Internet DRAFT - draft-acharya-ipsecme-esp-ecmp
draft-acharya-ipsecme-esp-ecmp
IP Security Maintenance and Extensions Working Group D. Acharya
Internet-Draft H. Holbrook
Intended status: Informational Arista Networks, Inc.
Expires: 23 October 2023 21 April 2023
UDP encapsulated ESP for ECMP
draft-acharya-ipsecme-esp-ecmp-00
Abstract
This document modifies [RFC3948] to allow the UDP source port of a
UDP-Encapsulated ESP packet to provide entropy for ECMP load
balancing between IPSec tunnel endpoints. This document provides
guidelines for safely allowing this behavior and falling back to the
encapsulation defined in [RFC3948] when a NAT gateway is discovered
in the path.
About This Document
This note is to be removed before publishing as an RFC.
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esp-ecmp/.
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This Internet-Draft will expire on 23 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
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. UDP-Encapsulated ESP Header Format . . . . . . . . . . . . . 3
3. ECMP and IPsec sequence check . . . . . . . . . . . . . . . . 4
4. Interaction with NAT-Traversal . . . . . . . . . . . . . . . 4
5. Conventions and Definitions . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
Equal Cost Multi-Path (ECMP) can be used to balance traffic across
multiple paths between 2 end-points. An important requirement is to
have packets belonging to the same “flow” use the same path to
prevent reordering of packets within a flow.
IPsec can be used to secure traffic between two Tunnel End Points
(TEPs). Two ways of doing this are to use
* IPsec tunnel mode
* IPsec transport mode applied to the outer IP header of some other
tunneling mechanism e.g. VXLAN [RFC7348] or GRE [RFC2784]
Either way, one IPsec session, identified by outer IP addresses and
SPI value in the ESP header, can be used to protect packets belonging
to multiple “flows”. In this context, a “flow” is a sequence of
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packets with common inner header fields.. Examples of such inner
packet header fields are the original IP addresses of the payload
packet inside an IPsec tunnel.
The flow to which an IPsec encrypted packet belongs cannot generally
be identified because the inner packet headers are encrypted. This
document defines a mechanism that allows different flows using the
same IPsec session to take different paths, while still maintaining a
single path for each flow. In order to do this, the UDP source port
of a UDP-encapsulated ESP packet carries a “digest” of inner packet
headers. The “digest” enables this outer source port to be used for
load balancing in the transport network between TEPs.
2. UDP-Encapsulated ESP Header Format
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port | Destination Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ESP header [RFC4303] |
~ ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* It is RECOMMENDED that the UDP Source Port number be calculated
using a hash of fields from the inner packet e.g. the original IP
addresses of the payload packet inside the tunnel. When
calculating the UDP Source Port number in this manner, it is
RECOMMENDED that the value be in the dynamic/private port range
49152-65535 [RFC6335].
* The Destination Port MUST be the same as that used by IKE traffic,
per [RFC3948].
* The UDP Checksum SHOULD be transmitted as a zero value, per
[RFC3948].
* Receivers MUST NOT depend on the UDP checksum being a zero value,
per [RFC3948].
* The SPI field in the ESP header MUST NOT be a zero value, per
[RFC3948].
Note that the use of the UDP source port is consistent with its usage
in VXLAN, [RFC7348]
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3. ECMP and IPsec sequence check
When different flows take different paths between tunnel endpoints
there can be big differences in path-delay and out-of-order packets
are more likely to arrive outside the anti-replay window. Therefore,
it is RECOMMENDED that the IPsec anti-replay service, defined in
[RFC4301], be disabled for a session using UDP encapsulated ESP for
ECMP.
4. Interaction with NAT-Traversal
If IKE is configured to support NAT-Traversal and detects NAT along
the path between IKE peers, then UDP encapsulated ESP is used for
NAT-Traversal, per [RFC3947]. In that case, the UDP Source Port
number MUST be the same as that used by IKE traffic per [RFC3948],
which supersedes the recommendation in this document.
5. Conventions and Definitions
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.
6. Security Considerations
1. IPsec anti-replay service may have to be disabled when UDP
encapsulated ESP is used for ECMP. .
2. Some sort of flow-identification in the packet header is
necessary to make sure packets of a flow are routed in the same
path. That means the packets belonging to the same flow or a set
of flows can be identified by examining the Source Port in the
outer UDP header. This implies that
* The IPsec traffic distribution between different flows can be
observed.
* Some information about the inner header fields is leaked via the
UDP source port. However no more information is leaked than if
per-flow IPSec Transport Mode were used between Tunnel Endpoints.
The identification of the flow or the internal header fields, by
itself, may not pose a security threat.
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7. IANA Considerations
This document has no IANA actions.
8. References
8.1. 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/rfc/rfc2119>.
[RFC3947] Kivinen, T., Swander, B., Huttunen, A., and V. Volpe,
"Negotiation of NAT-Traversal in the IKE", RFC 3947,
DOI 10.17487/RFC3947, January 2005,
<https://www.rfc-editor.org/rfc/rfc3947>.
[RFC3948] Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M.
Stenberg, "UDP Encapsulation of IPsec ESP Packets",
RFC 3948, DOI 10.17487/RFC3948, January 2005,
<https://www.rfc-editor.org/rfc/rfc3948>.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
December 2005, <https://www.rfc-editor.org/rfc/rfc4301>.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
RFC 4303, DOI 10.17487/RFC4303, December 2005,
<https://www.rfc-editor.org/rfc/rfc4303>.
[RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
Cheshire, "Internet Assigned Numbers Authority (IANA)
Procedures for the Management of the Service Name and
Transport Protocol Port Number Registry", BCP 165,
RFC 6335, DOI 10.17487/RFC6335, August 2011,
<https://www.rfc-editor.org/rfc/rfc6335>.
[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>.
8.2. Informative References
[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
DOI 10.17487/RFC2784, March 2000,
<https://www.rfc-editor.org/rfc/rfc2784>.
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[RFC7348] Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
L., Sridhar, T., Bursell, M., and C. Wright, "Virtual
eXtensible Local Area Network (VXLAN): A Framework for
Overlaying Virtualized Layer 2 Networks over Layer 3
Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014,
<https://www.rfc-editor.org/rfc/rfc7348>.
Authors' Addresses
Dipankar Acharya
Arista Networks, Inc.
5453 Great America Pkwy
Santa Clara, CA 95054
United States of America
Email: dipankar@arista.com
Hugh Holbrook
Arista Networks, Inc.
5453 Great America Pkwy
Santa Clara, CA 95054
United States of America
Email: holbrook@arista.com
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