Unique Local IPv6 Unicast Addresses
draft-ietf-ipv6-unique-local-addr-09

INTERNET-DRAFT R. Hinden, Nokia
January 21, 2005 B. Haberman, JHU-APL
 Unique Local IPv6 Unicast Addresses
 <draft-ietf-ipv6-unique-local-addr-09.txt>
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 expires on July 26, 2005.
Abstract
 This document defines an IPv6 unicast address format that is globally
 unique and is intended for local communications, usually inside of a
 site. They are not expected to be routable on the global Internet.
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Table of Contents
 1.0 Introduction....................................................2
 2.0 Acknowledgments.................................................3
 3.0 Local IPv6 Unicast Addresses....................................3
 3.1 Format..........................................................3
 3.1.1 Background....................................................4
 3.2 Global ID.......................................................5
 3.2.1 Locally Assigned Global IDs...................................5
 3.2.2 Sample Code for Pseudo-Random Global ID Algorithm.............5
 3.2.3 Analysis of the Uniqueness of Global IDs......................6
 3.3 Scope Definition................................................7
 4.0 Operational Guidelines..........................................7
 4.1 Routing.........................................................7
 4.2 Renumbering and Site Merging....................................8
 4.3 Site Border Router and Firewall Packet Filtering................8
 4.4 DNS Issues......................................................9
 4.5 Application and Higher Level Protocol Issues....................9
 4.6 Use of Local IPv6 Addresses for Local Communications...........10
 4.7 Use of Local IPv6 Addresses with VPNs..........................11
 5.0 Global Routing Considerations..................................11
 5.1 From the Standpoint of the Internet............................11
 5.2 From the Standpoint of a Site..................................12
 6.0 Advantages and Disadvantages...................................12
 7.0 Security Considerations........................................13
 8.0 IANA Considerations............................................13
 9.0 References.....................................................13
 9.1 Normative References...........................................13
 9.2 Informative References.........................................14
 10.0 Authors' Addresses............................................15
 11.0 Change Log....................................................16
 12.0 Intellectual Property.........................................18
 13.0 Disclaimer of Validity........................................19
 14.0 Copyright Statement...........................................19
1.0 Introduction
 This document defines an IPv6 unicast address format that is globally
 unique and is intended for local communications [IPV6]. These
 addresses are called Unique Local IPv6 Unicast Addresses and are
 abbreviated in this document as Local IPv6 addresses. They are not
 expected to be routable on the global Internet. They are routable
 inside of a more limited area such as a site. They may also be
 routed between a limited set of sites.
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 Local IPv6 unicast addresses have the following characteristics:
 - Globally unique prefix (with high probability of uniqueness).
 - Well known prefix to allow for easy filtering at site
 boundaries.
 - Allows sites to be combined or privately interconnected without
 creating any address conflicts or requiring renumbering of
 interfaces using these prefixes.
 - Internet Service Provider independent and can be used for
 communications inside of a site without having any permanent or
 intermittent Internet connectivity.
 - If accidentally leaked outside of a site via routing or DNS,
 there is no conflict with any other addresses.
 - In practice, applications may treat these addresses like global
 scoped addresses.
 This document defines the format of Local IPv6 addresses, how to
 allocate them, and usage considerations including routing, site
 border routers, DNS, application support, VPN usage, and guidelines
 for how to use for local communication inside a site.
 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in [RFC 2119].
2.0 Acknowledgments
 The underlying idea of creating Local IPv6 addresses described in
 this document has been proposed a number of times by a variety of
 people. The authors of this draft do not claim exclusive credit.
 Credit goes to Brian Carpenter, Christian Huitema, Aidan Williams,
 Andrew White, Charlie Perkins, and many others. The authors would
 also like to thank Brian Carpenter, Charlie Perkins, Harald
 Alvestrand, Keith Moore, Margaret Wasserman, Shannon Behrens, Alan
 Beard, Hans Kruse, Geoff Huston, Pekka Savola, Christian Huitema, Tim
 Chown, Steve Bellovin, Alex Zinin, Tony Hain, Bill Fenner, Sam
 Hartman, and Elwyn Davies for their comments and suggestions on this
 document.
3.0 Local IPv6 Unicast Addresses
3.1 Format
 The Local IPv6 addresses are created using a pseudo-randomly
 allocated global ID. They have the following format:
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 | 7 bits |1| 40 bits | 16 bits | 64 bits |
 +--------+-+------------+-----------+-----------------------------+
 | Prefix |L| Global ID | Subnet ID | Interface ID |
 +--------+-+------------+-----------+-----------------------------+
 Where:
 Prefix FC00::/7 prefix to identify Local IPv6 unicast
 addresses.
 L Set to 1 if the prefix is locally assigned.
 Set to 0 may be defined in the future. See
 section 3.2 for additional information.
 Global ID 40-bit global identifier used to create a
 globally unique prefix. See section 3.2 for
 additional information.
 Subnet ID 16-bit Subnet ID is an identifier of a subnet
 within the site.
 Interface ID 64-bit Interface ID as defined in [ADDARCH].
3.1.1 Background
 There were a range of choices available when choosing the size of the
 prefix and Global ID field length. There is a direct tradeoff
 between having a Global ID field large enough to support foreseeable
 future growth and not using too much of the IPv6 address space
 needlessly. A reasonable way of evaluating a specific field length
 is to compare it to a projected 2050 world population of 9.3 billion
 [POPUL] and the number of resulting /48 prefixes per person. A range
 of prefix choices is shown in the following table:
 Prefix Global ID Number of Prefixes % of IPv6
 Length /48 Prefixes per Person Address Space
 /11 37 137,438,953,472 15 0.049%
 /10 38 274,877,906,944 30 0.098%
 /9 39 549,755,813,888 59 0.195%
 /8 40 1,099,511,627,776 118 0.391%
 /7 41 2,199,023,255,552 236 0.781%
 /6 42 4,398,046,511,104 473 1.563%
 A very high utilization ratio of these allocations can be assumed
 because the Global ID field does not require internal structure, and
 there is no reason to be able to aggregate the prefixes.
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 The authors believe that a /7 prefix resulting in a 41 bit Global ID
 space (including the L bit) is a good choice. It provides for a
 large number of assignments (i.e., 2.2 trillion) and at the same time
 uses less than .8% of the total IPv6 address space. It is unlikely
 that this space will be exhausted. If more than this were to be
 needed, then additional IPv6 address space could be allocated for
 this purpose.
3.2 Global ID
 The allocation of Global IDs is pseudo-random [RANDOM]. They MUST
 NOT be assigned sequentially or with well known numbers. This is to
 ensure that there is not any relationship between allocations and to
 help clarify that these prefixes are not intended to be routed
 globally. Specifically, these prefixes are not designed to
 aggregate.
 This document defines a specific local method to allocate Global IDs,
 indicated by setting the L bit to 1. Another method, indicated by
 clearing the L bit, may be defined later. Apart from the allocation
 method, all Local IPv6 addresses behave and are treated identically.
 The local assignments are self generated and do not need any central
 coordination or assignment, but have an extremely high probability of
 being unique.
3.2.1 Locally Assigned Global IDs
 Locally assigned Global IDs MUST be generated with a pseudo-random
 algorithm consistent with [RANDOM]. Section 3.2.2 describes a
 suggested algorithm. It is important that all sites generating
 Global IDs use a functionally similar algorithm to ensure there is a
 high probability of uniqueness.
 The use of a pseudo-random algorithm to generate Global IDs in the
 locally assigned prefix gives an assurance that any network numbered
 using such a prefix is highly unlikely to have that address space
 clash with any other network that has another locally assigned prefix
 allocated to it. This is a particularly useful property when
 considering a number of scenarios including networks that merge,
 overlapping VPN address space, or hosts mobile between such networks.
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3.2.2 Sample Code for Pseudo-Random Global ID Algorithm
 The algorithm described below is intended to be used for locally
 assigned Global IDs. In each case the resulting global ID will be
 used in the appropriate prefix as defined in section 3.2.
 1) Obtain the current time of day in 64-bit NTP format [NTP].
 2) Obtain an EUI-64 identifier from the system running this
 algorithm. If an EUI-64 does not exist, one can be created from
 a 48-bit MAC address as specified in [ADDARCH]. If an EUI-64
 cannot be obtained or created, a suitably unique identifier,
 local to the node, should be used (e.g. system serial number).
 3) Concatenate the time of day with the system-specific identifier
 creating a key.
 4) Compute an SHA-1 digest on the key as specified in [FIPS, SHA1];
 the resulting value is 160 bits.
 5) Use the least significant 40 bits as the Global ID.
 6) Concatenate FC00::/7, the L bit set to 1, and the 40 bit Global
 ID to create a Local IPv6 address prefix.
 This algorithm will result in a Global ID that is reasonably unique
 and can be used to create a locally assigned Local IPv6 address
 prefix.
3.2.3 Analysis of the Uniqueness of Global IDs
 The selection of a pseudo random Global ID is similar to the
 selection of an SSRC identifier in RTP/RTCP defined in section 8.1 of
 [RTP]. This analysis is adapted from that document.
 Since Global IDs are chosen randomly (and independently), it is
 possible that separate networks have chosen the same Global ID. For
 any given network with one or more random Global IDs that has inter-
 connections to other such networks, having a total of N such IDs, the
 probability that two or more of these IDs will collide can be
 approximated using the formula:
 P = 1 - exp(-N**2 / 2**(L+1))
 where P is the probability of collision, N is the number of
 interconnected Global IDs, and L is the length of the Global ID.
 The following table shows the probability of a collision for a range
 of connections using a 40 bit Global ID field.
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 Connections Probability of Collision
 2 1.81*10^-12
 10 4.54*10^-11
 100 4.54*10^-09
 1000 4.54*10^-07
 10000 4.54*10^-05
 Based on this analysis the uniqueness of locally generated Global IDs
 is adequate for sites planning a small to moderate amount of inter-
 site communication using locally generated Global IDs.
3.3 Scope Definition
 By default, the scope of these addresses is global. That is, they
 are not limited by ambiguity like the site-local addresses defined in
 [ADDARCH]. Rather, these prefixes are globally unique, and as such,
 their applicability is greater than site-local addresses. Their
 limitation is in the routability of the prefixes, which is limited to
 a site and any explicit routing agreements with other sites to
 propagate them (also see section 4.1). Also, unlike site-locals, a
 site may have more than one of these prefixes and use them at the
 same time.
4.0 Operational Guidelines
 The guidelines in this section do not require any change to the
 normal routing and forwarding functionality in an IPv6 host or
 router. These are configuration and operational usage guidelines.
4.1 Routing
 Local IPv6 addresses are designed to be routed inside of a site in
 the same manner as other types of unicast addresses. They can be
 carried in any IPv6 routing protocol without any change.
 It is expected that they would share the same Subnet IDs with
 provider based global unicast addresses if they were being used
 concurrently [GLOBAL].
 The default behavior of exterior routing protocol sessions between
 administrative routing regions must be to ignore receipt of and not
 advertise prefixes in the FC00::/7 block. A network operator may
 specifically configure prefixes longer than FC00::/7 for inter-site
 communication.
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 If BGP is being used at the site border with an ISP, the default BGP
 configuration must filter out any Local IPv6 address prefixes, both
 incoming and outgoing. It must be set both to keep any Local IPv6
 address prefixes from being advertised outside of the site as well as
 to keep these prefixes from being learned from another site. The
 exception to this is if there are specific /48 or longer routes
 created for one or more Local IPv6 prefixes.
 For link-state IGPs, it is suggested that a site utilizing IPv6 local
 addresses prefixes be contained either within one IGP domain or area.
 By containing an IPv6 local address prefix to a single link-state
 area or domain, the distribution of prefixes can be controlled.
4.2 Renumbering and Site Merging
 The use of Local IPv6 addresses in a site results in making
 communication using these addresses independent of renumbering a
 site's provider based global addresses.
 When merging multiple sites the addresses created with these prefixes
 are unlikely to need to be renumbered because all of the addresses
 have a high probability of being unique. Routes for each specific
 prefix would have to be configured to allow routing to work correctly
 between the formerly separate sites.
4.3 Site Border Router and Firewall Packet Filtering
 While no serious harm will be done if packets with these addresses
 are sent outside of a site via a default route, it is recommended
 that routers be configured by default to keep any packets with Local
 IPv6 addresses from leaking outside of the site and to keep any site
 prefixes from being advertised outside of their site.
 Site border routers and firewalls should be configured to not forward
 any packets with Local IPv6 source or destination addresses outside
 of the site unless they have been explicitly configured with routing
 information about specific /48 or longer Local IPv6 prefixes. This
 will ensure that packets with Local IPv6 destination addresses will
 not be forwarded outside of the site via a default route. The
 default behavior of these devices should be to install a "reject"
 route for these prefixes. Site border routers should respond with
 the appropriate ICMPv6 Destination Unreachable message to inform the
 source that the packet was not forwarded. [ICMPV6]. This feedback is
 important to avoid transport protocol timeouts.
 Routers that maintain peering arrangements between Autonomous Systems
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 throughout the Internet should obey the recommendations for site
 border routers unless configured otherwise.
4.4 DNS Issues
 At the present time AAAA and PTR records for locally assigned local
 IPv6 addresses are not recommended to be installed in the global DNS.
 The operational issues relating to this are beyond the scope of this
 document.
 For background on this recommendation, the concern about adding AAAA
 and PTR records to the global DNS for locally assigned Local IPv6
 addresses stems from the lack of complete assurance that the prefixes
 are unique. There is a small possibility that the same PTR record
 might be registered by two different organizations. Due to this
 concern, adding AAAA records is thought to be unwise because matching
 PTR records can not be registered
4.5 Application and Higher Level Protocol Issues
 Application and other higher level protocols can treat Local IPv6
 addresses in the same manner as other types of global unicast
 addresses. No special handling is required. This type of address
 may not be reachable, but that is no different from other types of
 IPv6 global unicast address. Applications need to be able to handle
 multiple addresses that may or may not be reachable at any point in
 time. In most cases this complexity should be hidden in APIs.
 From a host's perspective this difference shows up as different
 reachability than global unicast and could be handled by default that
 way. In some cases it is better for nodes and applications to treat
 them differently from global unicast addresses. A starting point
 might be to give them preference over global unicast, but fall back
 to global unicast if a particular destination is found to be
 unreachable. Much of this behavior can be controlled by how they are
 allocated to nodes and put into the DNS. However it is useful if a
 host can have both types of addresses and use them appropriately.
 Note that the address selection mechanisms of [ADDSEL], and in
 particular the policy override mechanism replacing default address
 selection, are expected to be used on a site where Local IPv6
 addresses are configured.
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4.6 Use of Local IPv6 Addresses for Local Communication
 Local IPv6 addresses, like global scope unicast addresses, are only
 assigned to nodes if their use has been enabled (via IPv6 address
 autoconfiguration [ADDAUTO], DHCPv6 [DHCP6], or manually). They are
 not created automatically in the way that IPv6 link-local addresses
 are and will not appear or be used unless they are purposely
 configured.
 In order for hosts to autoconfigure Local IPv6 addresses, routers
 have to be configured to advertise Local IPv6 /64 prefixes in router
 advertisements, or a DHCPv6 server must have been configured to
 assign them. In order for a node to learn the Local IPv6 address of
 another node, the Local IPv6 address must have been installed in a
 naming system (e.g., DNS, proprietary naming system, etc.) For these
 reasons, it is straight forward to control their usage in a site.
 To limit the use of Local IPv6 addresses the following guidelines
 apply:
 - Nodes that are to only be reachable inside of a site: The local
 DNS should be configured to only include the Local IPv6
 addresses of these nodes. Nodes with only Local IPv6 addresses
 must not be installed in the global DNS.
 - Nodes that are to be limited to only communicate with other
 nodes in the site: These nodes should be set to only
 autoconfigure Local IPv6 addresses via [ADDAUTO] or to only
 receive Local IPv6 addresses via [DHCP6]. Note: For the case
 where both global and Local IPv6 prefixes are being advertised
 on a subnet, this will require a switch in the devices to only
 autoconfigure Local IPv6 addresses.
 - Nodes that are to be reachable from inside of the site and from
 outside of the site: The DNS should be configured to include
 the global addresses of these nodes. The local DNS may be
 configured to also include the Local IPv6 addresses of these
 nodes.
 - Nodes that can communicate with other nodes inside of the site
 and outside of the site: These nodes should autoconfigure global
 addresses via [ADDAUTO] or receive global address via [DHCP6].
 They may also obtain Local IPv6 addresses via the same
 mechanisms.
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4.7 Use of Local IPv6 Addresses with VPNs
 Local IPv6 addresses can be used for inter-site Virtual Private
 Networks (VPN) if appropriate routes are set up. Because the
 addresses are unique these VPNs will work reliably and without the
 need for translation. They have the additional property that they
 will continue to work if the individual sites are renumbered or
 merged.
5.0 Global Routing Considerations
 Section 4.1 provides operational guidelines that forbid default
 routing of local addresses between sites. Concerns were raised to
 the IPv6 working group and to the IETF as a whole that sites may
 attempt to use local addresses as globally routed provider-
 independent addresses. This section describes why using local
 addresses as globally-routed provider-independent addresses is
 unadvisable.
5.1 From the Standpoint of the Internet
 There is a mismatch between the structure of IPv6 local addresses and
 the normal IPv6 wide area routing model. The /48 prefix of an IPv6
 local addresses fits nowhere in the normal hierarchy of IPv6 unicast
 addresses. Normal IPv6 unicast addresses can be routed
 hierarchically down to physical subnet (link) level and only have to
 be flat-routed on the physical subnet. IPv6 local addresses would
 have to be flat-routed even over the wide area Internet.
 Thus, packets whose destination address is an IPv6 local address
 could be routed over the wide area only if the corresponding /48
 prefix were carried by the wide area routing protocol in use, such as
 BGP. This contravenes the operational assumption that long prefixes
 will be aggregated into many fewer short prefixes, to limit the table
 size and convergence time of the routing protocol. If a network uses
 both normal IPv6 addresses [ADDARCH] and IPv6 local addresses, these
 types of address will certainly not aggregate with each other, since
 they differ from the most significant bit onwards. Neither will IPv6
 local addresses aggregate with each other, due to their random bit
 patterns. This means that there would be a very significant
 operational penalty for attempting to use IPv6 local address prefixes
 generically with currently known wide area routing technology.
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5.2 From the Standpoint of a Site
 There are a number of design factors in IPv6 local addresses that
 reduce the likelihood that IPv6 local addresses will be used as
 arbitrary global unicast addresses. These include:
 - The default rules to filter packets and routes make it very
 difficult to use IPv6 local addresses for arbitrary use across
 the Internet. For a site to use them as general purpose unicast
 addresses, they would have to make sure that the default rules
 were not being used by all other sites and intermediate ISPs
 used for their current and future communication.
 - They are not mathematically guaranteed to be unique and are not
 registered in public databases. Collisions, while highly
 unlikely, are possible and a collision can compromise the
 integrity of the communications. The lack of public
 registration creates operational problems.
 - The addresses are allocated randomly. If a site had multiple
 prefixes that they wanted to be used globally the cost of
 advertising them would be very high as they could not be
 aggregated.
 - They have a long prefix (i.e, /48) so a single local address
 prefix doesn't provide enough address space to be used
 exclusively by the largest organizations.
6.0 Advantages and Disadvantages
6.1 Advantages
 This approach has the following advantages:
 - Provides Local IPv6 prefixes that can be used independently of
 any provider based IPv6 unicast address allocations. This is
 useful for sites not always connected to the Internet or sites
 that wish to have a distinct prefix that can be used to localize
 traffic inside of the site.
 - Applications can treat these addresses in an identical manner as
 any other type of global IPv6 unicast addresses.
 - Sites can be merged without any renumbering of the Local IPv6
 addresses.
 - Sites can change their provider based IPv6 unicast address
 without disrupting any communication using Local IPv6 addresses.
 - Well known prefix that allows for easy filtering at site
 boundary.
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 - Can be used for inter-site VPNs.
 - If accidently leaked outside of a site via routing or DNS, there
 is no conflict with any other addresses.
6.2 Disadvantages
 This approach has the following disadvantages:
 - Not possible to route Local IPv6 prefixes on the global Internet
 with current routing technology. Consequentially, it is
 necessary to have the default behavior of site border routers to
 filter these addresses.
 - There is a very low probability of non-unique locally assigned
 Global IDs being generated by the algorithm in section 3.2.3.
 This risk can be ignored for all practical purposes, but it
 leads to a theoretical risk of clashing address prefixes.
7.0 Security Considerations
 Local IPv6 addresses do not provide any inherent security to the
 nodes that use them. They may be used with filters at site
 boundaries to keep Local IPv6 traffic inside of the site, but this is
 no more or less secure than filtering any other type of global IPv6
 unicast addresses.
 Local IPv6 addresses do allow for address-based security mechanisms,
 including IPsec, across end to end VPN connections.
8.0 IANA Considerations
 The IANA is instructed to assign the FC00::/7 prefix for Unique Local
 IPv6 unicast addresses.
9.0 References
9.1 Normative References
 [ADDARCH] Hinden, R., S. Deering, S., "IP Version 6 Addressing
 Architecture", RFC 3513, April 2003.
 [FIPS] "Federal Information Processing Standards Publication",
 (FIPS PUB) 180-1, Secure Hash Standard, 17 April 1995.
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 [GLOBAL] Hinden, R., S. Deering, E. Nordmark, "IPv6 Global Unicast
 Address Format", RFC 3587, August 2003.
 [ICMPV6] Conta, A., S. Deering, "Internet Control Message Protocol
 (ICMPv6) for the Internet Protocol Version 6 (IPv6)
 Specification", RFC2463, December 1998.
 [IPV6] Deering, S., R. Hinden, "Internet Protocol, Version 6
 (IPv6) Specification", RFC 2460, December 1998.
 [NTP] Mills, David L., "Network Time Protocol (Version 3)
 Specification, Implementation and Analysis", RFC 1305,
 March 1992.
 [RANDOM] Eastlake, D. 3rd, S. Crocker, J. Schiller, "Randomness
 Recommendations for Security", RFC 1750, December 1994.
 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
 Requirement Levels", RFC 2119, BCP14, March 1997.
 [SHA1] D. Eastlake 3rd, P. Jones, "US Secure Hash Algorithm 1
 (SHA1)", RFC 3174, September 2001.
9.2 Informative References
 [ADDAUTO] Thomson, S., T. Narten, "IPv6 Stateless Address
 Autoconfiguration", RFC 2462, December 1998.
 [ADDSEL] Draves, R., "Default Address Selection for Internet
 Protocol version 6 (IPv6)", RFC 3484, February 2003.
 [DHCP6] Droms, R., et. al., "Dynamic Host Configuration Protocol
 for IPv6 (DHCPv6)", RFC3315, July 2003.
 [POPUL] Population Reference Bureau, "World Population Data Sheet
 of the Population Reference Bureau 2002", August 2002.
 [RTP] Schulzrinne, H., S. Casner, R. Frederick, V. Jacobson,
 "RTP: A Transport Protocol for Real-Time Applications"
 RFC3550, July 2003.
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10.0 Authors' Addresses
 Robert M. Hinden
 Nokia
 313 Fairchild Drive
 Mountain View, CA 94043
 USA
 phone: +1 650 625-2004
 email: bob.hinden@nokia.com
 Brian Haberman
 Johns Hopkins University
 Applied Physics Lab
 11100 Johns Hopkins Road
 Laurel, MD 20723
 USA
 phone: +1 443 778 1319
 email: brian@innovationslab.net
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11.0 Change Log
 Draft <draft-ietf-ipv6-unique-local-addr-09.txt>
 o Removed all mention of centrally assigned IPv6 local address
 addresses based on IESG comments. L=0 is left to be defined in
 the future.
 o Added new section titled "Global Routing Considerations" that
 discusses the issues relating to why using these addresses for
 general purpose unicast address on the global internet is not a
 good idea.
 o Several editorial changes.
 Draft <draft-ietf-ipv6-unique-local-addr-08.txt>
 o Moved sections 4-10, into one new section 4.0 titled
 "operational guidelines" to clarify the their scope.
 o Clarified routing requirements to make it clearer that these
 prefixes should not be routed on the global Internet.
 o Various editorial changes.
 Draft <draft-ietf-ipv6-unique-local-addr-07.txt>
 o Changed the format in section 3.1 in add a "L" (local/central)
 bit and reduced the size of the global-ID to 40 bits. This is
 equivalent to the previous separate prefixes and makes the
 document clearer.
 o Changed pseudo-random algorithm to use SHA-1 instead of MD5.
 o Moved [POPUL] to be an informative reference.
 o Added paragraph in Routing section to discuss the use of IGPs.
 o Various editorial changes.
 Draft <draft-ietf-ipv6-unique-local-addr-06.txt>
 o Clarify text to permit prefixes longer than /48 to be
 configured.
 o Changed text in section 7.0 to recommend that locally assigned
 IPv6 local addresses are not installed in the global DNS and
 removed text about consequences of if they were installed in the
 global DNS.
 o Clarify the text in section 5.1 to state that there is a high
 probability that there will be no address conflict when
 renumbering.
 o Several minor editorial changes.
 Draft <draft-ietf-ipv6-unique-local-addr-05.txt>
 o Removed the definition and technical requirements for centrally
 assigned local address. The Centrally assigned local addresses
 will be defined in a separate document. This document defines
 the specific prefixes to be used for centrally and locally
 assigned IPv6 local addresses, but only the locally assigned
 local addresses are defined here.
draft-ietf-ipv6-unique-local-addr-09.txt [Page 16]
INTERNET-DRAFT Unique Local IPv6 Unicast Addresses January 2005
 Draft <draft-ietf-ipv6-unique-local-addr-04.txt>
 o Clarified text in section 3.2.1 that central assigned prefixes
 should be assigned under the authority of a single allocation
 organization.
 o Added step to suggested pseudo-random algorithm that in the case
 of centrally assigned prefixes the computed Global IDs should be
 verified against the escrow.
 o Added new text to section 3.2.2 that explains in more detail the
 need for pseudo-random Global IDs (i.e., avoid duplicate
 allocations).
 o Rewrote section 7.0 to describe DNS AAAA and PTR records, and
 clarify when they might be installed in the global DNS.
 o Various editorial changes.
 Draft <draft-ietf-ipv6-unique-local-addr-03.txt>
 o Removed requirement of a fee per central allocation and updated
 IANA considerations to reflect this. Rewrote text to focus on
 the requirement to avoid hoarding of allocations.
 o Changed "filtering" and "black hole routes" to "reject" routes.
 o Changed uppers case requirements (i.e., MUST, SHOULD, etc.) to
 lower case in sections giving operational advice.
 o Removed paragraph mentioning "Multicast DNS".
 o Various editorial changes.
 Draft <draft-ietf-ipv6-unique-local-addr-02.txt>
 o Removed mention of 10 euro charge and changed text in section
 3.2.1 and IANA considerations to restate the requirement for low
 cost allocations and added specific requirement to prevent
 hording.
 o Added need to send ICMPv6 destination unreachable messages if
 packets are filtered or dropped at site boundaries.
 o Changed format section to list prefix sizes and definition, and
 changed discussion of prefix sizes to new background section.
 o Various editorial changes.
 Draft <draft-ietf-ipv6-unique-local-addr-01.txt>
 o Removed example of PIR as an example of an allocation authority
 and clarified the text that the IANA should delegate the
 centrally assigned prefix to an allocation authority.
 o Changed sample code for generating pseudo random Global IDs to
 not require any human input. Changes from using birthday to
 unique token (e.g., EUI-64, serial number, etc.) available on
 machine running the algorithm.
 o Added a new section analyzing the uniqueness properties of the
draft-ietf-ipv6-unique-local-addr-09.txt [Page 17]
INTERNET-DRAFT Unique Local IPv6 Unicast Addresses January 2005
 pseudo random number algorithm.
 o Added text to recommend that centrally assigned local addresses
 be used for site planning extensive inter-site communication.
 o Clarified that domain border routers should follow site border
 router recommendations.
 o Clarified that AAAA DNS records should not be installed in the
 global DNS.
 o Several editorial changes.
 Draft <draft-ietf-ipv6-unique-local-addr-00.txt>
 o Changed file name to become an IPv6 w.g. group document.
 o Clarified language in Routing and Firewall sections.
 o Several editorial changes.
 Draft <draft-hinden-ipv6-global-local-addr-02.txt>
 o Changed title and name of addresses defined in this document to
 "Unique Local IPv6 Unicast Addresses" with abbreviation of
 "Local IPv6 addresses".
 o Several editorial changes.
 Draft <draft-hinden-ipv6-global-local-addr-01.txt>
 o Added section on scope definition and updated application
 requirement section.
 o Clarified that, by default, the scope of these addresses is
 global.
 o Renumbered sections and general text improvements
 o Removed reserved Global ID values
 o Added pseudo code for local allocation submitted by Brian
 Haberman and added him as an author.
 o Split Global ID values into centrally assigned and local
 assignments and added text to describe local assignments
 Draft <draft-hinden-ipv6-global-local-addr-00.txt>
 o Initial Draft
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 made any independent effort to identify any such rights. Information
draft-ietf-ipv6-unique-local-addr-09.txt [Page 18]
INTERNET-DRAFT Unique Local IPv6 Unicast Addresses January 2005
 on the procedures with respect to rights in RFC documents can be
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 except as set forth therein, the authors retain all their rights.
draft-ietf-ipv6-unique-local-addr-09.txt [Page 19]