One document matched: draft-nielsen-v6ops-zeroconf-goals-01.txt
Differences from draft-nielsen-v6ops-zeroconf-goals-00.txt
Network Working Group K. Nielsen
INTERNET-DRAFT Ericsson
M. Morelli
Expires: March 2, 2005 Telecom Italia Lab
J. Palet
Consulintel
J. Soininen
Nokia
J. Wiljakka
Nokia
September 2, 2004
Goals for Zero-Configuration Tunneling
<draft-nielsen-v6ops-zeroconf-goals-01.txt>
Status of this memo
By submitting this Internet-Draft, I certify that any applicable
patent or other IPR claims of which I am aware have been disclosed,
and any of which I become aware will be disclosed, in accordance with
RFC 3668 (BCP 79).
By submitting this Internet-Draft, I accept the provisions of Section
[#3] of RFC 3667 (BCP 78).
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 cite them other than as "work in progress".
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/lid-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html
Abstract
This document describes the set of goals to be fulfilled by a Zero-
Configuration Tunneling protocol.
Zero-Configuration Tunneling here denotes a minimalistic IPv6-in-IPv4
automatic tunneling mechanism that could be used by a Service
Nielsen, et al. [Page 1]
INTERNET-DRAFT Zeroconf Tunneling Goals September, 2004
Provider to offer IPv6 connectivity to its customers in early phases
of IPv4 to IPv6 transition.
Table of Contents
1. Introduction.....................................................2
2. Terminology......................................................4
3. Scope and Limitations............................................4
3.1. IPv6 address allocation, Scope and Limitations:.............4
3.2. IPv6 tunnel link characteristics, Scope and Limitations:....5
4. Assumptions and Prerequisites....................................5
4.1. Applicability Assumptions...................................5
4.2. 3GPP Compliance Prerequisite................................6
5. Timing...........................................................6
6. Goals............................................................7
6.1. Simplicity..................................................7
6.2. Automated IPv6-in-IPv4 tunnel establishment.................7
6.3. Use native when available...................................7
6.4. Easy to deploy and Easy to Phase-out with no modifications on
existing equipment...............................................8
6.5. Tunnel Server End-point Discovery...........................8
6.6. Address Assignment..........................................8
6.7. Tunnel Link Sustainability..................................9
6.8. Tunnel End-Point Reachability Detection.....................9
6.9. Private and public IPv4 addresses...........................9
6.10. Scalability, Load Balancing................................9
6.11. Security..................................................10
7. Non Goals.......................................................10
7.1. NAT and Firewall Traversal.................................10
7.2. IPv6 DNS...................................................10
7.3. Extensibility..............................................11
7.4. Registration burden........................................11
8. Stateful or Stateless...........................................11
9. Security Considerations.........................................11
9.1. Threats to existing network infrastructures................12
9.2. Threats to nodes implementing Zero-Configuration Tunneling.12
9.2.1. Threats to end-hosts..................................13
9.2.2. Threats to Tunnel Servers.............................13
9.2.2.1. Tunnel State related risks.......................13
9.2.2.2. Traffic related risks............................14
9.2.2.3. Packet Delivery related threats..................14
9.3. Implications of Direct Tunneling...........................14
10. Acknowledgments................................................15
11. Authors Addresses..............................................15
12. Changes from draft-nielsen-v6ops-zeroconf-goals-00.txt.........16
13. Informative References.........................................17
Appendix A Out of Scope............................................18
Appendix B Open Issues.............................................18
1. Introduction
Nielsen, et. al. [Page 2]
INTERNET-DRAFT Zeroconf Tunneling Goals September, 2004
The IETF v6ops Working Group has identified and analyzed deployment
scenarios for IPv4/IPv6 transition mechanisms in various stages of
IPv6 deployment and IPv6 and IPv4 coexistence.
This work has been carried out for a number of different network
environments each with their particular characteristics: Enterprise,
ISP, Unmanaged and 3GPP networks, see e.g., [2], [3] and [4].
The work has identified a need for automatic IPv6-in-IPv4 tunneling
mechanisms that provide bidirectional IPv6-in-IPv4 tunneled
connectivity between dual stack end-nodes located at an IPv4-only
access network and dual-stack tunnel servers located at IPv6-IPv4
network boundaries within the Service Providers network.
The term Zero-Configuration Tunneling is used in this document to
denote an IPv6-in-IPv4 tunneling mechanism that fulfills the goals as
put forward here.
A Zero-Configuration Tunneling mechanism provides a basic set of
tunneling features only, and intentionally so. The scope of Zero-
Configuration Tunneling is not to provide emulation of the full suite
of native IPv6 connectivity functions as defined by [7], [8] and [9];
rather the focus is to provide a minimal set of features required for
automatic establishment of IPv6 connectivity.
The starting point for the definition of the set of goals to be
fulfilled by a Zero-Configuration Tunneling mechanism has been the
set of features required for the IPv6-in-IPv4 tunneling mechanism
envisaged to be needed during the early phases of IPv6 transition in
3GPP environments as described in [4].
The applicability of Zero-Configuration Tunneling may widen to other
transition scenarios.
For scenarios demanding advanced tunneling features, for example full
emulation of native (though tunneled) IPv6 connectivity, a more full-
fledged tunneling mechanism is envisaged to be deployed, see [5].
With respect to the latter, an analysis of appropriate mechanisms for
automatic discovery of the tunnel endpoint is being done in [6].
It should be emphasized that unless otherwise specified then in this
document the reference, IPv6-in-IPv4 encapsulation as defined in [1],
refers to the aspects of Protocol-41 encapsulation related to IPv4
header construction (except for source and destination address
determination), MTU and Fragmentation, Hop Limits and ICMP handling
as detailed in Section 3.1-3.6 of [1]. The particular aspects of
Configured IPv6-In-IPv4 Tunneling in the areas of IPv4 source and
destination address determination, tunnel link characteristics and
IPv6 Neighbor Discovery operation are not intended referred to by the
above reference.
Nielsen, et. al. [Page 3]
INTERNET-DRAFT Zeroconf Tunneling Goals September, 2004
2. Terminology
Zero-Configuration Tunneling site:
A logical IPv4 network over which IPv6 connectivity is provided to
dual-stack nodes by means of Zero-Configuration Tunneling.
Tunnel End-point:
A dual-stack node performing IPv6-in-IPv4 tunnel
encapsulation/decapsulation in accordance with Zero-Configuration
Tunneling.
Tunnel Server:
A dual-stack server node with IPv6 connectivity and which provides
IPv6 connectivity to client nodes by performing IPv6-in-IPv4 tunnel
encapsulation/decapsulation to/from client nodes in accordance with
Zero-Configuration Tunneling.
A Tunnel Server is likely to be a dual-stack router.
Tunnel Client:
A dual-stack node that obtains IPv6 connectivity by means of Zero-
Configuration Tunneling. A tunnel client relies on IPv6-in-IPv4
tunnel encapsulation/decapsulation to/from Tunnel Servers for IPv6
communications to native IPv6 nodes.
Direct Tunneling:
Direct tunnelling here refer to the case where end-hosts located
within the same Zero-Configuration Tunnelling site may circumvent the
Tunnel Server and communicate directly using the tunnel protocol.
3. Scope and Limitations
The scope of Zero-Configuration Tunneling is restricted to an
absolute minimal set of functions required to provide automatic IPv6
connectivity establishment to dual stack nodes by means of IPv6-in-
IPv4 encapsulation as defined in [1] to tunnel servers under the
assumptions and prerequisites described in Section 4.
Zero-Configuration Tunneling does not attempt to provide emulation of
the full set of native IPv6 connectivity functions as defined by [7],
[8] and [9].
3.1. IPv6 address allocation, Scope and Limitations:
The primary goal of Zero-Configuration Tunneling is to provide IPv6
connectivity to nodes on an individual basis. By this it is meant
that it is only an explicit goal to have a /128 address allocated for
global connectivity on the tunnel link. As such optimal IPv6
Nielsen, et. al. [Page 4]
INTERNET-DRAFT Zeroconf Tunneling Goals September, 2004
connectivity provisioning in Personal Area Network (PAN) scenarios is
not explicitly within the scope of Zero-Configuration Tunneling.
It is not explicitly within the scope of Zero-Configuration Tunneling
to support usage of privacy IPv6 extensions as defined in [12].
It is not explicitly within the scope to support usage of IPv6
multicast.
No goals are defined as to how address configuration should be
performed. This may be done based on legacy stateless or stateful
IPv6 address configuration mechanisms or by some altogether different
mechanism particular to the zero-configuration solution.
3.2. IPv6 tunnel link characteristics, Scope and Limitations:
Direct tunneling is neither an explicit goal nor explicitly excluded
in Zero-Configuration Tunneling.
It is not an explicit requirement for the zero-configuration tunnel
link to support IPv6 link-local multicast.
The tunnel protocol should allow for the formation of a link-local
address on the tunnel link. Though no particular usage of such an
address is explicitly demanded by the goals set forward here.
It is an explicit goal that nodes attached to a tunnel link must be
able to ascertain the reachability of neighbors with which it is
communicating (or wish to start communicate). This may be achieved
using IPv6 Neighbor Discovery mechanism ([13]) based on unicast link-
local packet exchanges (or link-local multicast if such is supported)
but it may also be achieved by altogether different mechanisms.
4. Assumptions and Prerequisites
4.1. Applicability Assumptions
Zero-Configuration Tunneling is a tunneling mechanism by the virtue
of which dual-stacks hosts, attached to IPv4-only networks links, can
use IPv6-in-IPv4 encapsulation as defined in [1] to tunnel servers
for global IPv6 connectivity.
The aim of the document is to define the set of goals to be fulfilled
by zero-configured tunneling when the following assumptions are made
on the deployment environment:
- IPv4 source addresses spoofing within the Zero-Configuration
Tunneling site is prevented.
- The Zero-Configuration Tunneling site is protected from proto-41
encapsulated packets arriving from external IPv4 networks.
Nielsen, et. al. [Page 5]
INTERNET-DRAFT Zeroconf Tunneling Goals September, 2004
- At least one authoritative DNS server is IPv4-enabled and at
least one recursive DNS server supports IPv4. Further IPv4 DNS
Server discovery is provided by already existing means/means
outside the scope of the tunnel protocol.
- There are no NATs in between the tunnel endpoints in the Zero-
Configuration Tunneling site.
- The Zero-Configuration Tunneling network is fully penetrable for
intra-site IPv6-in-IPv4 Protocol 41 traffic.
- The user is being authenticated to the network by means external
to the tunneling protocol and other than that no additional
authentication/registration mechanisms are required.
The above assumptions are believed to be readily applicable to the
3GPP tunneling transition scenario described in [4], section 3.1.
It is a prerequisite that the tunnel protocol must work in IPv4
network environments where IPv4 multicast is not provided.
4.2. 3GPP Compliance Prerequisite
It is a prerequisite that Zero-Configuration Tunneling should be
applicable in 3GPP wireless networks. When considering the
characteristics of 3GPP network links and mobile terminals / User
Equipment (UE), the following points need to be taken into account:
- Link bandwidth (tunnel overhead / usage cost)
- Link latency
- UE battery power and derived implications on memory and
processing power
It is thus an explicit requirement for Zero-Configuration Tunneling
to comply well with the constrained conditions put on the above
parameters by the 3GPP environments. The latter which commonly is
recognized as translating into requirements for the protocol to
operate with a limited number of message exchanges, small packet
sizes and simple message processing.
Here we shall refer to a protocol as being lightweight when its
demands on message exchanges, packet sizes and message processing
complexity are sufficiently light for it to be readily applicable in
environments characterized by the constrained conditions of 3GPP
networks (as described above).
As a mean to ensure that the protocol be lightweight it is considered
preferable for the protocol to provide a simple set of functions
only, even if it provides only a basic IPv6 service compared to the
native one. It is although acknowledged that additional functionality
doesn't necessarily automatically add complexity to the demands on
the aforementioned parameters.
5. Timing
Nielsen, et. al. [Page 6]
INTERNET-DRAFT Zeroconf Tunneling Goals September, 2004
For the purpose of 3GPP deployment it is a prerequisite that this
tunneling protocol is provided within a very restrictive timescale.
Zero-Configuration Tunneling is envisaged to be deployed in 3GPP
networks as an initial and temporary mechanism to provide limited
IPv6 connectivity services. Native IPv6 like connectivity is in 3GPP
environments envisaged to be feasible by virtue of true native IPv6
only.
Trial deployments, in which zero-configuration type of IPv6
connectivity is provided in 3GPP environments, are starting up using
experimental protocols at the time of writing this document.
6. Goals
The goals to be achieved by Zero-Configuration Tunneling are detailed
in the following subsections.
6.1. Simplicity
By simplicity, we understand a tunnel protocol that is easy to
implement in the targeted environment. Additionally, the protocol
should provide a reasonable, limited set of basic IPv6 connectivity
features.
Further by simplicity we imply that the protocol must be lightweight.
6.2. Automated IPv6-in-IPv4 tunnel establishment
The protocol should provide for the set up of IPv6-in-IPv4 tunnels,
based on IPv6-in_IPv4 encapsulation as defined in [1], from dual-
stack nodes, attached to IPv4-only networks, to Tunnel Servers.
The IPv6-in-IPv4 tunnels and the IPv6 connectivity must be
established in an automated manner, i.e. without requiring manual
intervention at any of the tunnel end-points at tunnel establishment
time.
The mechanism must be fully dynamic in the sense that it must not
require IP address information such as the IPv4 address of a Tunnel
Server and/or the IPv6 address(es) to use for IPv6 connectivity to be
configured on the Tunnel Clients beforehand.
6.3. Use native when available
The tunnel protocol should allow the usage of native IPv6
connectivity whenever such is available.
The protocol must in no way restrict the native IPv6 capabilities of
the client node.
Nielsen, et. al. [Page 7]
INTERNET-DRAFT Zeroconf Tunneling Goals September, 2004
The node should not use Zero-Configuration Tunneling when native IPv6
connectivity is available.
Comment: The fact that a node should not use Zero-Configuration
Tunneling when native IPv6 connectivity is available is not
considered to be a functional requirement on the tunnel protocol.
Rather it is considered related to when, and how, the node
(implementation) uses the Zero-Configuration Tunneling function.
6.4. Easy to deploy and Easy to Phase-out with no modifications on
existing equipment
The tunnel protocol should be easy to deploy into the existing IPv4
and IPv6 network infrastructure.
The tunnel protocol should have no major impact on protocols and
infrastructure nodes deployed in existing infrastructures providing
IPv4 and native IPv6 connectivity.
The tunnel protocol should coexist and work seamlessly together with
any native IPv6 infrastructure that gradually may be implemented in
the network. The tunnel protocol should have no negative implications
on how such are implemented.
The tunnel protocol must be easy to take out of service once native
IPv6 is available.
6.5. Tunnel Server End-Point Auto-Discovery
The tunnel protocol must provide a mechanism for automated end-point
discovery by the virtue of which end-hosts automatically and at run-
time can determine the IPv4 addresses of available Tunnel Servers.
The discovery mechanism should rely on intrinsic services, read
services already universally deployed, to the particular network
environment. It should not require the addition of additional IP
network infrastructure elements for this function only.
Comment: The analysis done in [6] may apply.
6.6. Address Assignment
The tunnel protocol must allow for the assignment of at least one
globally routable (/128) IPv6 unicast address to use for tunneled
IPv6 connectivity over the link provided by the Zero-Configuration
Tunneling mechanism.
It is preferable that the address assignment provides a stable
address, that is, an address that can be used for IPv6 connectivity
for a certain amount of time rather than solely one address per
higher layer session initiation.
Nielsen, et. al. [Page 8]
INTERNET-DRAFT Zeroconf Tunneling Goals September, 2004
6.7. Tunnel Link Sustainability
The tunnel link established in between a host deploying Zero-
Configuration Tunneling and an associated Tunnel Server should be
expected to remain in administrative active state for the lifetime of
the IPv6 address provided to the host.
The tunnel protocol must not mandate keep-alive messages to be
transmitted by the host simply in order to sustain tunnel link
connectivity.
Motivation: The fact that a 3GPP terminal, for the single purpose of
transmitting keep-alive messages, could have to wake up the radio
periodically, send a packet over the radio and possibly wait for
response is undesirable for the following reasons:
- The terminal cannot, as otherwise anticipated, be in dormant
mode all the time it is idle. This has severe implications for
the battery consumption of the device.
- Radio resources are costly and sparse and consequently not to be
used for what is considered to be unnecessary traffic.
6.8. Tunnel End-Point Reachability Detection
The tunnel protocol must allow for means for one tunnel end-point to
verify the reachability of other tunnel end-points towards which it
intends to send packets.
The unicast neighbor reachability discovery functions provided by
IPv6 Neighbor Discovery ([13]), i.e., unicast NS/NA exchanges, should
be supported on the tunnel link.
6.9. Private and public IPv4 addresses
The tunnel protocol must work over IPv4 sites deploying both private
and public IPv4 addresses.
Furthermore, the tunnel protocol should work with both dynamic and
static IPv4 address allocation.
Motivation: Private IPv4 addresses are widely used in current 3GPP
networks.
6.10. Scalability, Load Balancing
In order to ensure the scalability of the tunnel service, in terms of
not limiting the number of simultaneous connections to the service
and consequently limiting possible service denial situations, it
should be possible for a Service Provider to load-balance those
connections among several available Tunnel Servers.
Nielsen, et. al. [Page 9]
INTERNET-DRAFT Zeroconf Tunneling Goals September, 2004
Load balancing should be planned already during the early phases of
deployment. Given adequate planning it should be possible for a
Service Provider to seamlessly deploy additional Tunnel Servers in
order to support an increased amount of Tunnel Clients.
Comment: This may be achieved using load balancing functions provided
by the Tunnel Server End-point Discovery mechanism as detailed in
[14].
6.11. Security
The tunnel protocol should not impose any new vulnerability to the
existing network infrastructure.
The tunnel protocol should not impose any new vulnerability to the
nodes implementing the tunnel protocol than what is already present
in existing multi-access IPv6 networks, where multiple hosts are
served by the same router or possibly multiple routers.
7. Non Goals
Non-goals of zero-configured tunneling are detailed in the following
subsections.
With the term Non-goals we refer to features that generally are
believed to be applicable to tunneling, but which are not among the
minimal set of required features of Zero-Configuration Tunneling. The
latter primarily because of the prerequisites for Zero-Configuration
Tunneling and/or because of the assumptions made on the applicability
environments for Zero-Configuration Tunneling, e.g., see Section 4.
7.1. NAT and Firewall Traversal
NAT and Firewall traversal is not required due to the assumptions on
the applicability environment.
Moreover to minimize the tunneling overhead applied to the packets as
well as in order to minimize the number of tunnel set-up signaling
messages exchanged on the link, it is preferable that the protocol
does not deploy the UDP encapsulation techniques, on which mechanisms
able to traverse NATs and Firewalls normally rely.
7.2. IPv6 DNS
By virtue of the assumptions on the applicability environments, the
dual stack end-hosts can use IPv4 DNS discovery mechanisms and IPv4
transport for DNS services.
Given that IPv4 based DNS services are already available, it is not
considered a requirement that the end-host should be able to deploy
Nielsen, et. al. [Page 10]
INTERNET-DRAFT Zeroconf Tunneling Goals September, 2004
IPv6 based DNS services. Consequently, the tunnel protocol does not
need to provide IPv6 DNS discovery mechanisms.
7.3. Extensibility
As a minimal tunneling mechanism Zero-Configuration Tunneling targets
IPv6 connectivity provisioning only. The protocol does not need to be
readily extendable to other encapsulation mechanisms, e.g., IPv4-in-
IPv6.
7.4. Registration burden
Tunnel service registration is not required due to the assumptions on
the applicability environment.
In order to keep the simplicity and minimize the tunnel overhead it
is desirable that the tunnel protocol not in itself (e.g., in order
to meet the goals put forward in this document) mandates
authenticated registration of the user.
8. Stateful or Stateless
By a stateful mechanism we mean a mechanism that require the Tunnel
Server to maintain tunnel state per client it serves.
Tunnel state here is considered to be any parameter kept by the
server per client and without which the server is unable to serve the
client (receive packets from/send packets to).
Tunnel state must be distinguished from state used to optimize the
packet delivery function of the tunnel server and which is kept in a
fixed or upper limited amount of memory space, such as, e.g.,
reachability information.
It should be emphasized that this document makes no deliberate
assumptions on whether a Zero-Configuration Tunneling solution should
be based on a stateful or stateless Tunnel Server mechanism. Indeed
it is anticipated that the goals of zero-configuration as put forward
here could be served both by a stateless as well as by a stateful
mechanism.
9. Security Considerations
It is assumed that the following assumptions of Section 4 are valid
in the particular network environment:
- IPv4 source addresses spoofing within the Zero-Configuration
Tunneling site is prevented.
- The Zero-Configuration Tunneling site is protected from proto-41
encapsulated packets arriving from external IPv4 networks.
Nielsen, et. al. [Page 11]
INTERNET-DRAFT Zeroconf Tunneling Goals September, 2004
It is worthwhile to note that together these assumptions imply that
the IPv4 source of all protocol-41 tunneled packets is legitimate.
9.1. Threats to existing network infrastructures
As stated in Section 6.11 the tunnel protocol should not impose any
new vulnerability to the existing network infrastructure.
The following have been identified as potential threats opened up for
by the deployment of Zero-Configuration Tunneling:
- As the tunnel service is un-authenticated (not registered) it
may be possible to use a tunnel server to reflect tunneled
packets into the network, similar to the 6to4-reflection attacks
identified in [10].
- The Zero-configuration site must be kept fully penetrable for
intra-site IPv6-in-IPv4 protocol-41 encapsulated packets. This
may open up for threats to end-hosts that rely on the network
infrastructure to filter out bogus protocol-41 encapsulated
packets.
- Zero-configuration tunneling may open up for threats to other
mechanisms in the network that rely on Protocol-41
encapsulation.
Detailed analysis of the validity of these threats will have to
depend on the particular zero-configuration solution. In general it
could be noted that attacks based on the above threats largely should
be preventable if the end-hosts in the network implement appropriate
drop policies, either simple drop all protocol-41 policies or more
differentiated policies based, e.g., on source addresses.
9.2. Threats to nodes implementing Zero-Configuration Tunneling
The following considerations apply to the situation where Zero-
Configuration Tunneling is deployed in between tunnel servers and
end-hosts only.
Special security considerations for the usage of Zero-Configuration
Tunneling for direct tunneling in between end-hosts is given in
Section 9.3.
As stated in Section 6.11 the tunnel protocol should not impose any
new vulnerability to the nodes implementing the tunnel protocol than
what is already present in existing multi-access IPv6 networks where
multiple hosts are served by the same router or possible multiple
routers.
Here it is implicitly assumed that the tunnel server(s) take the role
of default routers and the end-nodes using Zero-Configuration
Tunneling for IPv6 connectivity the role of hosts in multi-access
environments.
Nielsen, et. al. [Page 12]
INTERNET-DRAFT Zeroconf Tunneling Goals September, 2004
9.2.1. Threats to end-hosts
Given that all IPv4 sources of protocol-41 tunneled packets can be
assumed to be legitimate, threats stemming from encapsulated packets
sourced by nodes (addresses) other than nodes (addresses) which the
end-hosts recognize as tunnel servers (identified by addresses) can,
if not already an intrinsic part of the zero-configuration protocol,
easily be mitigated by the implementation of appropriate
differentiated (source addresses) drop policies in the end-hosts,
i.e., accept only if source is tunnel server.
In current multi-access IPv6 networks hosts need to trust on the
benevolence of their default routers as well as hosts must trust that
anyone impersonating as a router is indeed one, see, e.g., the trust
models and threats described in [11].
Future multi-access IPv6 networks may rely on SEND mechanisms, i.e.,
mechanisms developed in the SEND WG in order to mitigate the threats
described in [11], to establish a trust relations ship in between
host and routers.
Given that IPv4 source address spoofing is not possible in Zero-
Configuration Tunneling sites, then
- for an end-host to trust that packets it perceives as stemming
from tunnel servers do actually stem from such - as well as û
- for an end-host to trust on the benevolence of its tunnel
servers,
it suffices that a trustworthy tunnel server end-point discovery
mechanism, read discovery of benevolent tunnel servers IPv4
address(es), is implemented.
In open environments, such as, e.g., the 3GPP environment, it is
assumed a prerequisite that a trustworthy zero-configuration tunnel
server end-point discovery mechanism is implemented.
9.2.2. Threats to Tunnel Servers
Zero-Configuration Tunneling may be deployed over very large IPv4
sites with low density of active tunnel clients but with a very high
number of dormant, but potential tunnel clients. Therefore Denial of
Service prevention by strict over provisioning of Tunnel Server
capacity is unlikely to be performed.
9.2.2.1. Tunnel State related risks
If the Tunnel Server relies on state to be kept per tunnel client
that it serves, the server risks resource exhaustion.
In this situation it is a security prerequisite that no node, whether
located within or outside the Zero-Configuration Tunneling site, can
Nielsen, et. al. [Page 13]
INTERNET-DRAFT Zeroconf Tunneling Goals September, 2004
initiate initialization of tunnel state for other entities than
itself.
Given this prerequisite, then for tunnel server resource exhaustion
by tunnel state creation to be categorized as a security threat,
rather than a case of under provisioning, requires a large number of
tunnel clients to operate in co-action. This is thus not considered a
plausible threat.
9.2.2.2. Traffic related risks
Tunnel encapsulation is recognized as being more resource demanding
than mere packet forwarding. Given the same traffic load a Tunnel
Server must thus be more generously provisioned that a corresponding
router for it not to be more likely to get overthrown by large
unexpected amounts of traffic than the router.
The authors have found no plausible treats to the tunnel service, due
to large unexpected amounts of traffic needing encapsulation, which
can be classified as a security threat rather than a case of under
provision. This regardless of whether the traffic is due to a surge
in the density of active tunnel clients or due to a surge in the
traffic streams set-up by active clients.
9.2.2.3. Packet Delivery related threats
One potential risk related to packet delivery has been identified.
This risk is the equivalent of the threat to routers in multi-access
environments described in [11], Section 4.3.2.
The risk is associated with the special case where the tunnel
protocol requires special resource demanding and/or temporary state
creation actions to be taken by the Tunnel Server for delivery of
packets destined for not recently addressed Tunnel Clients. The
situation where such actions must be performed for all packets at all
times is considered to be unlikely. The actions required could be
buffering of packets while the reachability of the destined node is
being verified.
In case a malicious node (located either within or outside the zero-
configuration site) is able to continuously send packets to
continuously changing nodes, which by the Tunnel Server is perceived
as being existing or potential client nodes, the malicious node may
be able to exhaust the Tunnel Servers capability of delivering
packets by saturating the packet buffering mechanism and the
reachability state table as well as by keeping the Tunnel Server busy
determining the reachability state of the ever changing client nodes.
9.3. Implications of Direct Tunneling
Nielsen, et. al. [Page 14]
INTERNET-DRAFT Zeroconf Tunneling Goals September, 2004
In case direct tunneling in between end-hosts is provided by the
tunneling protocol, it will not (as described in Section 9.2.1) be
possibly for end-hosts to filter out received Protocol-41
encapsulated packets based on whether the IPv4 source is an address
belonging to a trusted Tunnel Server as such behavior evidently would
break direct tunneling.
As other end-hosts generally are non-trusted, direct tunneling may
thus open up for attacks against IPv6 ingress filtering.
Detailed analysis of the validity of this threat will have to depend
on the particular zero-configuration solution.
10. Acknowledgments
Prior work by J. Mulahusic on the requirements for UE tunneling has
been considered in the initial stage of the work.
This work has benefited from input and comments provided by Fred
Templin in the initial phase of the work.
Thanks are due to Pekka Savola for many helpful comments and
suggestions for improvements.
Corresponding work on assisted-tunneling, [5], has been an
inspiration for the Zero-Configuration Tunneling work.
The authors would like to acknowledge the European Commission support
in the co-funding of the Euro6IX project, where part of this work is
being developed.
11. Authors Addresses
Mario Morelli
Telecom Italia Lab.
Via Guglilmo Reiss Romoli, 274
I-10148 Turin,
Italy
Phone: +39 011 228 7790
Fax: +39 011 228 5069
Email: mario.morelli@tilab.com
Karen Egede Nielsen
Ericsson
Skanderborgvej 232
8260 Viby J
Denmark
Nielsen, et. al. [Page 15]
INTERNET-DRAFT Zeroconf Tunneling Goals September, 2004
Phone: + 45 89 38 51 00
Email: karen.e.nielsen@ericsson.com
Jordi Palet Martinez
Consulintel
San Jose Artesano, 1
Alcobendas - Madrid
E-28108 - Spain
Phone: +34 91 151 81 99
Fax: +34 91 151 81 98
EMail: jordi.palet@consulintel.es
Jonne Soininen
Nokia
Linnoitustie 6
02600 ESPOO
Finland
Phone: +358 7180 08000
EMail: jonne.soininen@nokia.com
Juha Wiljakka
Nokia
Visiokatu 3
33720 TAMPERE
Finland
Phone: +358 7180 48372
EMail: juha.wiljakka@nokia.com
12. Changes from draft-nielsen-v6ops-zeroconf-goals-00.txt
- Aimed to clarify what is meant by full suite of native Ipv6
connectivity functions.
- Aimed to clarify what is meant when referring to IPv6-in-IPv4
encapsulation as defined in [1].
- Aimed to clarify the accepted limitations of the IPv6
connectivity service provided by Zero-Configuration Tunneling
compared to the full suite of native IPv6
Nielsen, et. al. [Page 16]
INTERNET-DRAFT Zeroconf Tunneling Goals September, 2004
- Added that it is a prerequisite that Zero-Configuration
Tunneling can work over IPv4 networks where Ipv4 multicast is
not supported.
- Clarified goal, Section 6.3, on usage of native IPv6 when
available.
- Added goal on load sharing and scalability, Section 6.10.
- Added Section 8, discussing state or no state.
- Changed Section 6.8 on reachability detection to refer to
unicast Neighbor Discovery techniques rather than IPv6 NUD.
- Added material to the section on threats to tunnel servers,
9.2.2.
- Added section, Section 9.3, discussing particular security
considerations for usage of direct tunneling.
- Added text under Acknowledgements
- Specified references as informative.
- Performed various Editorial changes.
13. Informative References
[1] Nordmark, E., Basic Transition Mechanisms for IPv6 Hosts and
Routers, draft-ietf-v6ops-mech-v2-04.txt (work in progress),
July 2004.
[2] Lind, M., Scenarios and Analysis for Introducing IPv6 into ISP
Networks, draft-ietf-v6ops-isp-scenarios-analysis-03.txt (work
in progress), June 2004.
[3] Huitema, C., Evaluation of Transition Mechanisms for Unmanaged
Networks, draft-ietf-v6ops-unmaneval-03.txt (work in progress),
June 2004.
[4] Wiljakka, J., Analysis on IPv6 Transition in 3GPP Networks,
draft-ietf-v6ops-3gpp-analysis-10.txt (work in progress), May
2004.
[5] Durand, A., Requirements for assisted tunneling, draft-ietf-
v6ops-assisted-tunneling-requirements-00.txt (work in progress),
June 2004.
[6] Palet, J., Analysis of IPv6 Tunnel End-point Discovery
Mechanisms, draft-palet-v6ops-tun-auto-disc-01.txt (work in
progress), June 2004.
[7] Wasserman, M., Recommendations for IPv6 in 3GPP standards, RFC
3314.
[8] Loughney, J., IPv6 Node Requirements, draft-ietf-ipv6-node-
requirements-10.txt (work in progress), August 2004.
Nielsen, et. al. [Page 17]
INTERNET-DRAFT Zeroconf Tunneling Goals September, 2004
[9] IAB, IESG, IAB/IESG Recommendations on IPv6 Address Allocations
to Sites, RFC 3177.
[10] Savola, P., Security Considerations for 6to4, draft-ietf-v6ops-
6to4-security-04.txt (work in progress), July 2004.
[11] Nikander, P., IPv6 Neighbor Discovery (ND) Trust Models and
Threats, RFC 3756.
[12] Narten, T., Privacy Extensions for Stateless Address
Autoconfiguration in IPv6, RFC 3041.
[13] Narten, T., Neighbor Discovery for IP Version 6 (IPv6), RFC
2461.
[14] Jordi, P., draft-palet-v6ops-solution-tun-auto-disc-00 (work in
progress), September 2004.
Appendix A Out of Scope
[Editor's Note: This appendix can be removed in a future revision of
this document]
The following issues have been considered as being out of scope of
this work.
DNS:
DNS registration of the IPv6 addresses allocated to dual stack nodes
while deploying Zero-Configuration Tunneling for IPv6 connectivity.
Mobile IPv6:
Support of Mobile IPv6 usage over the tunnel-link; here under
potential mechanisms required to support MIPv6 movement detection as
well as fast tunnel set-up for Mobile IPv6 session survivability.
Appendix B Open Issues
[Editor's Note: This appendix can be removed in a future revision of
this document]
Allow NATs that support proto-41 forwarding:
Should the no NATs assumption be relaxed to allow only NATs which
support proto-41 forwarding ?
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
Nielsen, et. al. [Page 18]
INTERNET-DRAFT Zeroconf Tunneling Goals September, 2004
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 IETF's procedures with respect to rights in IETF Documents can
be found in RFC 3667 (BCP 78) and RFC 3668 (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.
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.
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.
This Internet-Draft expires March 2, 2005.
Nielsen, et. al. [Page 19]
| PAFTECH AB 2003-2026 | 2026-04-23 10:58:01 |