RFC4360]. This is not meant to be an inclusive list of all the possible actions, but only a subset that can be interpreted consistently across the network. Additional actions can be defined as either requiring standards or as vendor specific.Implementations SHOULD provide mechanisms that map an arbitrary BGP community value (normal or extended) to filtering actions that require different mappings in different systems in the network. For instance, providing packets with a worse-than-best-effort, per-hop behavior is a functionality that is likely to be implemented differently in different systems and for which no standard behavior is currently known. Rather than attempting to define it here, this can be accomplished by mapping a user-defined community value to platform-/network-specific behavior via user configuration.The default action for atraffic filteringmatching Flow Specification is to acceptIP traffic that matches that particular rule.the packet (treat the packet according to the normal forwarding behaviour of the system). This document defines the following extended communities values shown in Table 2 in the form0x8xnn0xttss wherenntt indicates the type and ss indicates thesub-type.sub-type of the extended community. Encodings for these extended communities are described below.+-----------+----------------------+--------------------------------++--------------+--------------------------+-------------------------+ | community | action | encoding |+-----------+----------------------+--------------------------------+| 0xttss | | | +--------------+--------------------------+-------------------------+ | 0x8006 | traffic-rate-bytes | 2-byte ASN, 4-byte | | | (Section 7.1) | float | | TBD | traffic-rate-packets | 2-byte ASN, 4-byte | | | (Section 7.1) | float | | 0x8007 | traffic-action (Section | bitmask | | | 7.3) | | | 0x8008 | rt-redirect AS-2byte | 2-octet AS, 4-octet | | | (Section 7.4) | value | | 0x8108 | rt-redirect IPv4 | 4-octet IPv4addres, 2-octetaddress, | | | (Section 7.4) | 2-octet value | | 0x8208 | rt-redirect AS-4byte | 4-octet AS, 2-octet | | | (Section 7.4) | value | | 0x8009 | traffic-marking (Section | DSCP value |+-----------+----------------------+--------------------------------+| | 7.5) | | +--------------+--------------------------+-------------------------+ Table 2: Traffic Filtering Action Extended CommunitiesSomeMultiple Traffic Filtering Actions defined in this document may be present for a single Flow Specification and SHOULD be applied to the trafficaction communitiesflow (for example traffic-rate-bytes and rt-redirect can be applied to packets at the same time). If not all of the Traffic Filtering Actions can be applied to a traffic flow they should be treated as interfering Traffic filtering actions (see below). Some Traffic Filtering Actions may interfere with eachother.other even contradict. Section7.67.7 of thisspecificationdocument provides general considerations on suchtraffic actionTraffic Filtering Action interference. Any additional definition ofa traffic actions specified by additional standards documents or vendor documents MUSTTraffic Filtering Actions SHOULD specifyifthetrafficactioninteractsto take if those Traffic Filtering Actions interfere (also withanexistingtraffic actions, and provide error handling per [RFC7606]. Multiple traffic actions may be present for a single NLRI. The traffic actions are processed in ascending order of the sub-type found in the BGP Extended Communities. If not all of them can be processed the filter SHALL NOT be applied at all (for example: if for a given flow there are the action communities rate-limit-bytes and traffic-marking attached, and the plattform does not support one of them also the other shall not be applied for that flow).Traffic Filtering Actions). Alltraffic actionsTraffic Filtering Actions are specified as transitive BGP Extended Communities. 7.1. Traffic Rate in Bytes (traffic-rate-bytes) sub-type 0x06 The traffic-rate-bytes extended community uses the following extended community encoding: The first two octets carry the 2-octet id, which can be assigned from a 2-byte AS number. When a 4-byte AS number is locally present, the 2 least significant bytes of such an AS number can be used. This value is purely informational and SHOULD NOT be interpreted by the implementation. The remaining 4 octets carry the maximum rate information in IEEE floating point [IEEE.754.1985] format, units being bytes per second. A traffic-rate of 0 should result on all traffic for the particular flow to be discarded. On encoding the traffic-rate MUST NOT be negative. On decoding negative values MUST be treated as zero (discard all traffic). Interferes with: No other BGP Flow Specificationtraffic actionTraffic Filtering Action in this document. 7.2. Traffic Rate in Packets (traffic-rate-packets) sub-type TBD The traffic-rate-packets extended community uses the same encoding as the traffic-rate-bytes extended community. The floating point value carries the maximum packet rate in packets per second. A traffic- rate-packets of 0 should result in all traffic for the particular flow to be discarded. On encoding the traffic-rate-packets MUST NOT be negative. On decoding negative values MUST be treated as zero (discard all traffic). Interferes with: No other BGP Flow Specificationtraffic actionTraffic Filtering Action in this document. 7.3. Traffic-action (traffic-action) sub-type 0x07 The traffic-action extended community consists of 6 bytes of which only the 2 least significant bits of the 6th byte (from left to right) arecurrently defined. 40 41 42 43 44 45 46 47 +---+---+---+---+---+---+---+---+ | reserveddefined by this document as shown in Figure 5. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |STraffic Action Field |T+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |+---+---+---+---+---+---+---+---+Tr. Action Field (cont.) |S|T| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: Traffic-action Extended Community Encoding where S and T are defined as: o T: Terminal Action (bit 47): When this bit is set, the traffic filtering engine willapplyevaluate any subsequentfiltering rulesFlow Specifications (as defined by the ordering procedure). If not set, the evaluation of the trafficfilterfilters stops when thisruleFlow Specification isapplied.evaluated. o S: Sample (bit 46): Enables traffic sampling and logging for this FlowSpecification.Specification (only effective when set). oreserved: should always be set to 0 by the originator and not be evaluated by the receiving BGP speaker.Traffic Action Field: Other Traffic Action Field (see Section 12) bits unused in this specification. The use of the Terminal Action (bit 47) may result in more than onefilter-ruleFlow Specification matching a particular traffic flow. All theflow actionsTraffic Filtering Actions from theserulesFlow Specifications shall be collected and applied. In case of interferingtraffic actionsTraffic Filtering Actions it is an implementation decision whichactionsTraffic Filtering Actions are selected. See also Section7.6.7.7. Interferes with: No other BGP Flow Specificationtraffic actionTraffic Filtering Action in this document. 7.4. RT Redirect (rt-redirect) sub-type 0x08 The redirect extended community allows the traffic to be redirected to a VRF routing instance that lists the specified route-target in its import policy. If several local instances match this criteria, the choice between them is a local matter (for example, the instance with the lowest Route Distinguisher value can be elected). Thisextended communityExtended Community allows 3 different encodings formats for the route-target (type 0x80, 0x81, 0x82).IsIt uses the same encoding as the Route Targetextended community [RFC4360]. It should be noted that the low-order nibble of the Redirect's Type field corresponds to the Route TargetExtended Communityformat field (Type). (Seein Sections3.1, 3.2,3.1 (type 0x80: 2-octet AS, 4-octet value), 3.2 (type 0x81: 4-octet IPv4 address, 2-octet value) and 4 of [RFC4360]plusand Section 2 (type 0x82: 4-octet AS, 2-octet value) of[RFC5668].) The low-order[RFC5668] with the high-order octet(Sub-Type)of theRedirect Extended Community remains 0x08 for all three encodingsType field 0x80, 0x81, 0x82 respectively and the low-order of theBGP Extended Communities (AS 2-byte, AS 4-byte, and IPv4 address).Type field (Sub-Type) always 0x08. Interferes with:AllNo otherredirect functions.BGP Flow Specification Traffic Filtering Action in this document. 7.5. Traffic Marking (traffic-marking) sub-type 0x09 The traffic marking extended community instructs a system to modify the DSCP bits in the IP header ([RFC2474] Section 3) of a transiting IP packet to the correspondingvalue. This extended community is encoded as a sequence of 5 zero bytes followed by the DSCPvalue encoded in the 6 least significant bits of6th byte.the extended community value as shown in Figure 6. The extended is encoded 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | reserved | reserved | reserved | reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | reserved | r.| DSCP | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 6: Traffic Marking Extended Community Encoding o DSCP: new DSCP value for the transiting IP packet. o reserved, r.: SHOULD be set to 0 on encoding, and MUST be ignored during decoding. Interferes with: No other BGP Flow Specificationtraffic actionTraffic Filtering Action in this document. 7.6.Considerations on Traffic Action Interference Since traffic actions are represented asInteraction with other Filtering Mechanisms in Routers Implementations SHOULD provide mechanisms that map an arbitrary BGPextendedcommunityvalues, traffic actions may interferevalue (normal or extended) to Traffic Filtering Actions that require different mappings in different systems in the network. For instance, providing packets witheach other (ie. there maya worse-than-best-effort, per- hop behavior is a functionality that is likely to bemoreimplemented differently in different systems and for which no standard behavior is currently known. Rather thanoneattempting to define it here, this can be accomplished by mapping a user-defined community value to platform-/network-specific behavior via user configuration. 7.7. Considerations on Traffic Filtering Action Interference Since Traffic Filtering Actions are represented as BGP extended community values, Traffic Filtering Actions may interfere with each other (e.g. there may be more than one conflictingtraffic-rate actiontraffic-rate-bytes Traffic Filtering Action associated with a singleflow-filter).Flow Specification). TrafficactionFiltering Action interference has no impact on BGP propagation offlow filtersFlow Specifications (all communities are propagated according to policies). If aflow filterFlow Specification associated with interferingflow actionsTraffic Filtering Actions is selected for packet forwarding, it isaan implementation decision which of the interferingtraffic actionsTraffic Filtering Actions are selected. Implementors of this specification SHOULD document the behaviour of their implementation in such cases.If required, operatorsOperators are encouraged to make use of the BGP policy framework supported by their implementation in order to achieve a predictable behaviour (ie. match - replace - delete communities on administrative boundaries). See also Section 13. 8. Dissemination of Traffic Filtering in BGP/MPLS VPN Networks Provider-based Layer 3 VPN networks, such as the ones using a BGP/ MPLS IP VPN [RFC4364] control plane, may have different traffic filtering requirements than Internet service providers. But also Internet service providers may use those VPNs for scenarios like having the Internet routing table in a VRF, resulting in the same traffic filtering requirements as defined for the global routing table environment within this document. This documentproposesdefines an additional BGP NLRI type (AFI=1, SAFI=134) value, which can be used to propagatetraffic filtering informationFlow Specification in a BGP/MPLS VPN environment. The NLRI format for this address family consists of a fixed-length Route Distinguisher field (8 bytes) followed bya Flow Specification, followingtheencoding defined above inFlow Specification NLRI value Section4.2 of this document.4.2. The NLRI length field shall include both the 8 bytes of the Route Distinguisher as well as the subsequent FlowSpecification.Specification NLRI value. The resulting encoding is shown in Figure 7. +------------------------------+ | length (0xnn or 0xfn nn) | +------------------------------+ | Route Distinguisher (8 bytes)| +------------------------------+ | NLRI value (variable) | +------------------------------+Flow-spec NLRI for MPLS Propagation of this NLRI is controlled by matching Route Target extended communities associated with the BGP path advertisement with the VRF import policy, using the same mechanism as described in "BGP/ MPLS IP VPNs" [RFC4364].Figure 7: Flow Specificationrules received via thisNLRIapply only to traffic that belongs to the VRF(s) in which it is imported. By default, traffic received from a remote PE is switched via an MPLS forwarding decision and is not subject to filtering. Contrary to the behavior specified for the non-VPN NLRI, flow rules are accepted by default, when received from remote PE routers. 8.1. Validation Procedures for BGP/MPLS VPNs The validation procedures are the same as for IPv4. 8.2. Traffic Actions Rules The traffic action rules are the same as for IPv4. 9. Limitations of Previous Traffic Filtering Efforts 9.1. Limitations in Previous DDoS Traffic Filtering Efforts The popularity of traffic-based, denial-of-service (DoS) attacks, which often requires the network operator to be able to use traffic filters for detection and mitigation, brings with it requirements that are not fully satisfied by existing tools. Increasingly, DoS mitigation requires coordination among several service providers in order to be able to identify traffic source(s) and because the volumes of traffic may be such that they will otherwise significantly affect the performance of the network. Several techniques are currently used to control traffic filtering of DoS attacks. Among those, one of the most common is to inject unicast route advertisements corresponding to a destination prefix being attacked (commonly known as remote triggered blackhole RTBH). One variant of this technique marks such route advertisements with a community that gets translated into a discard Next-Hop by the receiving router. Other variants attract traffic to a particular node that serves as a deterministic drop point. Using unicast routing advertisements to distribute traffic filtering information has the advantage of using the existing infrastructure and inter-AS communication channels. This can allow, for instance, a service provider to accept filtering requests from customersforaddress space they own. There are several drawbacks, however. An issue that is immediately apparent is the granularity of filtering control: only destination prefixes may be specified. Another areaMPLS Propagation ofconcern is the fact that filtering information is intermingled with routing information. The mechanism defined inthisdocument is designed to address these limitations. We use the Flow SpecificationNLRIdefined above to convey information about traffic filtering rules for traffic thatissubject to modified forwarding behavior (actions). The actions are defined ascontrolled by matching Route Target extended communitiesand include (but are not limited to) rate-limiting (including discard), traffic redirection, packet rewriting. 9.2. Limitations in Previous BGP/MPLS Traffic Filtering Efforts Provider-based Layer 3 VPN networks, such asassociated with theonesBGP path advertisement with the VRF import policy, usingathe same mechanism as described in BGP/ MPLS IPVPN [RFC4364] control plane, may have different traffic filtering requirements than Internet service providers. In these environments, the VPN customer network often hasVPNs [RFC4364]. Flow Specifications received via this NLRI apply only to trafficfiltering capabilities towards their external network connections (e.g., firewall facing public network connection). Less common isthat belongs to thepresence of traffic filtering capabilities between different VPN attachment sites. In an any-to-any connectivity model,VRF(s) in which it istheimported. By default,this means that site-to-sitetrafficis unfiltered. In circumstances wherereceived from asecurity threat does get propagated inside the VPN customer network, there mayremote PE is switched via an MPLS forwarding decision and is notbe readily available mechanismssubject toprovide mitigation via traffic filter. But also Internet service providers may use those VPNsfiltering. Contrary to the behavior specified forscenarios like havingtheInternet routing table in a VRF. Therefore, limitations described in Section 9.1 also apply to this section. The BGPnon-VPN NLRI, FlowSpecification addresses these limitations. 10.Specifications are accepted by default, when received from remote PE routers. The validation procedure (Section 6) and Traffic Filtering Actions (Section 7) are the same as for IPv4. 9. Traffic Monitoring Traffic filtering applications require monitoring and traffic statistics facilities. While this is animplementation-specificimplementation specific choice, implementations SHOULD provide: o A mechanism to log the packet header of filtered traffic. o A mechanism to count the number of matches for a givenflow specification rule.Flow Specification. 10. Error-Handling Error handling according to [RFC7606] SHOULD apply to this specification. This document introduces Traffic Filtering Action Extended Communities. Malformed Traffic Filtering Action Extended Communities in the sense of [RFC7606] Section 7.14. are Extended Community values that cannot be decoded according to Section 7 of this document. 11.Error-Handling andFuture NLRI Extensions Future Flow Specification extensions may introduce new Flow Specification components. Incaseorder to facilitate such extensions of the Flow Specification NLRI, in addition to the cases described in [RFC7606], if BGP encounters anerror in aunknown Flow Specification component in an UPDATEmessagemessage, it SHOULD also treat this message asTreat-as-withdraw according toTreat-as- withdraw as specified in [RFC7606] Section 2.Possible reasons for an error are (for more reasons see also [RFC7606]): o Incorrect implementation of thisThe specification- the encoding/ decodingofthe NLRI or traffic action extended-communities do not comply with this specification. o Unknown Flow Specification extensions - The sending party has implementeda new Flow SpecificationNLRI extension unknown toComponent Type SHOULD clearly identify what thereceiving party. In ordercriteria used tofacilitate future extensions ofmatch packets forwarded by theFlow Specification NLRI,router is. This criteria should be meaningful across router hops and not depend on values that change hop-by-hop such as TTL or Layer 2 encapsulation. Such extensions SHOULD also specify a way to encodea "always-true"an "always-match" match condition within the newly introducedcomponents.components (this is a match condition, encoded with the newly introduced components: If present on its own, matches all flows). This match condition can be used to propagate (and apply) certainfiltersFlow Specifications only if a specific extension is known to theimplemenation.implementation. 12. IANA Considerations This section complies with [RFC7153]. 12.1. AFI/SAFI Definitions IANA maintains a registry entitled "SAFI Values". For the purpose of this work, IANAupdatedis requested to update theregistryfollowing SAFIs to read according to the table below (Note: This document obsoletes both RFC7674 andallocated two additional SAFIs:RFC5575 and all references to those documents should be deleted from the registry below): +-------+------------------------------------------+----------------+ | Value | Name | Reference | +-------+------------------------------------------+----------------+ | 133 |IPv4 disseminationDissemination of Flow Specification | [this | | | rules | document] | | 134 |VPNv4 disseminationL3VPN Dissemination of Flow | [this | | | Specification rules | document] | +-------+------------------------------------------+----------------+ Table 3: Registry: SAFI Values 12.2. Flow Component Definitions A Flow Specification consists of a sequence of flow components, which are identified by a an 8-bit component type. IANA has created and maintains a registry entitled "Flow Spec Component Types". IANA is requested to update the reference for this registry to [this document]. Furthermore the references to the values should be updated according to the table below (Note: This documentdefinesobsoletes both RFC7674 and RFC5575 and all references to those documents should be deleted from thefollowing Component Type Codes:registry below). +-------+--------------------+-----------------+ | Value | Name | Reference | +-------+--------------------+-----------------+ | 1 | Destination Prefix | [this document] | | 2 | Source Prefix | [this document] | | 3 | IP Protocol | [this document] | | 4 | Port | [this document] | | 5 | Destination port | [this document] | | 6 | Source port | [this document] | | 7 | ICMP type | [this document] | | 8 | ICMP code | [this document] | | 9 | TCP flags | [this document] | | 10 | Packet length | [this document] | | 11 | DSCP | [this document] | | 12 | Fragment | [this document] | +-------+--------------------+-----------------+ Table 4: Registry: Flow Spec Component Types In order to manage the limited number space and accommodate several usages, the following policies defined by [RFC8126] are used: +--------------+-------------------------------+ |RangeType Values | Policy | +--------------+-------------------------------+ | 0 |Invalid valueSpecification required | | [1 .. 12] | Defined by this specification | | [13 .. 127] | Specification required | | [128 .. 255] | First Come First Served| +--------------+-------------------------------+ Table 5: Flow Spec Component Types Policies The specification of a particular "Flow| +--------------+-------------------------------+ Table 5: Flow Spec ComponentType" must clearly identify what the criteria used to match packets forwarded by the router is. This criteria should be meaningful across router hops and not depend on values that change hop-by-hop such as TTL or Layer 2 encapsulation.Types Policies 12.3. Extended Community Flow Specification Actions The Extended Community Flow Specification Action types defined in this document consist of two parts: Type (BGP Transitive Extended Community Type) Sub-Type For the type-part, IANA maintains a registry entitled "BGP Transitive Extended Community Types". For the purpose of this work (Section 7), IANAupdatedis requested to update theregistryreferences tocontainthevalues listed below:following entries according to the table below (Note: This document obsoletes both RFC7674 and RFC5575 and all references to those documents should be deleted in the registry below): +-------+-----------------------------------------------+-----------+ | Type | Name | Reference | | Value | | | +-------+-----------------------------------------------+-----------+ |0x80 | Generic Transitive Experimental Use Extended | [RFC7153] | | | Community (Sub-Types are defined in the | | | | "Generic Transitive Experimental Use Extended | | | | Community Sub-Types" registry) | | |0x81 | Generic Transitive Experimental Use Extended | [this | | | Community Part 2 (Sub-Types are defined in | document] | | | the "Generic Transitive Experimental Use |[See| | | Extended Community Part 2 Sub-Types" |Note-1]| | | Registry) | | | 0x82 | Generic Transitive Experimental Use Extended | [this | | | Community Part 3 (Sub-Types are defined in | document] | | | the "Generic Transitive Experimental Use |[See| | | Extended Community Part 3 Sub-Types" |Note-1]| | | Registry) | | +-------+-----------------------------------------------+-----------+ Table 6: Registry:GenericBGP TransitiveExperimental UseExtended Community TypesNote-1: This document obsoletes RFC7674.For the sub-type part of the extended communityactionsTraffic Filtering Actions IANA maintainsand updatedthe followingregistries: +----------+-----------------------------------------+--------------+registries. IANA is requested to update all names and references according to the tables below and assign a new value for the "Flow spec traffic-rate-packets" Sub-Type (Note: This document obsoletes both RFC7674 and RFC5575 and all references to those documents should be deleted from the registries below). +----------+--------------------------------------------+-----------+ | Sub-Type | Name | Reference | | Value | | |+----------+-----------------------------------------+--------------++----------+--------------------------------------------+-----------+ | 0x06 | Flow spec traffic-rate-bytes | [this | | | | document] | | TBD | Flow spec traffic-rate-packets | [this | | | | document] | | 0x07 | Flow spec traffic-action (Use of the | [this | | | "Value" field is defined in the "Traffic | document] | | |"TrafficAction Fields" registry) |[See Note-2]| | 0x08 | Flow spec rt-redirect AS-2byte format | [this | | | | document] | | 0x09 | Flow spec traffic-remarking | [this | | | | document] |+----------+-----------------------------------------+--------------++----------+--------------------------------------------+-----------+ Table 7: Registry: Generic Transitive Experimental Use Extended Community Sub-TypesNote-2: This document obsoletes both RFC7674 and RFC5575. +-------------+---------------------------+-------------------------++----------------+--------------------------------+-----------------+ | Sub-Type Value | Name | Reference || Value | | | +-------------+---------------------------+-------------------------++----------------+--------------------------------+-----------------+ | 0x08 | Flow spec rt-redirect IPv4 | [this document][See| | |IPv4format |Note-3]|+-------------+---------------------------+-------------------------++----------------+--------------------------------+-----------------+ Table 8: Registry: Generic Transitive Experimental Use Extended Community Part 2 Sub-Types+-------------+----------------------------+------------------------++---------------+----------------------------------+----------------+ | Sub-Type | Name | Reference | | Value | | |+-------------+----------------------------+------------------------++---------------+----------------------------------+----------------+ | 0x08 | Flow spec rt-redirectAS-AS-4byte | [thisdocument] [See| | |4byteformat |Note-3]document] |+-------------+----------------------------+------------------------++---------------+----------------------------------+----------------+ Table 9: Registry: Generic Transitive Experimental Use Extended Community Part 3 Sub-TypesNote-3: This document obsoletes RFC7674, and becomesFurthermore IANA is requested to update theonlyreference forthis table.the registries "Generic Transitive Experimental Use Extended Community Part 2 Sub-Types" and "Generic Transitive Experimental Use Extended Community Part 3 Sub-Types" to [this document]. The "traffic-action" extended community (Section 7.3) defined in this document has 46 unused bits, which can be used to convey additional meaning. IANA created and maintains anewregistry entitled: "Traffic Action Fields". IANA is requested to update the reference for this registry to [this document]. Furthermore IANA is requested to update the references according to the table below. These values should beassigned via IETF Review rules only. The following traffic-action fields have been allocated:assigned via IETF Review rules only (Note: This document obsoletes both RFC7674 and RFC5575 and all references to those documents should be deleted from the registry below). +-----+-----------------+-----------------+ | Bit | Name | Reference | +-----+-----------------+-----------------+ | 47 | Terminal Action | [this document] | | 46 | Sample | [this document] | +-----+-----------------+-----------------+ Table 10: Registry: Traffic Action Fields 13. Security Considerations As long as Flow Specifications are restricted to match the corresponding unicast routing paths for the relevant prefixes (Section 6), the security characteristics of this proposal are equivalent to the existing security properties of BGP unicast routing. Any relaxation of the validation procedure described in Section 6 may allow unwanted Flow Specifications to be propagated and thus unwanted Traffic Filtering Actions may be applied to flows. Where the above mechanisms are not in place, this could open the door to further denial-of-service attacks such as unwanted traffic filtering, remarking or redirection. Deployment of specific relaxations of the validation within an administrative boundary of a network, defined by an AS or an AS- Confederation boundary, may be useful in some networks for quickly distributing filters to prevent denial-of-service attacks. For a network to utilize this relaxation, the BGP policies must support additional filtering since the origin AS field is empty. Specifications relaxing the validation restrictions SHOULD contain security considerations that provide details on the required additional filtering. For example, the use of [RFC6811] to enhance filtering within an AS confederation. Inter-provider routing is based on a web of trust. Neighboring autonomous systems are trusted to advertise valid reachability information. If this trust model is violated, a neighboring autonomous system may cause a denial-of-service attack by advertising reachability information for a given prefix for which it does not provideservice. As long as traffic filtering rules are restricted to match the corresponding unicast routing paths for the relevant prefixes, the security characteristicsservice (unfiltered address space hijack). Since validation ofthis proposal are equivalentthe Flow Specification is tied to theexisting security propertiesannouncement ofBGPthe best unicastrouting. However,route, thisdocument also specifies traffic filtering actions thatmayneed custom additional verification on the receiver side. See Section 14. Where it is not the case,also cause thiswould open the doorvalidation tofurther denial- of-service attacks.fail and consequently prevent Flow Specifications from being accepted by a peer. Possible mitigations are [RFC6811] and [RFC8205]. Enabling firewall-like capabilities in routers without centralized management could make certain failures harder to diagnose. For example, it is possible to allow TCP packets to pass between a pair of addresses but not ICMP packets. It is also possible to permit packets smaller than 900 or greater than 1000 bytes to pass between a pair of addresses, but not packets whose length is in the range 900- 1000. Such behavior may be confusing and these capabilities should be used with care whether manually configured or coordinated through the protocol extensions described in this document.14. Operational Security ConsiderationsFlow Specification BGP speakers (e.g. automated DDoS controllers) not properly programmed, algorithms that are not performing as expected, or simply rogue systems may announce unintended Flow Specifications, send updates at a high rate or generate a high number of Flow Specifications. This may stress the receiving systems, exceed their maximum capacity or may lead to unwanted Traffic Filtering Actions being applied to flows. While the general verification of thetraffic filterFlow Specification NLRI is specified in this document (Section 6) thetraffic filtering actionsTraffic Filtering Actions received by a third party may need custom verification or filtering. In particular all non traffic-rate actions may allow a third party to modify packet forwarding properties and potentially gain access to other routing-tables/VPNs or undesired queues. This can be avoided by properfilteringfiltering/screening ofactionthe Traffic Filtering Action communities at network borders andby mapping user-defined communitiesonly exposing a predefined subset of Traffic Filtering Actions (see Section 7) toexpose certain forwarding properties tothird parties.Since verfication of the traffic filtering NLRIOne way to achieve this istiedby mapping user-defined communities, that can be set by the third party, to Traffic Filtering Actions and not accepting Traffic Filtering Action extended communities from third parties. This extension adds additional information to Internet routers. These are limited in terms of theannouncementmaximum number of data elements they can hold as well as thebest unicast route, a unfiltered address space hijack (e.g. advertisementnumber of events they are able to process in amore specific route) may cause this verificationgiven unit of time. Service providers need tofailconsider the maximum capacity of their devices andconsequently preventmay need to limit the number of FlowSpecification filters from beingSpecifications acceptedby a peer. 15. Original authorsand processed. 14. Contributors Barry Greene, Pedro Marques, Jared Mauch, Danny McPherson, and Nischal Sheth were authors onRFC5575,[RFC5575], and therefore are contributing authors on this document.16.15. Acknowledgements The authors would like to thank Yakov Rekhter, Dennis Ferguson, Chris Morrow, Charlie Kaufman, and David Smith for their comments for the comments on the originalRFC5575.[RFC5575]. Chaitanya Kodeboyina helped design the flow validation procedure; and Steven Lin and Jim Washburn ironed out all the details necessary to produce a working implementation in the originalRFC5575.[RFC5575]. A packet rateflowspec actionTraffic Filtering Action was alsodiscribeddescribed in aflowspec extentionFlow Specification extension draft and the authors like to thank Wesley Eddy, Justin Dailey and Gilbert Clark for their work.AdditionalAdditionally, the authors would like to thank Alexander Mayrhofer, Nicolas Fevrier, Job Snijders, Jeffrey Haas and Adam Chappell for their comments and review.17.16. References17.1.16.1. Normative References [IEEE.754.1985] IEEE, "Standard for Binary Floating-Point Arithmetic", IEEE 754-1985, August 1985. [ISO_IEC_9899] ISO, "Information technology -- Programming languages -- C", ISO/IEC 9899:2018, June 2018. [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, DOI 10.17487/RFC0768, August 1980, <https://www.rfc-editor.org/info/rfc768>. [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, DOI 10.17487/RFC0791, September 1981, <https://www.rfc-editor.org/info/rfc791>. [RFC0792] Postel, J., "Internet Control Message Protocol", STD 5, RFC 792, DOI 10.17487/RFC0792, September 1981, <https://www.rfc-editor.org/info/rfc792>. [RFC0793] Postel, J., "Transmission Control Protocol", STD 7, RFC 793, DOI 10.17487/RFC0793, September 1981, <https://www.rfc-editor.org/info/rfc793>. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>. [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers", RFC 2474, DOI 10.17487/RFC2474, December 1998, <https://www.rfc-editor.org/info/rfc2474>. [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, DOI 10.17487/RFC4271, January 2006, <https://www.rfc-editor.org/info/rfc4271>. [RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended Communities Attribute", RFC 4360, DOI 10.17487/RFC4360, February 2006, <https://www.rfc-editor.org/info/rfc4360>. [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private Networks (VPNs)", RFC4364,4364, DOI 10.17487/RFC4364, February 2006, <https://www.rfc-editor.org/info/rfc4364>. [RFC4456] Bates, T., Chen, E., and R. Chandra, "BGP Route Reflection: An Alternative to Full Mesh Internal BGP (IBGP)", RFC 4456, DOI10.17487/RFC4364, February10.17487/RFC4456, April 2006,<https://www.rfc-editor.org/info/rfc4364>.<https://www.rfc-editor.org/info/rfc4456>. [RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, "Multiprotocol Extensions for BGP-4", RFC 4760, DOI 10.17487/RFC4760, January 2007, <https://www.rfc-editor.org/info/rfc4760>. [RFC5668] Rekhter, Y., Sangli, S., and D. Tappan, "4-Octet AS Specific BGP Extended Community", RFC 5668, DOI 10.17487/RFC5668, October 2009, <https://www.rfc-editor.org/info/rfc5668>. [RFC7153] Rosen, E. and Y. Rekhter, "IANA Registries for BGP Extended Communities", RFC 7153, DOI 10.17487/RFC7153, March 2014, <https://www.rfc-editor.org/info/rfc7153>. [RFC7606] Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K. Patel, "Revised Error Handling for BGP UPDATE Messages", RFC 7606, DOI 10.17487/RFC7606, August 2015, <https://www.rfc-editor.org/info/rfc7606>. [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section inRFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, <https://www.rfc-editor.org/info/rfc8126>. [RFC8174] Leiba, B., "AmbiguityRFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, <https://www.rfc-editor.org/info/rfc8126>. [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>. 16.2. Informative References [I-D.ietf-idr-flow-spec-v6] McPherson, D., Raszuk, R., Pithawala, B., akarch@cisco.com, a., and S. Hares, "Dissemination of Flow Specification Rules for IPv6", draft-ietf-idr-flow-spec- v6-09 (work in progress), November 2017. [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 4303, DOI 10.17487/RFC4303, December 2005, <https://www.rfc-editor.org/info/rfc4303>. [RFC5575] Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J., and D. McPherson, "Dissemination of Flow Specification Rules", RFC 5575, DOI 10.17487/RFC5575, August 2009, <https://www.rfc-editor.org/info/rfc5575>. [RFC6811] Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R. Austein, "BGP Prefix Origin Validation", RFC 6811, DOI 10.17487/RFC6811, January 2013, <https://www.rfc-editor.org/info/rfc6811>. [RFC7674] Haas, J., Ed., "Clarification of the Flowspec Redirect Extended Community", RFC 7674, DOI 10.17487/RFC7674, October 2015, <https://www.rfc-editor.org/info/rfc7674>. [RFC8205] Lepinski, M., Ed. and K. Sriram, Ed., "BGPsec Protocol Specification", RFC 8205, DOI 10.17487/RFC8205, September 2017, <https://www.rfc-editor.org/info/rfc8205>. 16.3. URIs [1] https://github.com/stoffi92/flowspec-cmp Appendix A. Python code: flow_rule_cmp <CODE BEGINS> """ Copyright (c) 2019 IETF Trust and the persons identified as authors of the code. All rights reserved. Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Simplified BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info). """ import itertools import ipaddress def flow_rule_cmp(a, b): for comp_a, comp_b in itertools.zip_longest(a.components, b.components): # If a component type does not exist in one rule # this rule has lower precedence if not comp_a: return B_HAS_PRECEDENCE if not comp_b: return A_HAS_PRECEDENCE # higher precedence for lower component type if comp_a.component_type < comp_b.component_type: return A_HAS_PRECEDENCE if comp_a.component_type > comp_b.component_type: return B_HAS_PRECEDENCE # component types are equal -> type specific comparison if comp_a.component_type in (IP_DESTINATION, IP_SOURCE): # assuming comp_a.value, comp_b.value ofUppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>. 17.2. Informative References [I-D.ietf-idr-flow-spec-v6] McPherson, D., Raszuk, R., Pithawala, B., akarch@cisco.com, a., and S. Hares, "Disseminationtype # ipaddress.IPv4Network if comp_a.value.overlaps(comp_b.value): # longest prefixlen has precedence if comp_a.value.prefixlen > comp_b.value.prefixlen: return A_HAS_PRECEDENCE if comp_a.value.prefixlen < comp_b.value.prefixlen: return B_HAS_PRECEDENCE # components equal -> continue with next component elif comp_a.value > comp_b.value: return B_HAS_PRECEDENCE elif comp_a.value < comp_b.value: return A_HAS_PRECEDENCE else: # assuming comp_a.value, comp_b.value ofFlow Specification Rules for IPv6", draft-ietf-idr-flow-spec- v6-09 (work in progress), November 2017. [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 4303, DOI 10.17487/RFC4303, December 2005, <https://www.rfc-editor.org/info/rfc4303>. 17.3. URIs [1] https://github.com/stoffi92/flowspec-cmptype bytearray if len(comp_a.value) == len(comp_b.value): if comp_a.value > comp_b.value: return B_HAS_PRECEDENCE if comp_a.value < comp_b.value: return A_HAS_PRECEDENCE # components equal -> continue with next component else: common = min(len(comp_a.value), len(comp_b.value)) if comp_a.value[:common] > comp_b.value[:common]: return B_HAS_PRECEDENCE elif comp_a.value[:common] < comp_b.value[:common]: return A_HAS_PRECEDENCE # the first common bytes match elif len(comp_a.value) > len(comp_b.value): return A_HAS_PRECEDENCE else: return B_HAS_PRECEDENCE return EQUAL <CODE ENDS> AppendixA.B. Comparison with RFC 5575 This document includes numerous editorial changes toRFC5575.[RFC5575]. It also completely incorporates the redirect action clarification document [RFC7674]. It is recommended to read the entire document. The authors, however want to point out the following technical changes toRFC5575:[RFC5575]: Section 1 introduces the Flow Specification NLRI. InRFC5575[RFC5575] this NLRI was defined as an opaque-key in BGPs database. This specification has removed all references to a opaque-key property. BGP is able to understand the NLRI encoding. This change also resulted in a new section regarding error-handling and extensibility (Section 10 and Section 11). Section4.2.34.2.2.3 defines a numeric operator and comparison bit combinations. InRFC5575[RFC5575] the meaning of those bit combination was not explicitly defined and left open to the reader. Section4.2.34.2.2.3 - Section4.2.8,4.2.2.8, Section4.2.10,4.2.2.10, Section4.2.114.2.2.11 make use of the above numeric operator. The allowed length of the comparison value was not consistently defined inRFC5575.[RFC5575]. Section 7 defines alltraffic action extendedTraffic Filtering Action Extended communities as transitive extended communities.RFC5575[RFC5575] defined the traffic-rate action to be non-transitive and did not define the transitivity of the otheractionTraffic Filtering Action communities at all. Section 7.2 introduces a newtraffic filtering actionTraffic Filtering Action (traffic- rate-packets). This action did not exist inRFC5575.[RFC5575]. Section 7.4 contains the same redirect actions already defined inRFC5575[RFC5575] however, these actions have been renamed to"rt-redirect""rt- redirect" to make it clearer that the redirection is based on route-target. This section also completely incorporates the [RFC7674] clarifications of the Flowspec Redirect Extended Community. Section7.67.7 contains general considerations on interfering traffic actions. Section 7.3 also cross-references this section.RFC5575[RFC5575] did not mention this. Section1110 containsa modifiednew error handling. Section 11 describes graceful handling of unknown Flow Specification components togracefullyallow futureextensions of flow specification.extensions. Authors' Addresses Christoph Loibl Next Layer Communications Mariahilfer Guertel 37/7 Vienna 1150 AT Phone: +43 664 1176414 Email: cl@tix.at Susan Hares Huawei 7453 Hickory Hill Saline, MI 48176 USA Email: shares@ndzh.com Robert Raszuk Bloomberg LP 731 Lexington Ave New York City, NY 10022 USA Email: robert@raszuk.net Danny McPherson Verisign USA Email: dmcpherson@verisign.com Martin Bacher T-Mobile Austria Rennweg 97-99 Vienna 1030 AT Email: mb.ietf@gmail.com