Network Working Group E. Nordmark
Internet-Draft S. Chakrabarti
Expires: April 25, 2004 Sun Microsystems, Inc.
J. Laganier
ENS Lyon / Sun Microsystems, Inc.
October 26, 2003
IPv6 Socket API for Address Selection
draft-chakrabarti-ipv6-addrselect-api-02
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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This Internet-Draft will expire on April 25, 2004.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
The IPv6 default address selection document describes the rules for
selecting default address by the system and indicates that the
applications should be able to reverse the sense of system preference
of address selection for that application through possible API
extensions. However, no such socket API exists in the basic or
advanced IPv6 socket API documents. Hence this document specifies
socket level options add new flags for the getaddrinfo() API to
specify preferences for address selection that modify the default
address selection algorithm. The socket APIs described in this
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document will be particularly useful when Mobile IPv6 is used, for
IPv6 applications which want to choose between temporary and public
addresses, CGA (cryptographically generated addresses) and non-CGA
addresses, and applications which do not want the default preferences
with respect to address scopes.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Design Alternatives . . . . . . . . . . . . . . . . . . . . . 5
3. Example Usages . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Changes to the Socket Interface . . . . . . . . . . . . . . . 7
5. Changes to the protocol-independent nodename translation . . . 9
6. Application Requirements . . . . . . . . . . . . . . . . . . . 12
7. Implementation Notes . . . . . . . . . . . . . . . . . . . . . 14
8. Mapping to Default Address Selection Rules . . . . . . . . . . 15
9. IPv4-mapped IPv6 Addresses . . . . . . . . . . . . . . . . . . 17
10. Validation function for source address . . . . . . . . . . . . 18
11. Security Considerations . . . . . . . . . . . . . . . . . . . 19
12. Changes from previous version of draft . . . . . . . . . . . . 19
13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20
Normative References . . . . . . . . . . . . . . . . . . . . . 20
Informative References . . . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 21
A. Intellectual Property Statement . . . . . . . . . . . . . . . 21
Full Copyright Statement . . . . . . . . . . . . . . . . . . . 22
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1. Introduction
This document defines socket API extensions to support the non-
default choice of address selection by the applications. The IPv6
default address selection [1] document has specified the rules for
system default address selection for an outbound IPv6 packet.
Privacy considerations [6] have introduced "public" and "temporary"
addresses. IPv6 Mobility [3] introduces "home address" and "care-
of-address" definitions in the mobile systems. Some applications
might want to control whether large scope or small scope IPv6
addresses are preferred.
Although it is desirable to have default algorithms for address
selection, an application may want to reverse certain address
selection rules for efficiency and other application specific
reasons. Currently IPv6 socket API extensions provide mechanism to
choose a specific source address through simple bind() operation or
IPV6_PKTINFO socket option [5]. Thus in order to use bind() or
IPV6_PKTINFO socket option, the application itself must make sure
that the source address is appropriate for the destination address
(e.g., with respect to the interface used to send packets to the
destination). The application also needs to make sure about the
appropriate scope of source address with respect to the destination
address and so on. The mechanism presented in this document allows
the application to specify attributes of the source (and destination)
addresses it prefers while still having the system perform the rest
of address selection. For instance, if an application prefers to use
care-of-address of a mobile node as the source address and if the
mobile node has two care-of-addresses (one public and one temporary),
then the node would select the public care-of-address by following
the default address selection rule for public and temporary address.
A socket option has been deemed useful for this purpose, as it
enables an application to specify addesss selection preferences on a
per-socket basis. It can also provide the flexibility of enabling
and disabling address selection preferences in non-connected sockets.
The socket option uses a set of flags for address preferences. Since
source address selection and destination address ordering need to be
partially implemented in getaddrinfo() [2] the corresponding set of
flags are also defined for that routine.
Thus this document introduces several flags for address selection
preferences that alter the default address selection [1] for a number
of cases. It analyzes the usefulness of providing API functionality
for different default address selection rules; it provides API to
alter only those rules that are possibly used by certain class of
applications. In addition, it also considers CGA [7][8] and non-CGA
source addresses when CGA addresses are available in the system. In
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the future, more destination or source flags may be added to expand
the API as the needs may arise.
The approach in this document is to allow the application to specify
preferences for address selection and not to be able to specify hard
requirements. Thus for instance, an application can set a flag to
prefer a temporary source address, but if no temporary source
addresses are available at the node, a public address would be chosen
instead.
Specifying a 'requirement' for address selection is not adopted at
the application level due to the nature of unreliable transport
protocols where the failure of connect() operation may appear late in
absence of the required attribute of source address in the system.
This document defines a verification function which applications may
choose to use before sending data on a connected socket. By
"connected" socket we mean that a connect() call is done after
setting setsockopt() with the preference attributes. Note that
connect() can be used in UDP datagram sockets as well. The purpose
of checking the validation of address after connect() call ensures
the availability of the desired address type; an application using
only sendto() or sendmsg() cannot guarantee the validated address at
the time of sending data . The configuration of node may change or
the address may expire between setsockopt() setting and sendto() or
sendmsg() call.
Furthermore, the approach is to define two flags for each purpose, so
that an application can specify either that it prefers 'X' or prefers
'not X', or it can choose not to set either of the flags relating to
'X' and leave it up to the system default (see section 3.1). For
example, if setsockopt() with a preference to care-of-address is set,
but no flag is set to indicate a choice of temporary or public
address, then temporary vs. public source address selection will be
determined from the default source address selection [1] rules.
Thus not specifying either of "X" and "not X" leaves the "X" property
of the address selection at the system default.
This document only specifies the extensions for the socket API since
the socket API is already specified in RFCs [2]. The intent is that
this document serve as a model for the type of address selection
preferences that need to be expressable in other networking API such
as those found in middleware systems and the Java environment.
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2. Design Alternatives
Suggestions have been made that have flags per application instead of
per socket would be more flexible. However, this design stays with
per socket flags for the following reasons:
- while some system have per environment/application flags (such as
environment variables in Unix systems) this might not be available in
all systems which implement the socket API
- when an application links with some standard library that library,
unknown to the application, might be using the socket API.
Mechanisms that would provide per application flags would affect not
only the application itself but also the libraries' use of the socket
API with a large risk for unintended consequences.
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3. Example Usages
The examples discussed here are limited to applications supporting
Mobile IPv6, IPv6 Privacy Extensions and Cryptographically Generated
Addresses. Address selection document [1] recommends that home
addresses should be preferred over care-of-address when both are
configured. However, a mobile node may want to prefer care-of-
address as source address for DNS query in the foreign network as it
normally means a shorter and local return path compared to the route
via the mobile node's home-agent when the query contains home-address
as source address. Another example is IKE application which requires
care-of-address as its source address for the initial security
association pair with Home Agent [3] while the mobile node boots up
at the foreign network and wants to do the key exchange before a
successful home-registration. Also a Mobile IPv6 aware application
may want to toggle between home-address and care-of-address depending
on its location and state of the application. It may also want to
open different sockets and use home-address as source address for one
socket and care-of-address for the others.
In a non-mobile environment, similarly an application may prefer to
use temporary address as source address for certain cases. By
default, the source address selection rule selects "public" address
when both are available. For example, an application supporting web
browser and mail-server may want to use "temporary" address for the
former and "public" address for the mail-server as a mail-server may
require reverse path for DNS records for anti-spam rules.
Similarly, a node may be configured to use the cryptographically
generated addresses by default, as in Secure Neighbor Discovery, but
an application may prefer not to use it. For instance, fping, a
debugging tool which tests basic reachability of multiple
destinations by sending packets in parallel, may find that the cost
and time incurred in proof-of-ownership by CGA verification is not
justified. On the other hand, when a node is not configured for CGA
as default, an application may prefer using CGA by setting the socket
option. It may subsequently verify that it is truly bound to a CGA
by first calling getsockname() and then recomputing the CGA using the
public key of the node.
Besides the above examples, the defined address preference flags can
be used to specify or alter the system default values for largest
scope of addresses as well. An application may want to use only
link-local source address to contact a node with global destination
address on the same link, it can do so by setting the appropriate
source address preference flag in the application. By default the
system would have chosen global source address. This example assumes
that only link-local and global addresses are available on the nodes.
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4. Changes to the Socket Interface
IPv6 Basic API [2] defines socket options for IPv6. This document
adds a new socket option at the IPPROTO_IPV6 level. This socket
option is called IPV6_ADDR_PREFERENCES. It can be used with
setsockopt() and getsockopt() calls. This socket option takes a
32bit unsigned integer argument. The argument consists of a number
of flags where each flag indicates an address selection preference
which modifies one of the rules in the default address selection
specification.
The following flags are defined to alter or set the default rule of
source and destination address selection rules discussed in default
address selection specification [1].
<netinet/in.h>.
IPV6_PREFER_SRC_HOME /* Prefer Home Address as source */
IPV6_PREFER_SRC_COA /* Prefer Care-Of_address as source */
IPV6_PREFER_SRC_TMP /* Prefer Temporary address as source */
IPV6_PREFER_SRC_PUBLIC /* Prefer Public address as source */
IPV6_PREFER_SRC_CGA /* Prefer CGA address as source */
IPV6_PREFER_SRC_NONCGA /* Prefer a non-CGA address as source */
IPV6_PREFER_SRC_LARGESCOPE /* Prefer larger scope source */
IPV6_PREFER_SRC_SMALLSCOPE /* Prefer small(link-local) scope */
NOTE: No source preference flag for longest matching prefix is
defined here because it is believed to be handled by the policy table
defined in the default address selection specification.
Flags for altering Scope of destination addresses:
Flags corresponding to other destination address rules are not
defined in this document at this point. See section 8 for more
analysis and mapping of rules and different flags.
IPV6_PREFER_DST_LARGESCOPE /* Prefer larger scope for destination */
IPV6_PREFER_DST_SMALLSCOPE /* Prefer small scope for destination */
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The following example illustrates how it is used on a AF_INET6
socket:
uint32_t flags = IPV6_PREFER_SRC_COA;
if (setsockopt(s, IPPROTO_IPV6, IPV6_ADDR_PREFERENCES,
(char *) &flags, sizeof (flags)) == -1) {
perror("setsockopt IPV6_ADDR_REFERENCES");
}
When the IPV6_ADDR_PREFERENCES is successfully set with setsockopt(),
the option value given is used to specify address preference for any
connection initiation through the socket and all subsequent packets
sent via that socket. If no option is set, the system selects a
default value as per default address selection algorithm or by some
other equivalent means.
Setting conflicting flags at the same time results in the error
EINVAL. For example, setting 'X' and 'not X' is not allowed at the
same time. If flag is set as combination of 'X' and 'Y', and if 'Y'
is not applicable or available in the system, then the selected
address contains property of 'X' and system default for the property
of 'Y'. For example, a possible valid combination of flags can be:
IPV6_PREFER_SRC_PUBLIC | IPV6_PREFER_SRC_LARGESCOPE
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5. Changes to the protocol-independent nodename translation
Section 8 of Default Address Selection [1] document indicates
possible implementation strategies for getaddrinfo() [2]. One of
them suggests that getaddrinfo() collects available source/
destination pair from the network layer after being sorted at the
network layer with full knowledge of source address selection.
Another strategy is to call down to network layer to retrieve source
address information and then sort the list in the context of
getaddrinfo().
Thus if an application sets setsockopt() IPV6_ADDR_PREFERENCES option
to alter the default address selection rules , it is required that
the application calls getaddrinfo() with the corresponding
AI_PREFER_* flags specified in this section. This ensures that
getaddrinfo() function implementation has considered the address
preference desired by the application, as the destination address
selection rule is influenced by the order of source address
selection. This document also defines AI flags for destination SCOPE
which has direct impact on getaddrinfo() and destination address
selection interaction.
There is no corresponding destination address selection rule for
source address selection rule 7, in default address selection
document. However, this API provides a way for an application to
make sure that the source address preference set in setsockopt() is
taken into account by the getaddrinfo() function. Let's consider an
example to understand this scenario. DA and DB are two global
destination addresses and the node has two global addresses SA and SB
through interface A and B respectively. SA is a temporary address
while SB is a public address. The application has set
IPV6_PREFER_SRC_TMP in the setsockopt() flag. The route to DA points
to interface A and route to DB points to interface B. Thus when
AI_PREFER_SRC_TMP is set , getaddrinfo() returns DA before DB and SA
before SB likewise. Similarly, getaddrinfo() returns DB before DA
when AI_PREFER_SRC_PUBLIC is set in this example. Thus the source
address preference is taking effect into destination address
selection and as well as source address selection by the
getaddrinfo() function.
The following numerical example clarifies the above further.
Imagine a host with two addresses:
1234::1:1 public
9876::1:2 temporary
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The destination has the following two addresses:
1234::9:3
9876::9:4
By default getaddrinfo() will return the destination addresses in the
order
1234::9:3
9876::9:4
because the public source is preferred and 1234 matches more bits
with the public source address. On the other hand, if
AI_PREFER_SRC_TMP is set, getaddrinfo will return the addresses in
the reverse order since the temporary source address will be
preferred.
The following flags are added for the ai_flags in addrinfo data
structure defined in Basic IPv6 Socket API Extension [2].
AI_PREFER_SRC_HOME /* Prefer Home Address */
AI_PREFER_SRC_COA /* Prefer COA */
AI_PREFER_SRC_TMP /* Prefer Temporary Address */
AI_PREFER_SRC_PUBLIC /* Prefer Public Address */
AI_PREFER_SRC_CGA /* Prefer CGA Address */
AI_PREFER_SRC_NONCGA /* Prefer address other than CGA */
AI_PREFER_SRC_LARGESCOPE /* Prefer large(global) scope */
AI_PREFER_SRC_SMALLSCOPE /* Prefer small(local) scope */
AI_PREFER_DST_LARGESCOPE /* Prefer large(global) scope dest. */
AI_PREFER_DST_SMALLSCOPE /* Prefer small(local) scope dest.*/
The above flags are ignored for the AF_INET address family as the
address selection algorithm defined in section 5 of [1] only applies
to the IPv6 addresses.
If conflicting flags such as AI_PREFER_SRC_HOME and AI_PREFER_SRC_
COA are set, the getaddrinfo() fails with an error EAI_BADFLAGS [2].
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Some valid sequences of flags are:
AI_PREFER_SRC_HOME | AI_PREFER_SRC_PUBLIC
AI_PREFER_SRC_COA | AI_PREFER_SRC_PUBLIC
AI_PREFER_SRC_HOME | AI_PREFER_SRC_CGA
AI_PREFER_SRC_HOME | AI_PREFER_SRC_NONCGA
AI_PREFER_SRC_COA | AI_PREFER_SRC_CGA
AI_PREFER_SRC_COA | AI_PREFER_SRC_NONCGA
AI_PREFER_SRC_LARGESCOPE | AI_PREFER_DST_LARGESCOPE
AI_PREFER_SRC_SMALLSCOPE | AI_PREFER_DST_SMALLSCOPE
AI_PREFER_SRC_LARGESCOPE | AI_PREFER_DST_LARGESCOPE |
AI_PREFER_SRC_PUBLIC
All the constants mentioned in this section for ai_flags are defined
in <netdb.h>.
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6. Application Requirements
An application SHOULD call getsockopt() prior calling setsockopt() to
a particular address preference, in order to save the existing system
default values or the current values of the address preference flags.
However, setsockopt() with a flag value 0 resets the address
selection to the system default policy.
Example:
uint32_t save_flag, flags;
int optlen = sizeof (save_flag);
/* Save the existing IPv6_ADDR_PREFERENCE FLAG now */
if (getsockopt(s, IPPROTO_IPV6, IPV6_ADDR_PREFERENCES,
&save_flag, &optlen) == -1 {
perror("getsockopt IPV6_ADDR_REFERENCES");
}
flags = save_flag;
flags &= ~IPV6_PREFER_SRC_PUBLIC;
flags |= IPV6_PREFER_SRC_TMP;
if (setsockopt(s, IPPROTO_IPV6, IPV6_ADDR_PREFERENCES,
(char *) &flags, sizeof (flags)) == -1) {
perror("setsockopt IPV6_ADDR_REFERENCES");
}
Application MUST not set conflicting flags; the only conflicts that
are checked for are flag X and flag not-X being set at the same time.
Example of conflicting flags :
IPV6_PREFER_SRC_TMP | IPV6_PREFER_SRC_PUBLIC.
In order to allow different implementations to do different parts of
address selection in getaddrinfo() and in the protocol stack, this
specification requires that applications set the same flags when
calling getaddrinfo() and when calling setsockopt(). For example, if
the application sets IPV6_PREFER_SRC_COA flag, it must use
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AI_PREFER_SRC_COA flag when calling getaddrinfo(). If applications
are not setting the same flags the behavior of the implementation is
undefined.
It is envisioned that Mobile IPv6 applications may want to choose
Care-of-Address as source for short transaction (for efficiency)
while roaming, but still keep Home address as source address for long
lived communication for address stability. Thus it is recommended
that applications take this idea into consideration and use the
source address selection API for home-address and care-of -address
selection appropriately. Similarly, an application may choose to set
IPV6_PREFER_SRC_COA flag for datagram services; it uses home-address
as source when at home and uses care-of- address outside home-network
for short datagram transactions. This is an advantage of having
flexibility of "preference" vs. "requirement".
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7. Implementation Notes
o If either bind() or IPV6_PKTINFO socket option is set with a
specific source address in the same application along with the
address preferenc e socket option, then bind() or IPV6_PKTINFO
option takes precedence.
o setsockopt() and getsockopt() SHOULD ignore any address preference
flags for type of addresses that are not supported in the system.
The socket option calls should return error when invalid flag
values are passed to them. The invalid flag values are: flag X
and flag not-X (set at the same time), some flag that is not known
to the implementation.
o If an implementation supports both streams and datagram sockets,
it should implement the address preference mechanism API described
in this document on both cases.
o Implementation supporting this API must implement both AI flags
and socket option flags processing for portability of
applications.
o An implementation may choose to set the following flags by default
on the system. However, an implementation may choose to clear the
address preference flags by default indicating that system is
following default address selection rules.Thus it sets the address
preference flags only when it is set by the application. Thus the
change in address preference flag is only visible by that
application.
IPV6_PREFER_SRC_HOME
IPV6_PREFER_SRC_PUBLIC
IPV6_PREFER_SRC_SMALLSCOPE
IPV6_PREFER_SRC_CGA
IPV6_PREFER_DST_SMALLSCOPE
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8. Mapping to Default Address Selection Rules
This API defines only those flags that are deemed to be useful by the
applications to alter default address selection rules. Thus we
discuss the mapping of each set of flags to the corresponding rule
number in the address selection document[1].
Source address selection rule #4 (prefer home address):
IPV6_PREFER_SRC_HOME
IPV6_PREFER_SRC_COA
AI_PREFER_SRC_HOME
AI_PREFER_SRC_COA
Source address selection rule #7 (prefer public address) :
IPV6_PREFER_SRC_PUBLIC
IPV6_PREFER_SRC_TMP
AI_PREFER_SRC_PUBLIC
AI_PREFER_SRC_TMP
Source address selection rule #2 (prefer appropriate scope):
IPV6_PREFER_SRC_LARGESCOPE
IPV6_PREFER_SRC_SMALLSCOPE
AI_PREFER_SRC_LARGESCOPE
AI_PREFER_SRC_SMALLSCOPE
Destination address selection rule #8 ( prefer smaller scope):
IPV6_PREFER_DST_LARGESCOPE
IPV6_PREFER_DST_SMALLSCOPE
AI_PREFER_DST_LARGESCOPE
AI_PREFER_DST_SMALLSCOPE
Other destination rules (#4-prefer home address; #7-prefer native
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interfaces) could have been applicable. But the problem is that the
local system does not know about whether a destination address is a
tunnel-address for destination rule #7. It can only know for sure if
the destination address is one of its own. The flags defined for
source address selection rule #4 ( prefer home address) should also
take care of destination address selection rule #4. Thus at this
point, it was decided not to define flags for these destination
rules.
Other source address rules (that are not mentioned here) were also
deemed not applicable for changing its default notion per-application
basis.
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9. IPv4-mapped IPv6 Addresses
IPv4-mapped IPv6 addresses are supported in this API. In some cases
the IPv4-mapped addresses may not make much sense because the
attributes are IPv6 specific. For example, IPv6 temporary addresses
are not the same as private IPv4 addresses. However, the IPv4
mapped-address support may be useful for mobile home address and
care-of-address. At this point it is not understood whether this API
has any value to IPv4 addresses or AF_INET family of sockets.
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10. Validation function for source address
Sometimes an application may have a requirement to set a specific
source address without which it chooses to fail. In that situation,
'preferred' addresses do not guarantee the application requirement.
An application which requires to set a specific type of source
address must verify that the system indeed has a valid source
address for the desired source address type. A validation function
is defined for this purpose:
<netinet/in.h>.
boolean_t inet6_is_srcaddr(struct sockaddr_in6 * srcaddr,
uint32_t flags)
Where the flags contain the specified source preference flags. The
function expects a non-NULL input for srcaddr. It returns true when
srcaddr corresponds to a valid address in the node and that address
type satisfies the preference flag. If srcaddr input value does not
correspond to any address in the node or it does not match an
address which satisfy the preferences indicated, the function returns
false. Currently, the validation function seems meaningful only for
IPV6_PREFER_SRC_TMP, IPV6_PREFER_SRC_PUBLIC and
IPV6_PREFER_SRC_[NON]CGA flags. See the section on "Application
Requirements" for usage of preference flags in Mobile IPv6
applications. The scope preference flags do not guarantee validation
of largest scope when more than two scopes are configured. Thus the
above temporary/public and CGA/non-CGA flags are the predictable
choices for the validation function.
sockaddr_in6 structure must contain AF_INET6 as sin6_family. It also
must contain the scope_id information if the source address is a
link-local address.
This function should be able to handle multiple valid flags
combination as its second parameter. Invalid flag values result in
false return value.
The verification function can be useful for both TCP and UDP socket
applications that use connect().
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11. Security Considerations
This document conforms to the same security implications as specified
in IPv6 Basic Socket API [2] document. Allowing applications to
specify a preference for temporary addresses provides per-application
(and per-socket) ability to use the privacy benefits of the temporary
addresses.
12. Changes from previous version of draft
o Changed IPV6_SRC_PREFERENCES option to IPV6_ADDR_PREFERENCES to
include destination address preference for scope and for further
future enhancement which may include both source and destination
addresses.
o Added implementation and application requirements.
o Removed IPV6_PREFER_SRC_NATIVE and IPV6_PREFER_SRC_TUNNEL flags as
there is no corresponding source address rule in RFC3484.
Moreover it doesn't seem to make sense to add preference flags for
this destination addresses since:
- the local system doesn't in general know whether there is a
tunnel at the destination end and
- in the case (6to4) where the local system can tell there will
be a tunnel for a destination address the default policy table
already has a rule (for the 6to4 prefix).
Perhaps there should have been a source rule for tunnel vs.
native interface in default address selection specification in
which case it might have made sense to add a preference flag for
that.
o Added section on default address selection rule mapping.
o Added comments on using JAVA API.
o Added four new flags for destination scoped addresses as some
working group members felt the requirement of altering default
destination address scope.
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13. Acknowledgments
The authors like to thank members of mobile-ip and ipv6 working
groups for useful discussion on this topic. Richard Draves and Dave
Thaler suggested that getaddrinfo also needs to be considered along
with the new socket option. Gabriel Montenegro suggested that CGAs
may also be considered in this document. Thanks to Alain Durand,
Renee Danson, Alper Yegin, Francis Dupont, Michael Hunter, Sebastien
Roy, Robert Elz, Jinmei Tatuya, Pekka Savola, Itojun, Jim Bound, Jeff
Boote and Mika Liljeberg for useful discussions and suggestions.
Normative References
[1] Draves, R., "Default Address Selection for IPv6", RFC 3484,
August 2002.
[2] Gilligan, R., Thomson, S., Bound, J., McCann, J. and W. Stevens,
"Basic Socket Interface Extensions for IPv6", RFC 3493, March
2003.
Informative References
[3] Johnson, D., Perkins, C. and J. Arkko, "Mobility Support in
IPv6", draft-ietf-mobileip-ipv6-24.txt (work in progress), June
2003.
[4] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6),
Specification", RFC 2460, December 1998.
[5] Stevens, W., Thomas, M., Nordmark, E. and T. Jinmei, "Advanced
Sockets API for IPv6", RFC 3542, May 2003.
[6] Narten, T. and R. Draves, "Privacy Extensions for Stateless
Address Autoconfiguration in IPv6", RFC 3041, January 2001.
[7] Aura, T., "Cryptographically Generated Addresses (CGA)", draft-
ietf-send-cga-01.txt (work in progress), August 2003.
[8] Montenegro, G. and C. Castelluccia, "Statistically Unique and
Cryptographically Verifiable (SUCV) Identifiers and
Addresses.", NDSS 2002, February 2002.
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Authors' Addresses
Erik Nordmark
Sun Microsystems, Inc.
180, avenue de l'Europe
38334 Saint Ismier CEDEX
France
EMail: Erik.Nordmark@Sun.COM
Samita Chakrabarti
Sun Microsystems, Inc.
4150 Network Circle
Santa Clara, CA 95054
USA
EMail: Samita.Chakrabarti@Sun.COM
Julien Laganier
ENS Lyon / Sun Microsystems, Inc.
180, avenue de l'Europe
38334 Saint Ismier CEDEX
France
EMail: Julien.Laganier@Sun.COM
Appendix A. Intellectual Property Statement
This document only defines a source preference flag to choose
Cryptographically Generated Address (CGA) as source address when
applicable. CGA are obtained using public keys and hashes to prove
address ownership. Several IPR claims have been made about such
methods.
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Full Copyright Statement
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Acknowledgement
Funding for the RFC Editor function is currently provided by the
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