Packet Content Filter for BGP FlowSpec
draft-cui-idr-content-filter-flowspec-00
| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Yong Cui , Yujia Gao | ||
| Last updated | 2024-03-19 | ||
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draft-cui-idr-content-filter-flowspec-00
IETF Y. Cui
Internet-Draft Tsinghua University
Intended status: Informational Y. Gao
Expires: 21 September 2024 Zhongguancun Laboratory
20 March 2024
Packet Content Filter for BGP FlowSpec
draft-cui-idr-content-filter-flowspec-00
Abstract
The BGP Flow Specification enables the distribution of traffic filter
policies (traffic filters and actions) via BGP, facilitating DDoS
traffic filtering. However, the traffic filterer in FSv1 and FSv2
predominantly focuses on IP header fields, which may not adequately
address new types of DDoS attack traffic characterized by constant
patterns within the packet content. This document introduces a new
flow specification filter type designed for packet content filtering.
The match field includes offset-type, offset value, content-length,
and content-value, encoded in the Flowspec NLRI. This new filter
aims to augment DDoS defense capabilities.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 21 September 2024.
Copyright Notice
Copyright (c) 2024 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.
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2
2. Definitions and Acronyms . . . . . . . . . . . . . . . . . . 3
3. The Flow Specification for Packet Offset Filter . . . . . . . 3
3.1. Offset-type and Offset-value . . . . . . . . . . . . . . 3
3.2. Content-length and Content-value . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. Normative References . . . . . . . . . . . . . . . . . . . . 5
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
BGP flow specification describes the distribution of traffic filter
policies through BGP, allowing for efficient traffic management and
DDoS attack mitigation. Existing versions, FSv1 and FSv2, primarily
offer n-tuple matching conditions for policy enforcement, enabling
actions such as packet dropping, re-directing, or limitation, etc.
These filter rules can be propagated to all BGP peers simultaneously
without necessitating router configuration changes. Despite their
utility, FSv1 and FSv2 reliance on IP header fields for traffic
filtering is increasingly inadequate for countering DDoS attack.
DDoS attacks such as application-level Challenge Collapsar (CC)
attacks, ACK flood attacks, etc, feature distinct patterns within the
packet content with a large traffic.
This document delineates a new flow specification filter type that
facilitates packet content filtering, leveraging offset-type, offset
value, content-length, and content-value within the Flowspec NLRI to
enhance DDoS defense mechanisms.
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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2. Definitions and Acronyms
* DDoS: Distributed Denial of Service
* NLRI: Network Layer Reachability Information
* FSv1: Flow Specification Version 1, defined in [RFC8955] and
[RFC8956]
* FSv2: Flow Specification Version 2 define in [draft-hares-idr-
flowspec-v2-ddos-00]
3. The Flow Specification for Packet Offset Filter
This document specifies a new flow specification filter type that is
encoded in the BGP FS NLRI and we follow the FSv1 definition format
rightnow. The new filter is defined as follows:
Type TBD – Packet-Content
Encoding:< type (1 octet), [value]+>
The value field is encoded using offset-type, offset-value, content-
length and content-value.
Encoding: < offset-type (4 bits), offset-value (2 octets), content-
length (1 octets), content-value>
3.1. Offset-type and Offset-value
The offset-type and offset-value define the starting position of the
packet content used for matching. To avoid the effect of variable
header length on the offset, we use the hierarchical way like [draft-
khare-idr-bgp-flowspec-payload-match-08].The offset-tpye is defined
as follows:
+-------+-----------------------------+
| Value | Description of Offset Type |
+-------+-----------------------------+
| 0 | IP Header |
| 1 | IP Header Data |
| 2 | Data within TCP/UDP |
+-------+-----------------------------+
Figure 1： offset-type
Each offset-type is detailed as follows:
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* Offset-type 0 is defined as the start of the IP header.
* Offset-type 1 is defined as the start of the data portion of the
IP header after the IP options.
* Offset-type 2 is defined as start of the TCP or UDP data. Type 2
will only be used if it is the first packet of a fragment and the
Layer 4 transport protocol is TCP (6) or UDP (17). For other IP
protocols, type 1 or type 2 can be used.
The offset-value is defined as a 2-octet unsigned integer that
specifies the count of bytes to be bypassed from the offset-type's
starting position to match the packet content.
Example:
* By setting offset-type 0 and an offset-value of 0, the match is
configured to start precisely at the beginning of the IP header.
* By setting offset-type 1 and an offset-value of 2, the match will
start two bytes past the initial data portion of the IP header,
skipping over any IP options. This configuration, for example, in
UDP packets, specifically targets the start of the destination
port information.
* By setting offset-type 2 and an offset-value of 10, the match will
start ten bytes into the content of the TCP/UDP packet.
3.2. Content-length and Content-value
The content-length is a one octet unsigned integer field that
contains the length of the value field in octets. The content-value
is encoded as {content, mask}. Content and mask have a same length
which defined by the content-length.
The content provides a string to be matched. Their length is defined
by content-length. Based on the information provided by equipment
vendors and operators, 8octets is usually sufficient for the
identification of DDoS attacks.
Mask is a string containing 0 and 1, where 1 represents what will be
matched and 0 represents characters that can be ignored.
The content and mask are operated AND by bit to get the final content
of the packet that needs to be matched.
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4. IANA Considerations
In accordance with the procedures outlined for managing the "Flow
Spec Component Types" registry, IANA is hereby requested to assign a
new Type Value. This assignment is sought from the First Come First
Served range, as detailed below:
+------------+---------------------------+---------------+
| Type Value | Name | Reference |
+------------+---------------------------+---------------+
| TBD | Packet Content filter | this document |
+------------+---------------------------+---------------+
The introduction of the "Packet Content filter" Type Value is
purposed to expand the capability of BGP FSv1 by enabling more
granular control over traffic filtering.
This is especially pertinent for addressing complex patterns within
packet content that are characteristic of Distributed Denial of
Service (DDoS) attacks and other security challenges. The proposed
Packet Content filter facilitate the specification of detailed
criteria for traffic matching, including but not limited to, content
inspection at specific packet offsets. In the following update we
will add the definition of FSv2.
5. Security Considerations
No new security issues are introduced to the BGP protocol by this
specification
6. Normative References
[RFC8955] Loibl, C., Hares, S., Raszuk, R., McPherson, D., and M.
Bacher, "Dissemination of Flow Specification Rules",
RFC 8955, DOI 10.17487/RFC8955, December 2020,
<https://www.rfc-editor.org/rfc/rfc8955>.
[RFC8956] Loibl, C., Ed., Raszuk, R., Ed., and S. Hares, Ed.,
"Dissemination of Flow Specification Rules for IPv6",
RFC 8956, DOI 10.17487/RFC8956, December 2020,
<https://www.rfc-editor.org/rfc/rfc8956>.
[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/rfc/rfc2119>.
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[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
Acknowledgements
We wish to thank Susan Hares, Jeffery Hass and Li Yang for their
valuable comments and suggestions on this document.
Authors' Addresses
Yong Cui
Tsinghua University
Beijing, 100084
China
Email: cuiyong@tsinghua.edu.cn
URI: http://www.cuiyong.net/
Yujia Gao
Zhongguancun Laboratory
Beijing, 100094
China
Email: gaoyj@zgclab.edu.cn
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