IPv6
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...
This memo specifies an optional interim mechanism for IPv6 sites to
communicate with each other over the IPv4 network without explicit
...
... IPv4 network without explicit
tunnel setup, and for them to communicate with native IPv6 domains
via relay routers ...
... start-up transition tool used during the period of co-existence of
IPv4 and IPv6. It is not intended as a permanent solution.
...
...
The document defines a method for assigning an interim unique IPv6
address prefix to any site that currently has at least one globally
unique IPv4 address ...
... encapsulation mechanism for
transmitting IPv6 packets using such a prefix over the global IPv4
network. It also describes scenarios for using such prefixes ...
... prefixes during
the co-existence phase of IPv4 to IPv6 transition. Note that these
scenarios are only part of the total picture of transition to IPv6.
...
... IPv4 to IPv6 transition. Note that these
scenarios are only part of the total picture of transition to IPv6.
Also note that this is considered to be an interim solution and that
sites should migrate when possible to native IPv6 prefixes ...
... IPv6.
Also note that this is considered to be an interim solution and that
sites should migrate when possible to native IPv6 prefixes and native
IPv6 connectivity. This will be possible as soon as the site's ISP ...
... sites should migrate when possible to native IPv6 prefixes and native
IPv6 connectivity. This will be possible as soon as the site's ISP
offers native IPv6 connectivity ...
... IPv6 connectivity. This will be possible as soon as the site's ISP
offers native IPv6 connectivity.
...
... Section 5.2). It will introduce no new entries in the IPv4 routing
table, and exactly one new entry in the native IPv6 routing table
(see Section 5.10).
...
...
Although the mechanism is specified for an IPv6 site, it can equally
be applied to an individual IPv6 host or very small site, as long as
...
... Although the mechanism is specified for an IPv6 site, it can equally
be applied to an individual IPv6 host or very small site, as long as
it has at least one globally unique IPv4 address. However, the
...
...
The motivation for this method is to allow isolated IPv6 sites or
hosts, attached to a wide area network ...
... hosts, attached to a wide area network which has no native IPv6
support, to communicate with other such IPv6 domains or hosts ...
... hosts, attached to a wide area network which has no native IPv6
support, to communicate with other such IPv6 domains or hosts with
...
... method do not require IPv4-
compatible IPv6 addresses [MECH] or configured tunnels. In this way
...
... MECH] or configured tunnels. In this way
IPv6 gains considerable independence of the underlying wide area
network and can step over many hops of IPv4 subnets ...
... 6to4 encapsulation of IPv6 packets inside IPv4 packets occurs
at a point that is logically equivalent to an IPv6 ...
... IPv6 packets inside IPv4 packets occurs
at a point that is logically equivalent to an IPv6 interface,
with the link layer ...
... interface. It is
normally the border router between an IPv6 site and a wide-area
IPv4 network.
...
... 6to4 host:
an IPv6 host which happens to have at least one 6to4 address.
In all other respects it is a standard IPv6 host ...
... IPv6 host which happens to have at least one 6to4 address.
In all other respects it is a standard IPv6 host.
Note: an IPv6 node ...
... configured tunnel. Such a node may function as an IPv6 host using a
6to4 address on its configured tunnel ...
... configured tunnel interface, and it may also
serve as a IPv6 router for other hosts via a 6to4 ...
... 6to4 site:
a site running IPv6 internally using 6to4 addresses, therefore
containing at least one 6to4 ...
... IPv6 Prefix Allocation ...
... AGGR] for the 6to4 scheme.Its numeric value is 0x0002, i.e., it is
2002::/16 when expressed as an IPv6 address prefix.
...
...
The subscriber site is then deemed to have the following IPv6 address
prefix, without any further assignment procedures being necessary:
...
... subscriber site it can be used exactly
like any other valid IPv6 prefix, e.g., for automated address
assignment and discovery according to the normal mechanisms such as
[CONF ...
... Note that if the IPv4 address is assigned dynamically, the
corresponding IPv6 prefix will also be dynamic in nature, with the
same lifetime.
...
... and destination address selection must be appropriately implemented.
If the source IPv6 host sending a packet has at least one 2002::
address ...
... host sending a packet has at least one 2002::
address assigned to it, and if the set of IPv6 addresses returned by
the DNS for the destination host ...
... 6to4 address, and the other one has both a
6to4 and a native IPv6 address, then the 6to4 address should be used
for both.
...
... If both hosts have a 6to4 address and a native IPv6 address, then
either the 6to4 address should be used for both, or the native IPv6
address ...
... IPv6 address, then
either the 6to4 address should be used for both, or the native IPv6
address should be used for both. The choice should be configurable.
The default configuration should be native IPv6 for both.
...
... 6to4 address should be used for both, or the native IPv6
address should be used for both. The choice should be configurable.
The default configuration should be native IPv6 for both.
...
... 6to4 traffic is notionally
equivalent to an IPv6 interface, and is referred to below as a
pseudo ...
... RFC791] with an IPv4
protocol type of 41, the same as has been assigned [MECH] for IPv6
packets that are tunneled inside of IPv4 frames. The IPv4 header ...
... IPv4 addresses. One or both of
these will be identical to the V4ADDR field of an IPv6 prefix formed
as specified above (see section 5 for more details). The IPv4 packet
...
... as specified above (see section 5 for more details). The IPv4 packet
body contains the IPv6 header and payload.
...
... | Options | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 header and payload ... /
...
... RFC791], as will the
encapsulated IPv6 hop limit [IPV6]. Other considerations are as
described in Section 4.1.2 of [MECH ...
... able to send IPv4 packets with protocol type 41 to any of the others.
By definition, each site has an IPv6 prefix in the format defined in
Section 2. It will therefore create DNS records ...
... IPv4 address 192.1.2.3 will create DNS
records with the IPv6 prefix {FP=001,TLA=0x0002,NLA=192.1.2.3}/48
(i.e., 2002:c001:0203::/48). Site B which owns address ...
... will create DNS records with the IPv6 prefix
{FP=001,TLA=0x0002,NLA=9.254.253.252}/48 (i.e., 2002:09fe:fdfc::/48).
...
... queries the DNS for a host on site B. IPv6 packets are formed and
transmitted in the normal way within both sites.
...
... router # || || # router # ||
||IPv6 Site A ########## || ||IPv6 Site B ########## ||
||2002:c001:0203::/48 || ||2002:09fe:fdfc::/48 ||
...
... router # ||
||IPv6 Site A ########## || ||IPv6 Site B ########## ||
||2002:c001:0203::/48 || ||2002:09fe:fdfc::/48 ||
||_______________________________|| ||_______________________________||
...
... prefix, will be handled like
any other non-local IPv6 address, i.e., by a default or explicit
route towards the 6to4 border router ...
... additional sending and decapsulation rules are the only changes to
IPv6 forwarding, and they occur only at border routers. No IPv4
routing information is imported into IPv6 routing ...
... IPv6 forwarding, and they occur only at border routers. No IPv4
routing information is imported into IPv6 routing (nor vice versa).
...
... decapsulation rules configured in the 6to4
router. This router SHOULD also generate the appropriate IPv6 prefix
announcements [CONF, DISC ...
...
Although site A and site B will each need to run IPv6 routing
internally, they do not need to run an IPv6 exterior routing protocol ...
... Although site A and site B will each need to run IPv6 routing
internally, they do not need to run an IPv6 exterior routing protocol
in this simple scenario; IPv4 ...
... Mixed scenario with relay to native IPv6 ...
...
During the transition to IPv6 we can expect some sites to fit the
model just described (isolated sites whose only connectivity is the
IPv4 Internet ...
... IPv4 Internet), whereas others will be part of larger islands of
native or tunneled IPv6 using normal IPv6 TLA address space. The
...
... IPv4 Internet), whereas others will be part of larger islands of
native or tunneled IPv6 using normal IPv6 TLA address space. The
6to4 ...
... address space. The
6to4 sites will need connectivity to these native IPv6 islands and
vice versa. In the 6to4 model, this connectivity is accomplished by
...
... vice versa. In the 6to4 model, this connectivity is accomplished by
IPv6 routers which possess both 6to4 and native IPv6 addresses.
...
... IPv6 routers which possess both 6to4 and native IPv6 addresses.
Although they behave essentially as standard IPv6 routers, for the
...
... 6to4 and native IPv6 addresses.
Although they behave essentially as standard IPv6 routers, for the
purposes of this document they are referred to as relay routers to
...
... 6to4
domain and a given native IPv6 domain. There is nothing special
about it; it is simply a normal router which happens to have at least
...
... domain of each 6to4 site;
2. an exterior IPv6 routing domain interconnecting
a given set of 6to4 ...
... 6to4 routers
using a given relay router each have a default IPv6 route pointing to
the relay router ...
... 6to4 routers.
2.2 An IPv6 exterior routing protocol is used. The set of 6to4
routers using a given relay router ...
... routing protocol is used. The set of 6to4
routers using a given relay router obtain native IPv6 routes from the
relay router using a routing protocol ...
... BGP4+]. The relay router will advertise whatever native IPv6 routing
prefixes are appropriate on its 6to4 ...
... interface. These
prefixes will indicate the regions of native IPv6 topology that the
relay router ...
... relay router MUST advertise a route to 2002::/16 into the native
IPv6 exterior routing domain. It is a matter of routing policy ...
... far this routing advertisement of 2002::/16 is propagated in the
native IPv6 routing system. Since there will in general be multiple
relay routers advertising it, network operators ...
... 6to4 prefixes more specific than 2002::/16 must not be propagated in
native IPv6 routing, to prevent pollution of the IPv6 routing table
by elements ...
... prefixes more specific than 2002::/16 must not be propagated in
native IPv6 routing, to prevent pollution of the IPv6 routing table
by elements of the IPv4 routing ...
... IPv4 routing table. Therefore, a 6to4 site which
also has a native IPv6 connection MUST NOT advertise its 2002::/48
routing ...
... routing prefix on that connection, and all native IPv6 network
operators MUST filter out and discard any 2002:: routing ...
... prefix
advertisements longer than /16.
Sites which have at least one native IPv6 connection, in addition to
a 6to4 ...
... a 6to4 connection, will therefore have at least one IPv6 prefix which
is not a 2002:: prefix. Such sites' DNS ...
... route or the native route will
be used depends on IPv6 address selection by the individual hosts (or
even applications).
...
...
Now consider again the example of the previous section. Suppose an
IPv6 host on site B queries the DNS entry for a host ...
... router # || || # router # ||
########## || ||IPv6 Site B ########## ||
|| ||2002:09fe:fdfc::/48 ||
__Site A_____|| ||2001:0600::/48_________________||
...
... prefix according to some rule for multiple
prefixes, it will simply send packets to an IPv6 address formed with
the prefix {FP ...
... cooperative 6to4 user site. A variant of this is for an Internet
Service Provider, that already offers native IPv6 connectivity, to
operate a relay router. Technically this is no different from the
...
... on that interface. Routing policy within the native IPv6 routing
domain determines the scope of that advertisement, thereby limiting
...
... IPv6 packets received by the relay router whose next hop IPv6 address
matches 2002::/16 will be routed to its 6to4 pseudo ...
... 2.1 of Section 5.2), the relay router will be configured to accept
and relay all IPv6 traffic only from its client 6to4 ...
... 6to4 router served by the relay router will be configured with a
default IPv6 route to the relay router (for example, Site A's default
...
... route to the relay router (for example, Site A's default
IPv6 route ::/0 would point to the relay router's address ...
... domain (option 2.2
of Section 5.2), the relay router advertises IPv6 native routing
prefixes on its 6to4 pseudo ...
... chosen from among those reachable through the relay router's native
IPv6 interface. In the simplest case, a default route to the whole
...
... interface. In the simplest case, a default route to the whole
IPv6 address space could be advertised. When multiple relay routers
are in use, more specific routing prefixes ...
... routing
prefix into the native IPv6 domain and MUST NOT advertise any native
IPv6 routing prefixes ...
... prefix into the native IPv6 domain and MUST NOT advertise any native
IPv6 routing prefixes or a default IPv6 route ...
...
The only change to standard IPv6 forwarding is that every 6to4 router
(and only 6to4 routers ...
...
In the sending rule, "next hop" refers to the next IPv6 node that the
packet will be sent to, which is not necessarily the final
destination ...
... packet will be sent to, which is not necessarily the final
destination, but rather the next IPv6 neighbor indicated by normal
IPv6 routing ...
... IPv6 neighbor indicated by normal
IPv6 routing mechanisms. If the final destination is a 6to4 address,
...
...
A 6to4 site which has no IPv6 connections to the "native" IPv6
Internet can acquire effective connectivity to the v6 Internet ...
... 6to4 site which has no IPv6 connections to the "native" IPv6
Internet can acquire effective connectivity to the v6 Internet via a
"configured tunnel ...
... MECH]) to a
cooperating router which does have IPv6 access, but which does not
need to be a 6to4 router. Such tunnels ...
...
If there are multiple relay routers between native IPv6 and the 6to4
world, different parts of the 6to4 ...
... relays. The only complexity that this introduces is in the scoping
of 2002::/16 routing advertisements within the native IPv6 world.
Like any BGP4+ advertisements, their scope must be correctly defined
by routing policy ...
...
If there are multiple IPv6 stubs all interconnected by 6to4 through
the global IPv4 Internet ...
...
If multiple IPv6 stubs are interconnected through multiple, disjoint
IPv4 networks (i.e., a fragmented IPv4 ...
... IPv4 border router, thereby obtaining
a simple form of IPv6 multihoming by using multiple simultaneous IPv6
prefixes and multiple simultaneous relay routers ...
... a simple form of IPv6 multihoming by using multiple simultaneous IPv6
prefixes and multiple simultaneous relay routers.
...
... are followed, then a site can migrate from using 6to4 to using native
IPv6 connections over a long period of co-existence, with no need to
stop 6to4 ...
... 1. Run IPv6 on site using any suitable implementation. True native
IPv6, [6OVER4], or tunnels are all acceptable.
...
... appropriate 2002:: routing prefix locally. Configure IPv6 DNS
entries using this prefix. At this point the 6to4 ...
... prefix. At this point the 6to4 mechanism is
automatically available, and the site has obtained a "free" IPv6
prefix.
3. Identify a 6to4 relay router ...
... 6to4 relay router willing to relay the site's traffic
to the native IPv6 world. This could either be at another
cooperative 6to4 site, or an ISP ...
... domain, the site's
6to4 router will be configured with a default IPv6 route pointing to
that relay router ...
... BGP peerings.
4. When native external IPv6 connectivity becomes available, add a
second (native) IPv6 prefix to both the border router ...
... 4. When native external IPv6 connectivity becomes available, add a
second (native) IPv6 prefix to both the border router configuration
and the DNS configuration ...
... address selection rule
will determine when 6to4 and when native IPv6 will be used.
5. When 6to4 ...
... valid. The NAT box must also contain a fully
functional IPv6 router including the 6to4 mechanism. The address ...
... IPv4 NAT in this way offers the site
concerned a globally unique IPv6 /48 prefix, automatically, behind
the IPv4 address ...
... host behind the NAT can
become an IPv6 host with no need for additional address space
allocation, and no intervention by the Internet service provider ...
... outermost NAT has a unique IPv4 address. All IPv6 hosts in this
situation must use addresses derived from the 2002: prefix ...
... border router is combined with an RSIP border
router, it can support IPv6 hosts using 6to4 addresses, IPv4 hosts
...
... IPv4 address
allocation and the 6to4 function provides a stable IPv6 global
address to each host ...
... There is nothing to stop the above scenario being deployed within a
private corporate network as part of its internal transition to IPv6;
the corporate IPv4 backbone ...
... private network. The Intranet thereby obtains globally unique IPv6
addresses even if it is internally using private IPv4 addresses [RFC1918].
...
... routing will treat the local site's 2002::/48 prefix
exactly like a native IPv6 site prefix assigned to the local site.
There will also be an IGP ...
... prefix from relay routers into the native IPv6 domain, whose scope is
limited by routing policy. This is the only non-native IPv6 prefix ...
... IPv6 domain, whose scope is
limited by routing policy. This is the only non-native IPv6 prefix
advertised by BGP.
...
... It will be necessary for 6to4 routers to obtain routes to relay
routers in order to access the native IPv6 domain. In the simplest
case there will be a manually configured default IPv6 route ...
... relay
routers in order to access the native IPv6 domain. In the simplest
case there will be a manually configured default IPv6 route to a
relay router ...
... relay router. Such a route could be used to establish a BGP
session for the exchange of additional IPv6 routes.
...
... IPv4. Since 2002: prefixes behave exactly like standard
IPv6 prefixes, they will not create any new mechanisms for routing
loops in IPv6 ...
... IPv6 prefixes, they will not create any new mechanisms for routing
loops in IPv6 unless misconfigured. One very dangerous
misconfiguration would be an announcement of the 2002::/16 prefix
...
... routing prefix may be legitimately advertised into the
native IPv6 routing domain by a relay router, and into an IPv6 ...
... relay router, and into an IPv6 site's
local IPv6 routing domain; hence there is a risk of misconfiguration
causing it to be advertised into a 6to4 ...
... router will often be
unable to return an ICMPv6 message to the originating IPv6 node, due
to the lack of sufficient information in the "unreachable" message.
This means that the IPv4 network ...
... This means that the IPv4 network will appear as an undiagnosable link
layer for IPv6 operational purposes. Other considerations are as
described in Section 4.1.3 of [MECH].
...
... Implementors should be aware that, in addition to possible attacks
against IPv6, security attacks against IPv4 must also be considered.
...
... IPv4 must also be considered.
Use of IP security at both IPv4 and IPv6 levels should nevertheless
be avoided, for efficiency reasons. For example, if IPv6 is running
...
... IP security at both IPv4 and IPv6 levels should nevertheless
be avoided, for efficiency reasons. For example, if IPv6 is running
encrypted, encryption ...
... encryption of IPv4 would be redundant except if traffic
analysis is felt to be a threat. If IPv6 is running authenticated,
then authentication ...
... traffic is accepted. If this is for
any reason felt to be a security risk (for example, if IPv6 spoofing
is felt to be more likely than IPv4 ...
... Bob Hinden, Geoff Huston, Perry Metzger, Thomas Narten, Erik
Nordmark, Markku Savela, Ole Troan, Sowmini Varadhan, members of the
Compaq IPv6 engineering team, and other members of the NGTRANS
working group ...
... Hinden., R, O'Dell, M. and S. Deering, "An IPv6 Aggregatable Global Unicast Address Format", RFC 2374hist(-> 3587) ...
... Gilligan, R., Thomson, S., Bound, J. and W. Stevens, "Basic Socket Interface Extensions for IPv6", RFC 2553(-> 3493), March 1999. ...
... Marques, P. and F. Dupont, "Use of BGP-4 Multiprotocol Extensions for IPv6 Inter-Domain Routing", RFC 2545prop, March 1999. ...
... Thomson, S. and T. Narten, "IPv6 Stateless Address Autoconfiguration", RFC 2462draft, December 1998. ...
... Narten, T., Nordmark, E. and W. Simpson, "Neighbor Discovery for IP Version 6 (IPv6)", RFC 2461draft, December 1998. ...
... Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460draft, December 1998. ...
... Draves, R., "Default Address Selection for IPv6", Work in Progress. ...
... Gilligan, R. and E. Nordmark, "Transition Mechanisms for IPv6 Hosts and Routers", RFC 2893(-> 4213prop), August 2000. ...