Network Working Group F. Parent
Internet-Draft Hexago
Expires: April 1, 2005 A. Durand
SUN Microsystems,inc.
A. Baudot
France Telecom R&D
Oct 2004
Goals for Registered Assisted Tunneling
draft-ietf-v6ops-assisted-tunneling-requirements-01
Status of this Memo
This document is an Internet-Draft and is subject to all provisions
of section 3 of RFC 3667. By submitting this Internet-Draft, each
author represents that any applicable patent or other IPR claims of
which he or she is aware have been or will be disclosed, and any of
which he or she become aware will be disclosed, in accordance with
RFC 3668.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as
Internet-Drafts.
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."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on April 1, 2005.
Copyright Notice
Copyright (C) The Internet Society (2004).
Abstract
This document defines requirements for a tunnel set-up protocol that
could be used by an ISP to jumpstart its IPv6 offering to its
customers by providing them IPv6 connectivity through tunneling.
Parent, et al. Expires April 1, 2005 [Page 1]
Internet-Draft Goals for Registered Assisted Tunneling Oct 2004
Table of Contents
1. Goal and Scope of the Document . . . . . . . . . . . . . . . . 3
2. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Requirements for Simplicity . . . . . . . . . . . . . . . . . 5
4. Protocol Requirements . . . . . . . . . . . . . . . . . . . . 5
4.1 Address and Prefix Delegation . . . . . . . . . . . . . . 6
4.2 Registration . . . . . . . . . . . . . . . . . . . . . . . 6
4.3 Authentication . . . . . . . . . . . . . . . . . . . . . . 6
4.4 Confidentiality . . . . . . . . . . . . . . . . . . . . . 7
4.5 Service Discovery . . . . . . . . . . . . . . . . . . . . 7
4.6 NAT Traversal . . . . . . . . . . . . . . . . . . . . . . 7
4.7 Firewall Traversal . . . . . . . . . . . . . . . . . . . . 7
4.8 Accounting . . . . . . . . . . . . . . . . . . . . . . . . 8
5. General Requirements . . . . . . . . . . . . . . . . . . . . . 8
5.1 Scalability . . . . . . . . . . . . . . . . . . . . . . . 8
5.2 NAT Considerations . . . . . . . . . . . . . . . . . . . . 8
5.3 Keep-alive . . . . . . . . . . . . . . . . . . . . . . . . 9
5.4 Security . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.5 Traceability . . . . . . . . . . . . . . . . . . . . . . . 9
5.6 Phase Out . . . . . . . . . . . . . . . . . . . . . . . . 9
5.7 Extensibility . . . . . . . . . . . . . . . . . . . . . . 9
6. Compatibility with other Transition Mechanisms . . . . . . . . 10
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. Acknowlegements . . . . . . . . . . . . . . . . . . . . . . . 10
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
9.1 Normative References . . . . . . . . . . . . . . . . . . . . 11
9.2 Informative References . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 12
A. Changes from version 00 . . . . . . . . . . . . . . . . . . . 12
Intellectual Property and Copyright Statements . . . . . . . . 14
Parent, et al. Expires April 1, 2005 [Page 2]
Internet-Draft Goals for Registered Assisted Tunneling Oct 2004
1. Goal and Scope of the Document
The v6ops working group has worked on requirements and scenarios for
IPv6 deployment by soliciting input from network operators. This
work has identified a need for an "assisted tunneling" mechanism.
For example, an ISP starting its IPv6 offering to its customers
without upgrading its access network to support IPv6 could use a
"tunnel brokering solution" (section 5.1
[I-D.ietf-v6ops-isp-scenarios-analysis]) a la [RFC3053]. What has
been identified as missing from that document is a tunnel set-up
protocol.
In an ISP network, getting IPv6 connectivity to the customers
involves upgrading the access network to support IPv6, which can take
a long time and/or be costly. A tunneled infrastructure can be used
as a low cost migration path (section 5.1
[I-D.ietf-v6ops-isp-scenarios-analysis]).
With such an infrastructure, the ISP can connect its customers to its
IPv6 network using its production IPv6 address space, thus
facilitating migration towards native IPv6 deployment. The IPv6
deployment roadmap for connecting customers may become:
o assisted tunneling infrastructure to early adopters,
o native IPv6 to customers where economically justified,
o native IPv6 to all customers.
Contrary to automatic tunneling mechanism where the IPv4 address is
embedded inside the IPv6 address, no special format are imposed on
the IPv6 address used in assisted tunneling. Prefix delegation is
also possible. As the addressing space used during the transition to
native remains the same, the customer routing, filtering, accounting
stay the same, and there is no need to maintain any kind of relay.
"Assisted tunneling" is used in this document to describe a
transition mechanism where the parameters to configure a
bi-directional tunnel between an end-node (or leaf network) and a
router in the core of an ISP are exchanged through a tunnel set-up
protocol. Although this exchange can be automated, this remains
different from transition mechanisms like 6to4, Teredo or ISATAP. In
particular, assisted tunneling enables explicit access control to the
tunneled IPv6 connectivity, where the other transion mechanisms have
to rely on other kinds of control (e.g., access control based on the
IPv4 address). Also, assisted tunneling protocol negotiate the
tunnel parameters and does not depend on having the IPv4 address
inside the IPv6 address, for example.
Parent, et al. Expires April 1, 2005 [Page 3]
Internet-Draft Goals for Registered Assisted Tunneling Oct 2004
This document analyzes the requirements for such a tunnel set-up
protocol. The v6ops WG scenario and evaluation documents for
deploying IPv6 within common network environments are used as input
to this document.
2. Applicability
Assisted tunneling is applicable in different IPv6 transition
scenarios. The focus of this document is to define the requirements
to apply this mechanism in the IPv4 ISP context making the following
assumptions:
o ISP is offering IPv6 connectivity to its customers initially using
controlled tunneling infrastructure
[I-D.ietf-v6ops-isp-scenarios-analysis], section 5.1 "Steps in
Transitioning Customer Connection Networks"
o Provider network where deployment of IPv6 is done in a more
controlled manner or when the provider cannot rely on IPv4 related
authentication (e.g. roaming customers, users not connected to
ISP access network). In such networks, ease of debugging,
traceability, filtering and so on are important features.
o The customer configuration may be diverse, and not necessarily
predictable by the ISP. The protocol must be able to adapt to the
following cases, for example by choosing the most optimal tunnel
encapsulation depending on the presence of a NAT.
* a single node,
* a leaf network,
* using a globally routable IPv4 address,
* behind a NAT (customer or ISP owned),
* using dynamic IPv4 address (internally or externally to the
NAT)
There are actually two cases where the IPv4 address of the customer
tunnel end point can be dynamic, and both must be supported:
o The device used as tunnel end point is using a dynamic IPv4
address provided by the ISP.
o The device used as tunnel end point is located behind a customer
owned NAT box that is also acting as a local DHCP server. In that
case, the device IPv4 address may change after a reboot.
Parent, et al. Expires April 1, 2005 [Page 4]
Internet-Draft Goals for Registered Assisted Tunneling Oct 2004
Althought the main focus of this document is the ISP scenario,
assisted tunneling is applicable in other scenarios:
In unmanaged networks [RFC3904], assisted tunneling is applicable in
the case A where a gateway does not provide IPv6 at all (section 3),
and case C where a dual-stack gateway is connected to an IPv4-only
ISP (section 5).
In the enterprise scenario [I-D.ietf-v6ops-ent-analysis], assisted
tunneling can be used to support remote users connecting to the
enterprise network (section 7.5.2).
3. Requirements for Simplicity
The tunnel set-up protocol must be simple to implement and easy to
deploy. In particular, it should not depend on any complex, yet to
be designed, protocols or infrastructure pieces.
This protocol is a transition mechanism, thus does not need to be
perfect. As a matter of fact, making it perfect would be counter
productive, at it would first delay its definition, then make its
deployment more cumbersome and, last but not least, diminish the
incentives to deploy native IPv6.
4. Protocol Requirements
Assisted tunneling is aimed at production deployment which requires
the user to be authenticated (such as using a shared secret mechanism
Section 4.3). This can be to offer the tunneling service to roaming
users (users that are not directly connected to the ISP access
network), and/or restrict the service to specific users.
From a user point of view, an initial registration process may be
required before using the service. If the service provider uses an
existing authentication database (Section 4.2), this step may not be
needed.
From an ISP point of view, this makes a clear link between a tunnel
and a user (account). It provides some means to :
o meet requirements such as tracing (section 5.4
[I-D.ietf-v6ops-isp-scenarios-analysis])
o control service provision to valid and/or identified or even
selected users (section 5.2
[I-D.ietf-v6ops-isp-scenarios-analysis])
o less prone to denial of service attacks: Since every tunnel
Parent, et al. Expires April 1, 2005 [Page 5]
Internet-Draft Goals for Registered Assisted Tunneling Oct 2004
request are authenticated, it is more difficult to request
multiple tunnels to saturate the service.
o stay in touch with users
4.1 Address and Prefix Delegation
The protocol must support delegation of an IPv6 prefix. The length
of the IPv6 prefix delegated must be configurable on the server. The
protocol must be able to offer stable IPv6 prefixes to the
authenticated customers.
Assignment of an IPv6 address (/64) to the end-node must be
supported.
Since no special address format is imposed, the ISP's address space
can be used in the delegation (section 5.1
[I-D.ietf-v6ops-isp-scenarios-analysis])
4.2 Registration
The registration of credentials is external to the protocol. The
user may require registration prior to using this service (through
some web based service or other means). Or service provider may use
an existing authentication database to pre-register its users.
In order to allow a service provider to use its existing
authentication database, an implementation may provide hooks to
facilitate integration with the ISP management infrastructure (e.g.
RADIUS for AAA, billing) ([I-D.ietf-v6ops-isp-scenarios-analysis],
section 5.2).
The protocol may send information about registration procedure when a
non-registered client requests registered mode (ex: URL to provider
registration web page).
4.3 Authentication
Authentication can be used to control user has access to the IPv6
services (section 5.2 [I-D.ietf-v6ops-isp-scenarios-analysis])
The authentication mechanism supported should be compatible with
standardized methods that are generally deployed. In order to assure
interoperability, at least one common authentication method must be
supported. Other authentication may be supported and should be
negotiated between the client and server (e.g., SASL [RFC2222]).
Parent, et al. Expires April 1, 2005 [Page 6]
Internet-Draft Goals for Registered Assisted Tunneling Oct 2004
4.4 Confidentiality
Assisted tunneling can be used across networks which are not under
the service provider control (e.g., roaming users). The tunnel
set-up protocol should allow protection of the authentication data
Section 4.3. This can be achieve by selecting an authentication
mechanism that protects the credentials (e.g., digest-md5).
Protecting the tunneled data (IPv6 in this case) should be possible.
A possible usage scenario is when an enterprise's users is working
off-site and tunneling to the enterprise network (7.5.2
[I-D.ietf-v6ops-ent-analysis]). Mechanisms do exist to make this
possible, such as using IPsec over IPv6 [RFC2401].
[I-D.tschofenig-v6ops-secure-tunnels] may be applicable here but is
not analysed further.
4.5 Service Discovery
In order to facilitate deployment, the implementation should allow a
mechanism to discover the address of the server that will provide the
tunnel connectivity.
This discovery should be automatic when the protocol is used within
an ISP network. There is no service discovery requirements when used
outside the provider network (roaming users, 3rd party ISP).
Tunnel end-point discovery mechanism work
([I-D.palet-v6ops-tun-auto-disc] may be applicable here.
4.6 NAT Traversal
Tunneling through IPv4 NAT must be supported. The protocol should
detect if an IPv4 NAT is in the path during the set-up phase (Section
5.2). If a NAT is present, an extra level of encapsulation is
necessary to tunnel IPv6 across the NAT. If no NAT is detected,
IPv6-over-IPv4 tunneling (IP protocol 41) is usually enough (see also
Section 4.7).
NAT traversal is identified as a requirement in ISP scenarios
(section 5.1 [I-D.ietf-v6ops-isp-scenarios-analysis]) and unmanaged
scanarios (section 7, Recommendation 1 [RFC3904])
4.7 Firewall Traversal
Even if no NAT is in the tunnel path, there may be a firewall which
prohibits IP protocol 41. In such case, the tunnel encapsulation
selection based on NAT detection (Section 5.2) will select a tunnel
that will not work.
Parent, et al. Expires April 1, 2005 [Page 7]
Internet-Draft Goals for Registered Assisted Tunneling Oct 2004
In some cases, when the firewall is managed by the ISP or customer,
it can be configured to allow IP protocol 41. In such cases this may
not be an issue (section 5.1 [I-D.ietf-v6ops-isp-scenarios-analysis])
But in order to be functional in any situation (e.g., firewall
lacking feature), the assisted tunneling implementation must allow a
user to explicitly specify the desired tunnel encapsulation,
regardless of the NAT detection process.
4.8 Accounting
The assisted tunneling should include tools for managing and
monitoring the provided service. Such information can be used to
plan service capacity (traffic load) or billing information.
Some useful accounting data are (not exhaustive list):
o Tunnel counters (traffic in/out)
o User utilization (tunnel uptime)
o System logging (authentication failures, resource exhaustion,
etc.)
The interface used to provide such information can be through SNMP or
an AAA protocol (e.g., RADIUS accounting).
5. General Requirements
5.1 Scalability
The tunnel set-up protocol must be scalable. Typically, this
protocol should be deployable in an ISP or enterprise network.
A scalability requirement which is not related to the protocol itself
is to be able to deploy multiple servers inside the ISP network. To
do so, the server implementation would possibly need some load
balancing feature and an IPv6 IGP.
5.2 NAT Considerations
The assisted tunnel established by the protocol to be designed must
work with the existing infrastructure, in particular it must be
compatible with the various customer premise equipments available
today. This means that, in particular, the tunnels must be able to
traverse one or many NAT boxes of different kinds. There is no
requirement for any particular NAT traversal technology. However, as
NAT traversal usually requires an extra layer of encapsulation, the
Parent, et al. Expires April 1, 2005 [Page 8]
Internet-Draft Goals for Registered Assisted Tunneling Oct 2004
tunnel set-up protocol should be able to detect automatically the
presence of one or more NAT boxes in the path.
The implementation must provide an option to turn on extra
encapsulation manually. In order to assure interoperability, at
least one common tunnel encapsulation type must be supported.
5.3 Keep-alive
When a tunnel has to cross a NAT box, the mapping established by the
NAT must be preserved as long as the tunnel is in use. This is
usually achieved by sending keep alive messages across the tunnel.
Also, the same keep alive messages can enable the ISP tunnel end
point to perform garbage collection of its resources when tunnels are
not in use anymore. To enable those two functionalities, the tunnel
set-up protocol must include the transmission of keep-alive messages.
A client may choose not to send those messages (for example on ISDN
type links). In this case, the client should be able to handle a
tunnel disconnect event and be able to restart the set-up phase to
re-establish the tunnel.
5.4 Security
The tunnel set-up protocol must not introduce any new vulnerability
to the network. See security considerations in Section 7.
5.5 Traceability
In some production environment, traceability is an important
consideration ([I-D.ietf-v6ops-isp-scenarios-analysis], section 5.4).
The tunnel set-up protocol must be instrumentable to enable the
collection of usage data that can be used, for example, for capacity
planning.
5.6 Phase Out
This assisted tunneling mode is only a transition mechanism to enable
ISP to jump start IPv6 service without requiring an immediate global
upgrade of access networks and instead enabling a progressive roll
out. Once IPv6 is available natively in the access network
connecting a customer, there is no reason to keep using tunnels. So
the implementation should have a provision to enable the ISP to
signal the user to use native IPv6 instead.
5.7 Extensibility
The protocol must be extensible to support tunnel encapsulation other
than IPv6 over IPv4 and IPv6 over transport over IPv4. In
Parent, et al. Expires April 1, 2005 [Page 9]
Internet-Draft Goals for Registered Assisted Tunneling Oct 2004
particular, encapsulation of IPv4 over IPv6 (section 7
[I-D.ietf-v6ops-isp-scenarios-analysis], section 7 [RFC3904], section
6 [I-D.ietf-v6ops-ent-analysis]) or IPv6 over IPv6 could be defined.
6. Compatibility with other Transition Mechanisms
The tunnel set-up protocol is not required to be compatible with any
existing transition mechanism. Although, a great deal of experience
can be drawn from the operation of tunnel brokers currently using the
TSP protocol [I-D.blanchet-v6ops-tunnelbroker-tsp].
7. Security Considerations
The establishment of a tunnel can be compared to Mobile IP
technology, where traffic can be redirected to go from one place to
another one. So similar threats exists. In particular, when a
customer is asking for the set-up of a tunnel ending at IP address X,
the ISP should check:
o the customer is allowed to set-up this tunnel, i.e. he "owns" the
IPv6 prefix.
o the customer is allowed to terminate the tunnel where he said he
would, i.e. he "owns" the IPv4 tunnel endpoint.
The first check is an authentication issue. The second may be more
complex. The protocol must make sure that the tunnel is established
to the legitimate and authenticated destination. IPv4 return
routability checks could help this validation. Also, when the user
is within the ISP access network, strict ingress filtering can help
prevent IPv4 address spoofing.
8. Acknowlegements
This draft has greatly benefited from substantial inputs by Pekka
Savola.
The following people provided feedback on this work (in no particular
order): Carl Williams, Brian Carpenter, Christian Huitema, Jordi
Palet, Jeroen Massar, Erik Nordmark, Soohong Daniel Park, Suresh
Satapati, Fred Tremplin, Karim El-Malki, Tim Chown, Gert Doering,
Soliman Hesham.
Thanks to Mark Prior and Bernard Tuy for providing input from an ISP
perspective to validate many requirements.
Parent, et al. Expires April 1, 2005 [Page 10]
Internet-Draft Goals for Registered Assisted Tunneling Oct 2004
9. References
9.1 Normative References
[I-D.ietf-v6ops-ent-analysis]
Bound, J., "IPv6 Enterprise Network Analysis",
draft-ietf-v6ops-ent-analysis-00 (work in progress),
September 2004.
[I-D.ietf-v6ops-isp-scenarios-analysis]
Lind, M., Ksinant, V., Park, S., Baudot, A. and P. Savola,
"Scenarios and Analysis for Introducing IPv6 into ISP
Networks", draft-ietf-v6ops-isp-scenarios-analysis-03
(work in progress), June 2004.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3053] Durand, A., Fasano, P., Guardini, I. and D. Lento, "IPv6
Tunnel Broker", RFC 3053, January 2001.
[RFC3904] Huitema, C., Austein, R., Satapati, S. and R. van der Pol,
"Evaluation of IPv6 Transition Mechanisms for Unmanaged
Networks", RFC 3904, September 2004.
9.2 Informative References
[I-D.blanchet-v6ops-tunnelbroker-tsp]
Parent, F. and M. Blanchet, "IPv6 Tunnel Broker with the
Tunnel Setup Protocol(TSP)",
draft-blanchet-v6ops-tunnelbroker-tsp-01 (work in
progress), June 2004.
[I-D.huitema-v6ops-teredo]
Huitema, C., "Teredo: Tunneling IPv6 over UDP through
NATs", draft-huitema-v6ops-teredo-02 (work in progress),
June 2004.
[I-D.ietf-ngtrans-isatap]
Templin, F., Gleeson, T., Talwar, M. and D. Thaler,
"Intra-Site Automatic Tunnel Addressing Protocol
(ISATAP)", draft-ietf-ngtrans-isatap-22 (work in
progress), May 2004.
[I-D.palet-v6ops-tun-auto-disc]
Palet, J. and M. Diaz, "Evaluation of v6ops Auto-discovery
for Tunneling Mechanisms",
draft-palet-v6ops-tun-auto-disc-01 (work in progress),
Parent, et al. Expires April 1, 2005 [Page 11]
Internet-Draft Goals for Registered Assisted Tunneling Oct 2004
June 2004.
[I-D.tschofenig-v6ops-secure-tunnels]
Tschofenig, H., "Using IPsec to Secure IPv6-over-IPv4
Tunnels", draft-tschofenig-v6ops-secure-tunnels-01 (work
in progress), July 2004.
[RFC2222] Myers, J., "Simple Authentication and Security Layer
(SASL)", RFC 2222, October 1997.
[RFC2401] Kent, S. and R. Atkinson, "Security Architecture for the
Internet Protocol", RFC 2401, November 1998.
[RFC2831] Leach, P. and C. Newman, "Using Digest Authentication as a
SASL Mechanism", RFC 2831, May 2000.
Authors' Addresses
Florent Parent
Hexago
2875 boul. Laurier, suite 300
Sainte-Foy, QC G1V 2M2
Canada
EMail: Florent.Parent@hexago.com
Alain Durand
SUN Microsystems,inc.
17 Network circle UMPK17-202
Menlo Park, CA 94025
USA
EMail: Alain.Durand@sun.com
Alain Baudot
France Telecom R&D
42, rue des coutures
14066 Caen,
France
EMail: alain.baudot@rd.francetelecom.com
Appendix A. Changes from version 00
Parent, et al. Expires April 1, 2005 [Page 12]
Internet-Draft Goals for Registered Assisted Tunneling Oct 2004
o Non-registered mode removed (now covered in generic zero-conf
tunneling draft). Text throughout the document changed to reflect
this.
o
o Renamed title from "requirements" to "goals"
o Changed imperatives to lowercase
o /128 endpoints replaced by /64
o Removed DNS considerations
o Added many references to other v6ops scenario documents
o Removed the appendix on protocol requirements summary
o Removed references to 3GPP scenario
Parent, et al. Expires April 1, 2005 [Page 13]
Internet-Draft Goals for Registered Assisted Tunneling Oct 2004
Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Disclaimer of Validity
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Statement
Copyright (C) The Internet Society (2004). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
Parent, et al. Expires April 1, 2005 [Page 14]
