Internet DRAFT - draft-liang-lsr-ospf-flowspec-extensions
draft-liang-lsr-ospf-flowspec-extensions
LSR Working Group Q. Liang
Internet-Draft Q. Gao
Intended status: Standards Track H. Shi
Expires: 26 October 2023 Huawei Technologies
K. Patel
A. Lindem
Cisco Systems
24 April 2023
OSPF Extensions for Flow Specification
draft-liang-lsr-ospf-flowspec-extensions-01
Abstract
Dissemination of the Traffic flow information was first introduced in
the BGP protocol [RFC5575]. FlowSpec routes are used to distribute
traffic filtering rules used to filter Denial-of-Service (DoS)
attacks. For networks that only deploy an IGP (Interior Gateway
Protocol) (e.g., OSPF), it is required that the IGP is extended to
distribute Flow Specification or FlowSpec routes.
This document discusses use cases for distributing flow specification
(FlowSpec) routes using OSPF. Furthermore, this document defines a
OSPF FlowSpec Opaque Link State Advertisement (LSA) encoding format
that can be used to distribute FlowSpec routes, its validation
procedures for imposing the filtering information on the routers, and
a capability to indicate the support of FlowSpec functionality.
Requirements Language
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 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 26 October 2023.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Use Cases for OSPF based FlowSpec Distribution . . . . . . . 4
3.1. OSPF Campus Network . . . . . . . . . . . . . . . . . . . 4
3.2. BGP/MPLS VPN . . . . . . . . . . . . . . . . . . . . . . 4
3.2.1. Traffic Analyzer Deployed in Provider Network . . . . 5
3.2.2. Traffic Analyzer Deployed in Customer Network . . . . 6
3.2.3. Policy Configuration . . . . . . . . . . . . . . . . 6
4. OSPF Extensions for FlowSpec Rules . . . . . . . . . . . . . 7
4.1. FlowSpec LSA . . . . . . . . . . . . . . . . . . . . . . 7
4.1.1. OSPFv2 FlowSpec Opaque LSA . . . . . . . . . . . . . 7
4.1.2. OSPFv3 FlowSpec LSA . . . . . . . . . . . . . . . . . 9
4.2. OSPF FlowSpec Filters TLV . . . . . . . . . . . . . . . . 10
4.2.1. Interface-Set TLV . . . . . . . . . . . . . . . . . . 12
4.2.2. Order of Traffic Filtering Rules . . . . . . . . . . 13
4.2.3. Validation Procedure . . . . . . . . . . . . . . . . 13
4.3. OSPF FlowSpec Action TLV . . . . . . . . . . . . . . . . 14
4.3.1. Traffic-rate . . . . . . . . . . . . . . . . . . . . 15
4.3.2. Traffic-action . . . . . . . . . . . . . . . . . . . 15
4.3.3. Traffic-marking . . . . . . . . . . . . . . . . . . . 15
4.3.4. Redirect-to-IP . . . . . . . . . . . . . . . . . . . 16
4.4. Capability Advertisement . . . . . . . . . . . . . . . . 17
5. Redistribution of FlowSpec Routes . . . . . . . . . . . . . . 17
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
7. Security considerations . . . . . . . . . . . . . . . . . . . 18
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8. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 18
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
9.1. Normative References . . . . . . . . . . . . . . . . . . 18
9.2. Informative References . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20
1. Introduction
[RFC5575] defines Border Gateway Protocol protocol extensions that
can be used to distribute traffic flow specifications. One
application of this encoding format is to automate inter-domain
coordination of traffic filtering, such as what is required in order
to mitigate (distributed) denial-of-service attacks. [RFC5575]
allows flow specifications received from an external autonomous
system to be forwarded to a given BGP peer. However, in order to
block the attack traffic more effectively, it is better to distribute
the BGP FlowSpec routes to the customer network, which is much closer
to the attacker.
For the networks deploying only an IGP (e.g., OSPF), it is expected
to extend the IGP (OSPF in this document) to distribute FlowSpec
routes. This document discusses the use cases for distributing
FlowSpec routes using OSPF. Furthermore, this document also defines
a new OSPF FlowSpec Opaque Link State Advertisement (LSA) [RFC5250]
encoding format that can be used to distribute FlowSpec routes to the
edge routers in the customer network, its validation procedures for
imposing the filtering information on the routers, and a capability
to indicate the support of Flowspec functionality.
The semantic content of the FlowSpec extensions defined in this
document are identical to the corresponding extensions to BGP
([RFC5575] and [I-D.ietf-idr-flow-spec-v6]). In order to avoid
repetition, this document only concentrates on those parts of
specification where OSPF is different from BGP. The OSPF flowspec
extensions defined in this document can be used to mitigate the
impacts of DoS attacks.
2. Terminology
This section contains definitions for terms used frequently
throughout this document. However, many additional definitions can
be found in [RFC5250] and [RFC5575].
Flow Specification (FlowSpec): A flow specification is an n-tuple
consisting of several matching criteria that can be applied to IP
traffic, including filters and actions. Each FlowSpec consists of
a set of filters and a set of actions.
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3. Use Cases for OSPF based FlowSpec Distribution
For the networks deploying only an IGP (e.g., OSPF), it is expected
to extend the IGP (OSPF in this document) to distribute FlowSpec
routes, because when the FlowSpec routes are installed in the
customer network, they are closer to the attacker than when they are
installed in the provider network. Consequently, the attack traffic
could be blocked or the suspicious traffic could be limited to a low
rate as early as possible.
The following sub-sections discuss the use cases for OSPF based
FlowSpec route distribution.
3.1. OSPF Campus Network
For networks not deploying BGP, for example, the campus network using
OSPF, it is expected to extend OSPF to distribute FlowSpec routes as
shown in Figure 3. In this kind of network, the traffic analyzer
could be deployed with a router, then the FlowSpec routes from the
traffic analyzer need to be distributed to the other routers in this
domain using OSPF.
+--------+
|Traffic |
+---+Analyzer|
| +--------+
|
|FlowSpec
|
|
+--+-------+ +----------+ +--------+
| Router A +-----------+ Router B +--------+Attacker|
+----------+ +----------+ +--------+
| | |
| OSPF FlowSpec | Attack Traffic |
| | |
Figure 1: OSPF Campus Network
3.2. BGP/MPLS VPN
[RFC5575] defines a BGP NLRI encoding format to distribute traffic
flow specifications in BGP deployed network. However, in the BGP/
MPLS VPN scenario, the IGP (e.g., IS-IS, or OSPF) is used between the
PE (Provider Edge) and CE (Customer Edge) in many deployments. In
order to distribute the FlowSpec routes to the customer network, the
IGP needs to support FlowSpec route distribution. The FlowSpec
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routes are usually generated by the traffic analyzer or the traffic
policy center in the network. Depending on the location of the
traffic analyzer deployment, two different distribution scenarios are
discussed below.
3.2.1. Traffic Analyzer Deployed in Provider Network
The traffic analyzer (also acting as the traffic policy center) could
be deployed in the provider network as shown in Figure 1. If the
traffic analyzer detects attack traffic from the customer network
VPN1, it would generate the FlowSpec routes for preventing DoS
attacks. FlowSpec routes with a Route Distinguisher (RD) in the
Network Layer Reachability information (NRLI) corresponding to VPN1
are distributed from the traffic analyzer to the PE1 to which the
traffic analyzer is attached. If the traffic analyzer is also a BGP
speaker, it can distribute the FlowSpec routes using BGP [RFC5575].
Then the PE1 distributes the FlowSpec routes further to the PE2.
Finally, the FlowSpec routes need to be distributed from PE2 to the
CE2 using OSPF, i.e., to the customer network VPN1. As an attacker
is more likely in the customer network, FlowSpec routes installed
directly on CE2 could mitigate the impact of DoS attacks better.
+--------+
|Traffic |
+---+Analyzer| -----------
| +--------+ //- -\\
| /// \\\
|FlowSpec / \
| // \\
| | |
+--+--+ +-----+ | +-----+ +--------+ |
| PE1 +-------+ PE2 +-------+--+ CE2 +-------+Attacker| |
+-----+ +-----+ | +-----+ +--------+ |
| |
| | | | | |
| BGP FlowSpec | OSPF FlowSpec | Attack Traffic| |
| | \\ | | //
\ /
\\\ VPN1 ///
\\-- --//
---------
Figure 2: Traffic Analyzer deployed in Provider Network
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3.2.2. Traffic Analyzer Deployed in Customer Network
The traffic analyzer (also acting as the traffic policy center) could
be deployed in the customer network as shown in Figure 2. If the
traffic analyzer detects attack traffic, it would generate FlowSpec
routes to prevent associated DoS attacks. Then the FlowSpec routes
would be distributed from the traffic analyzer to the CE1 using OSPF
or another policy protocol (e.g., RESTful API over HTTP).
Furthermore, the FlowSpec routes need to be distributed throughout
the provider network via PE1/PE2 to CE2, i.e., to the remote customer
network VPN1 Site1. If the FlowSpec routes installed on the CE2, it
could block the attack traffic as close to the source of the attack
as possible.
+--------+
|Traffic |
+---+Analyzer|
| +--------+ --------
| //-- --\\
|FlowSpec // \\
| / \
| // \\
+--+--+ +-----+ +-----+ | +-----+ +--------+
| CE1 +--------+ PE1 +-------+ PE2 +--------+-+ CE2 +------+Attacker|
+-----+ +-----+ +-----+ | +-----+ +--------+
| |
| | | | | |
| OSPF FlowSpec | BGP FlowSpec| OSPF FlowSpec | Attack Traffic |
| | | | | |
| |
\\ //
\ VPN1 Site1 /
\\ //
\\-- --//
--------
Figure 3: Traffic Analyzer deployed in Customer Network
3.2.3. Policy Configuration
The CE or PE could deploy local filtering policies to filter OSPF
FlowSpec rules, for example, deploying a filtering policy to filter
the incoming OSPF FlowSpec rules in order to prevent illegal or
invalid FlowSpec rules from being applied.
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The PE should configure FlowSpec importing policies to control
importing action between the BGP IP/VPN FlowSpec RIB and the OSPF
Instance FlowSpec RIB. Otherwise, the PE couldn't transform a BGP
IP/VPN FlowSpec rule to an OSPF FlowSpec rule or transform an OSPF
FlowSpec rule to a BGP IP/VPN FlowSpec rule.
4. OSPF Extensions for FlowSpec Rules
4.1. FlowSpec LSA
4.1.1. OSPFv2 FlowSpec Opaque LSA
This document defines a new OSPFv2 flow specification Opaque Link
State Advertisement (LSA) encoding format that can be used to
distribute traffic flow specifications. This new OSPF FlowSpec
Opaque LSA is extended based on [RFC5250].
The OSPFv2 FlowSpec Opaque LSA is defined below in Figure 4:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Age | Options | LS Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opaque Type | Opaque ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| TLVs |
+ +
| ... |
Figure 4: OSPFv2 FlowSpec Opaque LSA
LS age: the same as defined in [RFC2328].
Options: the same as defined in [RFC2328].
LS type: A type-11 or type-10 Opaque-LSA SHOULD be originated.
Since the type-11 LSA has the same flooding scope as a type-5 LSA
as stated in [RFC5250], it will not be flooded into stub areas or
NSSAs (Not-So-Stubby Areas). When stub or NSSA areas are
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encountered in the scenario of flow spec, we may have to make our
choice, either making peace with it and filtering the DoS traffic
at ABRs or generating a new type-10 Opaque-LSA into stub/NSSA
areas, which may aggravate the burden of devices in that area.
Opaque type: OSPF FlowSpec Opaque LSA (Type Code: TBD1).
Opaque ID: the same as defined in [RFC5250].
Advertising Router: the same as defined in [RFC2328].
LS sequence number: the same as defined in [RFC2328].
LS checksum: the same as defined in [RFC2328].
Length: the same as defined in [RFC2328].
TLVs: one or more TLVs MAY be included in a FlowSpec Opaque LSA to
carry FlowSpec information.
The variable TLVs section consists of one or more nested Type/Length/
Value (TLV) tuples. Nested TLVs are also referred to as sub-TLVs.
The format of each TLV is shown in Figure 5:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Values... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: TLV Format
The Length field defines the length of the value portion in octets
(thus a TLV with no value portion would have a length of 0). The TLV
is padded to 4-octet alignment; padding is not included in the length
field (so a 3-octet value would have a length of 3, but the total
size of the TLV would be 8 octets). Nested TLVs are also 32-bit
aligned. For example, a 1-octet value would have the length field
set to 1, and 3 octets of padding would be added to the end of the
value portion of the TLV.
If FlowSpec Opaque LSA is Type-11 Opaque LSA, it is not flooded into
Stub and NSSA areas. As the traffic accessing a network segment
outside Stub and NSSA areas would be aggregated to the ABR, FlowSpec
rules could be applied on the ABR instead of disseminating them into
Stub and NSSA areas.
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4.1.2. OSPFv3 FlowSpec LSA
This document defines a new OSPFv3 flow specification LSA encoding
format that can be used to distribute traffic flow specifications.
This new OSPFv3 FlowSpec LSA is extended based on [RFC5340].
The OSPFv3 FlowSpec LSA is defined below in Figure 6:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Age | LS Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| TLVs |
+ +
| ... |
Figure 6: OSPFv3 FlowSpec LSA
LS age: the same as defined in [RFC5340].
LS type: the same as defined in [RFC5340]. The format of the LS
type is as follows:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|U |S2|S1| LSA Function Code |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
Figure 7: LSA Type
In this document, the U bit should be set indicating that the
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OSPFv3 FlowSpec LSA should be flooded even if it is not
understood. For the area scope, the S1 bit should be set and the
S2 should be clear. For the AS scope, the S1 bit should be clear
and the S2 bit should be set. A new LSA Function Code (TBD2)
needs to be defined for OSPFv3 FlowSpec LSA. To facilitate inter-
area reachability validation, any OSPFv3 router originating AS
scoped LSAs is considered an AS Boundary Router (ASBR).
Link State ID: the same as defined in [RFC5340].
Advertising Router: the same as defined in [RFC5340].
LS sequence number: the same as defined in [RFC5340].
LS checksum: the same as defined in [RFC5340].
Length: the same as defined in [RFC5340].
TLVs: one or more TLVs MAY be included in a OSPFv3 FlowSpec LSA to
carry FlowSpec information.
4.2. OSPF FlowSpec Filters TLV
The FlowSpec Opaque LSA carries one or more FlowSpec Filters TLVs and
corresponding FlowSpec Action TLVs. The OSPF FlowSpec Filters TLV is
defined below in Figure 8.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Filters (variable) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Filters (variable) ~
+ +
| ... |
Figure 8: OSPF FlowSpec Filters TLV
Type: the TLV type (Type Code: TBD3)
Length: the size of the value field in octets
Flags: One octet Field identifying Flags.
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0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| Reserved |S|
+-+-+-+-+-+-+-+-+
The least significant bit S is defined as a strict Filter check bit.
If set, Strict Validation rules outlined in the validation
Section 4.2.2 need to be enforced.
Filters: the same as "flow-spec NLRI value" defined in [RFC5575] and
[I-D.ietf-idr-flow-spec-v6].
Table 1: OSPF Supported FlowSpec Filters
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+======+=========================+===========================+
| Type | Description | RFC/ WG draft |
+======+=========================+===========================+
| 1 | Destination IPv4 Prefix | RFC5575 I-D.ietf-idr- |
| | Destination IPv6 Prefix | flow-spec-v6 |
+------+-------------------------+---------------------------+
| 2 | Source IPv4 Prefix | RFC5575 I-D.ietf-idr- |
| | Source IPv6 Prefix | flow-spec-v6 |
+------+-------------------------+---------------------------+
| 3 | IP Protocol Next Header | RFC5575 I-D.ietf-idr- |
| | | flow-spec-v6 |
+------+-------------------------+---------------------------+
| 4 | Port | RFC5575 |
+------+-------------------------+---------------------------+
| 5 | Destination port | RFC5575 |
+------+-------------------------+---------------------------+
| 6 | Source port | RFC5575 |
+------+-------------------------+---------------------------+
| 7 | ICMP type | RFC5575 |
+------+-------------------------+---------------------------+
| 8 | ICMP code | RFC5575 |
+------+-------------------------+---------------------------+
| 9 | TCP flags | RFC5575 |
+------+-------------------------+---------------------------+
| 10 | Packet length | RFC5575 |
+------+-------------------------+---------------------------+
| 11 | DSCP | RFC5575 |
+------+-------------------------+---------------------------+
| 12 | Fragment | RFC5575 |
+------+-------------------------+---------------------------+
| 13 | Flow Label | I-D.ietf-idr-flow-spec-v6 |
+------+-------------------------+---------------------------+
| 14 | Interface-Set | Described Below |
+------+-------------------------+---------------------------+
Table 1
4.2.1. Interface-Set TLV
The Interface-Set TLV is used to limit the FlowSpec rules to a set of
interfaces configured locally with the specified Group ID. The
Interface-Set TLV was inspired by
[I-D.litkowski-idr-flowspec-interfaceset] and uses similar encodings.
The Autonomous System (AS) number is not required since OSPF usage is
within a single AS.
The Interface-Set TLV is encoded as:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TBD, 14 Suggested | 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|O|I| Flags | Group ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
O : if set, the flow specification rule MUST be applied in outbound
direction to the interface set referenced by the specified Group ID.
I : if set, the flow specification rule MUST be applied in input
direction to the interface set referenced by the specified Group ID
Both flags can be set at the same time in the interface-set extended
community leading to flow rule to be applied in both directions. An
interface-set TLV with both flags set to zero MUST be treated as an
error and as consequence, the FlowSpec update MUST be ignore and an
error should be logged.
The Group Identifier is coded as a 16-bit number (values goes from 0
to 65535).
Multiple instances of the interface-set community may be present in a
Flow-Spec rule. This may appear if the flow rule need to be applied
to multiple set of interfaces.
4.2.2. Order of Traffic Filtering Rules
With traffic filtering rules, more than one rule may match a
particular traffic flow. The order of applying the traffic filter
rules is the same as described in Section 5.1 of [RFC5575] and in
Section 3.1 of [I-D.ietf-idr-flow-spec-v6].
4.2.3. Validation Procedure
[RFC5575] defines a validation procedure for BGP FlowSpec rules, and
[I-D.ietf-idr-bgp-flowspec-oid] describes a modification to the
validation procedure defined in [RFC5575] for the dissemination of
BGP flow specifications. The OSPF FlowSpec should support similar
features to mitigate the unnecessary application of traffic filter
rules. The OSPF FlowSpec validation procedure is described as
follows.
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When a router receives a FlowSpec rule including a destination prefix
filter from its neighbor router, it should consider the prefix filter
as a valid filter unless the S bit in the flags field of Filter TLV
is set. If the S bit is set, then the FlowSpec rule is considered
valid if and only if:
The originator of the FlowSpec rule matches the originator of the
best-match unicast route for the destination prefix embedded in
the FlowSpec.
The former rule allows any centralized controller to originate the
prefix filter and advertise it within a given OSPF network. The
latter rule, also known as a Strict Validation rule, allows strict
checking and enforces that the originator of the FlowSpec filter is
also the originator of the destination prefix.
When multiple equal-cost paths exist in the routing table entry, each
path could end up having a separate set of FlowSpec rules.
When a router receives a FlowSpec rule not including a destination
prefix filter from its neighbor router, the validation procedure
described above is not applicable.
The FlowSpec filter validation state is used by a speaker when the
filter is considered for an installation in its FIB. An OSPF speaker
MUST flood OSPF FlowSpec LSA as per the rules defined in [RFC2328]
regardless of the validation state of the prefix filters.
4.3. OSPF FlowSpec Action TLV
There are one or more FlowSpec Action TLVs associated with a FlowSpec
Filters TLV. Different FlowSpec Filters TLV could have the same
FlowSpec Action TLVs. The following OSPF FlowSpec action TLVs,
except Redirect, are same as defined in [RFC5575].
Redirect: IPv4 or IPv6 address. This IP address may correspond to a
tunnel, i.e., the redirect allows the traffic to be redirected to a
directly attached next-hop or a next-hop requiring a route lookup.
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+======+==================+=======================================+
|type | FlowSpec Action | RFC/WG draft |
+======+==================+=======================================+
|0x8006| traffic-rate | RFC5575 |
+------+------------------+---------------------------------------+
|0x8007| traffic-action | RFC5575 |
+------+------------------+---------------------------------------+
|0x8108| redirect-to-IPv4 | I-D.ietf-idr-flowspec-redirect-rt-bis |
+------+------------------+---------------------------------------+
|0x800b| redirect-to-IPv6 | I-D.ietf-idr-flow-spec-v6 |
+------+------------------+---------------------------------------+
|0x8009| traffic-marking | RFC5575 |
+------+------------------+---------------------------------------+
Table 2: Traffic Filtering Actions in [RFC5575], etc.
4.3.1. Traffic-rate
Traffic-rate TLV is encoded as:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TBD5,0x8006 suggested | 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Traffic-rate |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Traffic-rate: the same as defined in [RFC5575].
4.3.2. Traffic-action
Traffic-action TLV is encoded as:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TBD6, 0x8007 suggested | 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |S|T| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
S flag and T flag: the same as defined in [RFC5575].
4.3.3. Traffic-marking
Traffic-marking TLV is encoded as:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TBD7, 0x8009 suggested | 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | DSCP Value| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
DSCP value: the same as defined in [RFC5575].
4.3.4. Redirect-to-IP
Redirect-to-IPv4 is encoded as:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TBD8, 0x8108 suggested | 6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |C| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Redirect to IPv6 TLV is encoded as (Only for OSPFv3):
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TBD9, 0x800b suggested | 18 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IPv6 Address |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |C| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv4/6 Address: the redirection target address.
'C' (or copy) bit: when the 'C' bit is set, the redirection applies
to copies of the matching packets and not to the original traffic
stream [I-D.ietf-idr-flowspec-redirect-ip].
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4.4. Capability Advertisement
This document defines a capability bit for OSPF Router-Information
LSA [RFC7770] as FlowSpec Capability Advertisement bit. When set,
the OSPF router indicates its ability to support the FlowSpec
functionality. The FlowSpec Capability Advertisement bit has a value
to be assigned by IANA from OSPF Router Functional Capability Bits
Registry [I-D.ietf-ospf-rfc4970bis].
5. Redistribution of FlowSpec Routes
In certain scenarios, FlowSpec routes MAY get redistributed from one
protocol domain to another; specifically from BGP to OSPF and vice-
versa. When redistributed from BGP, the OSPF speaker SHOULD generate
an Opaque LSA for the redistributed routes and announce it within an
OSPF domain. An implementation MAY provide an option for an OSPF
speaker to announce a redistributed FlowSpec route within a OSPF
domain regardless of being installed in its local FIB. An
implementation MAY impose an upper bound on number of FlowSpec routes
that an OSPF router MAY advertise.
6. IANA Considerations
This document defines a new OSPFv2 Opaque LSA, i.e., OSPFv2 FlowSpec
Opaque LSA (Type Code: TBD1), which is used to distribute traffic
flow specifications.
This document defines a new OSPFv3 LSA, i.e., OSPFv3 FlowSpec LSA
(LSA Function Code: TBD2), which is used to distribute traffic flow
specifications.
This document defines OSPF FlowSpec Filters TLV (Type Code: TBD3),
which is used to describe the filters.
This document defines a new FlowSpec capability which need to be
advertised in an RI Opaque LSA. A new informational capability bit
needs to be assigned for OSPF FlowSpec feature (FlowSpec Bit: TBD4).
This document defines a new Router LSA bit known as a FlowSpec
Capability Advertisement bit. This document requests IANA to assign
a bit code type for FlowSpec Capability Advertisement bit from the
OSPF Router Functional Capability Bits registry.
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Type 1 - Destination IPv4/IPv6 Prefix
Type 2 - Source IPv4/IPv6 Prefix
Type 3 - IP Protocol/Next Header
Type 4 - Port
Type 5 - Destination port
Type 6 - Source port
Type 7 - ICMP type
Type 8 - ICMP code
Type 9 - TCP flags
Type 10 - Packet length
Type 11 - DSCP
Type 12 - Fragment
Type 13 - Flow Label
Type 14 - Interface-Set
This document defines a group of FlowSpec actions. The following TLV
types need to be assigned:
Type 0x8006(TBD5) - traffic-rate
Type 0x8007(TBD6) - traffic-action
Type 0x8009(TBD7) - traffic-marking
Type 0x8108(TBD8) - redirect to IPv4
Type 0x800b(TBD9) - redirect to IPv6
7. Security considerations
This extension to OSPF does not change the underlying security issues
inherent in the existing OSPF. Implementations must assure that
malformed TLV and Sub-TLV permutations do not result in errors which
cause hard OSPF failures.
8. Acknowledgement
The authors would also like to thank Jianjie You, Nan Wu, Peng Fan,
Burjiz Pithawala, Rashmi Shrivastava and Mike Dubrovsky for their
contribution to the original version of the document.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
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[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998,
<https://www.rfc-editor.org/info/rfc2328>.
[RFC5250] Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The
OSPF Opaque LSA Option", RFC 5250, DOI 10.17487/RFC5250,
July 2008, <https://www.rfc-editor.org/info/rfc5250>.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
<https://www.rfc-editor.org/info/rfc5340>.
[RFC5575] Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J.,
and D. McPherson, "Dissemination of Flow Specification
Rules", RFC 5575, DOI 10.17487/RFC5575, August 2009,
<https://www.rfc-editor.org/info/rfc5575>.
9.2. Informative References
[I-D.ietf-idr-bgp-flowspec-oid]
Uttaro, J., Filsfils, C., Smith, D., Alcaide, J., and P.
Mohapatra, "Revised Validation Procedure for BGP Flow
Specifications", Work in Progress, Internet-Draft, draft-
ietf-idr-bgp-flowspec-oid-03, 21 March 2016,
<https://www.ietf.org/archive/id/draft-ietf-idr-bgp-
flowspec-oid-03.txt>.
[I-D.ietf-idr-flow-spec-v6]
McPherson, D., Raszuk, R., Pithawala, B.,
akarch@cisco.com, a., and S. Hares, "Dissemination of Flow
Specification Rules for IPv6", Work in Progress, Internet-
Draft, draft-ietf-idr-flow-spec-v6-07, 19 March 2016,
<http://www.ietf.org/internet-drafts/draft-ietf-idr-flow-
spec-v6-07.txt>.
[I-D.ietf-idr-flowspec-redirect-ip]
Uttaro, J., Haas, J., Texier, M., Karch, A., Ray, S.,
Simpson, A., and W. Henderickx, "BGP Flow-Spec Redirect to
IP Action", Work in Progress, Internet-Draft, draft-ietf-
idr-flowspec-redirect-ip-02, 5 February 2015,
<https://www.ietf.org/archive/id/draft-ietf-idr-flowspec-
redirect-ip-02.txt>.
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[I-D.litkowski-idr-flowspec-interfaceset]
Litkowski, S., Simpson, A., Patel, K., and J. Haas,
"Applying BGP flowspec rules on a specific interface set",
Work in Progress, Internet-Draft, draft-litkowski-idr-
flowspec-interfaceset-03, 8 December 2015,
<https://www.ietf.org/archive/id/draft-litkowski-idr-
flowspec-interfaceset-03.txt>.
[RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
S. Shaffer, "Extensions to OSPF for Advertising Optional
Router Capabilities", RFC 7770, DOI 10.17487/RFC7770,
February 2016, <https://www.rfc-editor.org/info/rfc7770>.
Authors' Addresses
Qiandeng Liang
Huawei Technologies
Email: liangqiandeng@huawei.com
Qiangzhou Gao
Huawei Technologies
Email: gaoqiangzhou@huawei.com
Hang Shi
Huawei Technologies
Email: shihang9@huawei.com
Keyur Patel
Cisco Systems
170 W. Tasman Drive
San Jose, CA 95134
USA
Email: keyupate@cisco.com
Acee Lindem
Cisco Systems
301 Midenhall Way
Cary, NC 27519
USA
Email: acee@cisco.com
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