Internet Engineering Task Force P. Bergeon, Ed.
Internet-Draft Nokia
Intended status: Standards Track July 12, 2021
Expires: January 13, 2022
Flowspec TTL (Time to Live) Match
draft-bergeon-flowspec-ttl-match-00
Abstract
This document defines a new component type to match TTL (Time to
Live) values using BGP Flow Specification rules.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Definitions of Terms Used in This Memo . . . . . . . . . . . 2
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 2
4. Specification . . . . . . . . . . . . . . . . . . . . . . . . 3
5. Ordering of Flow Specifications Considerations . . . . . . . 3
6. Security Considerations . . . . . . . . . . . . . . . . . . . 3
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
8.1. Normative References . . . . . . . . . . . . . . . . . . 4
8.2. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
One general purpose of BGP Flowspec [RFC8955] is to distribute
firewall rules, also known as filtering or Access Control Lists
(ACLs) rules, in receiving routers for mitigation of denial-of-
service (DoS) attacks using flows specifications encoded as BGP NLRI
[RFC4271].
BGP Flowspec [RFC8955] defines 12 component types that can be used as
match criteria in filtering rules with destination prefix, source
prefix, IP protocol, port, destination port, source port, ICMP type,
ICMP code, TCP flags, packet length, DSCP and fragment.
The IP header field Time to Live (TTL) is a notable absent of the
component types defined in BGP Flowspec [RFC8955].
This document proposes to address this by adding support for a new
Flowspec component type to add support for TTL match.
2. Definitions of Terms Used in This Memo
NLRI - Network Layer Reachability Information.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14 [RFC2119]
[RFC8174] when, and only when, they appear in all capitals, as shown
here.
3. Motivation
As defined in [RFC0791], the TTL is an indication of an upper bound
on the lifetime of an internet datagram. It is set by the sender of
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the datagram and reduced by each router along the route where it is
processed.
This unique property of the IP header TTL field can make it
particularly useful for security and distributed-denial-of-service
(DDoS) mitigation.
Studies such as the one presented at NANOG 82 Tracing DDoS End-to-End
[1] highlight how filtering traffic based on TTL values can be used
as an effective mitigation for DDoS attacks at the IP edge of the
network. In particular, the TTL value can be used to differentiate
legitimate traffic from DDoS attack traffic generated by DDoS for
hire services.
Different IP edge routers of a given network under attack may see the
same attack traffic using slightly different TTL values, however
these routers can use a common set of filtering rules propagated via
BGP flowspec to mitigatie the attack using range(s) of TTL values.
4. Specification
This document defines a new Flowspec component type, value TBD, named
"TTL (Time to Live)".
Encoding: <type (1 octet), [numeric_op, value]+>
Defines a list of {numeric_op, value} pairs used to match the 8-bit
TTL field value.
This component type uses the Numeric Operator (numeric_op) as defined
already in [RFC8955] section 4.2.1.1.
Type TBD component values SHOULD be encoded as single octet
(numeric_op len=00).
5. Ordering of Flow Specifications Considerations
The ordering of Flow Specifications rules defined in [RFC8955]
remains unchanged and applies to the component type introduced in
this document.
6. Security Considerations
The new component type introduced in this document does not introduce
new security considerations other than the ones already defined in
[RFC8955].
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7. IANA Considerations
IANA is requested to assign a type from the First Come First Served
range of the "Flow Spec Component Types" registry:
+------------+--------------------+---------------+
| Type Value | Name | Reference |
+------------+--------------------+---------------+
| TBD | TTL (Time to Live) | this document |
+------------+--------------------+---------------+
Reference: this document
Registry Owner/Change Controller: IESG
Registration procedures:
+---------+-------------------------+
| Range | Registration Procedures |
+---------+-------------------------+
| 0-127 | IETF Review |
| 128-249 | First Come First Served |
| 250-254 | Experimental |
| 255 | Reserved |
+---------+-------------------------+
Note: a separate "owner" column is not provided because the owner of
all registrations, once made, is "IESG".
8. References
8.1. Normative References
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981,
<https://www.rfc-editor.org/info/rfc791>.
[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>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>.
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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/info/rfc8174>.
[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/info/rfc8955>.
8.2. URIs
[1] https://www.nanog.org/news-stories/nanog-tv/nanog-82-webcast/
tracing-ddos-end-to-end-in-2021/
Author's Address
Philippe Bergeon (editor)
Nokia
Email: philippe.bergeon@nokia.com
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