Internet DRAFT - draft-hain-templin-ipv6-limitedrange
draft-hain-templin-ipv6-limitedrange
IPv6 Working Group T. Hain
Internet-Draft Cisco Systems, Inc.
Expires: February 26, 2004 F. Templin
Nokia
August 28, 2003
Goals for an Addressing Scheme to Support Local Communications within
Sites
draft-hain-templin-ipv6-limitedrange-02.txt
Status of this Memo
This document is an Internet-Draft and is in full conformance with
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This Internet-Draft will expire on February 26, 2004.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
The IPv6 addressing architecture specifies global and local-use
unicast addressing schemes, but provides no operational guidelines
for their use. There is a perceived need for an addressing scheme
that supports local communications within sites. Of special interest
are "active sites", e.g., sites that are intermittently-connected or
disconnected from the global Internet, sites that frequently change
provider points of attachment, sites that temporarily or permanently
merge with other sites, multi-homed sites, etc. This memo will
discuss goals for an addressing scheme to support local
communications within sites.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1 Easy to Acquire . . . . . . . . . . . . . . . . . . . . . . 4
3.2 Stable . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.3 Multiple Link Support . . . . . . . . . . . . . . . . . . . 4
3.4 Well-known Prefix . . . . . . . . . . . . . . . . . . . . . 4
3.5 Globally Unique . . . . . . . . . . . . . . . . . . . . . . 5
3.6 Usable in the Absence of a Provider . . . . . . . . . . . . 5
3.7 Applicable in Managed/Unmanaged Environments . . . . . . . . 6
3.8 Compatible with Site Naming System . . . . . . . . . . . . . 6
3.9 Compatible with VPN . . . . . . . . . . . . . . . . . . . . 6
3.10 Multiple Addressing . . . . . . . . . . . . . . . . . . . . 6
4. Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.1 Border Filtering . . . . . . . . . . . . . . . . . . . . . . 7
4.2 Maintaining Confidentiality of the Address Space . . . . . . 7
4.3 Test Networks . . . . . . . . . . . . . . . . . . . . . . . 7
4.4 Address Caching . . . . . . . . . . . . . . . . . . . . . . 7
4.5 Mobile Router with Personal Area Network . . . . . . . . . . 7
4.6 Mobile Ad-hoc Networks (MANETs) . . . . . . . . . . . . . . 8
4.7 Asset Protection in Enterprise Networks . . . . . . . . . . 9
4.8 Home Networks . . . . . . . . . . . . . . . . . . . . . . . 9
5. Perceived Advantages of Limited Range Addressing Solutions . 10
6. Appeal for Alternative Proposals . . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . 11
8. Security Considerations . . . . . . . . . . . . . . . . . . 11
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
Normative References . . . . . . . . . . . . . . . . . . . . 11
Informative References . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 12
A. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 12
Intellectual Property and Copyright Statements . . . . . . . 13
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1. Introduction
The IPv6 addressing architecture [RFC3513] specifies global and
local-use unicast addresses. Global addresses are understood to have
unlimited range and may be used as the source and destination
addresses in packets that originate from any point on the connected
global IPv6 Internet. Local-use addresses are intended for use only
within the range of a single link/site, but their specification does
not address operational considerations and does not account for the
esoteric nature of terms such as "site".
There is a perceived need for an addressing scheme that supports
local communications within sites. Of special interest are "active
sites", e.g., sites that are intermittently-connected or disconnected
from the global Internet, sites that frequently change provider
points of attachment, sites that temporarily or permanently merge
with other sites, multi-homed sites, etc. This memo will discuss
goals for an addressing scheme to support local communications within
sites in the context of real world deployment scenarios.
2. Terminology
site:
an entity autonomously operating a network using IP and, in
particular, determining the addressing plan and routing policy for
that network. This is the same definition as [RFC3582].
active site:
a site that may be intermittently-connected or disconnected from
the global Internet, may frequently change provider points of
attachment, may have multiple concurrent provider points of
attachment, may temporarily or permanently merge with other sites,
etc.
range:
domain of applicability.
limited range:
a range bounded by, e.g., routing policies, filters, etc.
PI:
Provider Independent
PA:
Provider Aggregated
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VPN:
Virtual Private Network
3. Goals
There is a perceived need for an addressing scheme that supports
local communications within sites. One obvious solution alternative
is an easy-to-get, stable, PI space for use within a limited range as
this is consistent with current practices familiar to IPv4 network
managers. The following sections present goals that should be met by
any solution proposal. Proposals should be brought forward in a
timely fashion so that their merits can be evaluated with respect to
these goals.
3.1 Easy to Acquire
Some portion of the address space should be made available that
requires no public registration, payment, customer/provider
relationship, or approval. These addresses should be architecturally
supported and end-user-controlled.
3.2 Stable
Applications that enable local communications should use addresses
that support session stability (i.e., connection survivability)
during intermittent connectivity, site mergers, change to a new
provider, etc. In particular, session stability should not be
affected by renumbering events [BAKER].
3.3 Multiple Link Support
Addresses for local communications within sites should support
operation over multiple links, e.g., via L3 routing, L2 bridging or
some combination thereof. As such, subnetting consistent with the
recommendations in ([RFC3177], section 3) should be supported.
Link-local addresses in IPv6: "are designed to be used for addressing
on a single link for purposes such as automatic address
configuration, neighbor discovery, or when no routers are present"
([RFC3513], section 2.5.6). By definition, link-local addresses have
a single link range of operation and will not meet this goal.
3.4 Well-known Prefix
Placing portions of the address space in a common short prefix allows
everyone to filter it which prevents unwanted exposure in the case of
single point configuration errors. In this solution alternative, the
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common prefix should not end up in the global routing system, even
accidentally.
Addressing scheme proposals that use a well-known prefix provide
applications that choose to check with a hint that a filtering policy
has been applied somewhere in the network, though it does not by
itself indicate where the boundaries are. Proposals should state
clearly how filtering, privacy, etc will be supported.
3.5 Globally Unique
Addresses used by sites should be globally unique such that site
mergers will not result in collisions. Global uniqueness is based on
the statistical properties of address allocations, therefore
proposals should specify a suitable means for random prefix
generation. Addressing scheme proposals should also provide a
suitable means for conflict resolution, e.g., certification through a
central registry, distributed database, etc.
Sufficient global uniqueness is needed to support, e.g.:
o VPNs between enterprises
o dynamically created VPNs in support of temporary virtual
organizations
o service provider co-location of hosts that reside in the address
space of multiple customers
o formation of virtual organizations (Grids) among enterprises
o mergers and acquisitions of enterprises such that address spaces
do not collide
Achieving these goals does not require absolute uniqueness, but an
extremely low probability of collisions resulting in conflict is
desired. Proposals should therefore provide statistical analysis of
the uniqueness properties of the addressing scheme.
3.6 Usable in the Absence of a Provider
Active sites need addresses that can be used when there is no active
link to a provider. In the case of intermittently-connected sites,
provider access may be unavailable for long periods but this should
not disrupt local communications within the site. In the case of
sites moving to new provider points of attachment, frequent
renumbering events may occur but, again, local communications should
not be disrupted.
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PI addresses provide one solution alternative genre that also
appliies to cases where network managers want global access. The
issue is that PI addresses with no designed aggregation properties
may lead to global routing table explosion (if advertised outside the
site) given current routing technologies. For this reason, PI
addressing scheme proposals should either provide reasonable
aggregation properties or a detailed analysis of their interactions
with global routing technologies. PA and other non-PI proposals
should explain how the proposed addressing schemes will support local
communications in the presence of intermittent and/or disconnected
provider access.
3.7 Applicable in Managed/Unmanaged Environments
Some sites (e.g., large enterprises) may have network management
teams responsible for address planning while others (e.g., home
networks and personal area networks) may require unmanaged operation.
Addressing scheme proposals should provide general applicability in
any environment - be it managed or unmanaged.
3.8 Compatible with Site Naming System
Addresses for local communications within sites should be compatible
with the site's naming system. Examples include DNS, multicast name
resolution, static configuration, etc. In practice, it is expected
that addresses will be resolved only within the range of operation of
the naming system.
3.9 Compatible with VPN
Proposed addressing schemes should support VPN connections between
multiple sites, e.g., to form geographically-extended organizations.
Prefix delegations in effect at each constituent site should remain
valid when connected via VPN.
3.10 Multiple Addressing
Proposals that support concurrent use of limited & global range
addresses allow nodes in the site to implement individual security
policies about global visibility. This moves the security policy
decision from the edge to the originating device, which allows the
application which has enough information decide the appropriate
action. In the case of devices that move between subnets, it also
mitigates the need for continuous changes of access controls at the
edge.
Proposals that do not support multiple addressing should state
clearly how security policies can be enforced. In particular, they
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should clearly state how the originating devices can implement
security policies without the need for edge intervention when only a
single address is available.
4. Scenarios
Many anticipated IPv6 deployment scenarios require an addressing
scheme that meets the goals outlined in Section 3. Such an addressing
scheme should have general application and should minimally satisfy
the example scenarios outlined in the following subsections:
4.1 Border Filtering
Network managers limit specific applications to internal use, so they
configure them to only work with a filtered address range. This
simplifies the border filter to an address prefix, rather than
needing to employ deep packet inspection to track a potentially
dynamic range of ports.
4.2 Maintaining Confidentiality of the Address Space
Private space may be used to avoid exposing to competitors what
internal networks they are deploying and which office is coordinating
that effort. Network managers also don't have to expose business
plans to a registrar for evaluation for networks that are not
attached to the global Internet. Some have stated that if they are
required to register for public space for every internal use network,
they are more likely to pick random numbers than tip off the
competition.
4.3 Test Networks
Another significant use of private address space is test networks.
Frequently these are large, elaborate networks with a mix of public
and private address space. Use of random unallocated space runs the
risk of collision with legitimate addresses on remote networks.
4.4 Address Caching
Applications that cache IP addresses in ACLs or configurations are
susceptible to operational problems due to site renumbering. Examples
include license servers that use IP addresses, firewalls within the
site, web site access mechanisms to allow access to only certain
subnets, etc. Stable addressing for local communications within sites
is needed to satisfy such scenarios.
4.5 Mobile Router with Personal Area Network
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Multiaccess terminals that serve as routers between the operator and
a personal area network (PAN) of the user's locally-connected devices
are seen as a near-term deployment scenario. Access to the operator
may be intermittent, yet local communications within the PAN should
be supported even when no connection to the global Internet is
available. As mobile users travel about, multiple PANs may come
together in a common space such that two or more PANs merge. As such,
the address prefixes used in each PAN should be globally unique to
avoid collisions and provide a means for verifying ownership to
resolve conflicts.
4.6 Mobile Ad-hoc Networks (MANETs)
Numerous aspects of MANETs provide challenges for addressing schemes
that support local communications. The following scenarios provide
some specific examples:
4.6.1 Nomadic Nodes that form Temporal MANETs
Nomadic nodes with no pre-defined group affiliation are in actuality
singleton sites that may from time to time merge with other such
"sites" as they move about to form MANETs. Such MANETs may exist only
temporarily in space/time, but should allow local communications
between nodes even during rapidly-changing MANET dynamics. Therefore
each such nomadic node should have a pre-configured address that can
be injected into the intra-MANET routing protocol during the duration
of its visit to any such temporal MANET.
4.6.2 Groups of Nodes that Travel Together
As with the mobile PAN in Section 4.2, mobile ad-hoc networks of
nodes that travel together as a group may have long periods of
intermittent/disconnected access to the global Internet. Such
applications as disaster relief, coordinated missions, and
expeditionary forces may comprise numerous ad-hoc networks that may
merge, partition, or lose global connectivity from time to time. An
addressing scheme is needed for the continuous support of local
communications in such mobile ad-hoc networks.
4.6.3 Vehicular Networks
Vehicular networks may connect elements in an automobile to provide
sensory and situational awareness data to the driver. Periodic
contact with roadside Internet access points, other vehicles, etc.
may entail sharing public information (e.g., road conditions
encountered) while protecting private information (e.g., the
vehicle's speedometer reading). The addressing scheme should provide
a means for denoting both public and private components, e.g., for
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filtering at site borders.
Research ships at sea intermittently connect via INMARSAT, or when in
port, the shipboard network is connected to shore via Ethernet. Of
utmost importance is that the systems on board the ship all function,
providing data collection and analysis without interruption. Static
addressing is used on most intra-ship network components and servers.
It's quite expensive to operate a research ship, so eliminating
points of failure is important. Scientists on board collaborate with
colleagues back home by sharing of data and email. Currently private
address space is employed for several reasons: 1) it provides the
ability to allocate significant address space to each ship without
needing to worry about how many computers will be on a given cruise.
2) it provides separate address space for each ship. 3) it simplifies
filtering to ensure shipboard traffic is not permitted to transmit
out or bring up expensive satellite links.
4.7 Asset Protection in Enterprise Networks
Enterprise networks that protect private corporate assets (e.g.,
printers, faxes, robotics, sensors, etc.) require an addressing
scheme that remains stable even when VPN connections from outside
sites occur. Such VPN connections may arise from home users,
corporate mergers and acquisitions, bridging remote sites together,
etc. Prefixes used for protecting private assets should not end up in
the global routing system, even by accident.
4.8 Home Networks
Home networks with intermittent access to a service provider require
an addressing scheme that supports local communications even when the
service is unavailable. The addressing scheme should also protect
private assets from exposure to the global Internet and should allow
continuous operation when VPN connections to the office or other
extended sites are used.
An example chain of events that may arise in Home Networks and other
scenarios is:
o site A sets up a local network with no ISP connection; the network
should "just work" out of the box
o site A later connects to an ISP for external connectivity, but
uses filtering to avoid exposing internal addressing to the
outside
o in the meantime, site B performs corresponding actions
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o sometime later, sites A and B connect, e.g., via VPN, shared link,
etc. The sites can send local traffic to each other as well as
traffic out either of the sites' ISPs
o sometime later, site A disconnects from its ISP and site B's ISP
is used
o sometime later, site A disconnects from site B
o sometime later, site A registers with a new ISP
Such chains of events should not disrupt local communications within
sites A and B.
5. Perceived Advantages of Limited Range Addressing Solutions
Limited range addressing solutions allow filtering, and filtering
creates addressing boundaries no matter where the bits come from. The
point is that some addresses are only valid within the range defined
by the local network manager.
In the simple case, hosts that are allowed external access have a
policy that allows them to configure both global and limited range
prefixes, while those that are not allowed global access have a
policy that only allows limited range. Address selection policy
tables might need modifications to enable the selection of limited
range address space over global addresses. Given such modifications,
address selection rules will prefer the smallest range so internal
communications are forced to stay internal by the hard filter at the
border.
If an application chooses to assert a policy that is different from
the network manager's filtering rules, it will fail. Having a well
defined limited range address space that is known to have filtering
applied allows applications to have a hint about potential range
restrictions. We can choose to leave the network managers to figure
out their own adhoc mechanisms, or we can put them in a structured
limited range address space so that applications will have a chance
to react appropriately.
6. Appeal for Alternative Proposals
A limited range addressing scheme would seem a logical choice to
satisfy the requirements and real-life scenarios outlined in this
document, but the authors recognize that it may not be the ONLY
choice. Alternative solution proposals should be made available in a
timely fashion through full disclosure to the public domain so that
their merits can be evaluated. Such proposals should state clearly
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how they address the goals outlined in this document and should
include mathematical formulas analyzing the likelyhood of duplicate
address assignment, analysis of effects on address selection,
filtering/privacy considerations, etc.
7. IANA Considerations
This document does not introduce any IANA requirements.
8. Security Considerations
The concept of route filtering is frequently used as a tool to aid in
network security, so having a well-known range to filter enhances the
deployment of that tool.
Access control is one aspect of what limited range addressing
provides. It is a clear address space that service providers can put
in filters, and enterprise managers can filter without having to go
into detail about which specific devices on a subnet are allowed. It
does not comprise a full service security solution, and should not be
represented as such.
9. Acknowledgements
The authors acknowledge the contributions of numerous posts on the
ipng mailing list [IPNG] that led to a better understanding of the
issues. The following individuals are noted for their contributions:
Brian Carpenter, Tim Hartrick, Eliot Lear, Chirayu Patel, Michel Py,
Pekka Savola, Daniel Senie, Stephen Sprunk, Michael Thomas, and
Andrew White.
Normative References
[RFC3513] Hinden, R. and S. Deering, "Internet Protocol Version 6
(IPv6) Addressing Architecture", RFC 3513, April 2003.
Informative References
[BAKER] Baker, F., "Procedures for Renumbering an IPv6 Network
without a Flag Day",
draft-baker-ipv6-renumber-procedure-00 (work in progress),
April 2003.
[IPNG] "IPng mailing list archive: ftp://playground.sun.com/pub/
ipng/mail-archive".
[RFC3177] IAB and IESG, "IAB/IESG Recommendations on IPv6 Address",
RFC 3177, September 2001.
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[RFC3582] Abley, J., Black, B. and V. Gill, "Goals for IPv6
Site-Multihoming Architectures", RFC 3582, August 2003.
Authors' Addresses
Tony Hain
Cisco Systems, Inc.
500 108th Ave. NE
Bellevue, WA
EMail: alh-ietf@tndh.net
Fred L. Templin
Nokia
313 Fairchild Drive
Mountain View, CA 94043
Phone: +1 650 625 2331
EMail: ftemplin@iprg.nokia.com
Appendix A. Change Log
Changes since draft-01:
o Changed document ID; title
o Changed "Requirements" "to "Goals" in several places
o Incorporated comments from Chirayu Patel, Pekka Savola
o Expanded "scenarios" section with several new subsections,
including nomadic nodes in MANETs.
o Removed appendices
o Updated reference for RFC3582.
Changes since draft-00:
o Changed title, and removed linkage of requirements and the
particular solution alternative referred to as "limited range
addressing" in the previous draft. Thanks to Eliot Lear and
Michael Thomas for suggesting the change.
o Added real life example scenario from Andrew White
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