v6ops Working Group G. Van de Velde
Internet-Draft O. Troan
Intended status: Informational Cisco Systems
Expires: March 4, 2011 T. Chown
University of Southampton
August 31, 2010
Non-Managed IPv6 Tunnels considered Harmful
<draft-vandevelde-v6ops-harmful-tunnels-01.txt>
Abstract
IPv6 is ongoing and natively being deployed by a growing community
and it is important that the quality perception and traffic flows are
as optimal as possible. Ideally it would be as good as the IPv4
perceptive experience.
This paper looks into a set of transitional technologies where the
actual user has IPv6 connectivity through the means of IPv6-in-IPv4
tunnels. A subset of the available tunnels has the property of being
non-managed (i.e. 6to4 [RFC3056] and Teredo [RFC4380] ).
While native IPv6 deployments will keep growing it is uncertain or
even expected that non-managed IPv6 tunnels will be providing the
same user experience and operational quality as managed tunnels or
native IPv6 connectivity.
This paper will detail some considerations around non-managed tunnels
and will document the harmful element of these for the future growth
of networks and the Internet.
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 March 4, 2011.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Managed Tunnelling Properties . . . . . . . . . . . . . . . . 4
3. Tunnel User Experience Views . . . . . . . . . . . . . . . . . 5
4. Why do non-managed tunnels exist? . . . . . . . . . . . . . . 5
5. Non-Managed Tunnelling Properties . . . . . . . . . . . . . . 6
5.1. Performance . . . . . . . . . . . . . . . . . . . . . . . 6
5.2. Topological Considerations . . . . . . . . . . . . . . . . 7
5.3. Operational Provisioning . . . . . . . . . . . . . . . . . 7
5.4. Operational Troubleshooting . . . . . . . . . . . . . . . 7
5.5. Security . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.6. Content Services . . . . . . . . . . . . . . . . . . . . . 8
6. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 9
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
10.1. Normative References . . . . . . . . . . . . . . . . . . . 9
10.2. Informative References . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
While the Internet and networks continue to grow, it is found that
the deployment of IPv6 within these networks is an ongoing activity
due to global IPv4 address pool depletion. An important aspect is
that the quality, availability and security of the IPv6 connectivity
is as good as possible, and when possible even more advanced as the
IPv4 connectivity.
Historically IETF has been facilitating a variety of technologies and
procedures to deploy IPv6 successfully in addition to existing IPv4
connectivity. In general and for the sake of this draft these
procedures and technologies can be divided into three major groups:
(1) native (dual-stack) IPv6, (2) Tunnelled IPv6 and (3) Translation.
While native IPv6 deployments has been steadily growing, the value
and the drawbacks of some tunnelling mechanisms can be investigated.
Translational techniques provide a total different aspect of
considerations and applicability and is beyond the scope of this
paper. Transition techniques have been and still are in many cases
important for the bootstrapping of IPv6, this paper will look into a
range of property aspects of non-managed IPv6 tunnelling techniques.
Areas of perverse traffic paths, security considerations, lack of
business incentives to run tunnel relays/gateways, black holing and
ownership of supportability will be analysed. Finally the paper will
conclude that for the growth of IP connectivity, non-managed
tunnelling techniques are considered harmful especially for those
that want to access applications over the network through pervasive
IPv6 connectivityand have no particular interrest on how connectivity
to the applications is established (IPv4, translation, IPv6, etc...)
2. Managed Tunnelling Properties
A managed tunnel is a tunnel has a few properties supporting the
ownership and quality of the tunnel.
When using a managed service, there tends to be an administrative
entity which provides quality assurance and can take action if users
of the service are experiencing a degraded service. An example would
be 6rd tunnels [RFC5969]
In addition there is a general trust awareness and agreement between
the user of the managed tunnel service and the provider of the
managed tunnel service.
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3. Tunnel User Experience Views
The tunnel experience can be divided into three distinct segments:
(1) the End-user view, (2) the Enterprise View and (3) the Service
Provider View.
The End-user view exists mainly out of two different user profiles.
The technical power user and the general user mainly trying to reach
their favourite application on the network. The technical power user
may have a particular interrest to run IPv6 as a transport mechanism,
and if his upstream service provider has no native IPv6 connectivity
available, then non-managed tunneling mechanisms may provide a
solution satisfying to the immediate needs of the technical power
user. Alternatively, the general user trying to reach his favourite
network application, may have no interest or awareness of his IPv6
usage, particulary when non-managed tunnels are utilized.
The Enterprise View is a more traffic flows and network oriented
possitioning. When the upstream service provider does not have an
IPv6 offer, then the enterprise may start to rely upon a technology
as 6to4 [RFC3056]. However this technology has the potential of
creating quite perverse traffic paths when user want to reach
applications on the Internet. When user would like to reach other
6to4 [RFC3056] users, then more optimized traffic paths, generally
following the IPv4 traffic paths are realized
The final view is how a Internet service provider looks into non-
managed tunnel usage. A service provider may decide to deploy a 6to4
relay to increase the IPv6 quality of their customers. This a
service which require resources (money, maintenance, etc...). Often
the 6to4 relay service is not just (always) restricted to only the
service providers customers, which as result provides often results
in a demotivation to provide quality tunnel relay devices. From a
content service provider perspective the usage of non-managed tunnel
often results in measurable differences in RTT and reliability in
some cases, and hence are reluctant to bring all services to
mainstream IPv6 for all users 'just yet'.
4. Why do non-managed tunnels exist?
Non-managed tunnels exist due to a variety of reasons.
Early adopters: people and organisations with a desire to use new and
potentially market disrupting technologies and applications may have
a desire to use the latest IP even when the upstream provider doesn't
have an available service offering.
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Lock-step process to implement IPv6: It is not trivial to move a
system or an organisation in lock-step towards IPv6 and the aid of
tunnels help in this process.
The utilisation of tunnels aid in providing a de-coupling between
infrastructure readiness and application readiness, and hence
contribute to the development of both elements.
5. Non-Managed Tunnelling Properties
The properties of Non-managed tunnels span many different areas. In
this section the properties are analysed and segmented within
different areas of impact. In each case the comparison is made
between native IPv6 connectivity and connectivity through a non-
managed tunnel. A common property of non-managed tunnels is that
they often use well-known anycast addresses or other well known
addresses and anticipate upon the goodwill of middleware (typically a
relay or gateway) device to serve as a tunnel termination point. In
some cases, for example a 6to4 relay can be provided by a connected
responsible service provider, and hence good quality operation can be
guaranteed.
Non-managed tunnels often have asymmetric behaviour. There is an
outbound and an inbound connectivity behaviour from the tunnel
initiator. It is possible to influence the good quality tunnel
behaviour of the outbound connectivity (e.g. by explicit setting of
the 6to4 relay), however, influencing good inbound connectivity is
often an issue.
5.1. Performance
Deploying a tunnelling mechanism mostly results in encapsulation and
de-capsulation efforts. Often this activity has a performance impact
on the device, especially when the device does not use hardware
acceleration for this functionality. If the performance impact is
scoped into the device its lifetime through performance capacity
management then the actual impact is predictive. Non-deterministic
tunnels tend to have a non-predictive behaviour for capacity, and
hence application and network performance is non-predictive. The key
reason for this is the decoupling of the capacity management of the
tunnel aggregation devices from the capacity desired by users of the
aggregation devices.
During initial IPv6 deployment there have been mainly technical savvy
people that have been using non-managed tunnel technologies and it
has for many been working well. However, if non-managed tunnelling
would be deployed in mass and especially when enabled by default by
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CPE vendors or host vendors then those aggregation points could
become overloaded and result in bad performance. There are a few
measures that can be taken, i.e. upgrade the CPU power of the
aggregation device or its bandwidth available, however this may not
happen without the right motivation for the operator of the
aggregation device (i.e. cash flows, reputation, competitive reasons,
etc... ).
5.2. Topological Considerations
Due to non-managed IPv6 tunnels the traffic flows may result in sub-
optimal flows through the network topology between two communicating
devices. The impact for example can cause increase of the RTT and
packet loss, especially considering the availability (or better non-
availability) of tunnel aggregation/de-aggregation points of certain
topological areas or realms. The increase of non-managed tunnel
usage would amplify the negative impact on good quality connectivity.
For many operators of tunnel aggregation/de-aggregation devices there
is little motivation to increase the quality and number of available
devices within a topological area or logistical realm.
5.3. Operational Provisioning
Some elements regarding provisioning of both managed and non-managed
tunnels can be controlled, while others are beyond control or
influence of people and applications using tunnels. To make
applications highly reliable and performing, all elements within the
traffic path must provide an expected quality service and
performance. For managed tunnels, the user or provider of the tunnel
can exercise a degree of operational management and hence influence
good quality behaviour upon the tunnel especially upon the
aggregation and de-aggregation devices. In some cases even the
traffic path between both aggregation and de-aggregation can be
controlled. Non-managed tunnels however have less good quality
behaviour of both tunnel aggregation and de-aggregation devices
because often good quality behaviour is beyond the control or
influence of the tunnel user. For non-managed tunnels the tunnel
aggregator and/or tunnel de-aggregator are operated by a 3rd party
which may have a conflicting interest with the user of the non-
managed tunnel. An exception is where the use of the tunnel
mechanism is all within one ISP, or ISPs who are 'well coupled', e.g.
as happens between many NRENs.
5.4. Operational Troubleshooting
When one is using non-managed tunnels, then these tunnels may get
aggregated or de-aggregated by a 3rd party or a device outside the
control of a contracted service provider. Troubleshooting these
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devices these devices will be pretty hard for the tunnel user or to
work around the issue.
Also some tools like traceroute don't work too well on asymmetric
paths. Another aspect is that tunnels show as one hop in a
traceroute, not indicating where problems may be.
5.5. Security
For an aggregating or de-aggregating tunnel device it is a non-
trivial issue to separate the valid traffic from non-valid traffic
because it is from the aggregation device perspective almost
impossible to know -from- and -towards- about the tunnel traffic.
This imposes potential attacks on the available resources of the
aggregating/de-aggregating router. A detailed security analysis for
6to4 tunnels can be found in [RFC3964].
For the user of the non-managed IPv6 tunnel there is an underlying
trust that the aggregating/de-aggregating device is a trustworthy
device. However, some of the devices used are run by anonymous 3rd
parties outside the trusted infrastructure from the user perspective,
which is not an ideal situation. The usage of non-managed tunnels
increases the risk of rogue aggregation/de-aggregation devices and
may be open to malicious packet analyses or manipulation.
From the operator perspective, managing the aggregating/
de-aggregating tunnel device, there is a trust assumption that no-one
abuses the service. Abuse may impact preset or assumed service
quality levels, and hence the quality provided can be impacted
There is also an impact caused by ipv4 firewalling upon non-managed
tunnels. Common firewall policies recommend to block tunnels,
especially non-managed tunnels, because there is no trust that the
traffic within the tunnel is not of mallicious intend. This
restricts the applicability of some non-managed tunnel mechanisms
(e.g. 6to4). Other tunnel mechanisms have found manners to avoid
traditional firewall filtering (e.g. Teredo) and open the local
network infrastructure for mallicious influence (e.g. virus, worms,
infrastructure attacs, etc..).
5.6. Content Services
When providing content services a very important related aspect is
that these services are accessible with high reliability, are
trustworthy and have a high performance. Using non-managed tunnels
makes this a much harder equation and can result in all three
elements to suffer negatively, without the ability to uniquely
identify and resolve the root cause. The statistical impact of non-
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mnaged tunnels has been measured by some Internet Content providers
and is often an additional delay of O(100msec) (need to add reference
here)
This reduces the interest of content providers to provide content
services over IPv6 when non-managed tunnels are used.
6. Conclusion
Non-managed tunnels have properties impacting the growth of networks
and the Internet in a negative way. Consequences regarding black-
holing, perverse traffic paths, lack of business incentive and
operational management influence and security issues are a real
pragmatic concern, while universal supportability for the tunnel
relay services appear to be non-trivial. Due to these elements the
usage of non-managed tunnelling can be considered harmful for the
growth of networks and the Internet.
7. IANA Considerations
There are no extra IANA consideration for this document.
8. Security Considerations
There are no extra Security consideration for this document.
9. Acknowledgements
10. References
10.1. Normative References
10.2. Informative References
[RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains
via IPv4 Clouds", RFC 3056, February 2001.
[RFC3964] Savola, P. and C. Patel, "Security Considerations for
6to4", RFC 3964, December 2004.
[RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through
Network Address Translations (NATs)", RFC 4380,
February 2006.
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[RFC4798] De Clercq, J., Ooms, D., Prevost, S., and F. Le Faucheur,
"Connecting IPv6 Islands over IPv4 MPLS Using IPv6
Provider Edge Routers (6PE)", RFC 4798, February 2007.
[RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site
Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214,
March 2008.
[RFC5969] Townsley, W. and O. Troan, "IPv6 Rapid Deployment on IPv4
Infrastructures (6rd) -- Protocol Specification",
RFC 5969, August 2010.
Authors' Addresses
Gunter Van de Velde
Cisco Systems
De Kleetlaan 6a
Diegem 1831
Belgium
Phone: +32 2704 5473
Email: gvandeve@cisco.com
Ole Troan
Cisco Systems
Folldalslia 17B
Bergen N-5239
Norway
Phone: +47 917 38519
Email: ot@cisco.com
Tim Chown
University of Southampton
Highfield
Southampton, SO17 1BJ
United Kingdom
Phone: +44 23 8059 3257
Email: tjc@ecs.soton.ac.uk
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