BGP Flow Specification Version 2

BGP flow specification describes the distribution of filters and actions that apply when packets are received on a router with the flow specification function turned on. If one considers the reception of the packet as an event, then BGP flow specification describes a set of minimalistic Event-MatchCondition-Action (ECA) policies were the match-condition is defined in the BGP NLRI, and the action is defined either by the default condition (accept traffic) or actions defined in Extended BGP Communiites values . The initial set of policy and for this policy includes 12 types of match filters encoded in two application specific AFI/SAFIs for the IPv4 AFI. IP traffic: AFI:1, SAFI, 133; BGP/MPLS VPN AFI:1 VPN SAFI, 134) for IPv4. The popularity of these flow specification filters in deployment for DoS and SDN/NFV has led to the requirement for more BGP flow specification match filters in the NLRI and more BGP flow specification actions. This document describes distribution of two new BGP Flow Specification NLRI (2 AFI/SAFI pairs) that allow user-ordered list of traffic match filters, and user-ordered traffic match actions encoded in BGP Wide Communities. section 2 - Definitions, section 3 - Rules for dissemination of Flow Specification v2, section 4 - Optional Security, section 5 - IANA considerations, section 6 - security considerations. The rest of this section provides background on BGP Flow Specification filters interaction with I2RS Filter-Based RIBs carried by NETCONF/RESTCONF protocol. Figure 1 below is a logial description of BGP Flow Specification rules that combine filters in BGP NLRI with actions in BGP Extended communities.

+-----------------------------+ | Flow Specification (FS) | | Policy | +-----------------------------+ ^ ^ | | | | +--------^-------+ +-------^-------+ | FS Rule | | FS Rule | +----------------+ +---------------+ : : : : ......: :..... : : +---------V---------+ +----V-------------+ | Rule Condition | | Rule Action | | in BGP NLRIs | | in BGP extended | | SAFI 133, 134 | | Communities | +-------------------+ +------------------+ : : : : : : .....: . :..... .....: . :..... : : : : : : +----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 1: BGP Flow Specification Policy BGP Flow Specification (BGP-FS) ( and ) describes how to distribute the BGP Flow Specification policy as BGP routes which are locally configured on the originating BGP peer. Like BGP routes, if the BGP peer session drops then BGP Flow Specification routes are dropped. and do not indicate how the BGP Flow Specification policy is installed in the kernel.

describes the dissemination of flow specification rules policy is similar to the the statically configured Filter-Based RIB described in , and the I2RS Filter-Based RIB (, , ). These FB-RIBs start on the reception of a packet using match filters to match frames (L2) or packet data (L3/L4/Application), and perform actions as shown in figure 2.

+-----------+ +------------+ |Rule Group | | Rule Group | +-----------+ +------------+ ^ ^ | | | | +--------^-------+ +-------^-----------+ | Rule | | Rule | +----------------+ +-------------------+ : : : : :.................: : : : : |.........: : : +--V--+ +--V--+ : : | name| |order| .........: :..... +-----+ +-----+ : : : : +--------------V-------+ +--V------------+ | Rule Match condition | | Rule Action | +----------------------+ +---------------+ : : : : : : .....: . :..... .....: . :..... : : : : : : +----V---+ +---V----+ +--V---+ +-V------++--V-----++--V---+ | Match | | match | |match | | Action || action ||action| |Operator| |variable| |Value | |Operator||Variable|| Value| +--------+ +--------+ +------+ +--------++--------++------+ Figure 2: I2RS Filter-Based RIB Policy suggests that the storage of BGP Flow Specification routes in the kernel should utilize the same format as the statically configured FB-RIB and the I2RS ephemeral FB-RIB so that these traffic filters may be compared. This draft also proposes that precedence between these three sources of filters in the kernel (statically configured, I2RS ephemeral, and BGP ephemeral routes) can either set by local policy or defaults. If it is set by defaults suggests the default precedence between static, I2RS, and BGP-FS installed filters is: static FB-RIB -highest precedence (wins all ties) I2RS FB-RIB - middle preference (wins over BGP-FS originated routes, loses to static FB-RIB), BGP-FS installed Filters - lows preference (loses to static and I2RS FB-RIB)

NETCONF: The Network Configuration Protocol . RESTconf - http programmatic protocol to access yang modules BGPSEC - secure BGP . I2RS - Interface to Routing System . BGP Session ephemeral state - state which does not survive the loss of BGP peer, Ephemeral state - state which does not survive the reboot of a software module, or a hardware reboot. Ephemeral state can be ephemeral configuration state or operational state. configuration state - state which persist across a reboot of software module within a routing systsem or a reboot of a hardware routing device.

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 .

The BGP Flow Specification version 2 (BGP-FS v2) uses an NRLI with the format for AFI/SAFI (SAFI = TBD) for IP flow, and AFI/SAFI for BGP/MPLS (SAFI = TBD). This NLRI information is encoded using MP_READ_NRI and MP_UNREACH_NLRI attributes defined in . Whenever the corresponding application does not require Next-HOP information, this shall be encoded as zero-octet length Next Hop in the MP_REAC_NLRI and ignored upon receipt. Implementatinos wishing to exchange flow specificastion rules MUST use BGP's Capability Advertisement facility to exchange the Multiprotocol Extension Capability Code (Code 1) as defined in .

The AFI/SAFI NLRI for BGP Flow Specification has the format

+------------------------+ |length (2 octets) | +------------------------+ | Sub-TLVs (variable) | | +====================+ | | | order (2 octets) | | | +--------------------+ | | | type (2 octets) | | | +--------------------+ | | | length (2 octets) | | | +--------------------+ | | | value (variable) | | | |[multiples of | | | | 2 octets] | | | +====================+ | +------------------------+ Figure 16 - NRLI revision where: length - is the length of the NLRI, Sub-TLVs contain a user-ordered set of filter components as defined in and . The ranges are defined as: standard BGP Flow Specification filters (types 0x01 - 0x3FFFF), and vendor specific filters (types 0x4ffff to 0x7FFFF) with type values 0x8000 to 0xFFFFFFFF reserved for future use. Each sub-tlv has an length of 2 octets, and a variable length value (in multiples of 2 octets). Filters are process in the order specified by the user. If multiple filters exist for the same order, the strict filter ordering defined in and will be used for the filters with the same value for user order.

The BGP-FS version 2 actions are passed in a Wide Community atom with the following format.

+--------------------------+ | order (2 octets) | +--------------------------+ | Action type (2 octets) | +--------------------------+ | Action length (2 octets) | +--------------------------+ | Action Values (variable) | | (multiples of 2 octets) | +--------------------------+ Wide Community Atom figure 17 where: Action type (2 octets) - is the type of action. These actions can be standardized (0x0001 - 0x3ffff), vendor specific (0x40000-0x7FFFF), or reserved (0x0, 0x80000-0xFFFFFFFF). Action length - length of actions including variable field, Action values - value of actions (variable) defined in individual definitions. The BGP Flow Specification (BGP-FS) atom can be part of the Wide Community container (type 1) or the BGP Flow Specification Atom can be part of the BGP Flow Specification container (type 2) which will have:

+-----------------------------+ | Source AS Number (4 octets)| +-----------------------------+ | list of atoms (variable) | +-----------------------------+ figure 18

Same as and .

This section discusses the optional BGP Security additions for BGP-FS v2: BGPSEC , ROA and revised security for flow specification distributed from a centralized server within an AS . These optional security parameters can be applied per BGP peer.

does not require BGP Flow specifications to be passed BGPSEC . BGP FS v2 can be passed in BGPSEC, but it is not required.

BGP-FS v2 can utilize ROAs in the validation. If BGP-FS v2 is used with BGPSEC and ROA, the first thing is to vaildate 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: A BGP ROA has been received to validate the originator, and the route is the best-match unicast route for the destination prefix embedded in the match filter; or 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 validation rules of: The originator match of the flow specification matches the originator of the best-match unicast route for the destination prefix filter embedded in the flow specification", and No more specific unicast routes exist when compared with the flow destination prefix that have been received from a different neighboring AS than the best-match unicast route, which has been determined in step A. The best match is defined to be the longest-match NLRI with the highest preference.

The distribution of Flow Specifications from a centralized server supports mitigation of DoS attacks. suggests the following redefined procedure for validation for this case: A route is valid if the following conditions holds true: The originator of the flow specification matches the originator of the best-match unicast route for the destination prefix embedded in the flow specification. The AS_PATH and AS4_PATH attribute of the flow specification are empty (on originating AS) The AS_PATH and AS4_PATH attribute of the flow specification does not contain AS_SET and AS_SEQUENCE segments (on originating AS with AS Confederation) This reduced validation mechanism can be used for BGP-FS v2 within a single domain.

This section complies with This document requests: SAFI be defined for IPv4 (AFI = 1), IPv6 (AFI=2), L2VPN (AFI=25) for BGP-FS SAFI be defined for BGP/MPLS IPv4 (AFI = 1), IPv6 (AFI=2), L2VPN (AFI=25) for BGP-FS Registry be created for BGP-FS V2 filter component types with the following ranges: 0x00 - reserved 0x01 - 0x3FFFF - standards action 0x40000- 0x7FFFF - vendor specific filters 0x80000 -0xFFFFFFFF - reserved 0x80000 -0xFFFFFFFF - reserved Registry be created for BGP-FS v2 action types with the following ranges: 0x0 - reserved 0x01 - 0x3ffff - standards action 0x40000 - 0x7ffff - vendor actions 0x80000 - 0xFFFFFFF - reserved

The use of ROA improves on to check the route orgination is valid can improve the validation sequence for a multiple-AS environment. The use of BGPSEC 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 can provide adequate validation for distribution of flow specification within an 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.