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Versions: 00 01 02 03 RFC 3750

INTERNET DRAFT                                              C. Huitema
<draft-ietf-v6ops-unman-scenarios-00.txt>                    Microsoft
January 10, 2003                                            R. Austein
Expires July 10, 2003                              Bourgeois Dilettant
                                                        R. van der Pol
                                                            NLnet Labs

          Unmanaged Networks IPv6 Transition Scenarios

Status of this memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   This document is an Internet-Draft. 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.

Abstract

   In order to evaluate the suitability of transition mechanisms, we
   need to define the scenarios in which these mechanisms have to be
   used. One specific scope is the "unmanaged networks", which
   typically correspond to home networks or small office networks.

1       Introduction

   In order to evaluate the suitability of transition mechanisms, we
   need to define the environment or scope in which these mechanisms
   have to be used. One specific scope is the "unmanaged networks",
   which typically correspond to home networks or small office
   networks.

2       Topology

   The typical unmanaged network is composed of a single subnet,
   connected to the Internet through a single Internet Service Provider
   (ISP)connection. Several hosts are connected to the subnet:





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      +------+
      | Host +--+
      +------+  |
                |
      +------+  |
      | Host +--+                         +--------------
      +------+  |                         |
                :                   +-----+
                :  +---------+      |     |
                +--+ Gateway +------| ISP | Internet
                :  +---------+      |     |
                :                   +-----+
      +------+  |                         |
      | Host +--+                         +--------------
      +------+  |
                |
      +------+  |
      | Host +--+
      +------+

   Between the subnet and the ISP access link is a gateway, which may
   or may not perform NAT and firewall function. A key point of this
   configuration is that the gateway is typically not "managed". In
   most cases, it is a simple "appliance", which incorporates some
   static policies. There are however many cases in which the gateway
   is procured and configured by the ISP, and there are also some
   common cases in which we find two back to back gateways, one managed
   by the ISP and the other added by the owner of the unmanaged
   network.

   The access link between the unmanaged network and the ISP can be
   either static, i.e. a permanent connection, or dynamically
   established, i.e. a dial-up or ISDN connection.

   In a degenerate case, an unmanaged network can be constituted of a
   single host, directly connected to an ISP.

3       Applications

   Users may use or wish to use the unmanaged network services in four
   types of applications: local, client, servers and peer-to-peers.
   These applications may or may not run easily on today's network:
   their status vary.

3.1     Local applications

   Local applications are meant to only involve the hosts that are part
   of the unmanaged network. Typical examples are the sharing of file
   or printers.

   Local applications work effectively in IPv4 unmanaged networks, even

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   when the gateway performs NAT or firewall function. In fact,
   firewall services at the gateway are often deemed desirable, as they
   isolate the local applications from interference by Internet users.

3.2     Client applications

   Client applications are those that involve a client on the unmanaged
   network and a server at a remote location. A typical example is
   accessing a web server from a client inside the unmanaged network,
   or reading and sending e-mail with the help of a server outside the
   unmanaged network.

   Local applications tend to work correctly in IPv4 unmanaged
   networks, even when the gateway performs NAT or firewall function:
   these translation and firewall functions are precisely designed to
   enable client applications.

3.3     Peer-to-peer applications

   There are two kinds of peer-to-peer applications, the "local peer-
   to-peer" that only involve hosts on the unmanaged network, and the
   "remote peer-to-peer" that involve both hosts on the unmanaged
   network and hosts outside the network. We will only consider here
   the "remote peer-to-peer" applications, as the local peer-to-peer
   applications are a subset of the "local applications."

   Peer-to-peer applications are a restricted subset of the server
   applications, in which the services are only meant to be used by
   well identified peers outside the unmanaged network. These
   applications are often facilitated by a server outside the unmanaged
   networks. Examples of a peer-to-peer application would be a video-
   conference over IP, facilitated by a SIP server, or a distributed
   game application, facilitated by a "game lobby".

   Peer-to-peer applications often don't work well in unmanaged IPv4
   networks. Application developers often have to enlist the help of a
   "relay server", to effectively restructure the peer-to-peer
   connection in two back-to-back client/server connections.

3.4     Server applications

   Server applications involve running a server in the unmanaged
   network, for use by other parties outside the network. Examples
   would be running a web server or an e-mail server on one of the
   hosts inside the unmanaged network.

   Deploying these servers in most unmanaged IPv4 networks requires
   some special programming of the NAT or firewall, and is more complex
   when the NAT only publishes a small number of global IP addresses
   and relies on "port translation". In the common case in which the
   NAT manages exactly one global IP address and relies on "port
   translation", a given external port can only be used by one internal

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   server.

   Deploying servers usually requires providing the servers with a
   stable DNS name, and associating the global IPv4 address of the
   nat/firewall with that name. Since updating DNS is a management
   task, it somewhat falls outside the scope of an unmanaged network.
   On the other hand, it is also possible to use out-of-band
   techniques, such as cut-and-paste into an instant message system, to
   pass around the address of the target server.

4       Application requirements of an IPv6 unmanaged network

   As we transition to IPv6, we must meet the requirements of the
   various applications, which we can summarize in the following way:
   the applications that used to work well with IPv4 should continue
   working well during the transition; it should be possible to use
   IPv6 to deploy new applications that are currently hard to deploy in
   IPv4 networks; the deployment of these IPv6 applications should be
   simple and easy to manage.

   The application requirements are expressed in mostly three
   dimensions: connectivity, naming, and security. Connectivity issues
   include the provision of IPv6 addresses and their quality: do host
   need a global scope address, should this address be stable, or more
   precisely what should be the expected lifetime of the address.
   Naming issues include the management of names for the hosts: do
   hosts need a DNS-name, is inverse name resolution a requirement.
   Security issues include possible restriction to connectivity,
   privacy concerns, and generally speaking the security of the
   applications.

4.1     Requirements of local applications

   Local applications require local connectivity. They must continue
   working even if the unmanaged network is isolated from the Internet.

   Local applications typically use ad hoc naming systems. Many of
   these systems are proprietary; an example of standard system is the
   service location protocol (SLP).

   The security of local applications is enhanced if these applications
   can be effectively isolated from the global Internet.

4.2     Requirements of client applications

   Client applications require global connectivity. In an IPv6 network,
   we would expect the client to use a global IPv6 address, which will
   have to remain stable for the duration of the client-server session.

   Client applications typically use the domain name system to locate
   servers. In an IPv6 network, the client must be able to locate a DNS
   server.

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   Many servers try to look up a DNS name associated to the IP address
   of the client. In an IPv4 network, this IP address will often be
   allocated by the Internet service provider to the gateway, and the
   corresponding PTR record will be maintained by the ISP. In most
   cases, these PTR records are perfunctory, derived in an algorithmic
   fashion from the IPv4 address; the main information that they
   contain is the domain name of the ISP. Whether or not an equivalent
   function should be provided in an IPv6 network is unclear.

4.2.1   Privacy requirement of client applications

   We may debate whether the IPv6 networking service should be
   engineered to enhance the privacy of the clients, and specifically
   whether the support of RFC 3041 should be required. RFC 3041 enables
   hosts to pick IPv6 addresses in which the host identifier is
   randomized; this was designed to make sure that the IPv6 addresses
   and the host identifier cannot be used to track the Internet
   connections of a device's owner.

   Many observe that randomizing the host identifier portion of the
   address is only a half measure. If the unmanaged network address
   prefix remains constant, the randomization only hides which host in
   the unmanaged network originates a given connection, e.g. the
   children's computer versus their parents'. This would place the
   privacy rating of such connections on a par with that of IPv4
   connections originating from an unmanaged network in which a NAT
   manages a static IPv4 address; in both case, the IPv4 address or the
   IPv6 prefix can be used to identify the unmanaged network, e.g. the
   specific home from which the connection originated.

   Randomization of the host identifier does however provide benefits.
   First, if some of the hosts in the unmanaged network are mobile, the
   randomization destroys any correlation between the addresses used at
   various locations: the addresses alone could not be used to
   determine whether a given connection originates from the same laptop
   moving from work to home, or used on the road. Second, the
   randomization removes any information that could be extracted from a
   hardwired host identifier; for example, it will prevent outsiders to
   correlate a serial number with a specific brand of expensive
   electronic equipment, and to use this information for planning
   marketing campaigns or possibly burglary attempts.

   Randomization of the addresses is indeed not sufficient to guarantee
   privacy. Usage can be tracked by a variety of other means, from
   application level "cookies" to complex techniques involving data
   mining and traffic analysis. However, just because privacy can be
   breached by other means is not a sufficient reason to enable
   additional tracking through IPv6 addresses.

   Randomization of the host identifier has some cost: the address
   management in hosts is more complex for the hosts and the gateway

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   may have to maintain a larger cache of neighbor addresses; however,
   experience from existing implementation shows that these costs are
   not overwhelming. Given the limited benefits, it would be
   unreasonable to require that all hosts use privacy addresses;
   however, given the limited costs, it is reasonable to require that
   all unmanaged network allow use of privacy addresses by those hosts
   who so choose.

4.3     Requirements of peer-to-peer applications

   Peer-to-peer applications require global connectivity. In an IPv6
   network, we would expect the peers to use a global IPv6 address,
   which will have to remain stable for the duration of the peer-to-
   peer between client and server.

   Peer-to-peer applications often use ad hoc naming systems, sometimes
   derived from an "instant messaging" service. Many of these systems
   are proprietary; an example of standard system is the session
   initiation protocol (SIP). In these systems, the peers register
   their presence to a "rendezvous" server, using a name specific to
   the service; the case of SIP, they would use a SIP URL, of the form
   "sip:user@example.com". A peer to peer session typically starts by
   an exchange of synchronization messages through the rendezvous
   servers, during which the peers exchange the addresses that will be
   used for the session.

   There are multiple aspects to the security of peer-to-peer
   applications, many of which relate to the security of the rendezvous
   system. If we assume that the peers have been able to safely
   exchange their IPv6 addresses, the main security requirement is the
   capability to safely exchange data between the peers, without
   interference by third parties.

   Private conversations with developers of peer-to-peer applications
   showed that many would be willing to consider an "IPv6-only" model
   if they can get two guarantees:

   1) That there is no regression from IPv4, i.e. that all customers
   that could participate in a peer-to-peer application using IPv4 can
   also be reached by IPv6.

   2) That IPv6 provides a solution for at least some of their hard
   problems, i.e. enabling peers located behind an IPv4 NAT to
   participate in a peer-to-peer application.

   Requiring IPv6 connectivity for a popular peer-to-peer application
   could create what economists refer to as a "network effect", which
   in turn could significantly speed up the deployment of IPv6.

4.4     Requirements of server applications

   Server applications require global connectivity, which in an IPv6

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   network implies global addresses.

   Server applications normally rely on the publication of the server's
   address in the DNS. This, in turns, requires that the server be
   provisioned with a "global DNS name".

   The DNS entries for the server will have to be updated, preferably
   in real time, if the server's address changes. In practice, updating
   the DNS is slow, which implies that server applications will have a
   better chance of being deployed if the IPv6 addresses remain stable
   for a long period.

   The security of server applications depends mostly on the
   correctness of the server, and also on the absence of collateral
   effects: many incidents occur when the opening of a server on the
   Internet inadvertently enables remote access to some other services
   on the same host.

5       Stages of IPv6 deployment

   The deployment of IPv6 over time is expected to proceed from an
   initial state in which there is little or no deployment, to a final
   stage in which we might retire the IPv4 infrastructure. We expect
   this process to stretch over several years; we also expect it to not
   be synchronized, as different parties involved will deploy IPv6 at
   different pace. In order to get some clarity, we distinguish three
   entities involved in the transition of an unmanaged network: the ISP
   (possibly including ISP CPE), the home gateway and the hosts
   (computers and appliances). Each can support IPv4-only, both IPv4
   and IPv6 or IPv6-only. That gives us 27 possibilities.  We describe
   the most important cases. We will consider that in all cases the
   hosts are a combination of IPv4-only, dual stack and IPv6-only
   hosts.

   The cases we will consider are:

   A) Gateway does not provide IPv6
   B) ISP and gateway are dual stack
   C) Gateway is IPv6 capable, dual stack, ISP is not
   D) ISP is IPv6-only

   The case where the ISP is IPv6 capable but the gateway is not is
   similar to case A.

5.1     Case A, host deployment of IPv6 applications

   In this case the gateway doesn't provide IPv6; the ISP may or may
   not provide IPv6, but this is not relevant, since the non-upgraded
   gateway would prevent the hosts from using the ISP service. Some
   hosts will try to get IPv6 connectivity, in order to run
   applications that require IPv6, or work better with IPv6.


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5.1.1   Application support in Case A

   The focus of Case A is to enable communication between a host on the
   unmanaged network and some IPv6-only hosts outside of the network.
   The primary focus in the immediate future, i.e. for the early
   adopters of IPv6, will be peer-to-peer applications. However, as
   IPv6 deployment progresses, we will likely find a situation where
   some networks have IPv6-only services deployed, at which point we
   would like case A client applications to be able to access those
   services.

   Local applications are not a primary focus of Case A. At this stage,
   we expect all clients in the unmanaged network to have either IPv4
   only or dual stack support. Local applications can continue working
   using IPv4.

   Server applications are also not a primary focus of Case A. Server
   applications require DNS support, which is difficult to engineer for
   clients located behind a NAT. Besides, server applications, at this
   stage, cater mostly to IPv4 clients; putting up an IPv6-only server
   is not very attractive.

   In contrast, peer-to-peer applications are both attractive and easy
   to deploy: they are deployed in a coordinated fashion as part of a
   peer-to-peer network, which means that hosts can all receive some
   form of IPv6 upgrade; they often provide their own naming
   infrastructure, in which case they are not dependent on DNS
   services.

5.1.2   Addresses and connectivity in Case A

   We saw in 5.1.1 that a primary motivation for the deployment of IPv6
   connectivity in hosts is participation to peer-to-peer applications,
   and also to IPv6-only client applications. These applications
   require that all participating nodes get some form of IPv6
   connectivity, i.e. at least one globally reachable IPv6 address. The
   mechanism to provide connectivity to peers behind NAT should be easy
   to deploy, and light weight; it will have to involve tunneling over
   UDP, as this is the practical way to traverse a NAT. If servers are
   needed, these servers will in practice have to be deployed as part
   of the "support infrastructure" for the peer-to-peer network or for
   an IPv6 based service; economic reality implies that the cost of
   running these servers should be as low as possible.

5.1.3   Naming services in Case A

   At this phase of IPv6 deployment, hosts in the unmanaged domain have
   access to DNS services over IPv4, through the existing gateway. DNS
   resolvers are supposed to serve AAAA records, even if they only
   implement IPv4; the local hosts should thus be able to obtain the
   IPv6 addresses of IPv6-only servers.


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   Reverse lookup is hard to provide if the gateway is not upgraded.
   This is a potential issue for client applications. Some servers
   require a reverse lookup as part of accepting a client's connection,
   and may require that the direct lookup of the corresponding name
   matches the IPv6 address of the client. There is thus a requirement
   to either provide a reverse lookup solution, or make sure that IPv6
   servers do not require reverse lookup.

5.2     Case B, IPv6 connectivity with provider support

   In this case the ISP and gateway are dual stack. The gateway can use
   native IPv6 connectivity to the ISP and use an IPv6 prefix allocated
   by the ISP.

5.2.1   Application support in Case B

   If the ISP and the gateway are dual-stack, client applications,
   peer-to-peer applications and server applications can all be enabled
   easily on the unmanaged network.

   We expect the unmanaged network to include three kinds of hosts:
   IPv4 only, IPv6-only, and dual stack. Obviously, dual stack hosts
   can interact easily with either IPv4 only hosts or IPv6-only hosts,
   but an IPv4 only host and an IPv6-only host cannot communicate
   without a third party performing some kind of translation service.
   Our analysis concludes that unmanaged networks should not have to
   provide such translation services.

   The argument for providing translation services is that their
   availability would accelerate the deployment of IPv6-only devices,
   and thus the transition to IPv6. This is however a dubious argument,
   since it can also be argued that the availability of these
   translation services will reduce the pressure to provide IPv6 at
   all, and to just continue fielding IPv6-only devices. The remaining
   pressure to provide IPv6 connectivity would just be the difference
   in "quality of service" between a translated exchange and a native
   interconnect.

   The argument against translation service is the difficulty of
   providing these services for all applications, compared to the
   relative ease of installing dual stack solutions in an unmanaged
   network. Translation services can be provided either by application
   relays such as HTTP proxies, or by network level services such as
   NAT-PT. Application relays pose several operational problems: first,
   one must develop relays for all applications; second, one must
   develop a management infrastructure to provision the host with the
   addresses of the relays; in addition, the application may have to be
   modified if one wants to use the relay selectively, e.g. only when
   direct connection is not available. Network level translation poses
   similar problems: in practice, network level actions must be
   complemented by "application layer gateways" that will rewrite
   references to IP addresses in the protocol, and these relays tend to

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   be necessary for every application; hosts may need to be
   parameterized to use the translation service; and designing the
   right algorithm to decide when to translate DNS requests has proven
   very difficult.

   Not assuming translation services in the network appears both more
   practical and more robust. If the market requirement for a new
   device requires that it interacts with both IPv4 and IPv6 hosts, we
   may expect the manufacturers of these devices to program them with a
   dual stack capability; in particular, we expect general purpose
   systems such as personal computers to be effectively dual-stack. The
   only devices that are expected to be capable of only supporting IPv6
   are those who are designed for specific applications, which do not
   require interoperation with antique IPv4-only systems. We also
   observe that providing both IPv4 and IPv6 connectivity in an
   unmanaged network is not particularly difficult; indeed there is a
   well established experience of using IPv4 in these networks in
   parallel with other protocols such as for example IPX.

5.2.2   Addresses and connectivity in Case B

   In Case B, the upgraded gateway will behave as an IPv6 router; it
   will continue providing the IPv4 connectivity of a non-upgraded NAT.
   Nodes in the local network will obtain:

        - IPv4 natted addresses,
        - IPv6 link local addresses,
        - IPv6 global addresses.

   The hosts could also obtain IPv6 site local addresses, if the
   gateway advertises a site local prefix. This is as debatable: site
   local addresses provide some isolation to site local application
   from network connectivity events and network based attacks; however,
   managing non unique addresses can be problematic if some local hosts
   are multi-homed, as is common with VPN connections.

   To enable this scenario, the gateway need to use a mechanism obtain
   a global address prefix from the ISP, and advertise this address
   prefix to the hosts in the unmanaged network; several solutions will
   be assessed in a companion memo [EVAL].

5.2.3   Naming services in Case B

   At this phase of IPv6 deployment, hosts in the unmanaged domain have
   access to DNS services through the gateway. As the gateway and the
   ISP both support IPv4 and IPv6, these services may be accessible by
   the IPv4 only hosts using IPv4, by the IPv6-only hosts using IPv6,
   and by the dual stack hosts using either. Currently, IPv4 only hosts
   discover the IPv4 address of the local DNS server using DHCP; there
   must be a way for IPv6-only hosts to discover the IPv6 address of
   the DNS server.


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   There must be a way to resolve the name of local hosts to their IPv4
   or IPv6 addresses. Typing auto-configured IPv6 addresses in a
   configuration file is impractical; this implies either some form of
   dynamic registration of IPv6 addresses in the local service, or a
   dynamic address discovery mechanism. Possible solutions will be
   compared in the evaluation draft.

   The requirement to support server applications in the unmanaged
   network implies a requirement to publish the IPv6 addresses of local
   servers in the DNS. There are multiple solutions, including
   variations of domain name delegation. If we want to provide
   efficient reverse lookup functions, delegation of a fraction of the
   ip6.arpa tree is also required.

   The response to a DNS request should not depend of the protocol with
   which the request is transported: dual-stack hosts may indifferently
   use IPv4 or IPv6 to contact the local resolver; the choice of IPv4
   or IPv6 will be random; the value of the response should not depend
   of a random event.


5.3     Case C, IPv6 connectivity without provider support

   In this case the gateway is IPv6 capable, dual stack, the ISP is
   not.  The gateway has been upgraded and offers both IPv4 and IPv6
   connectivity the hosts. It cannot rely on the ISP for IPv6
   connectivity, because the ISP does not offer ISP connectivity yet.

5.3.1   Application support in Case C

   Application support in case C should be identical to that of case B.

5.3.2   Addresses and connectivity in Case C

   The upgraded gateway will behave as an IPv6 router; it will continue
   providing the IPv4 connectivity of non-upgraded NAT. Nodes in the
   local network will obtain:

        - IPv4 natted addresses,
        - IPv6 link local addresses,
        - IPv6 global addresses.

   The clients could also obtain IPv6 site local addresses, if the
   gateway advertises a site local prefix; this raises the same issues
   already discussed in case B.

   There are two ways to bring immediate IPv6 connectivity on top of an
   IPv4 only infrastructure: automatic tunnels provided by the [6TO4]
   technology, or configured tunnels. Both technologies have advantages
   and limitations, which will be studied in a companion document.

5.3.3   Naming services in Case C

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   The local naming requirements in case C are identical to the local
   naming requirements of case B, with two differences: delegation of
   domain names, and management of reverse lookup queries.

   A delegation of some domain name is required in order to publish the
   IPv6 addresses of servers in the DNS. As the ISP does not provide
   support for IPv6 in case C, the delegation mechanism will have to be
   provided independently of the IP connectivity mechanism.

   A specific mechanism for handling reverse lookup queries will be
   required if the gateway uses a dynamic mechanism such as 6to4 to
   obtain a prefix independently of any IPv6 ISP.

5.4     Case D, ISP stops providing native IPv4 connectivity

   In this case the ISP is IPv6-only, so the gateway looses IPv4
   connectivity, and is faced with an IPv6-only service provider. The
   gateway itself is dual stack, and the unmanaged network includes
   IPv4 only, IPv6-only and dual stack hosts. Any interaction between
   hosts in the unmanaged network and IPv4 hosts on the Internet will
   require the provision of some inter-protocol services by the ISP.

5.4.1   Application support in Case D

   At this phase of the transition, IPv6 hosts can perform all types of
   applications with other IPv6 hosts. IPv4 hosts in the unmanaged
   network will be able to perform local applications with IPv4 or dual
   stack local hosts.

   As in case B, we will assume that IPv6-only hosts will not interact
   with IPv4-only hosts, either local or remote. We must however assume
   that IPv4-only hosts and dual stack hosts will desire to interact
   with IPv4 services available on the Internet: the inability to do so
   would place the IPv6-only provider at a great commercial
   disadvantage compared to other Internet service providers.

   There are three possible ways that an ISP can provide hosts in the
   unmanaged network with access to IPv4 application: by using a set of
   application relays, by providing an address translation service, or
   by providing IPv4-over-IPv6 tunnels. Our analysis concludes that a
   tunnel service will be vastly preferable.

   We already mentioned the drawbacks of the application gateway
   approach when analyzing case B: it is necessary to provide relays
   for all applications, to develop a way to provision the hosts with
   the addresses of these relays, and to modify the applications so
   that they will only use the relays when needed. We also observe that
   in an IPv6-only ISP the application relays would only be accessible
   over IPv6, and would thus not be accessible by the "legacy" IPv4-
   only hosts. The application relay approach is thus not very
   attractive.

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   Providing a network address and protocol translation service between
   IPv6 and IPv4 would also have many drawbacks. As in case B, it will
   have to be complemented by "application layer gateways" that will
   rewrite references to IP addresses in the protocol; hosts may need
   to be parameterized to use the translation service; and we would
   have to solve DNS issues. In addition, in an IPv6-only ISP, an IPv6-
   to-IPv4 translation service would not be accessible by legacy IPv4-
   only hosts through the IPv6 only ISP service. The network level
   protocol translation service appears to not be very desirable.

   The proper alternative to application relays and network address
   translation is the provision of an IPv4-over-IPv6 service.

5.4.2   Addresses and connectivity in Case D

   The ISP assigns an IPv6 prefix to the unmanaged network, so hosts
   have a global IPv6 address and use it for global IPv6 connectivity.
   This will require delegation of an IPv6 address prefix, as
   investigated in case C.

   To enable IPv4 hosts and dual stack host to access remote IPv4
   services, the ISP must provide the gateway with at least one IPv4
   address, using some form of IPv4-over-IPv6 tunneling. Once such
   addresses have been provided, the gateway effectively acquires dual-
   stack connectivity; for hosts inside the unmanaged network, this
   will be indistinguishable from the connectivity obtained in case B
   or C.

5.4.3   Naming services in Case D

   The loss of IPv4 connectivity has a direct impact on the provision
   of naming services. An obvious consequence is the gateway will have
   to be provisioned with the address of a DNS server and with other
   DNS parameters, and that this provisioning will have to use IPv6
   mechanisms. Another consequence is that the DNS service in the
   gateway will only be able to use IPv6 connectivity to resolve
   queries; if local hosts perform DNS resolution autonomously, they
   will have the same restriction.

   On the surface, this seems to indicate that the local hosts will
   only be able to resolve names if the domain servers are accessible
   through an IPv6 address documented in a AAAA record. However, the
   DNS services are just one case of "IPv4 servers accessed by IPv6
   hosts": it should be possible to simply send queries through the
   address translation services to reach the IPv4 only servers.

   The gateway should be able to act as a "DNS proxy" for the remaining
   IPv4 only hosts.

6       Security Considerations


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   Security considerations are discussed as part of the applications'
   requirements. They include:

   -    the guarantee that local applications are only used locally,
   -    the protection of the privacy of clients
   -    the requirement that peer-to-peer connections are only used by
   authorized peers.

7       IANA Considerations

   This memo does not include any request to IANA.

8       Copyright

   The following copyright notice is copied from RFC 2026 [Bradner,
   1996], Section 10.4, and describes the applicable copyright for this
   document.

   Copyright (C) The Internet Society July 12, 2001. All Rights
   Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph
   are included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assignees.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS 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.

9       Intellectual Property

   The following notice is copied from RFC 2026 [Bradner, 1996],
   Section 10.4, and describes the position of the IETF concerning
   intellectual property claims made against this document.

   The IETF takes no position regarding the validity or scope of any

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INTERNET DRAFT   Unmanaged Networks IPv6 scenarios   January 10, 2003

   intellectual property or other rights that might be claimed to
   pertain to the implementation or use other technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights.  Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP-11.  Copies of
   claims of rights made available for publication 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 Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard.  Please address the information to the IETF Executive
   Director.

10      Acknowledgements

   This draft has benefited from extensive reviews by Tony Hain, Suresh
   K Satapati, and Margaret Wasserman.

11      References

   [EVAL] Evaluation of Transition Mechanisms for Unmanaged Networks,
   work in progress.

12      Authors' Addresses

   Christian Huitema
   Microsoft Corporation
   One Microsoft Way
   Redmond, WA 98052-6399
   Email: huitema@microsoft.com


   Rob Austein
   Email: sra@hactrn.net


   Ronald van der Pol
   Email: Ronald.vanderPol@surfnet.nl









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Table of Contents:

1 Introduction ....................................................   1
2 Topology ........................................................   1
3 Applications ....................................................   2
3.1 Local applications ............................................   2
3.2 Client applications ...........................................   3
3.3 Peer-to-peer applications .....................................   3
3.4 Server applications ...........................................   3
4 Application requirements of an IPv6 unmanaged network ...........   4
4.1 Requirements of local applications ............................   4
4.2 Requirements of client applications ...........................   4
4.2.1 Privacy requirement of client applications ..................   5
4.3 Requirements of peer-to-peer applications .....................   6
4.4 Requirements of server applications ...........................   6
5 Stages of IPv6 deployment .......................................   7
5.1 Case A, host deployment of IPv6 applications ..................   7
5.1.1 Application support in Case A ...............................   8
5.1.2 Addresses and connectivity in Case A ........................   8
5.1.3 Naming services in Case A ...................................   8
5.2 Case B, IPv6 connectivity with provider support ...............   9
5.2.1 Application support in Case B ...............................   9
5.2.2 Addresses and connectivity in Case B ........................  10
5.2.3 Naming services in Case B ...................................  10
5.3 Case C, IPv6 connectivity without provider support ............  11
5.3.1 Application support in Case C ...............................  11
5.3.2 Addresses and connectivity in Case C ........................  11
5.3.3 Naming services in Case C ...................................  11
5.4 Case D, ISP stops providing native IPv4 connectivity ..........  12
5.4.1 Application support in Case D ...............................  12
5.4.2 Addresses and connectivity in Case D ........................  13
5.4.3 Naming services in Case D ...................................  13
6 Security Considerations .........................................  13
7 IANA Considerations .............................................  14
8 Copyright .......................................................  14
9 Intellectual Property ...........................................  14
10 Acknowledgements ...............................................  15
11 References .....................................................  15
12 Authors' Addresses .............................................  15













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