draft-ietf-v6ops-unman-scenarios-00.txt   draft-ietf-v6ops-unman-scenarios-01.txt 
INTERNET DRAFT C. Huitema INTERNET DRAFT C. Huitema
<draft-ietf-v6ops-unman-scenarios-00.txt> Microsoft <draft-ietf-v6ops-unman-scenarios-01.txt> Microsoft
January 10, 2003 R. Austein June 3, 2003 R. Austein
Expires July 10, 2003 Bourgeois Dilettant Expires December 3, 2003 Bourgeois Dilettant
S. Satapati
Cisco Systems, Inc.
R. van der Pol R. van der Pol
NLnet Labs NLnet Labs
Unmanaged Networks IPv6 Transition Scenarios Unmanaged Networks IPv6 Transition Scenarios
Status of this memo Status of this memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
skipping to change at page 10, line ? skipping to change at page 10, line ?
reference material or to cite them other than as "work in progress." reference material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
Abstract Abstract
In order to evaluate the suitability of transition mechanisms, we In order to evaluate the suitability of IPv6 transition mechanisms,
need to define the scenarios in which these mechanisms have to be we need to define the scenarios in which these mechanisms have to be
used. One specific scope is the "unmanaged networks", which used. One specific scope is the "unmanaged network", which typically
typically correspond to home networks or small office networks. corresponds to a home or small office network. The scenarios are
specific to single link subnet, and are defined in terms of IP
connectivity supported by the home gateway and the ISP. We first
examine the generic requirements of four classes of applications:
local, client, peer to peer and server. Then, for each scenario, we
infer transition requirements by analyzing the needs for smooth
migration of applications from IPv4 to IPv6.
1 Introduction 1 Introduction
In order to evaluate the suitability of transition mechanisms, we In order to evaluate the suitability of transition mechanisms, we
need to define the environment or scope in which these mechanisms need to define the environment or scope in which these mechanisms
have to be used. One specific scope is the "unmanaged networks", have to be used. One specific scope is the "unmanaged networks",
which typically correspond to home networks or small office which typically correspond to home networks or small office
networks. networks.
This document studies the requirement posed by various transition
Huitema et al. [Page 1]
scenarios, and is organized in four main sections. Section 2 defines
the topology that we are considering. Section 3 presents the four
classes of applications that we consider for unmanaged networks:
local applications, client applications, peer-to-peer applications,
and server applications. Section 4 studies the requirements of these
four classes of applications. Section 5 analyses how these
requirements translate into four configurations which we expect to
encounter during IPv6 deployment: gateways which do not provide
IPv6, dual-stack gateways connected to dual-stack ISPs, dual-stack
gateways connected to IPv4-only ISPs, and IPv6-capable gateways
connected to IPv6-only ISPs. While these four configurations are
certainly not an exhaustive list of possible configurations, we
believe that they represent the common cases for unmanaged networks.
2 Topology 2 Topology
The typical unmanaged network is composed of a single subnet, The typical unmanaged network is composed of a single subnet,
connected to the Internet through a single Internet Service Provider connected to the Internet through a single Internet Service Provider
(ISP)connection. Several hosts are connected to the subnet: (ISP) connection. Several hosts may be connected to the subnet:
Huitema et al. [Page 1]
+------+ +------+
| Host +--+ | Host +--+
+------+ | +------+ |
| |
+------+ | +------+ |
| Host +--+ +-------------- | Host +--+ +--------------
+------+ | | +------+ | |
: +-----+ : +-----+
: +---------+ | | : +---------+ | |
+--+ Gateway +------| ISP | Internet +--+ Gateway +------| ISP | Internet
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+------+ | +------+ |
| |
+------+ | +------+ |
| Host +--+ | Host +--+
+------+ +------+
Between the subnet and the ISP access link is a gateway, which may 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 or may not perform NAT and firewall function. A key point of this
configuration is that the gateway is typically not "managed". In configuration is that the gateway is typically not "managed". In
most cases, it is a simple "appliance", which incorporates some most cases, it is a simple "appliance", which incorporates some
static policies. There are however many cases in which the gateway static policies. However, there are many cases in which the gateway
is procured and configured by the ISP, and there are also some 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 common cases in which we find two gateways back to back, one managed
by the ISP and the other added by the owner of the unmanaged by the ISP and the other added by the owner of the unmanaged
network. network.
The access link between the unmanaged network and the ISP can be The access link between the unmanaged network and the ISP might be
either static, i.e. a permanent connection, or dynamically either a static, permanent connection or a dynamic connection such
established, i.e. a dial-up or ISDN connection.
In a degenerate case, an unmanaged network can be constituted of a Huitema et al. [Page 2]
single host, directly connected to an ISP. as a dial-up or ISDN line.
In a degenerate case, an unmanaged network might consist of a single
host, directly connected to an ISP.
Our definition of unmanaged networks explicitly exclude networks
composed of multiple subnets. We will readily admit that some home
networks and some small business networks contain multiple subnets,
but in the current state of the technology these multiple subnet
networks are not "unmanaged": some competent administrator has to
explicitly configure the routers. We will thus concentrate on single
subnet networks, where no such competent operator is expected.
3 Applications 3 Applications
Users may use or wish to use the unmanaged network services in four Users may use or wish to use the unmanaged network services in four
types of applications: local, client, servers and peer-to-peers. types of applications: local, client, servers and peer-to-peers.
These applications may or may not run easily on today's network: These applications may or may not run easily on today's networks
their status vary. (some do, some don't).
3.1 Local applications 3.1 Local applications
Local applications are meant to only involve the hosts that are part "Local applications" are only meant to involve the hosts that are
of the unmanaged network. Typical examples are the sharing of file part of the unmanaged network. Typical examples would be file
or printers. sharing or printer sharing.
Local applications work effectively in IPv4 unmanaged networks, even Local applications work effectively in IPv4 unmanaged networks, even
Huitema et al. [Page 2]
when the gateway performs NAT or firewall function. In fact, when the gateway performs NAT or firewall function. In fact,
firewall services at the gateway are often deemed desirable, as they firewall services at the gateway are often deemed desirable, as they
isolate the local applications from interference by Internet users. isolate the local applications from interference by Internet users.
3.2 Client applications 3.2 Client applications
Client applications are those that involve a client on the unmanaged "Client applications" are those that involve a client on the
network and a server at a remote location. A typical example is unmanaged network and a server at a remote location. Typical
accessing a web server from a client inside the unmanaged network, examples would be accessing a web server from a client inside the
or reading and sending e-mail with the help of a server outside the unmanaged network, or reading and sending e-mail with the help of a
unmanaged network. server outside the unmanaged network.
Local applications tend to work correctly in IPv4 unmanaged Client applications tend to work correctly in IPv4 unmanaged
networks, even when the gateway performs NAT or firewall function: networks, even when the gateway performs NAT or firewall function:
these translation and firewall functions are precisely designed to these translation and firewall functions are designed precisely to
enable client applications. enable client applications.
3.3 Peer-to-peer applications 3.3 Peer-to-peer applications
There are two kinds of peer-to-peer applications, the "local peer- There are really two kinds of "peer-to-peer" applications: ones
to-peer" that only involve hosts on the unmanaged network, and the which only involve hosts on the unmanaged network, and ones which
"remote peer-to-peer" that involve both hosts on the unmanaged involve both one or more hosts on the unmanaged network and one or
network and hosts outside the network. We will only consider here more hosts outside the unmanaged network. We will only consider the
the "remote peer-to-peer" applications, as the local peer-to-peer latter kind of peer-to-peer applications, since the former can be
applications are a subset of the "local applications." considered a subset of the kind of local applications discussed
Peer-to-peer applications are a restricted subset of the server Huitema et al. [Page 3]
applications, in which the services are only meant to be used by in section 3.1.
well identified peers outside the unmanaged network. These
applications are often facilitated by a server outside the unmanaged Peer-to-peer applications are a restricted subset of "server
networks. Examples of a peer-to-peer application would be a video- applications" (discussed in section 3.4), in which the services are
conference over IP, facilitated by a SIP server, or a distributed only meant to be used by well-identified peers outside the unmanaged
game application, facilitated by a "game lobby". network. These applications are often facilitated by a server
outside the unmanaged networks. Examples of peer-to-peer
applications would be a video-conference over IP, facilitated by a
Session Invitation Protocol (SIP) server, or a distributed game
application, facilitated by a "game lobby".
Peer-to-peer applications often don't work well in unmanaged IPv4 Peer-to-peer applications often don't work well in unmanaged IPv4
networks. Application developers often have to enlist the help of a networks. Application developers often have to enlist the help of a
"relay server", to effectively restructure the peer-to-peer "relay server", in effect restructuring the peer-to-peer connection
connection in two back-to-back client/server connections. into a pair of back-to-back client/server connections.
3.4 Server applications 3.4 Server applications
Server applications involve running a server in the unmanaged "Server applications" involve running a server in the unmanaged
network, for use by other parties outside the network. Examples network for use by other parties outside the network. Typical
would be running a web server or an e-mail server on one of the examples would be running a web server or an e-mail server on one of
hosts inside the unmanaged network. the hosts inside the unmanaged network.
Deploying these servers in most unmanaged IPv4 networks requires Deploying these servers in most unmanaged IPv4 networks requires
some special programming of the NAT or firewall, and is more complex some special programming of the NAT or firewall, and is more complex
when the NAT only publishes a small number of global IP addresses when the NAT only publishes a small number of global IP addresses
and relies on "port translation". In the common case in which the and relies on "port translation". In the common case in which the
NAT manages exactly one global IP address and relies on "port NAT manages exactly one global IP address and relies on "port
translation", a given external port can only be used by one internal translation", a given external port can only be used by one internal
Huitema et al. [Page 3]
server. server.
Deploying servers usually requires providing the servers with a Deploying servers usually requires providing each server with a
stable DNS name, and associating the global IPv4 address of the stable DNS name, and associating a global IPv4 address with that
nat/firewall with that name. Since updating DNS is a management name, whether the address be that of the server itself or that of
task, it somewhat falls outside the scope of an unmanaged network. the router acting as a firewall or NAT. Since updating DNS is a
On the other hand, it is also possible to use out-of-band management task, it falls somewhat outside the scope of an unmanaged
techniques, such as cut-and-paste into an instant message system, to 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. pass around the address of the target server.
4 Application requirements of an IPv6 unmanaged network 4 Application requirements of an IPv6 unmanaged network
As we transition to IPv6, we must meet the requirements of the As we transition to IPv6, we must meet the requirements of the
various applications, which we can summarize in the following way: various applications, which we can summarize in the following way:
the applications that used to work well with IPv4 should continue applications that used to work well with IPv4 should continue
working well during the transition; it should be possible to use working well during the transition; it should be possible to use
IPv6 to deploy new applications that are currently hard to deploy in IPv6 to deploy new applications that are currently hard to deploy in
IPv4 networks; the deployment of these IPv6 applications should be IPv4 networks; and the deployment of these IPv6 applications should
simple and easy to manage. be simple and easy to manage, but the solutions should also be
robust and secure.
The application requirements are expressed in mostly three The application requirements for IPv6 Unmanaged Networks fall into
dimensions: connectivity, naming, and security. Connectivity issues
include the provision of IPv6 addresses and their quality: do host Huitema et al. [Page 4]
need a global scope address, should this address be stable, or more three general categories: connectivity, naming, and security.
precisely what should be the expected lifetime of the address. Connectivity issues include the provision of IPv6 addresses and
Naming issues include the management of names for the hosts: do their quality: do hosts need global addresses, should these
hosts need a DNS-name, is inverse name resolution a requirement. addresses be stable or, more precisely, what should the expected
Security issues include possible restriction to connectivity, lifetimes of these addresses be? Naming issues include the
privacy concerns, and generally speaking the security of the management of names for the hosts: do hosts need DNS names, and is
applications. 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 4.1 Requirements of local applications
Local applications require local connectivity. They must continue Local applications require local connectivity. They must continue to
working even if the unmanaged network is isolated from the Internet. work even if the unmanaged network is isolated from the Internet.
Local applications typically use ad hoc naming systems. Many of Local applications typically use ad hoc naming systems. Many of
these systems are proprietary; an example of standard system is the these systems are proprietary; an example of a standard system is
service location protocol (SLP). the service location protocol (SLP).
The security of local applications is enhanced if these applications The security of local applications will usually be enhanced if these
can be effectively isolated from the global Internet. applications can be effectively isolated from the global Internet.
4.2 Requirements of client applications 4.2 Requirements of client applications
Client applications require global connectivity. In an IPv6 network, Client applications require global connectivity. In an IPv6 network,
we would expect the client to use a global IPv6 address, which will 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. have to remain stable for the duration of the client-server session.
Client applications typically use the domain name system to locate Client applications typically use the domain name system to locate
servers. In an IPv6 network, the client must be able to locate a DNS servers. In an IPv6 network, the client must be able to locate a DNS
server. resolver.
Huitema et al. [Page 4]
Many servers try to look up a DNS name associated to the IP address 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 of the client. In an IPv4 network, this IP address will often be
allocated by the Internet service provider to the gateway, and the allocated by the Internet service provider to the gateway, and the
corresponding PTR record will be maintained by the ISP. In most corresponding PTR record will be maintained by the ISP. In many
cases, these PTR records are perfunctory, derived in an algorithmic cases, these PTR records are perfunctory, derived in an algorithmic
fashion from the IPv4 address; the main information that they fashion from the IPv4 address; the main information that they
contain is the domain name of the ISP. Whether or not an equivalent contain is the domain name of the ISP. Whether or not an equivalent
function should be provided in an IPv6 network is unclear. function should be provided in an IPv6 network is unclear.
4.2.1 Privacy requirement of client applications 4.2.1 Privacy requirement of client applications
We may debate whether the IPv6 networking service should be It is debatable whether the IPv6 networking service should be
engineered to enhance the privacy of the clients, and specifically engineered to enhance the privacy of the clients, and specifically
whether the support of RFC 3041 should be required. RFC 3041 enables whether support for RFC 3041 should be required. RFC 3041 enables
hosts to pick IPv6 addresses in which the host identifier is hosts to pick IPv6 addresses in which the host identifier is
randomized; this was designed to make sure that the IPv6 addresses randomized; this was designed to make sure that the IPv6 addresses
and the host identifier cannot be used to track the Internet and the host identifier cannot be used to track the Internet
connections of a device's owner. connections of a device's owner.
Many observe that randomizing the host identifier portion of the Many observe that randomizing the host identifier portion of the
Huitema et al. [Page 5]
address is only a half measure. If the unmanaged network address address is only a half measure. If the unmanaged network address
prefix remains constant, the randomization only hides which host in prefix remains constant, the randomization only hides which host in
the unmanaged network originates a given connection, e.g. the the unmanaged network originates a given connection, e.g. the
children's computer versus their parents'. This would place the children's computer versus their parents'. This would place the
privacy rating of such connections on a par with that of IPv4 privacy rating of such connections on a par with that of IPv4
connections originating from an unmanaged network in which a NAT connections originating from an unmanaged network in which a NAT
manages a static IPv4 address; in both case, the IPv4 address or the 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 IPv6 prefix can be used to identify the unmanaged network, e.g. the
specific home from which the connection originated. specific home from which the connection originated.
Randomization of the host identifier does however provide benefits. However, randomization of the host identifier does provide benefits.
First, if some of the hosts in the unmanaged network are mobile, the First, if some of the hosts in the unmanaged network are mobile, the
randomization destroys any correlation between the addresses used at randomization destroys any correlation between the addresses used at
various locations: the addresses alone could not be used to various locations: the addresses alone could not be used to
determine whether a given connection originates from the same laptop determine whether a given connection originates from the same laptop
moving from work to home, or used on the road. Second, the moving from work to home, or used on the road. Second, the
randomization removes any information that could be extracted from a randomization removes any information that could be extracted from a
hardwired host identifier; for example, it will prevent outsiders to hardwired host identifier; for example, it will prevent outsiders
correlate a serial number with a specific brand of expensive from correlating a serial number with a specific brand of expensive
electronic equipment, and to use this information for planning electronic equipment, and to use this information for planning
marketing campaigns or possibly burglary attempts. marketing campaigns or possibly burglary attempts.
Randomization of the addresses is indeed not sufficient to guarantee Randomization of the addresses is not sufficient to guarantee
privacy. Usage can be tracked by a variety of other means, from privacy. Usage can be tracked by a variety of other means, from
application level "cookies" to complex techniques involving data application level "cookies" to complex techniques involving data
mining and traffic analysis. However, just because privacy can be mining and traffic analysis. However, just because privacy can be
breached by other means is not a sufficient reason to enable breached by other means is not a sufficient reason to enable
additional tracking through IPv6 addresses. additional tracking through IPv6 addresses.
Randomization of the host identifier has some cost: the address Randomization of the host identifier has some cost: the address
management in hosts is more complex for the hosts and the gateway management in hosts is more complex for the hosts and the gateway
Huitema et al. [Page 5]
may have to maintain a larger cache of neighbor addresses; however, may have to maintain a larger cache of neighbor addresses; however,
experience from existing implementation shows that these costs are experience from existing implementation shows that these costs are
not overwhelming. Given the limited benefits, it would be not overwhelming. Given the limited benefits, it would be
unreasonable to require that all hosts use privacy addresses; unreasonable to require that all hosts use privacy addresses;
however, given the limited costs, it is reasonable to require that however, given the limited costs, it is reasonable to require that
all unmanaged network allow use of privacy addresses by those hosts all unmanaged networks allow use of privacy addresses by those hosts
who so choose. that choose to do so.
4.3 Requirements of peer-to-peer applications 4.3 Requirements of peer-to-peer applications
Peer-to-peer applications require global connectivity. In an IPv6 Peer-to-peer applications require global connectivity. In an IPv6
network, we would expect the peers to use a global IPv6 address, 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- which will have to remain stable for the duration of the peer-to-
peer between client and server. peer session.
Peer-to-peer applications often use ad hoc naming systems, sometimes Peer-to-peer applications often use ad hoc naming systems, sometimes
derived from an "instant messaging" service. Many of these systems derived from an "instant messaging" service. (Peer-to-peer
are proprietary; an example of standard system is the session applications that rely on the DNS for name resolution have the same
initiation protocol (SIP). In these systems, the peers register naming requirements as server applications, which are discussed in
their presence to a "rendezvous" server, using a name specific to the next section.) Many of these systems are proprietary; an example
the service; the case of SIP, they would use a SIP URL, of the form of a standard system is the session invitation protocol (SIP). In
"sip:user@example.com". A peer to peer session typically starts by
an exchange of synchronization messages through the rendezvous Huitema et al. [Page 6]
servers, during which the peers exchange the addresses that will be these systems, the peers register their presence to a "rendezvous"
used for the session. 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 with 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 There are multiple aspects to the security of peer-to-peer
applications, many of which relate to the security of the rendezvous applications, many of which relate to the security of the rendezvous
system. If we assume that the peers have been able to safely system. If we assume that the peers have been able to safely
exchange their IPv6 addresses, the main security requirement is the exchange their IPv6 addresses, the main security requirement is the
capability to safely exchange data between the peers, without capability to safely exchange data between the peers, without
interference by third parties. interference by third parties.
Private conversations with developers of peer-to-peer applications Private conversations by one of the authors with developers of peer-
showed that many would be willing to consider an "IPv6-only" model to-peer applications suggest that many would be willing to consider
if they can get two guarantees: an "IPv6-only" model if they can get two guarantees:
1) That there is no regression from IPv4, i.e. that all customers 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 who could participate in a peer-to-peer application using IPv4 can
also be reached by IPv6. also be reached by IPv6.
2) That IPv6 provides a solution for at least some of their hard 2) That IPv6 provides a solution for at least some of their hard
problems, i.e. enabling peers located behind an IPv4 NAT to problems, e.g. enabling peers located behind an IPv4 NAT to
participate in a peer-to-peer application. participate in a peer-to-peer application.
Requiring IPv6 connectivity for a popular 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 could create what economists refer to as a "network effect", which
in turn could significantly speed up the deployment of IPv6. in turn could significantly speed up the deployment of IPv6.
4.4 Requirements of server applications 4.4 Requirements of server applications
Server applications require global connectivity, which in an IPv6 Server applications require global connectivity, which in an IPv6
network implies global addresses. In an IPv4 network utilizing a
Huitema et al. [Page 6] NAT, for each service provided by a server, the NAT has to be
network implies global addresses. configured to forward packets sent to that service to the server
that offers the service.
Server applications normally rely on the publication of the server's Server applications normally rely on the publication of the server's
address in the DNS. This, in turns, requires that the server be address in the DNS. This, in turn, requires that the server be
provisioned with a "global DNS name". provisioned with a "global DNS name".
The DNS entries for the server will have to be updated, preferably The DNS entries for the server will have to be updated, preferably
in real time, if the server's address changes. In practice, updating in real time, if the server's address changes. In practice, updating
the DNS is slow, which implies that server applications will have a the DNS can be slow, which implies that server applications will
better chance of being deployed if the IPv6 addresses remain stable have a better chance of being deployed if the IPv6 addresses remain
for a long period. stable for a long period.
The security of server applications depends mostly on the The security of server applications depends mostly on the
correctness of the server, and also on the absence of collateral correctness of the server, and also on the absence of collateral
effects: many incidents occur when the opening of a server on the effects: many incidents occur when the opening of a server on the
Internet inadvertently enables remote access to some other services Internet inadvertently enables remote access to some other services
Huitema et al. [Page 7]
on the same host. on the same host.
5 Stages of IPv6 deployment 5 Stages of IPv6 deployment
The deployment of IPv6 over time is expected to proceed from an We expect the deployment of IPv6 to proceed from an initial state in
initial state in which there is little or no deployment, to a final which there is little or no deployment to a final stage in which we
stage in which we might retire the IPv4 infrastructure. We expect might retire the IPv4 infrastructure. We expect this process to
this process to stretch over several years; we also expect it to not stretch over many years; we also expect it to not be synchronized,
be synchronized, as different parties involved will deploy IPv6 at as different parties involved will deploy IPv6 at different paces.
different pace. In order to get some clarity, we distinguish three In order to get some clarity, we distinguish three entities involved
entities involved in the transition of an unmanaged network: the ISP in the transition of an unmanaged network: the ISP (possibly
(possibly including ISP CPE), the home gateway and the hosts including ISP consumer premise equipment (CPE)), the home gateway,
(computers and appliances). Each can support IPv4-only, both IPv4 and the hosts (computers and appliances). Each can support IPv4-
and IPv6 or IPv6-only. That gives us 27 possibilities. We describe only, both IPv4 and IPv6 or IPv6-only. That gives us 27
the most important cases. We will consider that in all cases the possibilities. We describe the most important cases. We will assume
hosts are a combination of IPv4-only, dual stack and IPv6-only that in all cases the hosts are a combination of IPv4-only, dual
hosts. stack and (perhaps) IPv6-only hosts.
The cases we will consider are: The cases we will consider are:
A) Gateway does not provide IPv6 A) a gateway which does not provide IPv6 at all;
B) ISP and gateway are dual stack B) a dual-stack gateway connected to a dual stack ISP;
C) Gateway is IPv6 capable, dual stack, ISP is not C) a dual stack gateway connected to an IPV4-only ISP; and
D) ISP is IPv6-only D) a gateway connected to an IPv6-only ISP
The case where the ISP is IPv6 capable but the gateway is not is In most of these cases we will assume that the gateway includes a
similar to case A. NAT: we realize that this is not always the case, but we submit that
it is common enough that we have to deal with it; furthermore, we
believe that the non-NAT variants of these cases map fairly closely
to this same set of cases. For example, the case in which there is
no NAT and the CPE is a bridge rather than a router maps fairly well
to cases B, C, or D, depending on which protocols the ISP supports;
similarly, the case in which the CPE is a router but is not a NAT
maps either to case B or case C depending on what the CPE router
supports. Last, note that the combination of an IPv6-capable ISP
with a gateway that doesn't support IPv6 is, in effect, equivalent
to case A.
5.1 Case A, host deployment of IPv6 applications 5.1 Case A, host deployment of IPv6 applications
In this case the gateway doesn't provide IPv6; the ISP may or may 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 not provide IPv6, but this is not relevant, since the non-upgraded
gateway would prevent the hosts from using the ISP service. Some gateway would prevent the hosts from using the ISP service. Some
hosts will try to get IPv6 connectivity, in order to run hosts will try to get IPv6 connectivity, in order to run
applications that require IPv6, or work better with IPv6. applications that require IPv6, or work better with IPv6. The hosts
in this case will have to handle the IPv6 transition mechanisms on
their own.
Huitema et al. [Page 7] There are two variations of this case, depending on the type of
service implemented by the gateway. In many cases, the gateway is a
direct obstacle to the deployment of IPv6, but a gateway which is
some form of bridge-mode CPE or which is a plain (neither
Huitema et al. [Page 8]
filtering nor NAT) router does not really fall into this category.
5.1.1 Application support in Case A 5.1.1 Application support in Case A
The focus of Case A is to enable communication between a host on the 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. unmanaged network and some IPv6-only hosts outside of the network.
The primary focus in the immediate future, i.e. for the early The primary focus in the immediate future, i.e. for the early
adopters of IPv6, will be peer-to-peer applications. However, as adopters of IPv6, will be peer-to-peer applications. However, as
IPv6 deployment progresses, we will likely find a situation where IPv6 deployment progresses, we will likely find a situation where
some networks have IPv6-only services deployed, at which point we some networks have IPv6-only services deployed, at which point we
would like case A client applications to be able to access those would like case A client applications to be able to access those
services. services.
Local applications are not a primary focus of Case A. At this stage, 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 we expect all clients in the unmanaged network to have either IPv4
only or dual stack support. Local applications can continue working only or dual stack support. Local applications can continue working
using IPv4. using IPv4.
Server applications are also not a primary focus of Case A. Server Server applications are also not a primary focus of Case A. Server
applications require DNS support, which is difficult to engineer for applications require DNS support, which is difficult to engineer for
clients located behind a NAT. Besides, server applications, at this clients located behind a NAT, which is likely to be present in this
stage, cater mostly to IPv4 clients; putting up an IPv6-only server case. Besides, server applications at present cater mostly to IPv4
is not very attractive. clients; putting up an IPv6-only server is not very attractive.
In contrast, peer-to-peer applications are both attractive and easy In contrast, peer-to-peer applications are probably both attractive
to deploy: they are deployed in a coordinated fashion as part of a and easy to deploy: they are deployed in a coordinated fashion as
peer-to-peer network, which means that hosts can all receive some part of a peer-to-peer network, which means that hosts can all
form of IPv6 upgrade; they often provide their own naming receive some form of IPv6 upgrade; they often provide their own
infrastructure, in which case they are not dependent on DNS naming infrastructure, in which case they are not dependent on DNS
services. services.
5.1.2 Addresses and connectivity in Case A 5.1.2 Addresses and connectivity in Case A
We saw in 5.1.1 that a primary motivation for the deployment of IPv6 We saw in 5.1.1 that the likely motivation for deployment of IPv6
connectivity in hosts is participation to peer-to-peer applications, connectivity in hosts in case A is a desire to use peer-to-peer and
and also to IPv6-only client applications. These applications client IPv6 applications. These applications require that all
require that all participating nodes get some form of IPv6 participating nodes get some form of IPv6 connectivity, i.e. at
connectivity, i.e. at least one globally reachable IPv6 address. The least one globally reachable IPv6 address.
mechanism to provide connectivity to peers behind NAT should be easy
to deploy, and light weight; it will have to involve tunneling over If the local gateway provides global IPv4 addresses to the local
UDP, as this is the practical way to traverse a NAT. If servers are hosts, then these hosts can individually exercise the mechanisms
needed, these servers will in practice have to be deployed as part described in case C, "IPv6 connectivity without provider support."
of the "support infrastructure" for the peer-to-peer network or for If the local gateway implements a NAT function, another type of
an IPv6 based service; economic reality implies that the cost of mechanism is needed. The mechanism to provide connectivity to peers
running these servers should be as low as possible. behind NAT should be easy to deploy, and light weight; it will have
to involve tunneling over a protocol that can easily traverse NAT,
either TCP or preferably UDP, as tunneling over TCP can result in
poor performances in case of time-outs and retransmission. 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.
Huitema et al. [Page 9]
5.1.3 Naming services in Case A 5.1.3 Naming services in Case A
At this phase of IPv6 deployment, hosts in the unmanaged domain have At this phase of IPv6 deployment, hosts in the unmanaged domain have
access to DNS services over IPv4, through the existing gateway. DNS access to DNS services over IPv4, through the existing gateway. DNS
resolvers are supposed to serve AAAA records, even if they only resolvers are supposed to serve AAAA records, even if they only
implement IPv4; the local hosts should thus be able to obtain the implement IPv4; the local hosts should thus be able to obtain the
IPv6 addresses of IPv6-only servers. IPv6 addresses of IPv6-only servers.
Huitema et al. [Page 8] Reverse lookup is difficult to provide for hosts on the unmanaged
Reverse lookup is hard to provide if the gateway is not upgraded. network if the gateway is not upgraded. This is a potential issue
This is a potential issue for client applications. Some servers for client applications. Some servers require a reverse lookup as
require a reverse lookup as part of accepting a client's connection, part of accepting a client's connection, and may require that the
and may require that the direct lookup of the corresponding name direct lookup of the corresponding name matches the IPv6 address of
matches the IPv6 address of the client. There is thus a requirement the client. There is thus a requirement either to provide a reverse
to either provide a reverse lookup solution, or make sure that IPv6 lookup solution, or to make sure that IPv6 servers do not require
servers do not require reverse lookup. reverse lookup.
5.2 Case B, IPv6 connectivity with provider support 5.2 Case B, IPv6 connectivity with provider support
In this case the ISP and gateway are dual stack. The gateway can use In this case the ISP and gateway are both dual stack. The gateway
native IPv6 connectivity to the ISP and use an IPv6 prefix allocated can use native IPv6 connectivity to the ISP and can use an IPv6
by the ISP. prefix allocated by the ISP.
5.2.1 Application support in Case B 5.2.1 Application support in Case B
If the ISP and the gateway are dual-stack, client applications, If the ISP and the gateway are dual-stack, client applications,
peer-to-peer applications and server applications can all be enabled peer-to-peer applications and server applications can all be enabled
easily on the unmanaged network. easily on the unmanaged network.
We expect the unmanaged network to include three kinds of hosts: We expect the unmanaged network to include three kinds of hosts:
IPv4 only, IPv6-only, and dual stack. Obviously, dual stack hosts IPv4 only, IPv6-only, and dual stack. Obviously, dual stack hosts
can interact easily with either IPv4 only hosts or IPv6-only 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 but an IPv4 only host and an IPv6-only host cannot communicate
without a third party performing some kind of translation service. without a third party performing some kind of translation service.
Our analysis concludes that unmanaged networks should not have to Our analysis concludes that unmanaged networks should not have to
provide such translation services. provide such translation services.
The argument for providing translation services is that their The argument for providing translation services is that their
availability would accelerate the deployment of IPv6-only devices, availability would accelerate the deployment of IPv6-only devices,
and thus the transition to IPv6. This is however a dubious argument, and thus the transition to IPv6. This is however a dubious argument,
since it can also be argued that the availability of these since it can also be argued that the availability of these
translation services will reduce the pressure to provide IPv6 at translation services will reduce the pressure to provide IPv6 at
all, and to just continue fielding IPv6-only devices. The remaining all, and to just continue fielding IPv4-only devices. The remaining
pressure to provide IPv6 connectivity would just be the difference pressure to provide IPv6 connectivity would just be the difference
in "quality of service" between a translated exchange and a native in "quality of service" between a translated exchange and a native
interconnect. interconnect.
The argument against translation service is the difficulty of The argument against translation service is the difficulty of
providing these services for all applications, compared to the providing these services for all applications, compared to the
relative ease of installing dual stack solutions in an unmanaged relative ease of installing dual stack solutions in an unmanaged
network. Translation services can be provided either by application network. Translation services can be provided either by application
relays such as HTTP proxies, or by network level services such as relays such as HTTP proxies, or by network level services such as
NAT-PT. Application relays pose several operational problems: first, NAT-PT. Application relays pose several operational problems: first,
one must develop relays for all applications; second, one must one must develop relays for all applications; second, one must
develop a management infrastructure to provision the host with the develop a management infrastructure to provision the host with the
addresses of the relays; in addition, the application may have to be 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 modified if one wants to use the relay selectively, e.g. only when
direct connection is not available. Network level translation poses direct connection is not available. Network level translation poses
similar problems: in practice, network level actions must be similar problems: in practice, network level actions must be
complemented by "application layer gateways" that will rewrite complemented by "application layer gateways" that will rewrite
references to IP addresses in the protocol, and these relays tend to references to IP addresses in the protocol, and while these relays
are not necessary for every application, they are necessary for
Huitema et al. [Page 9] enough applications to make any sort of generalized translation
be necessary for every application; hosts may need to be quite problematic; hosts may need to be parameterized to use the
parameterized to use the translation service; and designing the translation service; and designing the right algorithm to decide
right algorithm to decide when to translate DNS requests has proven when to translate DNS requests has proven very difficult.
very difficult.
Not assuming translation services in the network appears both more Not assuming translation services in the network appears to be both
practical and more robust. If the market requirement for a new more practical and more robust. If the market requirement for a new
device requires that it interacts with both IPv4 and IPv6 hosts, we device requires that it interact with both IPv4 and IPv6 hosts, we
may expect the manufacturers of these devices to program them with a may expect the manufacturers of these devices to program them with a
dual stack capability; in particular, we expect general purpose dual stack capability; in particular, we expect general purpose
systems such as personal computers to be effectively dual-stack. The systems such as personal computers to be effectively dual-stack. The
only devices that are expected to be capable of only supporting IPv6 only devices that are expected to be capable of only supporting IPv6
are those who are designed for specific applications, which do not are those who are designed for specific applications, which do not
require interoperation with antique IPv4-only systems. We also require interoperation with IPv4-only systems. We also observe that
observe that providing both IPv4 and IPv6 connectivity in an providing both IPv4 and IPv6 connectivity in an unmanaged network is
unmanaged network is not particularly difficult; indeed there is a not particularly difficult: we have a fair amount of experience
well established experience of using IPv4 in these networks in using IPv4 in unmanaged networks in parallel with other protocols
parallel with other protocols such as for example IPX. such as, for example, IPX.
5.2.2 Addresses and connectivity in Case B 5.2.2 Addresses and connectivity in Case B
In Case B, the upgraded gateway will behave as an IPv6 router; it In Case B, the upgraded gateway will act as an IPv6 router; it will
will continue providing the IPv4 connectivity of a non-upgraded NAT. continue providing the IPv4 connectivity, perhaps using NAT. Nodes
Nodes in the local network will obtain: in the local network will typically obtain:
- IPv4 natted addresses, - IPv4 addresses (from or via the gateway),
- IPv6 link local addresses, - IPv6 link local addresses, and
- IPv6 global addresses. - IPv6 global addresses.
The hosts could also obtain IPv6 site local addresses, if the In some networks, NAT will not be in use and the local hosts will
gateway advertises a site local prefix. This is as debatable: site actually obtain global IPv4 addresses NAT will not be in use. We
local addresses provide some isolation to site local application will not elaborate on this, as the availability of global IPv4
from network connectivity events and network based attacks; however, addresses does not bring any additional complexity to the transition
managing non unique addresses can be problematic if some local hosts mechanisms.
are multi-homed, as is common with VPN connections.
To enable this scenario, the gateway need to use a mechanism obtain To enable this scenario, the gateway needs to use a mechanism to
a global address prefix from the ISP, and advertise this address obtain a global IPv6 address prefix from the ISP, and advertise this
prefix to the hosts in the unmanaged network; several solutions will address prefix to the hosts in the unmanaged network; several
be assessed in a companion memo [EVAL]. solutions will be assessed in a companion memo [EVAL].
5.2.3 Naming services in Case B 5.2.3 Naming services in Case B
In case B, hosts in the unmanaged domain have access to DNS services
At this phase of IPv6 deployment, hosts in the unmanaged domain have through the gateway. As the gateway and the ISP both support IPv4
access to DNS services through the gateway. As the gateway and the and IPv6, these services may be accessible by the IPv4-only hosts
ISP both support IPv4 and IPv6, these services may be accessible by using IPv4, by the IPv6-only hosts using IPv6, and by the dual stack
the IPv4 only hosts using IPv4, by the IPv6-only hosts using IPv6, hosts using either. Currently, IPv4 only hosts usually discover the
and by the dual stack hosts using either. Currently, IPv4 only hosts IPv4 address of the local DNS resolver using DHCP; there must be a
discover the IPv4 address of the local DNS server using DHCP; there way for IPv6-only hosts to discover the IPv6 address of the DNS
must be a way for IPv6-only hosts to discover the IPv6 address of resolver.
the DNS server.
There must be a way to resolve the name of local hosts to their IPv4 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 or IPv6 addresses. Typing auto-configured IPv6 addresses in a
configuration file is impractical; this implies either some form of configuration file is impractical; this implies either some form of
dynamic registration of IPv6 addresses in the local service, or a dynamic registration of IPv6 addresses in the local service, or a
dynamic address discovery mechanism. Possible solutions will be dynamic address discovery mechanism. Possible solutions will be
compared in the evaluation draft. compared in the evaluation draft.
The requirement to support server applications in the unmanaged The requirement to support server applications in the unmanaged
network implies a requirement to publish the IPv6 addresses of local network implies a requirement to publish the IPv6 addresses of local
servers in the DNS. There are multiple solutions, including servers in the DNS. There are multiple solutions, including domain
variations of domain name delegation. If we want to provide name delegation. If efficient reverse lookup functions are to be
efficient reverse lookup functions, delegation of a fraction of the provided, delegation of a fraction of the ip6.arpa tree is also
ip6.arpa tree is also required. required.
The response to a DNS request should not depend of the protocol with The response to a DNS request should not depend on the protocol by
which the request is transported: dual-stack hosts may indifferently which the request is transported: dual-stack hosts may use either
use IPv4 or IPv6 to contact the local resolver; the choice of IPv4 IPv4 or IPv6 to contact the local resolver, the choice of IPv4 or
or IPv6 will be random; the value of the response should not depend IPv6 may be random, and the value of the response should not depend
of a random event. of a random event.
DNS transition issues in a dual IPv4/IPv6 network are discussed in
[DNSOPV6].
5.3 Case C, IPv6 connectivity without provider support 5.3 Case C, IPv6 connectivity without provider support
In this case the gateway is IPv6 capable, dual stack, the ISP is In this case the gateway is dual stack, but the ISP is not. The
not. The gateway has been upgraded and offers both IPv4 and IPv6 gateway has been upgraded and offers both IPv4 and IPv6 connectivity
connectivity the hosts. It cannot rely on the ISP for IPv6 the hosts. It cannot rely on the ISP for IPv6 connectivity, because
connectivity, because the ISP does not offer ISP connectivity yet. the ISP does not offer ISP connectivity yet.
5.3.1 Application support in Case C 5.3.1 Application support in Case C
Application support in case C should be identical to that of case B. Application support in case C should be identical to that of case B.
5.3.2 Addresses and connectivity in Case C 5.3.2 Addresses and connectivity in Case C
The upgraded gateway will behave as an IPv6 router; it will continue The upgraded gateway will behave as an IPv6 router; it will continue
providing the IPv4 connectivity of non-upgraded NAT. Nodes in the providing the IPv4 connectivity, perhaps using NAT. Nodes in the
local network will obtain: local network will obtain:
- IPv4 natted addresses, - IPv4 addresses (from or via the gateway),
- IPv6 link local addresses, - IPv6 link local addresses,
- IPv6 global 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 There are two ways to bring immediate IPv6 connectivity on top of an
IPv4 only infrastructure: automatic tunnels provided by the [6TO4] IPv4 only infrastructure: automatic tunnels, e.g. provided by the
technology, or configured tunnels. Both technologies have advantages [6TO4] technology, or configured tunnels. Both technologies have
and limitations, which will be studied in a companion document. advantages and limitations, which will be studied in a companion
document.
There will be some cases where the local hosts actually obtain
global IPv4 addresses. We will not discuss this scenario, as it does
not make the use of transition technology harder, or more complex.
Case A has already examined how hosts could obtain IPv6 connectivity
individually.
5.3.3 Naming services in Case C 5.3.3 Naming services in Case C
The local naming requirements in case C are identical to the local The local naming requirements in case C are identical to the local
naming requirements of case B, with two differences: delegation of naming requirements of case B, with two differences: delegation of
domain names, and management of reverse lookup queries. domain names, and management of reverse lookup queries.
A delegation of some domain name is required in order to publish the 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 IPv6 addresses of servers in the DNS.
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 A specific mechanism for handling reverse lookup queries will be
required if the gateway uses a dynamic mechanism such as 6to4 to required if the gateway uses a dynamic mechanism such as 6to4 to
obtain a prefix independently of any IPv6 ISP. obtain a prefix independently of any IPv6 ISP.
5.4 Case D, ISP stops providing native IPv4 connectivity 5.4 Case D, ISP stops providing native IPv4 connectivity
In this case the ISP is IPv6-only, so the gateway looses IPv4 In this case the ISP is IPv6-only, so the gateway loses IPv4
connectivity, and is faced with an IPv6-only service provider. The connectivity, and is faced with an IPv6-only service provider. The
gateway itself is dual stack, and the unmanaged network includes gateway itself is dual stack, and the unmanaged network includes
IPv4 only, IPv6-only and dual stack hosts. Any interaction between IPv4 only, IPv6-only and dual stack hosts. Any interaction between
hosts in the unmanaged network and IPv4 hosts on the Internet will hosts in the unmanaged network and IPv4 hosts on the Internet will
require the provision of some inter-protocol services by the ISP. require the provision of some inter-protocol services by the ISP.
5.4.1 Application support in Case D 5.4.1 Application support in Case D
At this phase of the transition, IPv6 hosts can perform all types of At this phase of the transition, IPv6 hosts can participate in all
applications with other IPv6 hosts. IPv4 hosts in the unmanaged types of applications with other IPv6 hosts. IPv4 hosts in the
network will be able to perform local applications with IPv4 or dual unmanaged network will be able to perform local applications with
stack local hosts. IPv4 or dual stack local hosts.
As in case B, we will assume that IPv6-only hosts will not interact 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 with IPv4-only hosts, either local or remote. We must however assume
that IPv4-only hosts and dual stack hosts will desire to interact that IPv4-only hosts and dual stack hosts will desire to interact
with IPv4 services available on the Internet: the inability to do so with IPv4 services available on the Internet: the inability to do so
would place the IPv6-only provider at a great commercial would place the IPv6-only provider at a great commercial
disadvantage compared to other Internet service providers. disadvantage compared to other Internet service providers.
There are three possible ways that an ISP can provide hosts in the 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 unmanaged network with access to IPv4 applications: by using a set
application relays, by providing an address translation service, or of application relays, by providing an address translation service,
by providing IPv4-over-IPv6 tunnels. Our analysis concludes that a or by providing IPv4-over-IPv6 tunnels. Our analysis concludes that
tunnel service will be vastly preferable. a tunnel service seems to be vastly preferable.
We already mentioned the drawbacks of the application gateway We already mentioned the drawbacks of the application gateway
approach when analyzing case B: it is necessary to provide relays approach when analyzing case B: it is necessary to provide relays
for all applications, to develop a way to provision the hosts with for all applications, to develop a way to provision the hosts with
the addresses of these relays, and to modify the applications so the addresses of these relays, and to modify the applications so
that they will only use the relays when needed. We also observe that 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 in an IPv6-only ISP the application relays would only be accessible
over IPv6, and would thus not be accessible by the "legacy" IPv4- over IPv6, and would thus not be accessible by the "legacy" IPv4-
only hosts. The application relay approach is thus not very only hosts. The application relay approach is thus not very
attractive. attractive.
Providing a network address and protocol translation service between Providing a network address and protocol translation service between
IPv6 and IPv4 would also have many drawbacks. As in case B, it will IPv6 and IPv4 would also have many drawbacks. As in case B, it will
have to be complemented by "application layer gateways" that will have to be complemented by "application layer gateways" that will
rewrite references to IP addresses in the protocol; hosts may need rewrite references to IP addresses in the protocol; hosts may need
to be parameterized to use the translation service; and we would 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- have to solve DNS issues. The network level protocol translation
to-IPv4 translation service would not be accessible by legacy IPv4- service doesn't appear to be very desirable.
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 The preferable alternative to application relays and network address
translation is the provision of an IPv4-over-IPv6 service. translation is the provision of an IPv4-over-IPv6 service.
5.4.2 Addresses and connectivity in Case D 5.4.2 Addresses and connectivity in Case D
The ISP assigns an IPv6 prefix to the unmanaged network, so hosts The ISP assigns an IPv6 prefix to the unmanaged network, so hosts
have a global IPv6 address and use it for global IPv6 connectivity. have a global IPv6 address and use it for global IPv6 connectivity.
This will require delegation of an IPv6 address prefix, as This will require delegation of an IPv6 address prefix, as
investigated in case C. investigated in case C.
To enable IPv4 hosts and dual stack host to access remote IPv4 To enable IPv4 hosts and dual stack host to access remote IPv4
services, the ISP must provide the gateway with at least one IPv4 services, the ISP must provide the gateway with at least one IPv4
address, using some form of IPv4-over-IPv6 tunneling. Once such address, using some form of IPv4-over-IPv6 tunneling. Once such
addresses have been provided, the gateway effectively acquires dual- addresses have been provided, the gateway effectively acquires dual-
stack connectivity; for hosts inside the unmanaged network, this stack connectivity; for hosts inside the unmanaged network, this
will be indistinguishable from the connectivity obtained in case B will be indistinguishable from the IPv4 connectivity obtained in
or C. case B or C.
5.4.3 Naming services in Case D 5.4.3 Naming services in Case D
The loss of IPv4 connectivity has a direct impact on the provision The loss of IPv4 connectivity has a direct impact on the provision
of naming services. An obvious consequence is the gateway will have of naming services. In many IPv4 unmanaged networks, hosts obtain
to be provisioned with the address of a DNS server and with other their DNS configuration parameters from the local gateway, typically
DNS parameters, and that this provisioning will have to use IPv6 through the DHCP service. If the same mode of operation is desired
mechanisms. Another consequence is that the DNS service in the in case D, the gateway will have to be provisioned with the address
gateway will only be able to use IPv6 connectivity to resolve of a DNS resolver and with other DNS parameters, and this
queries; if local hosts perform DNS resolution autonomously, they provisioning will have to use IPv6 mechanisms. Another consequence
will have the same restriction. 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 On the surface, this seems to indicate that the local hosts will
only be able to resolve names if the domain servers are accessible only be able to resolve names if the domain servers are accessible
through an IPv6 address documented in a AAAA record. However, the through an IPv6 address documented in an AAAA record. However, the
DNS services are just one case of "IPv4 servers accessed by IPv6 DNS services are just one case of "IPv4 servers accessed by IPv6
hosts": it should be possible to simply send queries through the hosts": it should be possible to simply send queries through the
address translation services to reach the IPv4 only servers. IPv4 connectivity services to reach the IPv4 only servers.
The gateway should be able to act as a "DNS proxy" for the remaining The gateway should be able to act as a recursive DNS name server for
IPv4 only hosts. the remaining IPv4 only hosts.
6 Security Considerations 6 Security Considerations
Security considerations are discussed as part of the applications' Security considerations are discussed as part of the applications'
requirements. They include: requirements. They include:
- the guarantee that local applications are only used locally, - the guarantee that local applications are only used locally,
- the protection of the privacy of clients - the protection of the privacy of clients
- the requirement that peer-to-peer connections are only used by - the requirement that peer-to-peer connections are only used by
authorized peers. authorized peers.
The security solutions currently used in IPv4 networks include a
combination of firewall functions in the gateway, authentication and
authorization functions in the applications, encryption and
authentication services provides by IP security, Transport Layer
Security and application specific services, and host-based security
products such as anti-virus software, and host firewalls. The
applicability of these tools in IPv6 unmanaged networks will be
studied in a companion document.
7 IANA Considerations 7 IANA Considerations
This memo does not include any request to IANA. This memo does not include any request to IANA.
8 Copyright 8 Copyright
The following copyright notice is copied from RFC 2026 [Bradner, The following copyright notice is copied from RFC 2026 [Bradner,
1996], Section 10.4, and describes the applicable copyright for this 1996], Section 10.4, and describes the applicable copyright for this
document. document.
skipping to change at page 15, line 25 skipping to change at page 16, line 48
can be obtained from the IETF Secretariat. can be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive this standard. Please address the information to the IETF Executive
Director. Director.
10 Acknowledgements 10 Acknowledgements
This draft has benefited from extensive reviews by Tony Hain, Suresh This draft has benefited from the comments of the members of the
K Satapati, and Margaret Wasserman. IETF V6OPS working group, and from extensive reviews by Chris
Fischer, Tony Hain, Kurt Erik Lindqvist, Erik Nordmark, Pekka
Savola, and Margaret Wasserman.
11 References 11 References
Normative References
[RFC791] J. Postel, "Internet Protocol", RFC 791, September 1981.
[RFC2460] Deering, S., and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
[RFC2461] Narten, T., Nordmark, E., and W. Simpson, "Neighbor
Discovery for IP Version 6 (IPv6)", RFC 2461, December 1998.
[RFC2462] Narten, T., and S. Thomson, "IPv6 Stateless Address
Autoconfiguration", RFC 2462, December 1998.
Informative references
[EVAL] Evaluation of Transition Mechanisms for Unmanaged Networks, [EVAL] Evaluation of Transition Mechanisms for Unmanaged Networks,
work in progress. work in progress.
[RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.
J., and E. Lear, "Address Allocation for Private Internets", RFC
1918, February 1996.
[RFC3056] Carpenter, B., and K. Moore, "Connection of IPv6 Domains
via IPv4 Clouds", RFC 3056, February 2001.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP:
Session Initiation Protocol", RFC 3261, June 2002.
[RFC3022] Srisuresh, P., and K. Egevang. "Traditional IP Network
Address Translator (Traditional NAT)", RFC 3022, January 2001.
[RFC2993] T. Hain. "Architectural Implications of NAT", RFC 2993,
November 2000.
[RFC2608] Guttman, E., Perkins, C., Veizades, J., and M. Day.
"Service Location Protocol, Version 2", RFC 2993, June 1999.
[RFC3041] Narten, T., and R. Draves. "Privacy Extensions for
Stateless Address Autoconfiguration in IPv6", RFC 3041, January
2001.
[DNSOPV6] A. Durand. "IPv6 DNS transition issues", Work in progress.
[DNSINADDR] D. Senie. "Requiring DNS IN-ADDR Mapping", Work in
progress.
12 Authors' Addresses 12 Authors' Addresses
Christian Huitema Christian Huitema
Microsoft Corporation Microsoft Corporation
One Microsoft Way One Microsoft Way
Redmond, WA 98052-6399 Redmond, WA 98052-6399
Email: huitema@microsoft.com Email: huitema@microsoft.com
Rob Austein Rob Austein
Email: sra@hactrn.net Email: sra@hactrn.net
Suresh Satapati
Cisco Systems, Inc.
San Jose, CA 95134
USA
EMail: satapati@cisco.com
Ronald van der Pol Ronald van der Pol
Email: Ronald.vanderPol@surfnet.nl NLnet Labs
Kruislaan 419
1098 VA Amsterdam
NL
Email: Ronald.vanderPol@nlnetlabs.nl
Table of Contents: Table of Contents:
1 Introduction .................................................... 1 1 Introduction .................................................... 1
2 Topology ........................................................ 1 2 Topology ........................................................ 2
3 Applications .................................................... 2 3 Applications .................................................... 3
3.1 Local applications ............................................ 2 3.1 Local applications ............................................ 3
3.2 Client applications ........................................... 3 3.2 Client applications ........................................... 3
3.3 Peer-to-peer applications ..................................... 3 3.3 Peer-to-peer applications ..................................... 3
3.4 Server applications ........................................... 3 3.4 Server applications ........................................... 4
4 Application requirements of an IPv6 unmanaged network ........... 4 4 Application requirements of an IPv6 unmanaged network ........... 4
4.1 Requirements of local applications ............................ 4 4.1 Requirements of local applications ............................ 5
4.2 Requirements of client applications ........................... 4 4.2 Requirements of client applications ........................... 5
4.2.1 Privacy requirement of client applications .................. 5 4.2.1 Privacy requirement of client applications .................. 5
4.3 Requirements of peer-to-peer applications ..................... 6 4.3 Requirements of peer-to-peer applications ..................... 6
4.4 Requirements of server applications ........................... 6 4.4 Requirements of server applications ........................... 7
5 Stages of IPv6 deployment ....................................... 7 5 Stages of IPv6 deployment ....................................... 8
5.1 Case A, host deployment of IPv6 applications .................. 7 5.1 Case A, host deployment of IPv6 applications .................. 8
5.1.1 Application support in Case A ............................... 8 5.1.1 Application support in Case A ............................... 9
5.1.2 Addresses and connectivity in Case A ........................ 8 5.1.2 Addresses and connectivity in Case A ........................ 9
5.1.3 Naming services in Case A ................................... 8 5.1.3 Naming services in Case A ................................... 10
5.2 Case B, IPv6 connectivity with provider support ............... 9 5.2 Case B, IPv6 connectivity with provider support ............... 10
5.2.1 Application support in Case B ............................... 9 5.2.1 Application support in Case B ............................... 10
5.2.2 Addresses and connectivity in Case B ........................ 10 5.2.2 Addresses and connectivity in Case B ........................ 11
5.2.3 Naming services in Case B ................................... 10 5.2.3 Naming services in Case B ................................... 11
5.3 Case C, IPv6 connectivity without provider support ............ 11 5.3 Case C, IPv6 connectivity without provider support ............ 12
5.3.1 Application support in Case C ............................... 11 5.3.1 Application support in Case C ............................... 12
5.3.2 Addresses and connectivity in Case C ........................ 11 5.3.2 Addresses and connectivity in Case C ........................ 12
5.3.3 Naming services in Case C ................................... 11 5.3.3 Naming services in Case C ................................... 13
5.4 Case D, ISP stops providing native IPv4 connectivity .......... 12 5.4 Case D, ISP stops providing native IPv4 connectivity .......... 13
5.4.1 Application support in Case D ............................... 12 5.4.1 Application support in Case D ............................... 13
5.4.2 Addresses and connectivity in Case D ........................ 13 5.4.2 Addresses and connectivity in Case D ........................ 14
5.4.3 Naming services in Case D ................................... 13 5.4.3 Naming services in Case D ................................... 14
6 Security Considerations ......................................... 13 6 Security Considerations ......................................... 15
7 IANA Considerations ............................................. 14 7 IANA Considerations ............................................. 15
8 Copyright ....................................................... 14 8 Copyright ....................................................... 15
9 Intellectual Property ........................................... 14 9 Intellectual Property ........................................... 16
10 Acknowledgements ............................................... 15 10 Acknowledgements ............................................... 16
11 References ..................................................... 15 11 References ..................................................... 16
12 Authors' Addresses ............................................. 15 12 Authors' Addresses ............................................. 17
 End of changes. 

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