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<rfc category="std" docName="draft-hares-idr-rfc5575bis-01.txt" ipr="trust200902" updates="7674" obsoletes="5575" >
<front>
<title abbrev="RFC5575bis">Dissemination of Flow Specification Rules</title>
<author fullname="Susan Hares" initials="S" surname="Hares">
<organization>Huawei</organization>
<address>
<postal>
<street>7453 Hickory Hill</street>
<city>Saline</city>
<region>MI</region>
<code>48176</code>
<country>USA</country>
</postal>
<email>shares@ndzh.com</email>
</address>
</author>
<date year="2016" />
<area>Routing Area</area>
<workgroup>IDR Working Group</workgroup>
<keyword>RFC</keyword>
<keyword>Request for Comments</keyword>
<keyword>I-D</keyword>
<keyword>Internet-Draft</keyword>
<keyword>Replaces:RFC5575 </keyword>
<keyword> Dissemination of Flow Specification Rules</keyword>
<abstract>
<t>
This document updates RFC5575 which defines a Border Gateway Protocol Network Layer
Reachability Information (BGP NLRI) encoding format 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 (IPv4, IPv6),
MPLS addresses, L2VPN addresses, and NV03 encapsulation of IP addresses.
The information is carried via the BGP, thereby reusing protocol
algorithms, operational experience, and administrative processes such
as inter-provider peering agreements.
</t>
<t>
There are three applications of that encoding format:
1) automation of inter-domain coordination of traffic
filtering, such as what is required in order to mitigate
(distributed) denial-of-service attacks; 2) enable
traffic filtering in the context of a BGP/MPLS VPN service,
and 3) aid centralized control of traffic in a SDN or NFV context.
Some of deployments of these three applications can be handled by
the strict ordering of the BGP NLRI traffic flow filters, and the
strict actions encoded in the Extended Community Flow Specification
actions. Other deployments (especially SDN/NFV) need to be able
to allow the user to order the flow specification. Another BGP
Flow Specification (version 2) is being defined for user-ordered filters,
and user-ordered actions encoded in Wide Communities.
</t>
<t>
This document provides the definition of a BGP NLRI which carries traffic
flow specification filters, and Extended Community values which
encode the actions a routing system can take if a packet matches
the traffic flow filters. The specification requires that the
BGP Flow Specification traffic filters follows a string ordering, and
that the BGP Flow Specification Extended Communities actions are processed
in a defined order. This BGP Flow Specification is denoted as
BGP Flow Specification version 1.
</t>
<t>
There are three applications of that encoding format:
1) automation of inter-domain coordination of traffic
filtering, such as what is required in order to mitigate
(distributed) denial-of-service attacks; 2) enable
traffic filtering in the context of a BGP/MPLS VPN service,
and 3) aid centralized control of traffic in a SDN or NFV context.
Some of deployments of these three applications can be handled by
the strict ordering of the BGP NLRI traffic flow filters, and the
strict actions encoded in the Extended Community Flow Specification
actions. Other deployments (especially SDN/NFV) need to be able
to allow the user to order the flow specification. Another BGP
Flow Specification (version 2) is being defined for user-ordered filters,
and user-ordered actions encoded in Wide Communities.
</t>
</abstract>
</front>
<middle>
<section anchor="intro" title="Introduction">
<t>
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.
</t>
<t>
These traffic policy mechanisms allow the router 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.
</t>
<t>
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.
</t>
<t>
This document defines a general procedure to encode flow
specification rules for aggregated traffic flows so that they can be
distributed as a BGP <xref target="RFC5575"></xref> NLRI. Additionally, we define the
required mechanisms to utilize this definition to the problem of
immediate concern to the authors: intra- and inter-provider
distribution of traffic filtering rules to filter (distributed)
denial-of-service (DoS) attacks.
</t>
<t>
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. Flow
specifications can be seen as more specific routing entries to a
unicast prefix and are expected to depend upon the existing unicast
data information.
</t>
<t>
A flow specification received from an external autonomous system will
need to be validated against unicast routing before being accepted.
If the aggregate traffic flow defined by the unicast destination
prefix is forwarded to a given BGP peer, then the local system can
safely install more specific flow rules that may result in different
forwarding behavior, as requested by this system.
</t>
<t>The key technology components required to address the class of
problems targeted by this document are:
<list style="numbers">
<t> Efficient point-to-multipoint distribution of control plane
information.
</t>
<t>Inter-domain capabilities and routing policy support.
</t>
<t>Tight integration with unicast routing, for verification
purposes.
</t>
</list>
</t>
<t>
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.
</t>
<t>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.
</t>
<t>In many deployments of BGP Flow Specification, the flow specification information
has replace existing host length route advertisements.
</t>
<t>
Experience with previous BGP extensions has also shown that the
maximum capacity of BGP speakers has been gradually increased
according to expected loads. Taking into account Internet unicast
routing as well as additional applications as they gain popularity.
</t>
<t>
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).
</t>
<t>
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.
</t>
<t>In current deployments, the information distributed by the flow-spec
extension is originated both manually as well as automatically. The
latter by systems that are able to detect malicious flows. When
automated systems are used, care should be taken to ensure their
correctness as well as to limit the number and advertisement rate of
flow routes.
</t>
<t>
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:
<list style="symbols">
<t>IPv6 <xref target="I-D.ietf-idr-flow-spec-v6"></xref>,
</t>
<t> MAC address for L2VPN <xref target="I-D.ietf-idr-flowspec-l2vpn"></xref>,
</t>
<t>NV03 encapsulation <xref target="I-D.ietf-idr-flowspec-nvo3"></xref> and,
</t>
<t>MPLS (<xref target="I-D.ietf-idr-flowspec-mpls-match"></xref>,
<xref target="I-D.ietf-idr-bgp-flowspec-label"></xref>).
</t></list>
</t>
<t>
These additions to BGP Flow Specification IPv4 are included in a separate documents
to allow implementers the choice of implementing portions of the
BGP Flow specification.
</t>
</section>
<section title="Definitions of Terms Used in This Memo">
<t>
<list style="hanging">
<t hangText="NLRI - ">Network Layer Reachability Information.
</t>
<t hangText="RIB - ">Routing Information Base.
</t>
<t hangText="Loc-RIB - ">Local RIB.
</t>
<t hangText="AS - ">Autonomous System number.
</t>
<t hangText="VRF - ">Virtual Routing and Forwarding instance.
</t>
<t hangText="PE - ">Provider Edge router
</t>
</list>
</t>
<t>
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 <xref target="RFC2119"></xref>
</t>
</section>
<section title="Flow Specifications">
<t>
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 defined flow if it matches all the specified
criteria.
</t>
<t>A given flow 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.
</t>
<t> A particular application is identified by a specific (Address Family
Identifier, Subsequent Address Family Identifier (AFI, SAFI)) pair
<xref target="RFC4760"></xref> 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.
</t>
<t>BGP itself treats the NLRI as an opaque 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.
</t>
<t>
Standard BGP policy mechanisms, such as UPDATE filtering by NLRI
prefix and community matching, SHOULD apply to the Flow specification
defined NLRI-type. 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.
</t>
</section>
<section title="Traffic Filtering">
<t>
Traffic filtering policies have been traditionally considered to be
relatively static. Limitations of the static mechanisms caused
this mechanism to be designed for the three new applications of traffic filtering
(prevention of traffic-based, denial-of-service (DOS) attacks,
traffic filtering in the context of BGP/MPLS VPN service, and
centralized traffic control for SDN/NFV networks) requires
coordination among service providers and/or coordination
among the AS within a service provider. Section 8 has
details on the limitation of previous mechanisms and why
BGP Flow Specification version 1 provides a solution for
to prevent DOS and aid BGP/MPLS VPN filtering rules.
</t>
<t>
This flow specification NLRI defined above to
convey information about traffic filtering rules for traffic that
should be discarded or handled in 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.
</t>
<t>
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:
<list style="symbols">
<t>IPv4 flow specification identifier (AFI=1, SAFI=133) along with specific semantic rules
for IPv4 routes, and
</t>
<t>BGP NLRI type (AFI=1, SAFI=134)
value, which can be used to propagate traffic filtering information
in a BGP/MPLS VPN environment.
</t>
</list>
</t>
<t>Distribution of the IPv4 Flow specification is described in section 6, and
distibution of BGP/MPLS traffic flow specification is described in section 8.
The traffic filtering actions are described in section 7.
</t>
<section title="Support for other AFIs">
<t>
Other documents shown in table 5 provide the
application identifiers for IPv6, L2VPN, NVO3 and MPLS. However, to
provide backward compatiblity with <xref target="RFC5575"></xref>
documents adhering to this specification do not need to support
IPv6, L2VPN, NV03, and MPLS AFI/SAFIs.
</t>
<t>
<figure>
<artwork>
Table 5 - AFI/SAFI values vs. application
+---+----+-----------+-----------------------------------+---+
|AFI|SAFI|Application| Document |Req|
+---+----+-----------+-----------------------------------+---+
| 1| 133| DDOS | this document |Yes|
| 1| 134| BGP/MPLS | this document | No|
+---+----------------+-----------------------------------+---+
| 2| 133| DDOS |draft-ietf-idr-flow-spec-v6 | No|
| 2| 134| BGP/MPLS |draft-ietf-idr-flow-spec-v6 | No|
+---+----+-----------+-----------------------------------+---+
| 25| 133| DDOS |draft-ietf-idr-flowspec-l2vpn | No|
| 25| 134| BGP/MPLS |draft-ietf-idr-flowspec-l2vpn | No|
+---+----+-----------+-----------------------------------+---+
|TBD| 133| DDOS |draft-ietf-idr-flowspec-mpls-label | No|
|TBD| 134| BGP/MPLS |draft-ietf-idr-flowspec-mpls-label | No|
+---+----+-----------+-----------------------------------+---+
|TBD| 133| DDOS |draft-ietf-idr-flowspec-nv03 | No|
|TBD| 134| BGP/MPLS |draft-ietf-idr-flowspec-nv03 | No|
+---+----+-----------+-----------------------------------+---+
</artwork>
</figure>
</t>
</section>
</section>
<section title="Dissemination of IPv4 FLow Specification Information">
<t>
We define a "Flow Specification" NLRI type that may include several
components such as destination prefix, source prefix, protocol,
ports, and others (see Tables 1-4 below). This NLRI is treated as an
opaque bit string prefix by BGP. Each bit string identifies
a key to a database entry with which a set of attributes can be associated.
</t>
<t>
This NLRI information is encoded using MP_REACH_NLRI and
MP_UNREACH_NLRI attributes as defined in <xref target="RFC4760"></xref>.
Whenever the corresponding application does not require Next-Hop
information, this shall be encoded as a 0-octet length Next Hop in
the MP_REACH_NLRI attribute and ignored on receipt.
</t>
<t>
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.
</t>
<t>
<figure>
<artwork>
+------------------------------+
| length (0xnn or 0xfn nn) |
+------------------------------+
| NLRI value (variable) |
+------------------------------+
Figure 1: Flow-spec NLRI for IPv4
</artwork>
</figure>
</t>
<t>
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 <xref target="RFC4760"></xref>.
The (AFI, SAFI) pair carried in the Multiprotocol Extension
Capability MUST be the same as the one used to identify a particular
application that uses this NLRI-type.
</t>
<section title="Length Encoding">
<t>
<list style="symbols">
<t>If the NLRI length value is smaller than 240 (0xf0 hex), the length
field can be encoded as a single octet. </t>
<t>Otherwise, it is encoded as
an extended-length 2-octet value in which the most significant nibble
of the first byte is all ones.</t>
</list>
</t>
<t>
In figure 1 above, values less-than 240 are encoded using two hex
digits (0xnn). Values above 240 are encoded using 3 hex digits
(0xfnnn). The highest value that can be represented with this
encoding is 4095. The value 241 is encoded as 0xf0f1.
</t>
</section>
<section title="NLRI Value Encoding">
<t>
The Flow specification NLRI-type consists of several optional
subcomponents. A specific packet is considered to match the flow
specification when it matches the intersection (AND) of all the
components present in the specification. The encoding of each
of the NLRI components begins with a type field as listed in
Table 1-4. Sections 4.2.1 to 4.2.12 contain the specific encodings for the
IPv4 IP layer and transport layer headings.
Additional filters encodiings for IPv6, L2VPN MAC Addresses, MPLS labels,
and encapsulations for Data Centers (e.g. NVO3) related are described in
other documents referenced above.
</t>
<t>
Flow specification components must follow strict type ordering by increasing
numerical order. A given component type may or may not be present in the specification,
but if present, it MUST precede any component of higher numeric type
value.
</t>
<t>
If a given component type within a prefix in unknown, the prefix in
question cannot be used for traffic filtering purposes by the
receiver. Since a flow specification has the semantics of a logical
AND of all components, if a component is FALSE, by definition it
cannot be applied. However, for the purposes of BGP route
propagation, this prefix should still be transmitted since BGP route
distribution is independent on NLRI semantics.
</t>
<t>The <type, value< encoding is chosen in order to allow for future
extensibility.
</t>
<t>
<figure>
<artwork>
Table 1 - NLRI Types (IP values)
+----+-------------------------+---------------------------+---+
|Type| NLRI component | Document |Req|
+----+-------------------------+---------------------------+---+
| 1 | IPv4 Destination Prefix |this document |Yes|
| | IPv6 Destination Prefix |draft-ietf-idr-flow-spec-v6| No|
+----+-------------------------+---------------------------+---+
| 2 | IPv4 Source Prefix |this document | No|
| | IPv6 Source Prefix |draft-ietf-idr-flow-spec-v6| No|
+----+-------------------------+---------------------------+---+
| 3 | IPv4 Protocol |this document | No|
| | IPv6 Next Header |draft-ietf-idr-flow-spec-v6| No|
+----+-------------------------+---------------------------+---+
| 4 | Transport Port |this document | No|
| | (TCP/UDP source or | | |
| | destination port | | |
+----+-------------------------+---------------------------+---+
| 5 | Destination Port |this document | No|
| | (TCP or UDP) | | |
+----+-------------------------+---------------------------+---+
| 6 | Source Port (TCP/UDP) |this document | No|
+----+-------------------------+---------------------------+---+
| 7 | ICMP type |this document | No|
+----+-------------------------+---------------------------+---+
| 8 | ICMP Code |this document | No|
+----+-------------------------+---------------------------+---+
| 9 | TCP flags |this document | No|
+----+-------------------------+---------------------------+---+
| 10 | IP Packet length |this document | No|
+----+-------------------------+---------------------------+---+
| 11 | DSCP |this document | No|
+----+-------------------------+---------------------------+---+
| 12 | IPv4 Fragment |this document | No|
+----+-------------------------+---------------------------+---+
| 13 | IPv6 Flow Label |draft-ietf-idr-flow-spec-v6| No|
+----+-------------------------+---------------------------+---+
</artwork>
</figure>
</t>
<t>
<figure>
<artwork>
Table 2 - NLRI Types (L2VPN values)
+----+-----------------+----------------------------------+---+
|Type| NLRI component | Document |Req|
+----+-----------------+----------------------------------+---+
|TBD1| MPLS Label |draft-ietf-idr-flowspec-mpls-match| No|
| | on label stack | | |
+----+-----------------+----------------------------------+---+
|TBD2| MPLS EXP bits |draft-ietf-idr-flowspec-mpls-match| No|
| | on top of label | | |
| | stack | | |
+----+-----------------+----------------------------------+---+
</artwork>
</figure>
</t>
<t>
<figure>
<artwork>
Table 3 - NLRI Types (L2VPN values)
+----+--------------------+-----------------------------+---+
|Type| NLRI component | Document |Req|
+----+--------------------+-----------------------------+---+
|TBD*| Ethernet type |draft-ietf-idr-flowspec-l2vpn| No|
+----+--------------------+-----------------------------+---+
| 14 | Flow Label |draft-ietf-idr-flowspec-l2vpn| No|
+----+--------------------+-----------------------------+---+
| 15 | Source MAC |draft-ietf-idr-flowspec-l2vpn| No|
+----+--------------------+-----------------------------+---+
| 16 | Destination MAC |draft-ietf-idr-flowspec-l2vpn| No|
+----+--------------------+-----------------------------+---+
| 17 | DSAP in LLC |draft-ietf-idr-flowspec-l2vpn| No|
+----+--------------------+-----------------------------+---+
| 18 | SSAP in LLC |draft-ietf-idr-flowspec-l2vpn| No|
+----+--------------------+-----------------------------+---+
| 19 | LLC control field |draft-ietf-idr-flowspec-l2vpn| No|
+----+--------------------+-----------------------------+---+
| 20 | SNAP |draft-ietf-idr-flowspec-l2vpn| No|
+----+--------------------+-----------------------------+---+
| 21 | VLAN ID |draft-ietf-idr-flowspec-l2vpn| No|
+----+--------------------+-----------------------------+---+
| 22 | VLAN COS |draft-ietf-idr-flowspec-l2vpn| No|
+----+--------------------+-----------------------------+---+
| 23 | Inner VLAN ID |draft-ietf-idr-flowspec-l2vpn| No|
+----+--------------------+-----------------------------+---+
| 24 | Inner VLAN COS |draft-ietf-idr-flowspec-l2vpn| No|
+----+--------------------+-----------------------------+---+
*conflict between IPv6 filters and L2VPN filters means this
idea type must be renumbered.
</artwork>
</figure>
</t>
<t>
<figure>
<artwork>
Table 4 - NV03 Encapsulations
+----+--------------------+-----------------------------+---+
|Type| NLRI component | Document |Req|
+----+--------------------+-----------------------------+---+
|TBD3| Delimiter type |draft-ietf-idr-flowspec-nv03 | No|
| | (VXLAN or NVGRE) | | |
+----+--------------------+-----------------------------+---+
|TBD4| VNID |draft-ietf-idr-flowspec-nv03 | No|
+----+--------------------+-----------------------------+---+
|TBD5| Flow ID (NVGRE) |draft-ietf-idr-flowspec-nv03 | No|
+----+--------------------+-----------------------------+---+ |
</artwork>
</figure>
</t>
<section title="Type 1 - Destination Prefix">
<t>
<list>
<t>Encoding: <type (1 octet), prefix length (1 octet), prefix>
</t>
<t>Defines: the destination prefix to match. Prefixes are encoded
as in BGP UPDATE messages, a length in bits is followed by
enough octets to contain the prefix information.
</t>
</list>
</t>
</section>
<section title="Type 2 - Source Prefix">
<t>
<list>
<t>Encoding: <type (1 octet), prefix-length (1 octet), prefix>
</t>
<t>Defines the source prefix to match.
</t>
</list>
</t>
</section>
<section title="Type 3 - Source Prefix">
<t>
<list>
<t>Encoding:<type (1 octet), [op, value]+>
</t>
<t>Contains a set of {operator, value} pairs that are used to
match the IP protocol value byte in IP packets.
</t>
<t>The operator byte is encoded as:
<figure>
<artwork>
0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| e | a | len | 0 |lt |gt |eq |
+---+---+---+---+---+---+---+---+
Numerical operator
</artwork>
</figure>
</t>
<t>e - end-of-list bit. Set in the last {op, value} pair in the list.
</t>
<t>a - AND bit. If unset, the previous term is logically ORed
with the current one. If set, the operation is a logical
AND. It should be unset in the first operator byte of a
sequence. The AND operator has higher priority than OR
for the purposes of evaluating logical expressions.
</t>
<t>len - length of the value field for this operand is given
as (1 << len).
</t>
<t>lt - less than comparison between data and value.
</t>
<t>gt - greater than comparison between data and value.
</t>
<t>eq -equality between data and value
</t>
</list>
</t>
<t>The bits lt, gt, and eq can be combined to produce "less or
equal", "greater or equal", and inequality values
</t>
</section>
<section title="Type 4 - Port">
<t>
<list>
<t>Encoding:<type (1 octet), [op, value]+>
</t>
<t>Defines a list of {operation, value} pairs that matches source
OR destination TCP/UDP ports. This list is encoded using the
numeric operand format defined above. Values are encoded as 1-
or 2-byte quantities.
</t>
<t>
Port, source port, and destination port components evaluate to
FALSE if the IP protocol field of the packet has a value other
than TCP or UDP, if the packet is fragmented and this is not
the first fragment, or if the system in 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
<xref target="RFC4303"></xref> encryption.
</t>
</list>
</t>
</section>
<section title="Type 5 - Destination Port">
<t>
<list>
<t>Encoding:<type (1 octet), [op, value]+>
</t>
<t> Defines a list of {operation, value} pairs used to match the
destination port of a TCP or UDP packet. Values are encoded as
1- or 2-byte quantities
</t>
</list>
</t>
</section>
<section title="Type 6 - Destination Port">
<t>
<list>
<t>Encoding:<type (1 octet), [op, value]+>
</t>
<t> Defines a list of {operation, value} pairs used to match the
source port of a TCP or UDP packet. Values are encoded as
1- or 2-byte quantities
</t>
</list>
</t>
</section>
<section title="Type 7 - ICMP type">
<t>
<list>
<t>Encoding:<type (1 octet), [op, value]+>
</t>
<t>Defines a list of {operation, value} pairs used to match the
type field of an ICMP packet. Values are encoded using a
single byte.
</t>
<t>The ICMP type and code specifiers evaluate to FALSE whenever
the protocol value is not ICMP.
</t>
</list>
</t>
</section>
<section title="Type 8 - ICMP code">
<t>
<list>
<t>Encoding:<type (1 octet), [op, value]+>
</t>
<t>
Defines a list of {operation, value} pairs used to match the
code field of an ICMP packet. Values are encoded using a
single byte.
</t>
</list>
</t>
</section>
<section title="Type 9 - ICMP code">
<t>
<list>
<t>Encoding:<type (1 octet), [op, bitmask]+>
</t>
<t>Bitmask values can be encoded as a 1- or 2-byte bitmask. When
a single byte is specified, it matches byte 13 of the TCP
header <xref target="RFC0793"></xref>, which contains
bits 8 though 15 of the 4th 32-bit word.
When a 2-byte encoding is used, it matches bytes
12 and 13 of the TCP header with the data offset field having a
"don't care" value.
</t>
<t>
As with port specifiers, this component evaluates to FALSE for
packets that are not TCP packets.
</t>
<t>This type uses the bitmask operand format, which differs from
the numeric operator format in the lower nibble.
<figure>
<artwork>
0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| e | a | len | 0 | 0 |not| m |
+---+---+---+---+---+---+---+---+
Bitmask format
</artwork>
</figure>
</t>
</list>
</t>
<t>
<list style="hanging">
<t hangText="e, a, len - Most significant nibble:"> (end-of-list bit, AND
bit, and length field), as defined for in the
numeric operator format.
</t>
<t hangText="not - NOT bit."> If set, logical negation of operation.
</t>
<t hangText="m - Match bit."> If set, this is a bitwise match operation
defined as "(data AND value) == value"; if unset, (data AND value) evaluates
to TRUE if any of the bits in the value mask are set in the data
</t>
</list>
</t>
</section>
<section title="Type 10 - Packet length">
<t>
<list>
<t>Encoding:<type (1 octet), [op, bitmask]+>
</t>
<t>Defines match on the total IP packet length (excluding Layer 2 but
including IP header). Values are encoded using 1- or 2-byte
quantities.</t>
</list>
</t>
</section>
<section title="Type 11 - DSCP (Diffserv Code Point)">
<t>
<list>
<t>Encoding:<type (1 octet), [op, value]+>
</t>
<t> Defines a list of {operation, value} pairs used to match the
6-bit DSCP field <xref target="RFC2474"></xref>.
Values are encoded using a single
byte, where the two most significant bits are zero and the six
least significant bits contain the DSCP value.
</t>
</list>
</t>
</section>
<section title="Type 12 - Fragment">
<t>
<list>
<t>Encoding:<type (1 octet), [op, bitmask]+>
</t>
<t> Uses bitmask operand format defined above in section 5.2.9.
</t>
<t>
<figure>
<artwork>
0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| Reserved |LF |FF |IsF|DF |
+---+---+---+---+---+---+---+---+
</artwork>
</figure>
</t>
<t>Bitmask values:
<list style="symbol">
<t>Bit 7 - Don't fragment (DF)
</t>
<t>Bit 6 - Is a fragment (IsF)
</t>
<t>Bit 5 - First fragment (FF)
</t>
<t>Bit 4 - Last fragment (LF)
</t>
</list>
</t>
</list>
</t>
</section>
<section title="Examples of Encodings">
<t>
An example of a flow specification encoding for: "all packets to
10.0.1/24 and TCP port 25".
</t>
<t>
<figure>
<artwork>
+------------------+----------+----------+
| destination | proto | port |
+------------------+----------+----------+
| 0x01 18 0a 00 01 | 03 81 06 | 04 81 19 |
+------------------+----------+----------+
</artwork>
</figure>
</t>
<t>
Decode for protocol:
<figure>
<artwork>
+-------+----------+------------------------------+
| Value | | |
+-------+----------+------------------------------+
| 0x03 | type | |
| 0x81 | operator | end-of-list, value size=1, = |
| 0x06 | value | |
+-------+----------+------------------------------+
</artwork>
</figure>
</t>
<t>
An example of a flow specification encoding for: "all packets to
10.0.1/24 from 192/8 and port {range [137, 139] or 8080}".
<figure>
<artwork>
+------------------+----------+-------------------------+
| destination | source | port |
+------------------+----------+-------------------------+
| 0x01 18 0a 01 01 | 02 08 c0 | 04 03 89 45 8b 91 1f 90 |
+------------------+----------+-------------------------+
</artwork>
</figure>
</t>
<t>
Decode for port:
<figure>
<artwork>
+--------+----------+------------------------------+
| Value | | |
+--------+----------+------------------------------+
| 0x04 | type | |
| 0x03 | operator | size=1, >= |
| 0x89 | value | 137 |
| 0x45 | operator | "AND", value size=1, <= |
| 0x8b | value | 139 |
| 0x91 | operator | end-of-list, value-size=2, = |
| 0x1f90 | value | 8080 |
+--------+----------+------------------------------+
</artwork>
</figure>
This constitutes an NLRI with an NLRI length of 16 octets.
</t>
</section>
</section>
<section title="Ordering of Traffic Filtering Rules">
<t>
With traffic filtering rules, more than one rule may match a
particular traffic flow. Thus, it is necessary to define the order
at which rules get matched and applied to a particular traffic flow.
This ordering function must be such that it must not depend on the
arrival order of the flow specification's rules and must be constant
in the network.
</t>
<t>
The relative order of two flow specification rules is determined by
comparing their respective components. The algorithm starts by
comparing the left-most components of the rules. If the types
differ, the rule with lowest numeric type value has higher precedence
(and thus will match before) than the rule that doesn't contain that
component type. If the component types are the same, then a type-
specific comparison is performed.
</t>
<t>
For IP prefix values (IP destination and source prefix) precedence is
given to the lowest IP value of the common prefix length; if the
common prefix is equal, then the most specific prefix has precedence.
</t>
<t>
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 by the ISO C standard.
For strings of different lengths, the common prefix is compared. If
equal, the longest string is considered to have higher precedence
than the shorter one.
</t>
<t>
<figure>
<artwork>
Pseudocode:
flow_rule_cmp (a, b)
{
comp1 = next_component(a);
comp2 = next_component(b);
while (comp1 || comp2) {
// component_type returns infinity on end-of-list
if (component_type(comp1) < component_type(comp2)) {
return A_HAS_PRECEDENCE;
}
if (component_type(comp1) > component_type(comp2)) {
return B_HAS_PRECEDENCE;
}
if (component_type(comp1) == IP_DESTINATION || IP_SOURCE) {
common = MIN(prefix_length(comp1), prefix_length(comp2));
cmp = prefix_compare(comp1, comp2, common);
// not equal, lowest value has precedence
// equal, longest match has precedence
} else {
common =
MIN(component_length(comp1), component_length(comp2));
cmp = memcmp(data(comp1), data(comp2), common);
// not equal, lowest value has precedence
// equal, longest string has precedence
}
}
return EQUAL;
}
</artwork>
</figure>
</t>
<t>
When other AFI families are specified for BGP Flow specifications,
this logic MUST be expanded. Other AFI families include IPv6,
MPLS, L2VPN, and NV03 encapsulation.
</t>
</section>
<section title="Validation Procedure">
<t>Flow specifications received from a BGP peer and 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 set of attributes to advertise.
</t>
<t>
The first step of the BGP Route Selection procedure (Section 9.1.2 of
<xref target="RFC4271"></xref> 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.
</t>
<t>
The concept can be extended, in the case of flow specification NLRI,
to allow other validation procedures.
</t>
<t>
A flow specification NLRI must be validated such that it is
considered feasible if and only if:
<list>
<t>a) The originator of the flow specification matches the originator of
the best-match unicast route for the destination prefix embedded
in the flow specification.
</t>
<t>b) There are no more specific unicast routes, 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).
</t>
</list>
</t>
<t>
By originator of a BGP route, we mean either the BGP originator path
attribute, as used by route reflection, or the transport address of
the BGP peer, if this path attribute is not present.
</t>
<t>
The underlying concept is that the neighboring AS that advertises the
best unicast route for a destination is allowed to advertise flow-
spec 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
that filtering rule.
</t>
<t>
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.
</t>
<t>
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.
</t>
</section>
</section>
<section title="Traffic Filtering Actions">
<t>
This specification defines a minimum set of filtering actions that it
standardizes as BGP extended community values <xref target="RFC4360"></xref>.
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.
</t>
<t>
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.
</t>
<t>
The default action for a traffic filtering flow specification is to
accept IP traffic that matches that particular rule.
</t>
<t>This document defines the following extended communities values
shown in table X in the form 0x8xnn where nn indicates the sub-type.
<figure>
<artwork>
Table 5 - Traffic Action Extended Communities
Defined in this document
+--------+-----------------------+-------------------------------------+
| type | extended community | encoding |
+--------+-----------------------+-------------------------------------+
| 0x8006 | traffic-rate in bytes | 2-byte ASN, 4-byte float |
| 0x8007 | traffic-action | bitmask |
| 0x8008 | redirect AS-2byte | 2-octet AS, 4-octet Value |
| 0x8108 | redirect IPv4 | 4-octet IPv4 Address, 2-octet Value |
| 0x8208 | redirect AS-4byte | 4-octet AS, 2-octet Value |
| 0x8009 | traffic-marking | DSCP value |
+--------+--------------------+----------------------------------------+
</artwork>
</figure>
Encodings for these extended communities are described below.
</t>
<t>
Some traffic action communities may interfere with each other.
Section x.x of this specification provides rules for handling interference
between specific types of traffic actions, and error handling
based on <xref target="RFC7606"></xref> in section.
Each definition of a traffic action MUST specify any interface
with any other traffic actions, any impact on
flow specification process, and error handling
per <xref target="RFC7606"></xref>.
</t>
<t>The traffic actions are processed in ascending order
of the sub-type found in the BGP Extended Communities.
</t>
<section title="Traffic Rate in bytes (sub-type 0x06)">
<t>The traffic-rate extended community is a non-
transitive extended community across the autonomous-system
boundary and uses following extended community encoding:
</t>
<t>
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.
</t>
<t>
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.
</t>
<t>Interfers with: Traffic Rate in packets. Process
traffic rate in bytes (sub-type 0x06) action before
traffic rate action (sub-type TBD).
</t>
</section>
<section title=" Traffic-action (sub-type 0x07)">
<t>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) are currently defined.
</t>
<t>
<figure>
<artwork>
40 41 42 43 44 45 46 47
+---+---+---+---+---+---+---+---+
| reserved | S | T |
+---+---+---+---+---+---+---+---+
</artwork>
</figure>
</t>
<t>where S and T are defined as:
<list style="symbols">
<t>T: Terminal Action (bit 47): When this bit is set, the traffic
filtering engine will apply any subsequent filtering rules (as
defined by the ordering procedure). If not set, the evaluation
of the traffic filter stops when this rule is applied.
</t>
<t>S:Sample (bit 46): Enables traffic sampling and logging for this
flow specification.
</t>
</list>
</t>
<t>Interfers with: No other BGP Flow Specification traffic action in
this document.
</t>
</section>
<section title="IP Redirect (sub-type 0x08)">
<t>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). This extended community uses the same
encoding as the Route Target extended community [RFC4360].
</t>
<t>
It should be noted that the low-order nibble of the Redirect's Type
field corresponds to the Route Target Extended Community format field
(Type). (See Sections 3.1, 3.2, and 4 of <xref target="RFC4360"></xref>
plus Section 2 of <xref target="RFC5668"></xref>.)
The low-order octet (Sub-Type) of the Redirect Extended
Community remains 0x08 for all three encodings of the
BGP Extended Communities (AS 2-byte, AS 4-byte, and IPv4 address).
</t>
<t>Interfers with: All other redirect functions. All redirect
functions are mutually exclusive. If this redirect function
exists, then no other redirect functions can be processed.</t>
</section>
<section title="Traffic Marking (sub-type 0x09)">
<t> The traffic marking extended community instructs a
system to modify the DSCP bits of a transiting IP packet to the
corresponding value. This extended community is encoded as a
sequence of 5 zero bytes followed by the DSCP value encoded in the
6 least significant bits of 6th byte.
</t>
<t>Interfers with: No other action in this document.</t>
</section>
<section title="Rules on Traffic Action interference">
<t>
The following traffic Actions may interfere with each other:
<list style="symbols">
<t>redirect actions, </t>
<t>traffic rate actions, and </t>
<t>encapsulation actions.</t>
</list>
</t>
<t>
This specification has the following rules regaarding
multiple traffic actions to prevent the interference:
<list style="numbers">
<t>All redirect actions are mutually exclusive.
Presence of more than one results in no redirect.</t>
<t>If multiple rate actions are present, these
are applied in ascending order of the sub-type.
</t>
<t>Some actions are unique, and may operate independently.
For example, an MPLS push/pop action is unique.
</t>
<t>Each additional flow specification Action must specify:
<list style="symbols">
<t>whether it is a redirect or rate action,</t>
<t>whether the action is unique or if it
interfers with other actions,
</t>
<t>If the action interfers with other actions,
the handling must be specified if both
the action and other interfering actions
exist are associated with a Flow specification
NLRI.</t>
</list>
</t>
</list>
</t>
</section>
</section>
<section title="Dissemination of Traffic Filtering in BGP/MPLS VPN Networks">
<t>
Provider-based Layer 3 VPN networks, such as the ones using a BGP/
MPLS IP VPN <xref target="RFC4364"></xref> control plane, have different traffic filtering
requirements than Internet service providers.
This document proposes an additional BGP NLRI type (AFI=1, SAFI=134)
value, which can be used to propagate traffic filtering information
in a BGP/MPLS VPN environment.
</t>
<t>
The NLRI format for this address family consists of a fixed-length
Route Distinguisher field (8 bytes) followed by a flow specification,
following the encoding defined above in section x of this document. The NLRI length
field shall include both the 8 bytes of the Route Distinguisher as
well as the subsequent flow specification.
</t>
<t>
<figure>
<artwork>
+------------------------------+
| length (0xnn or 0xfn nn) |
+------------------------------+
| Route Distinguisher (8 bytes)|
+------------------------------+
| NLRI value (variable) |
+------------------------------+
Figure 2: Flow-spec NLRI for MPLS
</artwork>
</figure>
</t>
<t>
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].
</t>
<t>
Flow specification rules received via this NLRI apply 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.
</t>
<t>
Contrary to the behavior specified for the non-VPN NLRI, flow rules
are accepted by default, when received from remote PE routers.
</t>
<section title="Validation Procedures for BGP/MPLS VPNs">
<t>The validation procedures are the same as for IPv4.
</t>
</section>
<section title="Traffic Actions Rules">
<t>The traffic action rules are the same as for IPv4.</t>
</section>
</section>
<section title="Limitations of Previous Traffic Filtering Efforts">
<section title="Limitations in Previous DDOS Traffic Filtering Efforts">
<t>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.
</t>
<t>
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.
</t>
<t>
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. 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.
</t>
<t>
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 customers for
address space they own.
</t>
<t>
There are several drawbacks, however. An issue that is immediately
apparent is the granularity of filtering control: only destination
prefixes may be specified. Another area of concern is the fact that
filtering information is intermingled with routing information.
</t>
<t>
The mechanism defined in this document is designed to address these
limitations. We use the flow specification NLRI defined above to
convey information about traffic filtering rules for traffic that
should be discarded.
</t>
</section>
<section title="Limitations in Previous BGP/MPLS Traffic Monitoring">
<t>
Provider-based Layer 3 VPN networks, such as the ones using a BGP/
MPLS IP VPN <xref target="RFC4364"></xref> control plane, have different traffic filtering
requirements than Internet service providers.
</t>
<t>
In these environments, the VPN customer network often has traffic
filtering capabilities towards their external network connections
(e.g., firewall facing public network connection). Less common is
the presence of traffic filtering capabilities between different VPN
attachment sites. In an any-to-any connectivity model, which is the
default, this means that site-to-site traffic is unfiltered.
</t>
<t>
In circumstances where a security threat does get propagated inside
the VPN customer network, there may not be readily available
mechanisms to provide mitigation via traffic filter.
</t>
<t>The BGP Flow Specification version 1 addresses these limitations.
</t>
</section>
<section title="Limitations in BGP Flow Specification for SDN/NFV Applications">
<t>
The SDN/NFV applications which use centralized control of network
traffic via dynamic distribution of traffic filters can utilize the
BGP Flow Specification version 1 described in this draft with a fixed
order to traffic filter matches. However, for control of large amounts of
data a user-defined order to traffic matches and actions may be required.
</t>
</section>
</section>
<section title="Traffic Monitoring">
<t>
Traffic filtering applications require monitoring and traffic
statistics facilities. While this is an implementation-specific
choice, implementations SHOULD provide:
<list style="symbols">
<t> A mechanism to log the packet header of filtered traffic.
</t>
<t>A mechanism to count the number of matches for a given flow
specification rule.
</t>
</list>
</t>
</section>
<section anchor="IANA" title="IANA Considerations">
<t>This section complies with <xref target="RFC7153"></xref>
</t>
<section title="AFI/SAFI Definitions">
<t>
For the purpose of this work, IANA has allocated values for two
SAFIs: SAFI 133 for IPv4 dissemination of flow specification rules
and SAFI 134 for VPNv4 dissemination of flow specification rules.
</t>
</section>
<section title="Flow Component definitions">
<t>A flow specification consists of a sequence of flow components, which
are identified by a an 8-bit component type. Types must be assigned
and interpreted uniquely. The current specification defines types 1
though 12, with the value 0 being reserved.
</t>
<t>IANA created and maintains a new registry entitled: "Flow Spec
Component Types". The following component types have been
registered:
<list>
<t>Type 1 - Destination Prefix
</t>
<t>Type 2 - Source Prefix
</t>
<t>Type 3 - IP Protocol
</t>
<t>Type 4 - Port
</t>
<t>Type 5 - Destination port
</t>
<t>Type 6 - Source port
</t>
<t>Type 7 - ICMP type
</t>
<t>Type 8 - ICMP code
</t>
<t>Type 9 - TCP flags
</t>
<t>Type 10 - Packet length
</t>
<t>Type 11 - DSCP
</t>
<t>Type 12 - Fragment
</t>
</list>
</t>
<t>In order to manage the limited number space and accommodate several
usages, the following policies defined by RFC 5226 [RFC5226] are
used:
<figure>
<artwork>
+--------------+-------------------------------+
| Range | Policy |
+--------------+-------------------------------+
| 0 | Invalid value |
| [1 .. 12] | Defined by this specification |
| [13 .. 127] | Specification Required |
| [128 .. 255] | First Come First Served |
+--------------+-------------------------------+
</artwork>
</figure>
</t>
<t>
The specification of a particular "flow component type" 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.
</t>
<t>
The "traffic-action" extended community defined in this document has
46 unused bits, which can be used to convey additional meaning. IANA
created and maintains a new registry entitled: "Traffic Action
Fields". These values should be assigned via IETF Review rules only.
The following traffic-action fields have been allocated:
<list>
<t>47 Terminal Action
</t>
<t>46 Sample
</t>
<t>0-45 Unassigned
</t>
</list>
</t>
</section>
<section title="Extended Community Flow Specification Actions">
<t>The Extended Community FLow Specification Action types
consists of two parts: BGP Transitive Extended Community types
and a set of sub-types.
</t>
<t>IANA has updated the following "BGP Transitive Extended Community Types"
registries to contain the values listed below:
<list style="hanging">
<t hangText="0x80 - ">Generic Transitive Experimental Use Extended Community Part 1
(Sub-Types are defined in the "Generic Transitive
Experimental Extended Community Part 1 Sub-Types" Registry)
</t>
<t hangText="0x81 - ">Generic Transitive Experimental Use Extended Community Part 2
(Sub-Types are defined in the "Generic Transitive
Experimental Extended Community Part 2 Sub-Types" Registry)
</t>
<t hangText="0x82 - ">Generic Transitive Experimental Use Extended Community Part 3
(Sub-Types are defined in the "Generic Transitive
Experimental Use Extended Community Part 3 Sub-Types"
Registry)
</t>
</list>
</t>
<t>
<figure>
<artwork>
RANGE REGISTRATION PROCEDURE
0x00-0xbf First Come First Served
0xc0-0xff IETF Review
SUB-TYPE VALUE NAME REFERENCE
0x00-0x05 unassigned
0x06 traffic-rate [this document]
0x07 traffic-action [this document]
0x08 Flow spec redirect IPv4 [RFC5575] [RFC7674]
[this document]
0x09 traffic-marking [this document]
0x10-0xff Unassigned [this document]
</artwork>
</figure>
</t>
</section>
</section>
<section title="Security Considerations">
<t>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
provide service.
</t>
<t> As long as traffic filtering rules are restricted to match the
corresponding unicast routing paths for the relevant prefixes, the
security characteristics of this proposal are equivalent to the
existing security properties of BGP unicast routing.
</t>
<t> Where it is not the case, this would open the door to further denial-
of-service attacks.
</t>
<t> 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.
</t>
</section>
<section title="Original RFC5575 authors">
<t>Barry Greene, MuPedro Marques, Jared Mauch, Danny McPherson, Robert Rasuzk,
and Nischal Sheth were authors on <xref target="RFC5575"></xref>, and therefore
are contributing authors on this document.
</t>
<t>Note: Any original authors that want to work on this text will
be added in as authors. </t>
</section>
<section title="Acknowledgements">
<t>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 original <xref target="RFC5575"></xref>. 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 original <xref target="RFC5575"></xref>.
</t>
<t>Additional acknowledgements for this document will be included here.
</t>
</section>
</middle>
<back>
<references title="Normative References">
&RFC0793;
&RFC2119;
&RFC2474;
&RFC4271;
&RFC4360;
&RFC4364;
&RFC4760;
&RFC4761;
&RFC4762;
&RFC5226;
&RFC5668;
&RFC5575;
&RFC6241;
&RFC6482;
&RFC7153;
&RFC7223;
&RFC7606;
&RFC7674;
</references>
<references title="Informative References">
&RFC4303;
&RFC6074;
&RFC6483;
&I-D.ietf-idr-flowspec-l2vpn;
&I-D.ietf-idr-flow-spec-v6;
&I-D.ietf-idr-bgp-flowspec-oid;
&I-D.ietf-idr-wide-bgp-communities;
&I-D.ietf-idr-flowspec-packet-rate;
&I-D.ietf-idr-flowspec-nvo3;
&I-D.ietf-idr-flowspec-mpls-match;
&I-D.ietf-idr-bgp-flowspec-label;
&I-D.ietf-idr-flowspec-interfaceset;
</references>
</back>
</rfc>| PAFTECH AB 2003-2026 | 2026-04-24 04:26:00 |