Network Working Group F. Templin, Ed.
Internet-Draft Boeing Research & Technology
Intended status: Informational January 05, 2016
Expires: July 8, 2016
AERO Minimal Encapsulation
draft-templin-aeromin-02.txt
Abstract
Asymmetric Extended Route Optimization (AERO) specifies both a
control messaging and data packet forwarding facility for managing
tunnels over an enterprise network or other Internetwork. Although
AERO can operate with any tunnel encapsulation format, the base
document considers Generic UDP Encapsulation (GUE) as the default.
This document presents minimal encapsulation formats for AERO using
other encapsulation types.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Minimal AERO Encapsulation . . . . . . . . . . . . . . . . . 3
3. When to Insert an Encapsulation Fragment Header . . . . . . . 4
4. Considerations for Using Minimal Encapsulation . . . . . . . 4
5. AERO Operation Over Native Links . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . 5
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
9.1. Normative References . . . . . . . . . . . . . . . . . . 5
9.2. Informative References . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
Asymmetric Extended Route Optimization (AERO) [I-D.templin-aerolink]
specifies both a control messaging and data packet forwarding
facility for forwarding Internet Protocol (IP) packets [RFC0791]
[RFC2460] over an enterprise network or other Internetwork through a
process known as tunneling. Although AERO can operate with any
tunnel encapsulation format, the base document specifies the
insertion of a User Datagram Protocol (UDP) header [RFC0768] between
the inner and outer IP headers per the Generic UDP Encapsulation
(GUE) [I-D.ietf-nvo3-gue] specification. This document presents
minimal encapsulation formats for AERO using other encapsulation
types.
AERO can use common minimal encapsulations such as IP-in-IP
[RFC2003][RFC2473][RFC4213], Generic Routing Encapsulation (GRE)
[RFC2784][RFC2890] and others. The encapsulation is therefore only
differentiated from non-AERO tunnels through the application of AERO
control messaging.
Regardless of the encapsulation type, AERO requires an encapsulation
layer fragment header that serves the same purpose as for GUE
fragmentation [I-D.herbert-gue-fragmentation] . For simple IP-in-IP
encapsulation, an IPv6 fragment header is inserted directly between
the inner and outer IP headers when needed, i.e., even if the outer
header is IPv4. The IPv6 Fragment Header is identified to the outer
IP layer by its IP protocol number, and the Next Header field in the
IPv6 Fragment Header identifies the inner IP header version. For GRE
encapsulation, a GRE fragmentation header is inserted within the GRE
header as specified in [I-D.templin-intarea-grefrag]. Other tunnel
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types similarly require an encapsulation layer fragment header in
order to properly support AERO.
2. Minimal AERO Encapsulation
Figure 1 shows the AERO IP-in-IP minimal encapsulation format before
any fragmentation is applied:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Outer IPv4 Header | | Outer IPv6 Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|IPv6 Fragment Header (optional)| |IPv6 Fragment Header (optional)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Inner IP Header | | Inner IP Header | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
~ ~ ~ ~
~ Inner Packet Body ~ ~ Inner Packet Body ~
~ ~ ~ ~
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Minimal Encapsulation in IPv4 Minimal Encapsulation in IPv6
Figure 1: Minimal Encapsulation Format using IP-in-IP
GRE encapsulation can be used instead of simple IP-in-IP
encapsulation when GRE facilities such as keys and checksums are
desired. In that case, AERO can include a GRE fragmentation header
in the encapsulation [I-D.templin-intarea-grefrag] as shown in
Figure 2:
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Outer IP Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GRE Header |
| (with checksum, key, etc..) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GRE Fragment Header (optional)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Inner IP Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ ~
~ Inner Packet Body ~
~ ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Minimal Encapsulation Using GRE
Figure 2: Minimal Encapsulation Using GRE
3. When to Insert an Encapsulation Fragment Header
An encapsulation fragment header is inserted whenever the AERO tunnel
ingress needs to apply fragmentation to accommodate packets that must
be delivered without loss due to a size restriction. Fragmentation
is performed on the inner packet while encapsulating each inner
packet fragment in identical outer IP and any additional
encapsulation headers. Fragmentation follows the same procedure as
for standard IPv6 fragmentation.
The fragment header can also be inserted in order to include a
coherent Identification value with each packet, e.g., to aid in
Duplicate Packet Detection (DPD). In this way, networking devices
can cache the Identification values of recently-seen packets and use
the cached values to determine whether a newly-arrived packet is in
fact a duplicate.
Finally, the Identification value within each packet could provide a
rough indicator of packet reordering, e.g., in cases when the tunnel
egress wishes to discard packets that are grossly out of order.
4. Considerations for Using Minimal Encapsulation
Minimal encapsulation is preferred in environments where GUE
encapsulation would add unnecessary overhead. For example, certain
low-bandwidth wireless data links may benefit from a reduced
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encapsulation overhead. This is not likely to be a prime
consideration for many modern wireless data links nor for most modern
wired-line data links.
GUE encapsulation can traverse network paths that are inaccessible to
minimal encapsulation, e.g., for crossing Network Address Translators
(NATs). More and more, network middleboxes are also being configured
to discard packets that include anything other than a well-known IP
protocol such as UDP and TCP. It may therefore be necessary to
consider the potential for middlebox filtering before enabling
minimal encapsulation in a given environment.
5. AERO Operation Over Native Links
AERO can also operate over native links using no encapsulation at
all. In that case, AERO Clients can identify AERO Servers on the
link through their link-layer MAC addresses, and the AERO DHCPv6-PD,
mobility management and route optimization facilities operate on the
native link the same as over an NBMA tunnel overlay. Furthermore,
AERO Clients can manage associations with multiple Servers for fault
tolerance purposes.
6. IANA Considerations
This document introduces no IANA considerations.
7. Security Considerations
Security considerations are discussed in the base AERO specification
[I-D.templin-aerolink].
8. Acknowledgements
TBD
9. References
9.1. Normative References
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
DOI 10.17487/RFC0768, August 1980,
<http://www.rfc-editor.org/info/rfc768>.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981,
<http://www.rfc-editor.org/info/rfc791>.
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[RFC2003] Perkins, C., "IP Encapsulation within IP", RFC 2003,
DOI 10.17487/RFC2003, October 1996,
<http://www.rfc-editor.org/info/rfc2003>.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <http://www.rfc-editor.org/info/rfc2460>.
[RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in
IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473,
December 1998, <http://www.rfc-editor.org/info/rfc2473>.
[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
DOI 10.17487/RFC2784, March 2000,
<http://www.rfc-editor.org/info/rfc2784>.
[RFC2890] Dommety, G., "Key and Sequence Number Extensions to GRE",
RFC 2890, DOI 10.17487/RFC2890, September 2000,
<http://www.rfc-editor.org/info/rfc2890>.
[RFC4213] Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms
for IPv6 Hosts and Routers", RFC 4213,
DOI 10.17487/RFC4213, October 2005,
<http://www.rfc-editor.org/info/rfc4213>.
9.2. Informative References
[I-D.herbert-gue-fragmentation]
Herbert, T. and F. Templin, "Fragmentation option for
Generic UDP Encapsulation", draft-herbert-gue-
fragmentation-02 (work in progress), October 2015.
[I-D.ietf-nvo3-gue]
Herbert, T., Yong, L., and O. Zia, "Generic UDP
Encapsulation", draft-ietf-nvo3-gue-02 (work in progress),
December 2015.
[I-D.templin-aerolink]
Templin, F., "Asymmetric Extended Route Optimization
(AERO)", draft-templin-aerolink-63 (work in progress),
August 2015.
[I-D.templin-intarea-grefrag]
Templin, F., "GRE Tunnel Fragmentation", draft-templin-
intarea-grefrag-01 (work in progress), August 2015.
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Author's Address
Fred L. Templin (editor)
Boeing Research & Technology
P.O. Box 3707
Seattle, WA 98124
USA
Email: fltemplin@acm.org
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