Network Working Group                                           B. Aboba
INTERNET-DRAFT                                                 D. Thaler
Category: Informational                            Microsoft Corporation
Expires: April 11, 2008                                    Loa Andersson
11 October 2007                                                 Acreo AB
                                             Internet Architecture Board

               Principles of Internet Host Configuration

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
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   This Internet-Draft will expire on April 11, 2008.

Copyright Notice

   Copyright (C) The IETF Trust (2007).


   This document describes principles of Internet host configuration.
   It covers issues relating to configuration of Internet layer
   parameters, as well as parameters affecting higher layer protocols.

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Table of Contents

1.  Introduction..............................................    3
      1.1 Terminology ........................................    3
2.  Principles ...............................................    6
      2.1 Minimize Configuration .............................    6
      2.2 Less is More .......................................    6
      2.3 Diversity is Not a Benefit .........................    7
      2.4 Lower Layer Independence ...........................    8
      2.5 Configuration is Not Access Control ................    9
3.  Additional Discussion ....................................   10
      3.1 General Purpose Mechanisms .........................   10
      3.2 Service Discovery Protocols ........................   10
      3.3 Fate Sharing .......................................   11
4.  Security Considerations ..................................   12
      4.1 Configuration Authentication .......................   13
5.  IANA Considerations ......................................   14
6.  References ...............................................   14
      6.1 Informative References .............................   14
Acknowledgments ..............................................   16
Appendix A - IAB Members .....................................   16
Authors' Addresses ...........................................   17
Full Copyright Statement .....................................   18
Intellectual Property ........................................   18

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1.  Introduction

   This document describes principles of Internet host configuration.
   It covers issues relating to configuration of Internet layer
   parameters, as well as parameters affecting higher layer protocols.

   In recent years, a number of architectural questions have arisen, for
   which we provide guidance to protocol developers:

      o What protocol layers and general approaches are most appropriate
        for configuration of various parameters.

      o The relationship between parameter configuration and service

      o The relationship between network access authentication and host

      o The role of link-layer protocols and tunneling protocols
        in Internet host configuration.

   The role of the link-layer and tunneling protocols is particularly
   important, since it can affect the properties of a link as seen by
   higher layers (for example, whether privacy extensions specified in
   "Privacy Extensions for Stateless Address Autoconfiguration in IPv6"
   [RFC3041] are available to applications).

1.1.  Terminology

link      A communication facility or medium over which nodes can
          communicate at the link-layer, i.e., the layer immediately
          below IP.  Examples are Ethernets (simple or bridged), PPP
          links, X.25, Frame Relay, or ATM networks as well as internet
          (or higher) layer "tunnels", such as tunnels over IPv4 or IPv6

on link   An address that is assigned to an interface on a specified

off link  The opposite of "on link"; an address that is not assigned to
          any interfaces on the specified link.

   Internet layer configuration is defined as the configuration required
   to support the operation of the Internet layer.  This includes IP
   address(es), subnet prefix(es), default gateway(s), mobility
   agent(s), boot service configuration and other parameters.

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IP address(es)
          Internet Protocol (IP) address configuration includes both
          configuration of link-scope addresses as well as global
          addresses.  Configuration of IP addresses is an important
          step, since this enables a host to fill in the source address
          in the packets it sends, as well as to receive packets
          destined to that address.  As a result, the host can receive
          unicast IP packets, rather than requiring that IP packets be
          sent to the broadcast or multicast address.  Configuration of
          an IP address also enables the use of IP fragmentation, since
          packets sent from the unknown address cannot be reliably
          reassembled (since fragments from multiple hosts using the
          unknown address might be reassembled into a single IP packet).
          Configuration of an IP address also enables use of Internet
          layer security facilities such as IPsec specified in "Security
          Architecture for the Internet Protocol" [RFC4301].

Subnet prefix(es)
          Once a subnet prefix is configured, hosts with an IP address
          can exchange unicast IP packets with on-link hosts.

Default gateway(s)
          Once a default gateway is configured, hosts with an IP address
          can send and receive unicast IP packets from off-link hosts,
          assuming unobstructed connectivity.

Mobility agent(s)
          While Mobile IPv4 [RFC3344] and Mobile IPv6 [RFC3775] include
          their own mechanisms for locating home agents, it is also
          possible for mobile nodes to utilize dynamic home agent

Other parameters
          Internet layer parameter configuration also includes
          configuration of per-host parameters (e.g. hostname) and per-
          interface parameters (e.g.  IP Time-To-Live (TTL),
          enabling/disabling of IP forwarding and source routing, and
          Maximum Transmission Unit (MTU)).

Boot service configuration
          Boot service configuration is defined as the configuration
          necessary for a host to obtain and perhaps also to verify an
          appropriate boot image.  This is appropriate for diskless
          hosts looking to obtain a boot image via mechanisms such as
          the Trivial File Transfer Protocol (TFTP) [RFC1350], Network
          File System (NFS) [RFC3530] and Internet Small Computer
          Systems Interface (iSCSI) [RFC3720][RFC4173].  It also may be
          useful in situations where it is necessary to update the boot

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          image of a host that supports a disk, such as in the Preboot
          eXecution Environment (PXE) [PXE][RFC4578].  While strictly
          speaking boot services operate above the Internet layer, where
          boot service is used to obtain the Internet layer code, it may
          be considered part of Internet layer configuration.

   Higher-layer configuration is defined as the configuration required
   to support the operation of other components above the Internet
   layer.  This includes, for example:

Name Service Configuration
          The configuration required for the host to resolve names.
          This includes configuration of the addresses of name
          resolution servers, including IEN 116, Domain Name Service
          (DNS), Windows Internet Name Service (WINS), Internet Storage
          Name Service (iSNS) and Network Information Service (NIS)
          servers, and the setting of name resolution parameters such as
          the NetBIOS node type, the DNS domain and search list, etc.
          It may also include the transmission or setting of the host's
          own name.  Note that Link local name resolution services (such
          as NetBIOS [RFC1001], LLMNR [RFC4795] and mDNS [mDNS])
          typically do not require configuration.

          Once the host has completed name service configuration, it is
          capable of resolving names using name resolution protocols
          that require configuration.  This not only allows the host to
          communicate with off-link hosts whose IP address is not known,
          but to the extent that name services requiring configuration
          are utilized for service discovery, this also enables the host
          to discover services available on the network or elsewhere.

Time Service Configuration
          Time service configuration includes configuration of servers
          for protocols such as the Simple Network Time Protocol (SNTP)
          and the Network Time Protocol (NTP).  Since accurate
          determination of the time may be important to operation of the
          applications running on the host (including security
          services), configuration of time servers may be a prerequisite
          for higher layer operation.  However, it is typically not a
          requirement for Internet layer configuration.

Other service configuration
          This can include discovery of additional servers and devices,
          such as printers, Session Initiation Protocol (SIP) proxies,

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2.  Principles

   This section describes basic principles of Internet host

2.1.  Minimize Configuration

   Anything that can be configured can be misconfigured.  RFC 1958
   [RFC1958] Section 3.8 states: "Avoid options and parameters whenever
   possible.  Any options and parameters should be configured or
   negotiated dynamically rather than manually."

   That is, to minimize the possibility of configuration errors,
   parameters should be automatically computed (or at least have
   reasonable defaults) whenever possible.  For example, the
   Transmission Control Protocol (TCP) [RFC793] does not require
   configuration of the Maximum Segment Size, but is able to compute an
   appropriate value.

   Some protocols support self-configuration mechanisms, such as
   capability negotiation or discovery of other hosts that implement the
   same protocol.

2.2.  Less is More

   The availability of standardized, simple mechanisms for general-
   purpose Internet host configuration is highly desirable.  RFC 1958
   [RFC1958] states, "Performance and cost must be considered as well as
   functionality" and "Keep it simple.  When in doubt during design,
   choose the simplest solution."

   To allow protocol support in more types of devices, it is important
   to minimize the footprint requirement.  For example, Internet hosts
   span a wide range of devices, from embedded devices operating with
   minimal footprint to supercomputers.  Since the resources (e.g.
   memory and code size) available for host configuration may be very
   small, it is desirable for a host to be able to configure itself in
   as simple a manner as possible.

   One interesting example is IP support in pre-boot execution
   environments.  Since by definition boot configuration is required in
   hosts that have not yet fully booted, it is often necessary for pre-
   boot code to be executed from Read Only Memory (ROM), with minimal
   available memory.  In PXE, prior to obtaining a boot image, the host
   is typically only able to communicate using IP and the User Datagram
   Protocol (UDP).  This is one reason why Internet layer configuration
   mechanisms typically depend only on IP and UDP.  After obtaining the
   boot image, the host will have the full facilities of TCP/IP

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   available to it, including support for reliable transport protocols,
   IPsec, etc.

   In order to reduce complexity, it is desirable for Internet layer
   configuration mechanisms to avoid dependencies on higher layers.
   Since embedded hosts may wish to minimize the code included within a
   boot ROM, availability of higher layer facilities cannot be
   guaranteed during Internet layer configuration.  In fact, it cannot
   even be guaranteed that all Internet layer facilities will be
   available.  For example, IP fragmentation and reassembly may not work
   reliably until a host has obtained an IP address.

2.3.  Diversity is Not a Benefit

   The number of host configuration mechanisms should be minimized.
   Diversity in Internet host configuration mechanisms presents several

          As configuration diversity increases, it becomes likely that a
          host will not support the configuration mechanism(s) available
          on the network to which it has attached, creating
          interoperability problems.

Footprint In order to interoperate, hosts need to implement all
          configuration mechanisms used on the link layers they support.
          This increases the required footprint, a burden for embedded

          To support diversity in host configuration mechanisms,
          operators would need to support multiple configuration
          services to ensure that hosts connecting to their networks
          could configure themselves.  This represents an additional
          expense for little benefit.

Latency   As configuration diversity increases, hosts supporting
          multiple configuration mechanisms may spend increasing effort
          to determine which mechanism(s) are supported.  This adds to
          configuration latency.

Conflicts Whenever multiple mechanisms are available, it is possible
          that multiple configuration(s) will be returned.  To handle
          this, hosts would need to merge potentially conflicting
          configurations.  This would require conflict resolution logic,
          such as ranking of potential configuration sources, increasing
          implementation complexity.

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Additional traffic
          To limit configuration latency, hosts may simultaneously
          attempt to obtain configuration by multiple mechanisms.  This
          can result in increasing on-the-wire traffic, both from use of
          multiple mechanisms as well as from retransmissions within
          configuration mechanisms not implemented on the network.

Security  Support for multiple configuration mechanisms increases the
          attack surface of the host.

2.4.  Lower Layer Independence

   RFC 1958 [RFC1958] states, "Modularity is good. If you can keep
   things separate, do so."

   It is becoming increasingly common for hosts to support multiple
   network access mechanisms, including dialup, wireless and wired local
   area networks, wireless metropolitan and wide area networks, etc.  As
   a result, it is desirable for hosts to be able to configure
   themselves on multiple networks without adding configuration code
   specific to a new link layer.

   As a result, it is highly desirable for Internet host configuration
   mechanisms to be independent of the underlying lower layer.  That is,
   the link layer protocol (whether it be a physical link, or a virtual
   tunnel link) should only be explicitly aware of link-layer parameters
   (although it may configure link-layer parameters - see Section 2.1).
   Introduction of lower layer dependencies increases the likelihood of
   interoperability problems and adds to the number of Internet layer
   configuration mechanisms that hosts need to implement.

   Lower layer dependencies can be best avoided by keeping Internet host
   configuration above the link layer, thereby enabling configuration to
   be handled for any link layer that supports IP.  In order to provide
   media independence, Internet host configuration mechanisms should be
   link-layer protocol independent.

   While there are examples of IP address assignment within the link
   layer (such as in the Point-to-Point Protocol (PPP) IPv4CP
   [RFC1332]), the disadvantages of this approach have now become
   apparent.  The main disadvantages include the extra complexity of
   implementing different mechanisms on different link layers, and the
   difficulty in adding new parameters which would require defining a
   mechanism in each link layer protocol.

   For example, PPP IPv4CP and Internet Protocol Control Protocol (IPCP)
   extensions for name service configuration [RFC1877] were developed at
   a time when the Dynamic Host Configuration Protocol (DHCP) [RFC2131]

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   had not yet been widely implemented on access devices or in service
   provider networks.  However, in IPv6 where link layer independent
   mechanisms such as stateless address configuration [RFC2462] and
   DHCPv6 [RFC3736] are available, PPP IPv6CP [RFC2472] instead simply
   configures an Interface-Identifier which is similar to a MAC address.
   This enables PPP IPv6CP to avoid having to duplicate DHCPv6

   In contrast, Internet Key Exchange Version 2 (IKEv2) [RFC4306]
   utilizes the same approach as PPP IPv4CP by defining a Configuration
   Payload for Internet host configuration for both IPv4 and IPv6.  As
   pointed out in [RFC3456], leveraging DHCP has advantages in terms of
   address management integration, address pool management,
   reconfiguration and fail-over.  On the other hand, the IKEv2 approach
   reduces the number of exchanges.

   Extensions to link layer protocols for the purpose of Internet,
   transport or application layer configuration (including server
   configuration) should be avoided.  Such extensions can negatively
   affect the properties of a link as seen by higher layers.  For
   example, if a link layer protocol (or tunneling protocol) configures
   individual IPv6 addresses and precludes using any other addresses,
   then applications that desire privacy extensions [RFC3041] may not
   function well.  Similar issues may arise for other types of
   addresses, such as Cryptographically Generated Addresses [RFC3972].

   Avoiding lower layer dependencies is desirable even where the lower
   layer is link independent.  For example, while the Extensible
   Authentication Protocol (EAP) [RFC3748] may be run over any link
   satisfying the requirements of [RFC3748] Section 3.1, many link
   layers do not support EAP and therefore Internet layer configuration
   mechanisms with EAP dependencies would not usable on all links that
   support IP.

2.5.  Configuration is Not Access Control

   Network access authentication is a distinct problem from Internet
   host configuration.  Network access authentication is best handled
   independently of the configuration mechanisms in use for the Internet
   and higher layers.

   For example, attempting to control access by requiring authentication
   in order to obtain configuration parameters (such as an IP address)
   has little value if the user can manually configure the host.  Having
   an Internet (or higher) layer protocol authenticate clients is
   appropriate to prevent resource exhaustion of a scarce resource on
   the server, but not for preventing rogue hosts from obtaining access
   to a link.  Note that client authentication is not required for

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   Stateless DHCPv6 [RFC3736] since it does not result in allocation of
   any limited resources on the server.

3.  Additional Discussion

3.1.  General Purpose Mechanisms

   Protocols should either be self-configuring (especially where fate
   sharing is important), or use general-purpose configuration
   mechanisms (such as DHCP or a service discovery protocol, as noted in
   Section 3.2).  The choice should be made taking into account the
   architectural principles discussed in Section 2.

   Given the number of Internet host configuration mechanisms that have
   already been defined, there is no justification for hard coding of
   service IP addresses or domain names.  Taking into account the
   problems resulting from the proliferation of these mechanisms, there
   is no apparent need for the development of additional general-purpose
   configuration mechanisms.

   When defining a new host parameter, protocol designers should first
   consider whether configuration is indeed necessary (see Section 2.1).
   If configuration is necessary, in addition to considering fate
   sharing (see Section 3.3), protocol designers should consider:

      1. The organizational implications for administrators.  For
         example, routers and servers are often administered by
         different sets of individuals, so that configuring a router
         with server parameters may require cross-group collaboration.

      2. Whether the parameter is a per-interface or a global
         parameter.  For example, most standard general purpose
         configuration protocols run on a per-interface basis and hence
         are more appropriate for per-interface parameters.

3.2.  Service Discovery Protocols

   Higher-layer configuration often includes configuring server
   addresses.  The question arises as to how this differs from "service
   discovery" as provided by Service Discovery protocols such as the
   Service Location Protocol Version 2 (SLPv2) [RFC2608].

   In general-purpose configuration mechanisms such as DHCP, server
   instances are considered equivalent.  In service discovery protocols,
   on the other hand, a host desires to find a server satisfying a
   particular set of criteria, which may vary by request.

   Service discovery protocols such as SLPv2 can support discovery of

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   servers on the Internet [RFC3832], not just those within the local
   administrative domain.  General-purpose configuration mechanisms such
   as DHCP, on the other hand, typically assume the server(s) in the
   local administrative domain contain the authoritative set of

   For the service discovery problem (i.e., where the criteria varies on
   a per-request basis, even from the same host), protocols should
   either be self-discovering (if fate sharing is critical), or use
   general purpose service discovery mechanisms.

   In order to avoid a dependency on multicast routing, it is necessary
   for a host to either restrict discovery to services on the local link
   or to discover the location of the Directory Agent (DA).  Therefore
   the use of service discovery protocols beyond the local link is
   typically dependent on a parameter configuration mechanism.  As a
   result, service discovery protocols are typically not appropriate for
   use in obtaining basic Internet layer configuration, although they
   can be used to obtain higher-layer configuration for parameters that
   don't meet the assumptions above made by general-purpose
   configuration mechanisms.

3.3.  Fate Sharing

   If a server (or set of servers) is needed to get a set of
   configuration parameters, "fate sharing" ([RFC1958] Section 2.3) is
   preserved if the servers are ones without which the parameters could
   not be used, even if they were obtained via other means.  The
   possibility of incorrect information being configured is minimized if
   there is only one machine which is authoritative for the information
   (i.e., there is no need to keep multiple authoritative servers in
   sync).  For example, learning default gateways via Router
   Advertisements provides perfect fate sharing.  That is, gateway
   addresses can be obtained if and only if they can actually be used.
   Similarly, obtaining DNS server configuration from a DNS server would
   provide fate sharing since the configuration would only be obtainable
   if the DNS server were available.

   While fate sharing is a desirable property of a configuration
   mechanism, in many situations fate sharing is imperfect or
   unavailable.  When utilized to discover services on the local link,
   service discovery protocols typically provide for fate sharing, since
   hosts providing service information typically also provide the
   services.  However, where service discovery is assisted by a DA, the
   ability to discover services is dependent on whether the DA is
   operational, even though the DA is typically not involved in the
   delivery of the service.  Since the DA and service agents (SAs) can
   be out of synchronization, it is possible for the DA to provide user

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   agents (UAs) with service information that is no longer current.  For
   example, service descriptions provided to the DA by SAs might be
   included in response to service discovery queries sent by UAs even
   after the SAs were no longer operational.  Similarly, recently
   introduced SAs might not yet have registered their services with the
   DA.  Thus, fate sharing can be imperfect.

   Similar limitations exist for other server-based configuration
   mechanisms such as DHCP.  Typically DHCP servers do not check for the
   liveness of the configuration information they provide, or do not
   discover new configuration information automatically.  As a result,
   there is no guarantee that configuration information will be current.

   "IPv6 Host configuration of DNS Server Information Approaches"
   [RFC4339] Section 3.3 discusses the use of well-known anycast
   addresses for discovery of DNS servers.  The use of anycast addresses
   enables fate sharing, even where the anycast address is provided by
   an unrelated server.  However, in order to be universally useful,
   this approach would require allocation of a well-known anycast
   address for each service.

4.  Security Considerations

   Secure IP configuration presents a number of challenges.  Secure
   configuration mechanisms include SEcure Neighbor Discovery (SEND)
   [RFC3971] for stateless address autoconfiguration, or DHCP
   authentication for stateful address configuration.  DHCPv4 [RFC2131]
   initially did not include support for security; this was added in
   [RFC3118].  DHCPv6 [RFC3736] included security support.  However,
   DHCP authentication is not widely implemented for either DHCPv4 or

   PPP [RFC1661] does not support secure negotiation within IPv4CP
   [RFC1332] or IPv6CP [RFC2472], enabling an attacker with access to
   the link to subvert the negotiation.  In contrast, IKEv2 [RFC4306]
   provides encryption, integrity and replay protection for
   configuration exchanges.

   A number of issues exist with various classes of parameters, as
   discussed in Section 2.6, [RFC3756] Section 4.2.7, [RFC3118] Section
   1.1, and [RFC3315] Section 23.  Given the potential vulnerabilities
   resulting from implementation of these options, it is currently
   common for hosts to restrict support for DHCP options to the minimum
   set required to provide basic TCP/IP configuration.

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4.1.  Configuration Authentication

   In addition to denial-of-service and man-in-the-middle attacks,
   attacks on configuration mechanisms may target particular parameters.
   Since boot configuration determines the boot image to be run by the
   host, a successful attack on boot configuration could result in an
   attacker gaining complete control over a host.  As a result, it is
   particularly important that boot configuration be secured.

   The techniques available for securing Internet layer configuration
   are inherently limited, since classic security protocols such as
   IPsec [RFC4301] or TLS [RFC4346] cannot be used since an IP address
   is not yet available.

   In situations where link layer security is provided, and the Network
   Access Server (NAS) acts as a DHCP relay or server, protection can be
   provided against rogue DHCP servers, provided that the NAS filters
   incoming DHCP packets from unauthorized sources.  However, explicit
   dependencies on lower layer security mechanisms are limited by the
   "lower layer independence" principle (section 2.4).

   As a result, configuration security is typically implemented within
   the configuration protocols themselves.  For example, IPv6 supports
   SEcure Neighbor Discovery (SEND) [RFC3971], DHCPv4 supports DHCP
   authentication [RFC3118], and DHCPv6 supports an equivalent facility

   Higher layer configuration typically does not have this problem.
   When DHCP authentication is supported, higher-layer configuration
   parameters provided by DHCP can be secured.  However, even if a host
   does not support DHCPv6 authentication, higher-layer configuration
   via Stateless DHCPv6 [RFC2462] can still be secured with IPsec.
   Possible exceptions can exist where security facilities are not
   available until later in the boot process.

   For example, it may be difficult to secure boot configuration even
   once the Internet layer has been configured, if security
   functionality is not available until after boot configuration has
   been completed.  For example, it is possible that Kerberos, IPsec or
   TLS will not be available until later in the boot process.

   Where public key cryptography is used to authenticate and integrity
   protect configuration, hosts need to be configured with trust anchors
   in order to validate received configuration messages.  For a node
   that visits multiple administrative domains, acquiring the required
   trust anchors may be difficult.  This is left as an area for future

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5.  IANA Considerations

   This document has no actions for IANA.

6.  References

6.1.  Informative References

[mDNS]    Cheshire, S. and M. Krochmal, "Multicast DNS", June 2005.


[PXE]     Henry, M. and M. Johnston, "Preboot Execution Environment
          (PXE) Specification", September 1999,

[RFC793]  Postel, J., "Transmission Control Protocol", STD 7, RFC 793,
          September 1981.

[RFC1001] NetBIOS Working Group in the Defense Advanced Research
          Projects Agency, Internet Activities Board, and End-to-End
          Services Task Force, "Protocol standard for a NetBIOS service
          on a TCP/UDP transport: Concepts and methods", STD 19, RFC
          1001, March 1987.

[RFC1332] McGregor, G., "PPP Internet Control Protocol", RFC 1332,
          Merit, May 1992.

[RFC1350] Sollins, K., "The TFTP Protocol (Revision 2)", STD 33, RFC
          1350, July 1992.

[RFC1661] Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51, RFC
          1661, July 1994.

[RFC1877] Cobb, S., "PPP Internet Protocol Control Protocol Extensions
          for Name Server Addresses", RFC 1877, December 1995.

[RFC1958] Carpenter, B., "Architectural Principles of the Internet", RFC
          1958, June 1996.

[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
          March 1997.

[RFC2462] Thomson, S. and T. Narten, "IPv6 Stateless Address
          Autoconfiguration", RFC 2462, December 1998.

[RFC2472] Haskin, D. and E. Allen, "IP Version 6 over PPP", RFC 2472,
          December 1998.

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[RFC2608] Guttman, E., et al., "Service Location Protocol, Version 2",
          RFC 2608, June 1999.

[RFC3041] Narten, T. and R. Draves, "Privacy Extensions for Stateless
          Address Autoconfiguration in IPv6", RFC 3041, January 2001.

[RFC3118] Droms, R. and W. Arbaugh, "Authentication for DHCP Messages",
          RFC 3118, June 2001.

[RFC3315] Droms, R., Ed., Bound, J., Volz,, B., Lemon, T., Perkins, C.
          and M. Carney, "Dynamic Host Configuration Protocol for IPv6
          (DHCPv6)", RFC 3315, July 2003.

[RFC3344] Perkins, C., "IP Mobility Support for IPv4", RFC 3344, August

[RFC3456] Patel, B., Aboba, B., Kelly, S. and V. Gupta, "Dynamic Host
          Configuration Protocol (DHCPv4) Configuration of IPsec Tunnel
          Mode", RFC 3456, January 2003.

[RFC3530] Shepler, S., Callaghan, B., Robinson, D., Thurlow, R., Beame,
          C., Eisler, M. and D. Noveck, "Network File System (NFS)
          version 4 Protocol", RFC 3530, April 2003.

[RFC3720] Satran, J., Meth, K., Sapuntzakis, C. Chadalapaka, M.  and E.
          Zeidner, "Internet Small Computer Systems Interface (iSCSI)",
          RFC 3720, April 2004.

[RFC3736] Droms, R., "Stateless Dynamic Host Configuration Protocol
          (DHCP) Service for IPv6", RFC 3736, April 2004.

[RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J. and H.
          Levkowetz, "Extensible Authentication Protocol (EAP)", RFC
          3748, June 2004.

[RFC3756] Nikander, P., Kempf, J. and E. Nordmark, "IPv6 Neighbor
          Discovery (ND) Trust Models and Threats", RFC 3756, May 2004.

[RFC3775] Johnson, D., Perkins, C. and J. Arkko, "Mobility Support in
          IPv6", RFC 3775, June 2004.

[RFC3832] Zhao, W., Schulzrinne, H., Guttman, E., Bisdikian, C. and W.
          Jerome, "Remote Service Discovery in the Service Location
          Protocol (SLP) via DNS SRV", RFC 3832, July 2004.

[RFC3971] Arkko, J., Kempf, J., Sommerfeld, B., Zill, B. and P.
          Nikander, "SEcure Neighbor Discovery (SEND)", RFC 3971, March

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INTERNET-DRAFT         Internet Host Configuration       11 October 2007

[RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", RFC
          3972, March 2005.

[RFC4173] Sarkar, P., Missimer, D. and C. Sapuntzakis, "Bootstrapping
          Clients using the iSCSI Protocol", RFC 4173, September 2005.

[RFC4301] Kent, S. and K. Seo, "Security Architecture for the Internet
          Protocol", RFC 4301, December 2005.

[RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", RFC
          4306, December 2005.

[RFC4339] Jeong, J., "IPv6 Host Configuration of DNS Server Information
          Approaches", RFC 4339, February 2006.

[RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security
          (TLS) Protocol Version 1.1", RFC 4346, April 2006.

[RFC4578] Johnston, M. and S. Venaas, "Dynamic Host Configuration
          Protocol (DHCP) Options for the Intel Preboot eXecution
          Environment (PXE)", RFC 4578, November 2006.

[RFC4795] Aboba, B., Thaler, D. and L. Esibov, "Link-Local Multicast
          Name Resolution (LLMNR)", RFC 4795, January 2007.


   Bob Hinden, Pasi Eronen, Jari Arkko, Pekka Savola and James Kempf
   provided valuable input on this document.

Appendix A - IAB Members at the time of this writing

   Loa Andersson
   Leslie Daigle
   Elwyn Davies
   Kevin Fall
   Olaf Kolkman
   Barry Leiba
   Kurtis Lindqvist
   Danny McPherson
   David Oran
   Eric Rescorla
   Dave Thaler
   Lixia Zhang

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Authors' Addresses

   Bernard Aboba
   Microsoft Corporation
   One Microsoft Way
   Redmond, WA 98052

   Phone: +1 425 706 6605
   Fax:   +1 425 936 7329

   Dave Thaler
   Microsoft Corporation
   One Microsoft Way
   Redmond, WA 98052


   Loa Andersson
   Acreo AB


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