| Internet-Draft | BGP FlowSpec v2 | January 2022 |
| Hares, et al. | Expires 28 July 2022 | [Page] |
BGP flow specification version 1 (FSv1) defined in RFC 8955, RFC 8956, and RFC 9117 describes the distribution of traffic filter policy (traffic filters and actions) distributed via BGP. Multiple applications have used BGP FSv1 to distribute traffic filter policy. These applications include the following: mitigation of denial of service (DoS), enabling traffic filtering in BGP/MPLS VPNs, centralized traffic control of router firewall functions, and SFC traffic insertion.¶
During the deployment of BGP FSv1 a number of issues were detected due to lack of consistent TLV encoding for rules for flow specifications, lack of user ordering of filter rules and/or actions, and lack of clear definition of interaction with BGP peers not supporting FSv1. Version 2 of the BGP flow specification (FSv2) protocol addresses these features. In order to provide a clear demarcation between FSv1 and FSv2, a different NLRI encapsulates FSv2.¶
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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/.¶
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This Internet-Draft will expire on 28 July 2022.¶
Copyright (c) 2022 IETF Trust and the persons identified as the document authors. All rights reserved.¶
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Modern IP routers have the capability to forward traffic and to classify, shape, rate limit, filter, or redirect packets based on administratively defined policies. These traffic policy mechanisms allow the operator to define match rules that operate on multiple fields within header of an IP data packet. The traffic policy allows actions to be taken upon a match to be associated with each match rule. These rules can be more widely defined as "event-condition-action" (ECA) rules where the event is always the reception of a packet.¶
BGP ([RFC4271]) flow specification as defined by [RFC8955], [RFC8956], [RFC9117] specifies the distribution of traffic filter policy (traffic filters and actions) via BGP to a mesh of BGP peers (IBGP and EBGP peers). The traffic filter policy is applied when packets are received on a router with the flow specification function turned on. The flow specification protocol defined in [RFC8955], [RFC8956], and [RFC9117] will be called BGP flow specification version 1 (BGP FSv1) in this draft.¶
Some modern IP routers also include the abilities of firewalls which can match on a sequence of packet events based on administrative policy. These firewall capabilities allow for user ordering of match rules and user ordering of actions per match.¶
Multiple deployed applications currently use BGP FSv1 to distribute traffic filter policy. These applications include: 1) mitigation of Denial of Service (DoS), 2) traffic filtering in BGP/MPLS VPNS, and 3) centralized traffic control for networks utilizing SDN control of router firewall functions, 4) classifiers for insertion in an SFC, and 5) filters for SRv6 (segment routing v6).¶
During the deployment of BGP flow specification v1, the following issues were detected:¶
Networks currently cope with some of these issues by limiting the type of traffic filter policy sent in BGP. Current Networks do not have a good workaround/solution for applications that receive but do not understand FSv1 policies.¶
This document defines version 2 of the BGP flow specification protocol to address these shortcomings in BGP FSv1. Version 2 of BGP flow specification will be denoted as BGP FSv2.¶
BGP FSv1 as defined in [RFC8955], [RFC8956], and [RFC9117] specified 2 SAFIs (133, 134) to be used with IPv4 AFI (AFI = 1) and IPv6 AFI (AFI=2).¶
This document specifies 2 new SAFIs (TBD1, TBD2) for FSv2 to be used with 5 AFIs (1, 2, 6, 25, and 31) to allow user-ordered lists of traffic match filters for user-ordered traffic match actions encoded in Communities (Wide or Extended) or a SubTLV of the FSv2 NRLI.¶
FSv1 and FSv2 use different AFI/SAFIs to send flow specification filters. Since BGP route selection is performed per AFI/SAFI, this approach can be termed "ships in the night" based on AFI/SAFI.¶
FSv1 is a critical component of deployed applications. Therefore, this specification defines how FSv2 will interact with BGP peers that support either FSv2 or FSv1 or BGP peers that do not support either FSv1 or FSv2. It is expected that a transition to FSv2 will occur over time as new applications require FSv2 extensibility and user-defined ordering for rules and actions or network operators tire of the restrictions of FSv1 such as error handling issues and restricted topologies.¶
Section 2 contains the definition of Flow specification, a short review of FSv1 and an overview of FSv2. Section 3 contains the encoding rules for FSv2 and user-based encoding sent via BGP. Section 4 describes how to validate FSv2 NLRI. Section 5 discusses how to order FSV2 rules. Section 6 covers combining FSv2 user-ordered match rules and FSv1 rules. Section 6 also discusses how to combine user-ordered actions, FSv1 actions, and default actions. Sections 7-10 address an alternate security mechanism, considerations for IANA, security in deployments, and scalability aspirations.¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD 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.¶
A BGP Flow Specification is an n-tuple containing one or more match criteria that can be applied to IP traffic, traffic encapsulated in IP traffic or traffic associated with IP traffic. The following are examples of such traffic: IP packet or an IP packet inside a L2 packet (Ethernet), an MPLS packet, and SFC flow.¶
A given Flow Specification NLRI may be associated with a set of path attributes depending on the particular application, and attributes within that set may or may not include reachability information (e.g., NEXT_HOP). Extended Community or Wide Community attributes (well-known or AS-specific) MAY be used to encode a set of pre-determined actions.¶
A particular application is identified by a specific AFI/SAFI (Address Family Identifier/Subsequent Address Family Identifier) and corresponds to a distinct set of RIBs. Those RIBs should be treated independently of each other in order to assure noninterference between distinct applications.¶
BGP processing treats the NLRI as a key to entries in AFI/SAFI BGP databases. Entries that are placed in the Loc-RIB are then associated with a given set of semantics which are application dependent. Standard BGP mechanisms such as update filtering by NLRI or by attributes such as AS_PATH or large communities apply to the BGP Flow Specification defined NLRI-types.¶
Network operators can control the propagation of BGP routes by enabling or disabling the exchange of routes for a particular AFI/SAFI pair on a particular peering session. As such, the Flow Specification may be distributed to only a portion of the BGP infrastructure.¶
The FSv1 NLRI defined in [RFC8955] and [RFC8956] include 13 match conditions encoded for the following AFI/SAFIs:¶
If one considers the reception of the packet as an event, then BGP FSv1 describes a set of Event-MatchCondition-Action (ECA) policies where:¶
The flow specification conditions and actions combine to make up FSv1 specification rules. Each FSv1 NLRI must have a type 1 component (destination prefix). Extended Communities with FSv1 actions can be attached to a single NLRI or multiple NLRIs in a BGP packet.¶
Within an AFI/SAFI pair, FSv1 rules are ordered based on the components in the packet (types 1-13) ordered from left-most to right-most and within the component types by value of the component. Rules are inserted in the rule list by component-based order where an FSv1 rule with existing component type has higher precedence than one missing a specific component type,¶
Since FSv1 specifications ([RFC8955], [RFC8956], and [RFC9117]) specify that the FSv1 NLRI MUST have a destination prefix (as component type 1) embedded in the flow specification, the FSv1 rules with destination components are ordered by IP Prefix comparison rules for IPv4 ([RFC8955]) and IPv6 ([RFC8956]). [RFC8955] specifies that more specific prefixes (aka longest match) have higher precedence than that of less specific prefixes and that for prefixes of the same length the lower IP number is selected (lowest IP value). [RFC8955] specifies that if the offsets within component 1 are the same, then the longest match and lowest IP comparison rules from [RFC8955] apply. If the offsets are different, then the lower offset has precedence.¶
These rules provide a set of FSv1 rules ordered by IP Destination Prefix by longest match and lowest IP address. [RFC8955] also states that the requirement for a destination prefix component "MAY be relaxed by explicit configuration" Since the rule insertions are based on comparing component types between two rules in order, this means the rules without destination prefixes are inserted after all rules which contain destination prefix component.¶
The actions specified in FSv1 are:¶
Figure 1 shows a diagram of the FSv1 logical data structures with 5 rules. If FSv1 rules have destination prefix components (type=1) and FSv1 rule 5 does not have a destination prefix, then FSv1 rule 5 will be inserted in the policy after rules 1-4.¶
+--------------------------------------+
| Flow Specification (FS) |
| Policy |
+--------------------------------------+
^ ^ ^
| | |
| | |
+--------^----+ +-------^-------+ +-------------+
| FS Rule 1 | | FS Rule 2 | ... | FS rule 5 |
+-------------+ +---------------+ +-------------+
: :
: :
...: :........
: :
+---------V---------+ +----V-------------+
| Rule Condition | | Rule Action |
| in BGP NLRIs | | in BGP extended |
| AFIs: 1 and 2 | | Communities |
| SAFI 133, 134 | | |
+-------------------+ +------------------+
: : : : : :
.....: . :..... .....: . :.....
: : : : : :
+----V---+ +---V----+ +--V---+ +-V------+ +--V-----++--V---+
| Match | | match | |match | | Action | | action ||action|
|Operator| |Variable| |Value | |Operator| |variable|| Value|
|*1 | | | | | |(subtype| | || |
+--------+ +--------+ +------+ +--------+ +--------++------+
*1 match operator may be complex.
Figure 2-1: BGP Flow Specification v1 Policy
¶
Flow Specification v2 allows the user to order the flow specification rules and the actions associated with a rule. Each FSv2 rule may have one or more match conditions and one or more associated actions.¶
This FSv2 specification supports the components and actions for the following:¶
The FSv2 specification for tunnel traffic is outside the scope of this specification. The FSv1 specification for tunneled traffic is in [I-D.ietf-idr-flowspec-nvo3].¶
FSv2 operates in the ships-in-the night model with FSv1 so network operators can manipulate FSv2 and FSv1 using configuration parameters. Since the lack of deterministic ordering was problem FSv1, this specification provides rules and protocol features to keep filters in a deterministic order between FSv1 and FSv2.¶
The basic principles regarding ordering of flow specification filter rules are:¶
2) FSv2 rules are ordered based on user-specified order.¶
3) FSv2 rules are added starting with Rule 1 and FSv1 rules are added after FSv2 rules¶
4) An FSv2 peer may receive BGP NLRI routes from a FSv1 peer or a BGP peer that does not support FSv1 or FSv2. The capabilities sent by a BGP peer indicate whether the AFI/SAFI can be received (FSv1 NLRI or FSv2 NLRI).¶
5) Associate a chain of actions to rules based on user-defined action number (1-n). (optional)¶
Figure 2-2 provides a logical diagram of the FSv2 structure¶
+--------------------------------+
| Rule Group |
+--------------------------------+
^ ^ ^
| |--------- |
| | ------
| | |
+--------^-------+ +-------^-----+ +---^-----+
| Rule1 | | Rule2 | ... | Rule-n |
+----------------+ +-------------+ +---------+
: : : :
:.................: : : :
: |.........: : :
+--V--+ +--V--+ : :
| name| |order| .........: :.....
+-----+ +-----+ : :
: :
+----------------V----+ +-----V----------------+
|Rule Match condition | | Rule Action |
+---------------------+ +----------------------+
: : : : : : : : |
+--V--+ : : : +--V---+ : : : V
| Rule| : : : |action| : : : +-----------+
| name| : : : |order | : : : |action name|
+-----+ : : : +------+ : : : +-----------+
: : : : : :.............
: : : : : :
.....: . :..... ..: :...... :
: : : : : :
+----V---+ +---V----+ +--V---+ +-V------+ +--V-----+ +--V---+
| Match | | match | |match | | Action | | action | |action|
|Operator| |variable| |Value | |Operator| |Variable| | Value|
+--------+ +--------+ +------+ +--------+ +--------+ +------+
Figure 2-2: BGP FSv2 Data storage
¶
The BGP FSv2 uses an NRLI with the format for AFIs for IPv4 (AFI = 1), IPv6 (AFI = 2), L2 (AFI = 6), L2VPN (AFI=25), and SFC (AFI=31) with two following SAFIs to support transmission of the flow specification which supports user ordering of traffic filters and actions for IP traffic and IP VPN traffic.¶
This NLRI information is encoded using MP_REACH_NLRI and MP_UNREACH_NLRI attributes defined in [RFC4760]. When advertising FSv2 NLRI, the length of the Next-Hop Network Address MUST be set to 0. Upon reception, the Network Address of the Next-Hop field MUST be ignored.¶
Implementations wishing to exchange flow specification rules MUST use BGP's Capability Advertisement facility to exchange the Multiprotocol Extension Capability Code (Code 1) as defined in [RFC4760], and indicate a capability for flow specification v2 (Code TBD3).¶
The AFI/SAFI NLRI for BGP Flow Specification version 2 (FSv2) has the format:¶
+-------------------------------+ |length (2 octets) | +-------------------------------+ | Sub-TLVs (variable) | | +===========================+ | | | order (4 octets) | | | +---------------------------+ | | | identifier (4 octets) | | | +---------------------------+ | | | type (2 octets) | | | +---------------------------+ | | | length-Subtlv (2 octets) | | | +---------------------------+ | | | value (variable) | | | +===========================+ | +-------------------------------+ Figure 3-1: FSv2 format¶
where:¶
length: length of field including all SubTLVs in octets.¶
type: contains a type for FSv2 TLV format of the NRLI (2 octets) which can be:¶
The format of the IP header TLV value field is shown in figure 4. The AFI/SAFI field includes the AFI (2 octets), SAFI (1 octet). The AFI will be 1 (IPv4) or 2 (IPv6) and the SAFI will be TBD1 or, for the VPN case, TBD2. The IP header for the VPN case is specified in section 3.5.¶
+-------------------------------+
| +--------------------------+ |
| | AFI/SAFI field (3) | |
| +--------------------------+ |
| | (subTLVs)+ | |
| +==========================+ |
+-------------------------------+
Figure 3-2 - IP Header TLV
¶
Where: AFI is 1 (IPv4) or 2 (IPv6) and SAFI is TBD1.¶
Each SubTLV has the format:¶
+-------------------------------+
| SubTLV type (1 octet) |
+-------------------------------+
| length (1 octet) |
+ ------------------------------+
| value (variable) |
+-------------------------------+
Figure 3-3 – IP header SubTLV format
¶
Where:¶
value: dependent on the subTLV¶
Many of the components use the operators [numeric_op] and [bitmask_op] defined in [RFC8955]¶
The list of valid SubTLV types are included in Table 2.¶
Table 2 IP SubTLV Types for IP Filters SubTLV-type Definition =========== ============ 1 – IP Destination prefix 2 – IP Source prefix 3 – IPv4 Protocol / IPv6 Upper Layer Protocol 4 – Port 5 – Destination Port 6 – Source Port 7 – ICMPv4 type / ICMPv6 type 8 – ICMPv4 code / ICPv6 code 9 – TCP Flags 10 – Packet length 11 – DSCP (Differentiated Services Code Point) 12 – Fragment 13 – Flow Label 14 - TTL 15 – Parts of SID 16 - MPLS Match 1: Label in Label stack 17 - MPLS Match 2: EXP bits in top Label¶
Ordering within the TLV in FSv2: The transmission of SubTLVs within a flow specification rule MUST be sent ascending order by SubTLV type. If the SubTLV types are the same, then the value fields are compared using mechanisms defined in [RFC8955] and [RFC8956] and MUST be in ascending order. NLRIs having TLVs which do not follow the above ordering rules MUST be considered as malformed by a BGP FSv2 propagator. This rule prevents any ambiguities that arise from the multiple copies of the same NLRI from multiple BGP FSv2 propagators. A BGP implementation SHOULD treat such malformed NLRIs as "Treat-as-withdraw" [RFC7606].¶
See [RFC8955], [RFC8956], and [I-D.ietf-idr-flowspec-srv6]. for specific details.¶
IPv4 Name: IP Destination Prefix (reference: [RFC8955])¶
IPv6 Name: IPv6 Destination prefix (reference: [RFC8956])¶
IPv4 length: Prefix length¶
IPv4 value: IPv4 Prefix (variable length)¶
IPv6 length: length of value¶
IPv6 value: [offset (1 octet)] [pattern (variable)] [padding(variable)]¶
If IPv6 length = 0 and offset = 0, then component matches every address. Otherwise, length must be offset "less than" length "less than" 129 or component is malformed.¶
IPv4 Name: IP Source Prefix (reference: [RFC8955])¶
IPv6 Name: IPv6 Source prefix (reference: [RFC8956])¶
IPv4 length: Prefix length¶
IPv4 value: Source IPv4 Prefix (variable length)¶
IPv6 length: length of value¶
IPv6 value: [offset (1 octet)] [pattern (variable)][padding(variable)]¶
If IPv6 length = 0 and offset = 0, then component matches every address. Otherwise, length must be offset < length < 129 or component is malformed.¶
IPv4 Name: IP Protocol IP Source Prefix (reference: [RFC8955])¶
IPv6 Name: IPv6 Upper-Layer Protocol: (reference: [RFC8956])¶
IPv4 length: variable¶
IPv4 value: [numeric_op, value]+¶
IPv6 length: variable¶
IPv6 value: [numeric_op, value}+¶
where the value following each numeric_op is a single octet.¶
IPv4/IPv6 Name: Port (reference: [RFC8955]), [RFC8956])¶
Filter defines: a set of port values to match either destination port or source port.¶
IPv4 length: variable¶
IPv4 value: [numeric_op, value]+¶
IPv6 length: variable¶
IPv6 value: [numeric_op, value]+¶
where the value following each numeric_op is a single octet.¶
Note-1: In the presence of the port component (destination or source port), only a TCP (port 6) or UDP (port 17) packet can match the entire flow specification. If the packet is fragmented and this is not the first fragment, then the system may not be able to find the header. At this point, the FSv2 filter may fail to detect the correct flow. Similarly, if other IP options or the encapsulating security payload (ESP) is present, then the node may not be able to describe the transport header and the FSv2 filter may fail to detect the flow.¶
This problem comes from the inheritance of the FSv1 filter component for port. If better resolution is desired, a new FSv2 filter should be defined.¶
Note-2: Although IPv6 allows for more than one Next Header field in the packet, the main goal of the Type 3 FSv2 component is to match the first upper layer protocol value.¶
IPv4/IPv6 Name: Destination Port (reference: [RFC8955]), [RFC8956])¶
Filter defines: a list of match filters for destination port for TCP or UDP within a received packet¶
Length: variable¶
Component Value format: [numeric_op, value]+¶
IPv4/IPv6 Name: Source Port (reference: [RFC8955]), [RFC8956])¶
Filter defines: a list of match filters for source port for TCP or UDP within a received packet¶
IPv4/IPv6 length: variable¶
IPv4/Ipv6 value: [numeric_op, value]+¶
IPv4: ICMP Type : Source Port (reference: [RFC8955])¶
Filter defines: Defines: a list of match criteria for ICMPv4 type¶
IPv6: ICMPv6 Type (reference: [RFC8956])¶
Filter defines: a list of match criteria for ICMPv6 type.¶
IPv4/IPv6 length: variable¶
IPv4/IPv6 value: [numeric_op, value]+¶
IPv4: ICMP Type : Source Port (reference: [RFC8955])¶
Filter defines: a list of match criteria for ICMPv4 code.¶
IPv6: ICMPv6 Type (reference: [RFC8956])¶
Filter defines: a list of match criteria for ICMPv6 code.¶
IPv4/IPv6 length: variable¶
IPv4/IPv6 value: [numeric_op, value]+¶
IPv4/IPv6: TCP Flags Code (reference: [RFC8955])¶
Filter defines: a list of match criteria for TCP Control bits¶
IPv4/IPv6 length: variable¶
IPv4/IPv6 value: [bitmask_op, value]+¶
Note: a 2 octets bitmask match is always used for TCP-Flags¶
IPv4/IPv6: Packet Length (reference: [RFC8955], [RFC8956])¶
Filter defines: a list of match criteria for length of packet (excluding L2 header but including IP header).¶
IPv4/IPv6 length: variable¶
IPv4/IPv6 value: [numeric_op, value]+¶
IPv4/IPv6: DSCP Code (reference: [RFC8955], [RFC8956])¶
Filter defines: a list of match criteria for DSCP code values to match the 6-bit DSCP field.¶
IPv4/IPv6 length: variable¶
IPv4/IPv6 value: [numeric_op, value]+¶
Note: This component uses the Numeric Operator (numeric_op) described in [RFC8955] in section 4.2.1.1. Type 11 component values MUST be encoded as single octet (numeric_op len=00).¶
The six least significant bits contain the DSCP value. All other bits SHOULD be treated as 0.¶
IPv4/IPv6: Fragment (reference: [RFC8955], [RFC8956])¶
Filter defines: a list of match criteria for specific IP fragments.¶
Length: variable¶
Component Value format: [bitmask_op, value]+¶
Bitmask values are:¶
0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| 0 | 0 | 0 | 0 |lf |FF |IsF| DF|
+---+---+---+---+---+---+---+---+
Figure 3-4
¶
Where:¶
IPv4/IPv6: Fragment (reference: [RFC8956])¶
Filter defines: a list of match criteria for 20-bit Flow Label in the IPv6 header field.¶
Length: variable¶
Component Value format: [numeric_op, value]+¶
TTL: Defines matches for 8-bit TTL field in IP header¶
Encoding: <[numeric_op, value]+>¶
where: value is a 1 octet value for TTL.¶
ordering: by full value of number_op concatenated with value¶
conflict: none¶
reference: draft-bergeon-flowspec-ttl-match-00.txt¶
IPv6: Service Identifier Matches (reference: [I-D.ietf-idr-flowspec-srv6]¶
Filter defines: a list of match bit match criteria for some combinations of the LOC (location), FUNCT (function) and ARG (arguments) fields in the SID or or whole SID.¶
Length: variable¶
Component Value format: [type, LOC-Len, FUNCT-Len, ARG-Len, [op, value]+]¶
where:¶
The total of three lengths (i.e., LOC length + FUNCT length + ARG length) MUST NOT be greater than 128. If it is greater than 128, an error occurs and it is treated as a withdrawal [RFC7606] and [RFC4760].¶
The operator (op) byte is encoded as:¶
0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| e | a | field type|lt |gt |eq |
+---+---+---+---+---+---+---+---+
Figure 3-5
¶
where:¶
field type:¶
The data' and value' used in lt, gt and eq are indicated by the field type in an operator and the value field following the operator.¶
The length of the value field depends on the field type and is the length of the SID parts being matched (see Table 3, Figure 3-6) in bytes, rounded up if that length is not a multiple of 8.¶
Table 3 - SID Parts fields
+-----------------------+------------------------------+
| Field Type | Value |
+=======================+==============================+
| SID's LOC | value of LOC bits |
+-----------------------+------------------------------+
| SID's FUNCT | value of FUNCT bits |
+-----------------------+------------------------------+
| SID's ARG | value of ARG bits |
+-----------------------+------------------------------+
| SID's LOC:FUNCT | value of LOC:FUNCT bits |
+-----------------------+------------------------------+
| SID's FUNCT:ARG | value of FUNCT:ARG bits |
+-----------------------+------------------------------+
| SID's LOC:FUNCT:ARG | value of LOC:FUNCT:ARG bits |
+-----------------------+------------------------------+
¶
------------------ SID, 128 bits ----------------
/ \
+-----------+-----------+-----------+----------------+
| LOC | FUNCT | ARG | ... |
+-----------+-----------+-----------+----------------+
\ / \ / \ / \ /
j bits k bits m bits 126-j-k-m bits
\ /
LOC:FUNCT, j+k bits
\ /
FUNCT:ARG, k+m bits
\ /
-- LOC:FUNCT:ARG, j+k+m bits –
Figure 3-6
¶
The operator byte is encoded as:¶
0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| e | a | i | pos | Resv |
+---+---+---+---+---+---+---+---+
Figure 3-7
¶
where:¶
whose meaning for various values is shown below:¶
The value field is encoded as:¶
1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3-8
¶
reference:¶
Encoding: <type (1 octet), [op, value]+>¶
The FSv2 actions may be sent in an Extended Community, a Wide Community, or within a FSv2 NLRI in the Action SubTLV.¶
The Extended Community encodes the Flow Specification actions in the Extended Community format [RFC4360].¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type high | Type low(*) | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Value (6 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3-9
¶
The Wide Community definition for FSv2 actions is as follows:¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 2 | Flags |C|T| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length |<sequence of FSv2-Action-TLV>+ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3-10
¶
where FSv2-Action-TLV is defined as:¶
FSv2-Action-TLV
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| action order | Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| <action-subTLVs> |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3-11
¶
Where action-SubTLVs have the format:¶
action-SubTLVs
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubTLV type (2 octet) | length type (2 octet) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| value (variable) |
+-------------------------------+
Figure 3-12
¶
The FSv2 Action TLV may be included in FSv2 NLRI.¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 2 | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| action-order | chain-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| length | value <SubTLVs>+ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3-13
¶
where:¶
Each Action SubTLV has the format:¶
+-------------------------------+
| SubTLV type (2 octet) |
+-------------------------------+
| length (2 octet) |
+-------------------------------+
| value (variable) |
+-------------------------------+
Figure 3-14
¶
Where:¶
Table 4 – FSv2 Action types
Action Description
====== ===========
00 reserved
01 ACO: action chain operation
02 TAIS: traffic actions per interface group
06 TRB: traffic rate limited by bytes
07 TA: traffic action (terminal/sample)
08 RDIP: Redirect IPv4
09 TM: mark DSCP value
10 TBA (to be assigned)
11 TBA (to be assigned)
12 TRP: traffic rate limited by packets
13 RDIPv6: redirect to IPv6
14 TISFC: SFC Classifier Info (moved from OD to OE)
15 RDIID: redirect to Indirection-id (move from 0x00)
16 MPLSLA: MPLS label action
17-21 TBA (to be assigned)
22 VLAN: VLAN-Action (0x16)[draft-ietf-idr-flowspec-l2vpn-17]
23 TPID: TPID-Action (0x17) [draft-ietf-idr-flowspec-l2vpn-17]
24-254 TBA (to be assigned)
255 reserved
Figure 3-15
¶
Ordering of actions within a rule:¶
SubTLV: 0x01¶
Length: variable¶
Value:¶
Actions may succeed or fail and an Action chain must deal with it. The default value stored for an action chain that does not have this action chain is "stop on failure".¶
where:¶
Interactions with other actions: Interactions with all other Actions¶
Ordering within Action type: By AC-Failure type¶
SubTLV: 0x02¶
Length: 8 octets (6 in extended community)¶
Value field: [4-octet-AS] [GroupID 2-octet] [action 2-octet]¶
where:¶
Group-ID: identifier for group in 2 octets (14 lower bits)¶
Action: determines inbound or outbound action where:¶
Value ordering: AS, then Group ID, then Action bytes.¶
Conflict: with any bi-direction action such as¶
Reference: [I-D.ietf-idr-flowspec-interfaceset]¶
SubTLV:0x06¶
Length: 8 octets¶
Value field:[4-octet-AS] [float (4 bytes)]¶
where:¶
[4-octet-AS]:4 byte AS number¶
Float: maximum byte rate in IEEE floating point [IEEE.754.19895 format] in units per second.¶
Value ordering: AS then float value¶
Action Conflict: traffic-rate-packets¶
SubTLV: 0x07¶
Length: 1¶
Value field: [1-octet action]¶
where the traffic action values are:¶
Value ordering: By traffic action values¶
Conflicts/Interactions: duplication of packets also occurs in:¶
SubTLV: 0x08¶
Length: 12 octets¶
Value field:¶
[4-byte-AS] [IPv4 address (4 octets] [ID (4 octets)] [Flag (1 octet)]¶
where:¶
Flag is 1 octet value with the following definitions:¶
Value ordering: 4-octet AS, then IP address, then ID (lowest to highest) with:¶
Conflicts/Interactions: Any redirection or traffic sampling found in:¶
SubTLV: 0x09¶
Length: 1 octet¶
Value: DSCP field with the 2 left most bits zero¶
The DSCP field format is:¶
0 1 2 3 4 5 6 7
+--+--+--+--+--+--+--+--+
|R |R | DSCP bits |
+--+--+--+--+--+--+--+--+
Figure 3-16
¶
where:¶
Ordering within Value: Based on DSCP value¶
Conflicts: none¶
SubTLV:12 (0xC)¶
Length: 8¶
Value field: [4-octet-AS] [float (4 octet)]¶
Where:¶
Float - specifies maximum rate [IEEE.754.185] format in packets per second.¶
Ordering within Value: Based on DSCP value¶
Conflicts: Traffic rate limited by bytes (0x06)¶
SubTLV: 13 (0xD)¶
Length: 24 octets¶
Value field: [4-octet-as] [IPv6-address (16 octets)] [local administrator (2 octets] [Flag (1 octets)]¶
where:¶
lag (1 octet) with the following definitions:¶
Ordering within Value: AS, then IPv6, the flag (low to high)¶
Conflicts/Interactions: Any redirection or traffic sampling found in:¶
SubTLV:(14, 0xE)¶
Length: 6 octets¶
Value field: [SPI (3 octets)][SI (1 octet)][SFT (2 octet)]¶
where:¶
Value ordering: SPI, then SI, then SFT (lowest to highest)¶
Conflicts/Interactions: Any redirection or traffic sampling found in:¶
SubTLV: 15 (0x0F)¶
Length: 6 octets¶
Value field:¶
[Flags (1 octet)] [ID-Type (1 octet)][Generalized-ID (4 octets)]
Figure 3-17
¶
where:¶
Flags: are defined as:¶
ID-Type: type of indirection ID with following values:¶
Value Ordering: first indirection ID, then Generalized ID¶
Action Value ordering: ID-Type by value (lowest to highest)¶
Conflicts/Interactions: Any redirection or traffic sampling found in:¶
reference: [I-D.ietf-idr-flowspec-path-redirect]¶
Function: MPLS Label actions¶
SubTLV: 16 (0x10)¶
Length: 6 octets¶
Value:¶
where Action:¶
+------+------------------------------------------------------------+
|Action| Function |
+------+------------------------------------------------------------+
| 0 | Push the MPLS tag |
+------+------------------------------------------------------------+
| 1 | Pop the outermost MPLS tag in the packet |
+------+------------------------------------------------------------+
| 2 | Swap the MPLS tag with the outermost MPLS tag in the packet|
+------+------------------------------------------------------------+
| 3~15 | Reserved |
+------+------------------------------------------------------------+
Figure 3-18
¶
Label Stack Entry
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label | Exp |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3-19
¶
Action Value ordering: ID-Type, then value (lowest to highest)¶
Value Ordering: order, action, label, Exp¶
Conflicts/Interactions: Any redirection for IP before MPLS¶
reference: [I-D.ietf-idr-bgp-flowspec-label]¶
Function: Rewrite inner or outer VLAN header¶
SubTLV: 22 (0x16)¶
Length: 6 octets¶
Value:¶
where:¶
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|PO1|PU1|SW1|RI1|RO1| Resv |PO2|PU2|SW2|RI2|RO2| Resv |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
Figure 3-20
¶
Value ordering: rewrite-actions, VLAN1, VLAN2, PCP-DE1, PCP-DE2¶
Conflicts: TIPD Action¶
reference: [I-D.ietf-idr-flowspec-l2vpn]¶
Function: Replace Inner or outer TP¶
SubTLV: 23 (0x17)¶
Length: 6 octets¶
Value:¶
Where: rewrite-actions are bitmask (2 octets) with 2 actions as follows:¶
0 15
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|TI|TO| Resv |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
Figure 3-21
¶
TI: Mapping inner Tag Protocol (TP) ID (typically a VLAN) action. If the TI flag is one, it indicates the inner TP ID should be replaced by a new TP ID, the new TP ID is TP ID1.¶
TO: Mapping outer TP ID action. If the TO flag is one, it indicates the outer TP ID should be replaced by a new TP ID, the new TP ID is TP ID2.¶
Resv: Reserved for future use. MUST be sent as zero and ignored on receipt¶
Value Ordering: rewrite-actions, TP-ID-1, TP-ID-2¶
Conflicts: VLAN action¶
reference:[I-D.ietf-idr-flowspec-l2vpn]¶
The SubTLV format is used for the Wide communities and for the action subTLVs in the NLRI.¶
Sub-TLV Action Action SubTLV Extended Community
type Name format format
======= ===== =============== ====================
1 ACO type: 1 (0x01) not applicable (n/a)
length:variable
2 TAIS type: 2 (0x02) type: 0x0702 or 0x4702
length:8 length: 6
[4-octet-as] [4-octet-AS]
[group-3-octet] [flags-group]
[flags-1-octet] (2 octets)
3-5 reserved
Sub-TLV Action Action SubTLV Extended Community
type Name format format
======= ===== =============== ====================
6 TRB type:6 (0x06) type:8006
length:8 length: 6 octets
[4-byte-AS] [2-byte-AS]
[float (4 octets)] [float (4 octets)]
7 TA type:7 type:8007
length:1 length:6 octets
flags: (1 octet) flags (6 octets)
8 RDIPv4 type:8 type:8008
length: 12 length: 6 octets
[4-byte-AS] [AS-2-octets]
[IPv4-address] [IPv4 address]
type:8108
length: 6 octets
[IPv4 address]
[ID-2 octets]
type:8208
length: 6 octets
[AS-4-octets]
[ID-2-octets]
9 TM type:9 type:8009
length:1 length: 6 octets
DSCP: 1 octet DSCP: 1 octet
10 type:10 (0X0A) TBA
11 type:11 (0x0B) TBA
12 TRP type:12 (0x0C) type: 0x800C
length: 8 octets length: 6 octets
[4-byte-AS] [2-byte-AS]
[float-4-octet] [float-4-octet]
13 RDIPv6 type:13 (0x0D) type:0x000C
length:22 length: 18 octets
[4-byte-AS] [IPv6-address (16)]
[IPv6-address (16)] [local-admin (2)]
[local-admin (2)]
Sub-TLV Action Action SubTLV Extended Community
type Name format format
======= ===== =============== ====================
14 TISFC type:14 (0x0E) type: 0xD (FSv1)
type: 0xE (FSv2)
length:6 length:6
SPI (3 octets) SPI (3 octets)
SI (1 octet) SI (1 octet)
SFT (2 octets) SFT (2 octets)
15 RDIID type:15 (0x0F) type: 0900 (FSv1)
length: 6 length 6
flags (1) flags (1)
ID-type (1) ID type (1)
G-ID (4 octets) G-ID (4-octets)
16 MPLSLA type:16 (0x10)
16-21 TBA -
22 VLAN type:22 (0x16) Type: (TBD)
length:6 length:6
[rewrite-action(2)] [rewrite-actions (2)]
[vlan-pcp-de-1 (2)] [vlan-pcp-de-1 (2)]
[vlan-pcp-de-2 (2)] [vlan-pcp-de-2 (2)]
23 TPID type:23 (0x17) Type: (TBD)
length:6 length:6
[rewrite-action(2)] [rewrite-actions (2)]
[TP-ID-1 (2)] [TP-ID-1 (2)]
[TP-ID-2 (2)] [TP-ID-2 (2)]
¶
The format of the L2 header TLV value field is shown in Figure 3-22. The AFI/SAFI field includes the AFI (2 octets), SAFI (1 octet).¶
+-------------------------------+
| +--------------------------+ |
| | AFI/SAFI field (3) | |
| +--------------------------+ |
| | L3 AFI (2) | |
| +--------------------------+ |
| | L2 filter length (2) | |
| +--------------------------+ |
| | (SubTLVs)+ (L2 then L3) | |
| +--------------------------+ |
+-------------------------------+
Figure 3-22 -L2 Header TLV value
¶
Where:¶
Each L2 SubTLV has the format shown in Figure 3-23. (The L3 SubTLVs are as defined in Section 4.1.)¶
Each SubTLV has the format:
+-------------------------------+
| SubTLV type (1 octet) |
+-------------------------------+
| length (1 octet) |
+ ------------------------------+
| value (variable) |
+-------------------------------+
Figure 3-23
¶
SubTLV type: A component type value defined in the "L2 Flow Specification Component Types" registry for L2 by [draft-ietf-idr-flowspec-l2vpn).¶
Where the SubTLVs have the following component types:¶
Component Types Table Component type Description ======= ================== 1 EtherType 2 Source MAC 3 Destination MAC 4 DSAP (destination service access point) 5 SSAP (source service access point) 6 control field in LLC 7 SNAP 8 VLAN ID 9 VPAN PCP 10 Inner VLAN ID 11 Inner VLAN PCP 12 VLAN DEI 13 VLAN DEI 14 Source MAC special bits 15 Destination MAC special bits Table 4 – L2 VPN components¶
See [I-D.ietf-idr-flowspec-l2vpn] for the details on the format and value fields for each component.¶
Value ordering: Ordering of L2 FSv2 rules will be by user-defined order of the rule. For FSv2 filters within the same rule, the ordering will be by component number and then by value within the component. See [I-D.ietf-idr-flowspec-l2vpn] for the ordering of the values within the component.¶
L2 VPN filtering using SAFI TBD2 is specified in section 3.6.¶
reference: [I-D.ietf-idr-flowspec-l2vpn]¶
The FSv2 filters allow for filtering of the SFC NLRI family of routes. The traffic NLRIs filtered are from SFC AFI/SAFI (AFI = 31, SAFI=9).¶
The FSv2 filters provide this filtering with SFC AFI (AFI=31) and SAFI for FSv2 filters (SAFI = TB1).¶
+--------------------------------------+
| +---------------------------------+ |
| | Tunneled AFI/SAFI field | |
| +---------------------------------+ |
| | | |
| | <subTLVs>+ | |
| +---------------------------------+ |
+--------------------------------------+
Figure 3-24
¶
Each SubTLV has the format:¶
+-------------------------------+
| SubTLV type (1 octet) |
+-------------------------------+
| length (1 octet) |
+ ------------------------------+
| value (variable) |
+-------------------------------+
Figure 3-25 – Tunneled SubTLV format
¶
The components listed are:¶
1 = SFIR RD Type (types 1, 2, 3)
2 = SFIR RD Value
3 = SFIR Pool ID
4 = SFIR MPLS context/label
5 = SFPR SPI
6 = SPF attribute fields
Table 6 – SFC Filter types
¶
Ordering is by: User-defined rule order, component number, and then value within component.¶
The format of the match filter for BGP/MPLS VPN IP traffic is very similar to the format for non-VPN IP traffic as defined in Section 4.1 except that the SAFI is TBD2 and the initial NLRI header has an 8-byte Route Distinguisher added to it as shown in Figure 3-26. The SubTLV format and filter components formats remain the same.¶
+-------------------------------+
| +--------------------------+ |
| | AFI/SAFI field (3) | |
| +--------------------------+ |
| | Route Distinguisher (8) | |
| +--------------------------+ |
| | (subTLVs)+ | |
| +--------------------------+ |
+-------------------------------+
Figure 3-26: VPN IP Filter Header
¶
The format of the match filter for BGP/MPLS VPN IP traffic is very similar to the format for non-VPN L2 traffic as defined in Section 4.3 except that the SAFI is TBD2 and the initial NLRI header has an 8-byte Route Distinguisher added to it right after the AFI/SAFI as shown in Figure 3-27 The SubTLV format and filter components formats remain the same.¶
+-------------------------------+
| +--------------------------+ |
| | AFI/SAFI field (3) | |
| +--------------------------+ |
| | Route Distinguisher (8) | |
| +--------------------------+ |
| | L3 AFI (2) | |
| +--------------------------+ |
| | L2 filter length (2) | |
| +--------------------------+ |
| | (subTLVs)+ | |
| +--------------------------+ |
+-------------------------------+
Figure 3-27: VPN L2 Filter Header
¶
The BGP Flow specification version 2 actions are passed in a Wide Community attribute with a BGP Wide Community container (type 01) [I-D.ietf-idr-wide-bgp-communities] with community FSv2 Actions (TBD4) defined from the IANA stream (I+value) The Wide Community attribute Target TLV, Exclude TLVs, and Parameter TLVs. The Parameter contains FSv2 Atom which contains a sequence of Action TLVs.¶
BGP Wide Community Container with FSv2 actions +----------------------------+ | Community: FSv2 Actions | +----------------------------+ | Source AS number | +----------------------------+ | Context AS number | +----------------------------+ | Target or Exclude TLVs + | (optional) | +----------------------------+ | Parameter TLV with | | FSv2 atom | +----------------------------+ figure 3-28 - BGP¶
+----------------------------+ | FSv2 Actions atom-id | +----------------------------+ | length (2 octets) | +----------------------------+ | <Action-Sub-TLVs>+ | +----------------------------+ Figure 3-29 - Flow Specification with IDs for Wide Community Actions¶
where:¶
The validation of FSv2 NLRI adheres to the combination of rules for general BGP FSv1 NLRI found in [RFC8955], [RFC8956], [RFC9117], and the specific additions made for SFC NLRI [RFC9015], and L2VPN NLRI [I-D.ietf-idr-flowspec-l2vpn].¶
To provide clarity, the full validation process for flow specification routes (FSv1 or FSv2) is described in this section rather than simply referring to the relevant portions of these RFCs. Validation only occurs after BGP UPDATE packet, the FSv2 NLRI and the path attributes relating to FSv2 (Extended community and Wide Community) have been determined to be well-formed. Any MALFORMED FSv2 NRLI is handled as a "TREAT as WITHDRAW".¶
Flow specification 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 the two routes for same prefix may be the same, BGP is still required to perform its path selection algorithm in order 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 unfeasible. In the context of IP routing information, this 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.¶
The FSv2 validation process validates the FSv2 NLRI with following unicast routes received over the same AFI (1 or 2) but different SAFIs:¶
The FSv2 validates L2 FSv2 NLRI with the following L2 routes received over the same AFI (25), but a different SAFI:¶
In the absence of explicit configuration, a Flow specification NLRI (FSv1 or FSv2) MUST be validated such that it is considered feasible if and only if all of the conditions are true:¶
b) One of the following conditions must hold true:¶
2. The AS_PATH attribute of the flow specification is empty or contains only an AS_CONFED_SEQUENCE segment [RFC5065].¶
However, this 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 the address of the originator in the ORIGINATOR_ID Attribute [RFC4456] or the source address of the BGP peer, if this path attribute is not present.¶
BGP implementation MUST enforce that the AS in the left-most position of the AS_PATH attribute of a Flow Specification Route (FSv1 or FSv2) received via the Exterior Border Gateway Protocol (eBGP) matches the AS in the left-most position of the AS_PATH attribute of the best-match unicast route for the destination prefix embedded in the Flow Specification (FSv1 or FSv2) NLRI.¶
The best-match unicast route may change over time independently of the Flow Specification NLRI (FSv1 or FSv2). Therefore, a revalidation of the Flow Specification MUST be performed whenever unicast routes change. Revalidation is defined as retesting rules a to c as described above.¶
Flow Specifications may be mapped actions using Extended Communities, Wide Communities or a FSv2 NLRI with an action TLV. The scaling of FSv2 actions implies that Extended Communities and wide communities which can associate an action to a large number of NLRIs will be most often used. Therefore, it is likely the FSv2 NLRI TLV for actions will be used for very few actions (such as the "die-die-die Internet worm" use case).¶
The ordering of precedence for these actions in the absence of user-defined ordering, is to follow the precedence of the FSv2 NLRI action TLV values (lowest to highest). If multiple items exist for the same action type, then ordering is described within each Action SubTLV. Extended Community actions should be translated to the Action SubTLV format for internal comparison.¶
Actions may conflict, duplicate, or complementation other actions. An example of conflict is the packet rate limiting by byte and by packet. An example of a duplicate is the request to copy or sample a packet under one of the redirect functions (RDIPv4, RDIPv6, RDIID, ) Each FSv2 actions in this document defines the potential conflicts or duplications. Specifications for new FSv2 actions outside of this specification MUST specify interactions or conflicts with any FSv2 actions (that appear in this specification or subsequent specification).¶
Well-formed syntactically correct actions should be linked to a filtering rule in the order the actions should be taken. If one action in the ordered list fails, the default procedure is for the action process for this rule to stop and flag the error via system management. By explicit configuration, the action processing may continue after errors.¶
Implementations MAY wish to log the actions taken by FS actions (FSv1 or FSv2).¶
The following two error handling rules must be followed by all BGP speakers which support FSv2:¶
The above two rules prevent any ambiguity that arises from the multiple copies of the same NLRI from multiple BGP FSv2 propagators.¶
A BGP implementation SHOULD treat such malformed NLRIs as 'Treat-as-withdraw'.¶
An implementation for a BGP speaker supporting both FSv1 and FSv2 must support the error handling for both FSv1 and FSv2. The storage of the BGP FSv1 and FSv2 must support both the AFI/SAFI and the configuration which translates FSv1 NLRI into FSv2 NLRI for order storage.¶
Flow Specification v2 allows the user to order flow specification rules and the actions associated with a rule. Each FSv2 rule has one or more match conditions and one or more actions associated with each rule.¶
This section describes how to order FSv2 filters received from a peer prior to transmission to another peer. The same ordering should be used for the ordering of forwarding filtering installed based on only FSv2 filters.¶
Section 7.0 describes how a BGP peer that supports FSv1 and FSv2 should order the flow specification filters during the installation of these flow specification filters into FIBs or firewall engines in routers.¶
The BGP distribution of FSv1 NLRI and FSv2 NLRI and their associated path attributes for actions (Wide Communities and Extended Communities) is "ships-in-the-night" forwarding of different AFI/SAFI information. This recommended ordering provides for deterministic ordering of filters sent by the BGP distribution.¶
The basic principles regarding ordering of rules are simple:¶
1) Rule-0 (zero) is defined to be 0/0 with the "permit-all" action¶
3) If multiple FSv2 NLRI have the same user-defined order, then the filters are ordered by type of FSv2 NRLI filters (see Table 1, section 4) with lowest numerical number have the best precedence.¶
For component types inherited from the FSv1 component types, there are the following two types of comparisons:¶
Notes:¶
The FSv2 specification allows for actions to be associated by:¶
Actions may be ordered by user-defined action order number from 1-n (where n is 2**16-2 and the value 2**16-1 is reserved.¶
Extended community actions are associated with order number 32768 [0x8000] or a specific configured value for the FSv2 domain.¶
Action user-order number zero is defined to have an Action type of "Set Action Chain operation" (ACO) (value 0x01) that defines the default action chain process. For details on "set action chain operation" see section 3.2.1 and 5.2.1 below.¶
If the user-defined action number for two actions are the same, then the actions are ordered by FSv2 action types (see Table 3 for a list of action types). If the user-defined action number and the FSv2 action types are the same, then the order must be defined by the FSv2 action.¶
The "Action Chain Operation" (ACO) changes the way the actions after the current action in an action chain are handled after a failure. If no action chain operations are set, then the default action of "stop upon failure" (value 0x00) will be used for the chain.¶
Use Case 1: Rate limit to 600 packets per second¶
Description: The provider will support 600 packets per second All Packets sampled for reporting purposes and packet streams over 600 packets per second will be dropped.¶
Suppose BGP Peer A has a¶
The FSv2 data base would store the following action chain:¶
at user-defined action order 10¶
at user-defined action order 11¶
Normal action:¶
When does the action chain stop?¶
The different options for Action chain ordering (ACO) have been worked on with NETCONF/RESTCONF configuration and actions.¶
Use case 2: Redirect traffic over limit to processing via SFC.¶
Description: The normal function is for traffic over the limit to be forwarded for offline processing and reporting to a customer.¶
Suppose we have the following 4 actions defined for a match:¶
These 4 filters rate limit a potential DDoS attack by: a) redirect the packet to indirection ID (for slower speed processing), sample to local hardware, and forward the attack traffic via a SFC to a data collection box.¶
The FSv2 action list for the match would look like this¶
If the redirect to a redirection ID fails, then Traffic Sample and sending the data to an SFC classifier for forwarding via SFC will not happen. The traffic is limited, but not redirect away from the network and a sample sent to DDOS processing via a SFC classifier.¶
Suppose the following 5 actions were defined for a FSV2 filter:¶
The FSv2 action list for the match would look like this:¶
If the redirect to a redirection ID fails, the action chain will continue on to sample the data and enact SFC classifier actions.¶
Note: The scaling for associating actions is better with Wide or Extended Communities which can be associated with many FSv2 filters. The FSv2 action with FSv2 NLRI should be used in rare cases such the use case of a pernicious Internet worm. In this case, Suppose we call the filter "Internet worm" particular filter match identifies the pernicious Internet worm that must be killed off and not be forwarded. Let us call the actions in the action chain "Die-Die-Internet-worm". For such a use case, the FSV2 actions to stop the packets are tied to the filter even though it may not scale or have issues in some deployments.¶
The FSv2 actions can be associated with a set of FSv2 NLRIs using Extended Communities and Wide Communities. A single community may set the actions for a large number of NLRI in a scalable fashion.¶
Some traffic patterns may detect a caustic worm that must killed once detected. If this traffic pattern is globally agreed upon and the actions agreed upon across the ASes within administrative domains, then for this rare case the NLRI can be encoded with an action chain.¶
Suppose the following 1 actions were defined for a FSV2 filter:¶
The use of traffic rate limit to zero bytes associated with the NLRI guarantees the traffic stops at the first filter. The continue on failure makes sure that each of these steps is completed.¶
Operators should use user-defined ordering to clearly specify the actions desired upon a match. The FSv2 actions default ordering is specified to provide deterministic order for actions which have the same user-defined order and same type.¶
FS Action Value Order
(lowest value to highest) (lowest to highest)
================================ ==============================
0x01: ACO: Action chain operation Failure flag
0x02: TAIS:Traffic actions per AS, then Group-ID, then Action ID
Interface group
0x03-0x05 to be assigned TBD
0x06: TRB: Traffic rate limit AS, then float value
by bytes
0x07: TA: Traffic Action traffic action value
0x08: RDIP: Redirect to IP AS, then IP Address, then ID
0x09: TM: Traffic Marking DSCP value (lowest to highest)
0x0A: AL2: Associated L2 Info. TBD
0x0B: AET: Associated E-tree Info. TBD
0x0C: TRP: Traffic Rate limit AS, then float value
by bytes
0x0D: RDIPv6: Traffic
Redirect to IPv6 AS, IPv6 value, then local Admin
0x0E: TISFC: Traffic insertion
to SFC SPI, then SI, the SFT
0xOF: Redirect to
Indirection-ID ID-type, then Generalized-ID
0x10: MPLSLA: MPLS Label stack order, action, label, Exp
0x16 – VLAN action rewrite-actions, VALN1, VLAN2,
PCP-DE1, PCP-DE2
0x17 – TPID action rewrite actions, TP-ID-1, TP-ID-2
Figure 6-1
¶
FSv2 allows the user to order flow specification rules and the actions associated with a rule. Each FSv2 rule has one or more match conditions and one or more actions associated with each rule.¶
FSv1 and FSv2 filters are sent as different AFI/SAFI pairs so FSv1 and FSv2 operate as ships-in-the-night. Some BGP peers in an AS may support both FSv1 and FSv2. Other BGP peers may support FSv1 or FSv2. Some BGP will not support FSv1 or FSV2. A coherent flow specification technology must have consistent best practices for ordering the FSv1 and FSv2 filter rules.¶
One simple rule captures the best practice: Order the FSv1 filters after the FSv2 filter by placing the FSv1 filters after the FSv2 filters.¶
To operationally make this work, all flow specification filters should be included the same data base with the FSv1 filters being assigned a user- defined order beyond the normal size of FSv2 user-ordered values. A few examples, may help to illustrate this best practice.¶
Example 1: User ordered numbering - Suppose you might have 1,000 rules for the FSv2 filters. Assign all the FSv1 user defined rules to 1,001 (or better yet 2,000). The FSv1 rules will be ordered by the components and component values.¶
Example 2: Storage of actions - All FSv1 actions are defined ordered actions in FSv2. Translate your FSv1 actions into FSv2 ordered actions for storing in a common FSv1-FSv2 flow specification data base.¶
Example 3: Mixed Flow Specification Support -¶
+---------+ +---------+
| A |=======================| C |
|FSv1+FSv2|. . .| FSv2 |
+---------+ . . +---------+
|| | \ . . . ||
|| | \ . . . . . . . . . . ||
|| | \ . . . ||
|| | \-----\ . . . ||
|| | \ . . . ||
+---------+ +------+ +-----+ ||
| E |-------| B |. . . .| D | ||
|FSv1+FSv2| | FSv1 | |no FS| ||
+---------+ +------+ +-----+ ||
|| . . ||
|| . . . . . . . . . . . . . . ||
|| ||
|========================================|
Double line = FSv2
Single line = FSv1
Dotted line = BGP peering with no FlowSpec
Figure 6-2: FSv1 and FVs2 Peering
¶
Operational issues drive the deployment of BGP flow specification as a quick and scalable way to distribute filters. The early operations accepted the fact validation of the distribution of filter needed to be done outside of the BGP distribution mechanism. Other mechanisms (NETCONF/RESTCONF or PCEP) have reply-request protocols.¶
These features within BGP have not changed. BGP still does not have an action-reply feature.¶
NETCONF/RESTCONF latest enhancements provide action/response features which scale. The combination of a quick distribution of filters via BGP and a long-term action in NETCONF/RESTCONF that ask for reporting of the installation of FSv2 filters may provide the best scalability.¶
The combination of NETCONF/RESTCONF network management protocols and BGP focuses each protocol on the strengths of scalability.¶
FSv2 will be deployed in webs of BGP peers which have some BGP peers passing FSv1, some BGP peers passing FSv2, some BGP peers passing FSv1 and FSv2, and some BGP peers not passing any routes.¶
The TLV encoding and deterministic behaviors of FSv2 will not deprecate the need for careful design of the distribution of flow specification filters in this mixed environment. The needs of networks for flow specification are different depending on the network topology and the deployment technology for BGP peers sending flow specification.¶
Suppose we have a centralized RR connected to DDoS processing sending out flow specification to a second tier of RR who distribute the information to targeted nodes. This type of distribution has one set of needs for FSv2 and the transition from FSv1 to FSv2¶
Suppose we have Data Center with a 3-tier backbone trying to distribute DDoS or other filters from the spine to combinational nodes, to the leaf BGP nodes. The BGP peers may use RR or normal BGP distribution. This deployment has another set of needs for FSv2 and the transition from FSv1 to FSV2.¶
Suppose we have a corporate network with a few AS sending DDoS filters using basic BGP from a variety of sites. Perhaps the corporate network will be satisfied with FSv1 for a long time.¶
These examples are given to indicate that BGP FSv2, like so many BGP protocols, needs to be carefully tuned to aid the mitigation services within the network. This protocol suite starts the migration toward better tools using FSv2, but it does not end it. With FSv2 TLVs and deterministic actions, new operational mechanisms can start to be understood and utilized.¶
This FSv2 specification is merely the start of a revolution of work - not the end.¶
This section discusses the optional BGP Security additions for BGP-FS v2 relating to BGPSEC [RFC8205] and ROA [RFC6482].¶
Flow specification v1 ([RFC8955] and [RFC8956]) do not comment on how BGP Flow specifications to be passed BGPSEC [RFC8205] BGP Flow Specification v2 can be passed in BGPSEC, but it is not required.¶
FSv1 and FSv2 may be sent via BGPSEC.¶
BGP FSv2 can utilize ROAs in the validation. If BGP FSv2 is used with BGPSEC and ROA, the first thing is to validate the route within BGPSEC and second to utilize BGP ROA to validate the route origin.¶
The BGP-FS peers using both ROA and BGP-FS validation determine that a BGP Flow specification is valid if and only if one of the following cases:¶
If the BGP Flow Specification NLRI has a IPv4 or IPv6 address in destination address match filter and the following is true:¶
If a BGP ROA has not been received that matches the IPv4 or IPv6 destination address in the destination filter, the match filter must abide by the [RFC8955] and [RFC8956] validation rules as follows:¶
The best match is defined to be the longest-match NLRI with the highest preference.¶
This section complies with [RFC7153].¶
IANA is requested to assign two SAFI Values in the registry at https://www.iana.org/assignments/safi-namespace from the Standard Action Range as follows:¶
Value Description Reference
----- ------------- ---------------
TBD1 BGP FSv2 [this document]
TBD2 BGP FSv2 VPN [this document]
¶
IANA is requested to assign a Capability Code from the registry at https://www.iana.org/assignments/capability-codes/ from the IETF Review range as follows:¶
Value Description Reference Controller
----- --------------------- --------------- ----------
TBD3 Flow Specification V2 [this document] IETF
¶
IANA is requested to indicate [this draft] as a reference on the following assignments in the Flow Specification Component Types Registry:¶
Value Description Reference
----- ------------------- ------------------------
1 Destination filter [RFC8955][RFC8956][this document]
2 Source Prefix [RFC8955][RFC8956][this document]
3 IP Protocol [RFC8955][RFC8956][this document]
4 Port [RFC8955][RFC8956][this document]
5 Destination Port [RFC8955][RFC8956][this document]
6 Source Port [RFC8955][RFC8956][this document]
7 ICMP Type [v4 or v6][RFC8955][RFC8956][this document]
8 ICMP Code [v4 or v6][RFC8955][RFC8956][this document]
9 TCP Flags [v4] [RFC8955][RFC8956][this document]
10 Packet Length [RFC8955][RFC8956][this document]
11 DSCP marking [RFC8955][RFC8956][this document]
12 Fragment [RFC8955][RFC8956][this document]
13 Flow Label [RFC8956][this document]
14 TTL [this document]
15 Partial SID [draft-ietf-idr-flowspec-srv6]
[this document]
16 MPLS Label Match 1 [this document]
[draft-ietf-idr-flowspec-mpls-match]
17 MPLS Label Match 2 [this document]
[draft-ietf-idr-flowspec-mpls-match]
¶
IANA is requested to create the following two new registries on a new "Flow Specification v2 TLV Types" web page.¶
Name: BGP FSv2 TLV types
Reference: [this document]
Registration Procedures: 0x01-0x3FFF Standards Action.
Type Use Reference
----- --------------- ---------------
0x00 Reserved [this document]
0x01 IP traffic rules [this document]
0x02 FSv2 Actions [this document]
0x03 L2 traffic rules [this document]
0x04 tunnel traffic rules [this document]
0x05 SFC AFI filter rules [this document]
0x06 BGP/MPLS VPN IP
traffic rules [this document]
0x07 BGP/MPLS VPN L2
traffic rules [this document]
0x08-0x3FFF Unassigned [this document]
0x4000-0x7FFF Vendor specific [this document]
0x8000-0xFFFF Reserved [this document]
¶
Name: BGP FSv2 Action types
Reference: [this document]
Registration Procedure: 0x01-0x3FFF Standards Action.
Type Use Reference
----- --------------- ---------------
0x00 Reserved [this document]
0x01 ACO: Action Chain Operation [this document]
0x02 TAIS: Traffic actions per
interface group [this document]
0x03 Unassigned [this document]
0x04 Unassigned [this document]
0x05 Unassigned [this document]
0x06 TRB: traffic rate
limited by bytes [this document]
0x07 TA: Traffic action
(terminal/sample) [this document]
0x08 RDIPv4: redirect IPv4 [this document]
0x09 TM: traffic marking (DSCP) [this document]
0x0A AL2: associate L2 Information [this document]
0x0B AET: associate E-Tree
information [this document]
0x0C TRP: traffic rate
limited by packets [this document]
0x0D RDIPv6: Redirect to IPv6 [this document]
0x0E TISFC: Traffic insertion
to SFC [this document]
0x0F RDIID: Redirect
to indirection-iD [this document]
0x10 MPLS Label Action [this document]
0x11 unassigned [this document]
0x12 unassigned [this document]
0x13 unassigned [this document]
0x14 unassigned [this document]
0x15 unassigned [this document]
0x16 VLAN action [this document]
0x17 TIPD action [this document]
0x18-
0x3ff Unassigned [this document]
0x4000-
0x7fff Vendor assigned [this document]
0x8000-
0xFFFF Reserved [this document]
¶
IANA is requested to assign values in the BGP Community Container Atom Type Registry¶
Name Type value ----- ----------- FSv2 action atom TBD5¶
IANA is requested to assign values from the Registered Type 1 BGP Wide Community Types:¶
Name type Value ------ ----------- FSv2 Actions TBD4¶
The use of ROA improves on [RFC8955] by checking to see of the route origination. This check can improve the validation sequence for a multiple-AS environment.¶
>The use of BGPSEC [RFC8205] to secure the packet can increase security of BGP flow specification information sent in the packet.¶
The use of the reduced validation within an AS [RFC9117] can provide adequate validation for distribution of flow specification within a single autonomous system for prevention of DDoS.¶
Distribution of flow filters may provide insight into traffic being sent within an AS, but this information should be composite information that does not reveal the traffic patterns of individuals.¶