\
Dynamic Host Configuration (DHC)                                G.R. Ren
Internet-Draft                                                   L.H. He
Intended status: Informational                                  Y.L. Liu
Expires: 23 June 2022                                Tsinghua University
                                                        20 December 2021


             DHCPv6 Extension Practices and Considerations
                   draft-rhl-dhc-dhcpv6-extensions-00

Abstract

   IP addresses assume an increasing number of attributes as
   communication identifiers to meet different requirements.  Privacy
   protection, accountability, security, and manageability of networks
   can be supported by extending the DHCPv6 protocol as required.  This
   document provides current extension practices and typical DHCPv6
   server software in terms of extensions, defines a general model of
   DHCPv6, discusses some extension points, and presents extension
   cases.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 23 June 2022.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components



Ren, et al.               Expires 23 June 2022                  [Page 1]


Internet-Draft       problem statement of mredhcpv6        December 2021


   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Current Extension Practices . . . . . . . . . . . . . . . . .   4
     3.1.  Standardized and Non-standardized DHCPv6 Extension
           Cases . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Current DHCPv6 Server Software Cases  . . . . . . . . . .   4
   4.  Extension Discussion  . . . . . . . . . . . . . . . . . . . .   5
     4.1.  DHCPv6 General Model  . . . . . . . . . . . . . . . . . .   5
     4.2.  Extension Points  . . . . . . . . . . . . . . . . . . . .   6
       4.2.1.  Messages  . . . . . . . . . . . . . . . . . . . . . .   6
       4.2.2.  Options . . . . . . . . . . . . . . . . . . . . . . .   6
       4.2.3.  Message Processing Functions  . . . . . . . . . . . .   7
       4.2.4.  Address Generation Mechanisms . . . . . . . . . . . .   7
     4.3.  Extension Principles  . . . . . . . . . . . . . . . . . .   8
   5.  Extension Cases . . . . . . . . . . . . . . . . . . . . . . .   8
     5.1.  Software Configurations . . . . . . . . . . . . . . . . .   9
     5.2.  Option Definition and Server Modification . . . . . . . .   9
     5.3.  Message Definition  . . . . . . . . . . . . . . . . . . .   9
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   IP addresses play an essential role in communication over the
   Internet.  Their generation and assignment are also closely linked to
   the privacy protection, accountability, security, and manageability
   of the network [I-D.gont-v6ops-ipv6-addressing-considerations].  The
   Dynamic Host Configuration Protocol for IPv6 (DHCPv6) [RFC8415] is an
   important network protocol that can be used to dynamically provide
   IPv6 addresses and other network configuration parameters to IPv6
   nodes.  DHCPv6 can be continuously extended and improved through new
   options, protocols, and message processing mechanisms.

   IP addresses assume an increasing number of properties as
   communication identifiers to meet different requirements.  For
   example, APNA [APNA] and PAVI [PAVI] use addresses to enhance source
   responsibility and privacy protection.  These requirements often need



Ren, et al.               Expires 23 June 2022                  [Page 2]


Internet-Draft       problem statement of mredhcpv6        December 2021


   to be reflected by IP address assignment protocols such as DHCPv6.
   Therefore, extensions to DHCPv6 are made to meet a wide variety of
   requirements, which is referred to as multi-requirement extensions to
   DHCPv6.  However, it is not easy to extend DHCPv6 to meet a variety
   of requirements.  Although DHCPv6 offers increasingly comprehensive
   functionality and DHCPv6 server software provides extension
   interfaces that allow administrators to change and customize the way
   they process and respond to DHCPv6 messages, there is still a lack of
   comprehensive understanding of where and how to extend in DHCPv6
   effectively.  Therefore, a detailed analysis is needed to clarify the
   issues and design principles and extract and unify design
   specifications to help better address the multi-demand scaling
   problem.

   In summary, with the large-scale deployment and application of IPv6,
   new scenarios such as Data Center Network, Internet of Things,
   Industrial Internet, and Integrated satellite-terrestrial networks
   put forward new requirements for IP address allocation, e.g., the
   scale of address allocation, the efficiency of address update and
   synchronization, the address generation algorithms (such as
   association with location, identifier, and other information), and
   the scope of dynamic address configuration service relay and
   collaboration.  At the same time, it also puts forward new
   requirements in network security, accountability, manageability, and
   privacy protection.  These are what we call "multiple requirements".
   Multi-requirement extensions for DHCPv6 is to meet new scenarios and
   new requirements through the expansion of new messages, options,
   message processing functions, or address generation mechanisms for
   DHCPv6.  Based on careful design principles, interfaces can be
   defined to support more customized multi-requirement extensions
   without sacrificing the stability of DHCPv6.

   Some people would suggest that administrators modify the open-source
   DHCPv6 server to solve their problems.  However, it takes
   considerable time to understand the code of an open-source DHCPv6
   server, not to mention the time-consuming task of debugging errors,
   failures, or system crashes caused by modifying complex modules.
   Another problem is that as open-source software evolves, the source
   code of the server software may change (new features or bug fixes).
   Once the latest version of the open-source server software comes out
   [kea_dhcp_hook_developers_guide], users may need to rewrite their
   code.  Therefore, the multi-requirement extensions to DHCPv6 to
   address the specific issues of administrators are essential and
   significant.







Ren, et al.               Expires 23 June 2022                  [Page 3]


Internet-Draft       problem statement of mredhcpv6        December 2021


   This document provides a survey of current extension practices and
   typical DHCPv6 server softwares on extensions and gives DHCPv6
   extension considerations by defining a DHCPv6 general model,
   discussing the extension problems, and presenting extension cases.

2.  Terminology

   Familiarity with DHCPv6 and its terminology, as defined in [RFC8415],
   is assumed.

   Multi-requirement extensions:  The multi-requirement extensions for
      DHCPv6 is to meet new scenarios and requirements by extending
      DHCPv6 with new messages, options, message processing features, or
      address generation mechanisms.

3.  Current Extension Practices

3.1.  Standardized and Non-standardized DHCPv6 Extension Cases

   Many documents attempt to extend DHCPv6.  They can be classified into
   three categories.

   Extended options    Most extensions for DHCPv6 are implemented in
                       this way.  New-defined options carry specific
                       parameters in DHCPv6 messages, which helps DHCPv6
                       clients or servers know the detailed situation
                       with each other.

   Extended messages   Some documents define new protocols that aim to
                       achieve specific goals, e.g., active leasequery
                       [RFC7653], General Address Generation and
                       Management System [GAGMS].

   Extended entities   Some documents introduce third-party entities
                       into the communications of DHCPv6 to achieve
                       specific goals and provide better services, e.g.,
                       authentication [RFC7037].

3.2.  Current DHCPv6 Server Software Cases

   A lot of commercial and open source DHCPv6 servers exist, including
   Cisco Prime Network Registrar (CPNR) DHCP [CPNR], DHCP Broadband
   [DHCP_Broadband], FreeRADIUS DHCP [FreeRADIUS_DHCP], ISC DHCP
   [ISC_DHCP], Kea DHCP [Kea_DHCP], Microsoft DHCP [Microsoft_DHCP],
   Nominum DHCP [Nominum_DHCP], VitalQIP [VitalQIP], and WIDE DHCPv6
   [WIDE_DHCPv6].  Commercial and open-source DHCPv6 software often
   considers the extensions of DHCPv6 servers because they cannot always
   meet the requirements that the administrators want.  For example,



Ren, et al.               Expires 23 June 2022                  [Page 4]


Internet-Draft       problem statement of mredhcpv6        December 2021


   CPNR DHCP server provides extension APIs and allows administrators to
   write extensions and functions to alter and customize how it handles
   and responds to DHCP requests.  A network operator usually decides
   what packet process to modify, how to modify, and which extension
   point to attach the extension.  Then the network operator writes the
   extension and adds the well-written extension to the extension point
   of the DHCP server.  Finally, the network operator reloads the DHCP
   server and debugs whether the server runs as it expects.  Similarly,
   Kea DHCP provides hook mechanisms, a well-designed interface for
   third-party code, to solve the problem that the DHCP server does not
   quite do what a network operator require.

4.  Extension Discussion

   This section elaborates multi-requirement extensions for DHCPv6.
   Section 4.1 describes the general model of DHCPv6, while Section 4.2
   analyzes the extension points and requirements.

4.1.  DHCPv6 General Model

   Figure 1 summarizes the DHCPv6 general model and its possible
   extensions: messages, options, message processing functions, and
   address generation mechanisms.

+-----------------+                  +----------------+
|  DHCPv6 client  | DHCPv6 messages  |  DHCPv6 relay  |
| +-------------+ |   with options   | +------------+ | External inputs
| |  Message    | |<---------------->| |  Message   | |<----------------
| | processing  | |                  | | relaying   | | e.g., RADIUS
| | functions   | |                  | | functions  | | option [RFC7037]
| +-------------+ |                  | +------------+ |
+-----------------+                  +----------------+
                                              ^
                              DHCPv6 messages |
                                with options  |
                                              |
                                              V
+-----------------+               +----------------------------+
|                 |   Extended    |        DHCPv6 server       |
|                 |   messages    | +-----------+ +----------+ |
|External entities|<------------->| |  Address  | | Message  | |
|                 |  e.g., Active | | generation| |processing| |
|                 |  leasequery   | | mechanisms| |functions | |
|                 |  [RFC7653]    | +-----------+ +----------+ |
+-----------------+               +----------------------------+

   Figure 1: DHCPv6 general model and its possible extensions.




Ren, et al.               Expires 23 June 2022                  [Page 5]


Internet-Draft       problem statement of mredhcpv6        December 2021


4.2.  Extension Points

4.2.1.  Messages

   On the one hand, new messages can be designed and added to the DHCPv6
   protocol to enrich its functionalities.  For example, [RFC5007]
   defines new leasequery messages to allow a requestor to retrieve
   information on the bindings for a client from one or more servers.
   [RFC5460] expands on the Leasequery protocol by defines new messages
   and allowing for bulk transfer of DHCPv6 binding data via TCP.
   [RFC7653] defines active leasequery messages to keep the requestor up
   to date with DHCPv6 bindings.  [RFC8156] defines failover messages to
   provide a mechanism for running two servers with the capability for
   either server to take over clients' leases in case of server failure
   or network partition.

   On the other hand, people are concerned about the security and
   privacy issues of the DHCPv6 protocol.  [RFC7824] describes the
   privacy issues associated with the use of DHCPv6, respectively.
   DHCPv6 does not provide privacy protection on messages and options.
   Other nodes can see the options transmitted in DHCPv6 messages
   between DHCPv6 clients and servers.  Extended messages can be
   designed to secure exchanges between DHCPv6 entities.

4.2.2.  Options

   DHCPv6 allows defining options to transmit parameters between DHCPv6
   entities for common requirements, e.g., DNS configurations [RFC3646],
   NIS configurations [RFC3898], SNTP configurations [RFC4075], relay
   agent subscriber-id [RFC4580], relay agent remote-id [RFC4649], FQDN
   configurations [RFC4704], relay agent echo request [RFC4994], network
   boot [RFC5970], Relay-Supplied Options [RFC6422], virtual subnet
   selection [RFC6607], client link-layer address [RFC6939], and
   softwire source binding prefix hint [RFC8539].  Also, these
   parameters may come from external entities.  For example, [RFC7037]
   defines RADIUS option to exchange authorization and identification
   information between the DHCPv6 relay agent and DHCPv6 server.

   In other cases, network operators may require DHCPv6 messages to
   transmit some self-defined options between clients and servers.
   Currently, the vendor-specific information option allows clients and
   servers to exchange vendor-specific information.  Therefore,
   administrative domains can define and use the sub-options of the
   vendor-specific information option to serve their private purposes.
   The content of the self-defined options may come from two sources:
   devices and users.  If the content of self-defined options comes from
   users, two methods can be used to solve the problem.  The first one
   is that the clients provide related interfaces to receive such



Ren, et al.               Expires 23 June 2022                  [Page 6]


Internet-Draft       problem statement of mredhcpv6        December 2021


   information, which is currently merely supported.  The second one is
   that DHCPv6 relays obtain such information and add it to the clients'
   requests.  But this always depends on other protocols to allow DHCPv6
   relays to get the information first.

4.2.3.  Message Processing Functions

   Although current commercial or open-source DHCPv6 server softwares
   provide comprehensive functionalities, they still cannot meet all
   customers' requirements of processing DHCPv6 requests.  Therefore,
   they will offer interfaces that customers can use to write their
   specific extensions to affect the way how DHCPv6 servers handle and
   respond to DHCP requests.  For example, a network operator may want
   his DHCPv6 server to communicate with external servers.  Thus, he may
   alter his DHCPv6 server through the given extensions to achieve such
   a goal.  However, not all DHCPv6 software considers this extension.

4.2.4.  Address Generation Mechanisms

   Currently, the DHCPv6 servers assign addresses, prefixes and other
   configuration options according to their configured policies.
   Generally, different networks may prefer different address generation
   mechanisms.  Several address generation mechanisms for SLAAC
   [RFC4862] (e.g., IEEE 64-bit EUI-64 [RFC2464], Constant, semantically
   opaque [Microsoft], Temporary [RFC4941], and Stable, semantically
   opaque [RFC7217]) proposed for different requirements can be utilized
   in DHCPv6 protocol as well.  Note that [RFC7943] is the DHCPv6
   version of Stable, semantically opaque [RFC7217].  The many types of
   IPv6 address generation mechanisms available have brought about
   flexibility and diversity.  Therefore, corresponding interfaces could
   be open and defined to allow other address generation mechanisms to
   be configured.

   Moreover, several basic operations are defined to support the design
   of IPv6 addresses generation mechanisms.  A new IPv6 address
   generation mechanism can be made up of the combination of the
   following basic operations.  Also, new basic operations can be
   defined to support new functions.

   Invert(x, n)           invert bit n of input x.

   Insert(x, n, s)        insert s after bit n of input x.

   Concatenate(x, y, ...)  concatenate input [x, y, ...] sequentially.

   Replace(x, n, m, s)    change from bit n to bit m of input x into s.





Ren, et al.               Expires 23 June 2022                  [Page 7]


Internet-Draft       problem statement of mredhcpv6        December 2021


                          Note that the length of s must be equal to
                          m-n+1.  When n=m, change only one bit of input
                          x.

   Truncate(x, n, m)      truncate from bit n to bit m of input x as the
                          output

   Encrypt(x, k)          use some specific encryption algorithm to
                          encrypt input x with key k.  Encryption
                          algorithms can be IDEA, AES, RSA, etc.

   Hash(x)                calculate the hash digest value of input x.
                          Hash algorithms can be MD5, SHA1, SHA256, etc.

   For example, temporary addresses in [RFC4941] can be expressed as
   tempAddr(eui64, history) = Replace(Truncate(Hash(Concatenate(eui64,
   history)), 0, 63), 6, 6, 0), where eui64 means the EUI-64 identifier
   defined in [RFC2464] and history means a history value defined in
   [RFC4941].

4.3.  Extension Principles

   The principles used to conduct multi-requirement extensions for
   DHCPv6 are summarized as follows:

      1) Do not change the basic design of DHCPv6.

      2) Use simpler interfaces to define and support more extensions.

5.  Extension Cases

   Administrative domains may enforce local policies according to their
   requirements, e.g., authentication, accountability.  Several kinds of
   multi-requirement extensions are presented in this section, including
   configurations in current DHCPv6 software, option definition and
   server modification, and message definition between DHCPv6 entities
   and third-party entities.  IPv6 addresses are related to
   manageability, security, traceability, and accountability of
   networks.  As DHCPv6 assigns IPv6 addresses to IPv6 nodes, it is
   important that DHCPv6 provides interfaces to allow administrative
   domains to conduct extensions to meet their multi-requirements.










Ren, et al.               Expires 23 June 2022                  [Page 8]


Internet-Draft       problem statement of mredhcpv6        December 2021


5.1.  Software Configurations

   Currently, many DHCPv6 servers provide administrative mechanisms,
   e.g., host reservation and client classification.  Host reservation
   is often used to assign certain parameters (e.g., IP addresses) to
   specific devices.  For example, a client with special access rights
   (e.g., a firewall rule that allows access based on the source's IP
   address) needs to keep its address allowed in the firewall
   configuration.  Another use case is a device with a mission-critical
   network service that needs access by IP address in case a DNS lookup
   fails.  Client classification is often used to differentiate between
   different types of clients and treat them accordingly in certain
   cases.  This classification allows DHCP addresses or options to be
   assigned based on specific device characteristics or some network
   identifier.  Grouping devices by client class makes it more
   convenient to perform bulk configuration settings.  A typical example
   is the network access security policy.  For example, a client class
   can be configured so that devices in that class are assigned IP
   addresses in subnets that are restricted to the public Internet due
   to security policies applied to the subnet/network on the router or
   firewall.

5.2.  Option Definition and Server Modification

   More complicated extensions of DHCPv6 are needed to meet specific
   requirements.  For example, considering such a requirement that
   DHCPv6 servers assign IPv6 addresses generated by user identifiers to
   the clients in a network to hold users accountable, two extensions
   should be fulfilled to meet this requirement.  The first one is that
   clients send their user identifiers to servers.  This can be achieved
   by defining and using sub-options of vendor-specific information
   option.  The second one is that servers use user identifiers to
   generate IP addresses.  To achieve this goal, extension mechanisms
   provided by the server software such as extension points in CPNR
   [CPNR] and hook mechanisms in Kea DHCP [Kea_DHCP] can be used.

5.3.  Message Definition

   Some extensions for DHCPv6 may need the support of third-party
   entities.  For example, [RFC7037] introduces RADIUS entities into the
   message exchanges between DHCPv6 entities for better service
   provision.  The authentication in [RFC7037] can also be used to meet
   the accountability requirement mentioned above because it is
   important to authenticate users first before assigning IP addresses
   generated from user identifiers.  Usually, this kind of extension
   requires the definition of messages communicated between DHCPv6
   entities and third-party entities, e.g., active leasequery [RFC7653].




Ren, et al.               Expires 23 June 2022                  [Page 9]


Internet-Draft       problem statement of mredhcpv6        December 2021


6.  Security Considerations

   Security issues related with DHCPv6 are described in Section 22 of
   [RFC8415].

7.  IANA Considerations

   This document does not include an IANA request.

8.  Acknowledgements

   The authors would like to thank Bernie Volz, Tomek Mrugalski, Sheng
   Jiang, and Jinmei Tatuya for their comments and suggestions that
   improved the [I-D.ren-dhc-mredhcpv6].  Some ideas and thoughts of
   [I-D.ren-dhc-mredhcpv6] are contained in this document.

9.  References

9.1.  Normative References

   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862,
              DOI 10.17487/RFC4862, September 2007,
              <https://www.rfc-editor.org/info/rfc4862>.

   [RFC8415]  Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A.,
              Richardson, M., Jiang, S., Lemon, T., and T. Winters,
              "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
              RFC 8415, DOI 10.17487/RFC8415, November 2018,
              <https://www.rfc-editor.org/info/rfc8415>.

9.2.  Informative References

   [APNA]     Lee, T.L., Pappas, C.P., Barrera, D.B., Szalachowski,
              P.S., and A.P. Perrig, "Source Accountability with Domain-
              brokered Privacy", December 2016.

   [CPNR]     Cisco, "Cisco Prime Network Registrar", 2018,
              <https://www.cisco.com/c/en/us/products/cloud-systems-
              management/prime-network-registrar/index.html>.

   [DHCP_Broadband]
              Weird Solutions, "DHCP Broadband", 2018,
              <https://www.weird-solutions.com/carrier-solutions/dhcp-
              broadband>.






Ren, et al.               Expires 23 June 2022                 [Page 10]


Internet-Draft       problem statement of mredhcpv6        December 2021


   [FreeRADIUS_DHCP]
              FreeRADIUS, "FreeRADIUS DHCP", 2017,
              <https://wiki.freeradius.org/features/DHCP>.

   [GAGMS]    Liu, Y.L., He, L.H., and G.R. Ren, "GAGMS: A Requirement-
              Driven General Address Generation and Management System",
              November 2017.

   [I-D.gont-v6ops-ipv6-addressing-considerations]
              Gont, F.G. and G.G. Gont, "IPv6 Addressing
              Considerations", February 2021.

   [I-D.jia-intarea-scenarios-problems-addressing]
              Jia, Y., Trossen, D., Iannone, L., Shenoy, N., Mendes, P.,
              and P. Liu, "Challenging Scenarios and Problems in
              Internet Addressing", Work in Progress, Internet-Draft,
              draft-jia-intarea-scenarios-problems-addressing-02, 23
              October 2021, <https://www.ietf.org/archive/id/draft-jia-
              intarea-scenarios-problems-addressing-02.txt>.

   [I-D.lhan-problems-requirements-satellite-net]
              Han, L. and R. Li, "Problems and Requirements of Satellite
              Constellation for Internet", Work in Progress, Internet-
              Draft, draft-lhan-problems-requirements-satellite-net-01,
              19 October 2021, <https://www.ietf.org/archive/id/draft-
              lhan-problems-requirements-satellite-net-01.txt>.

   [I-D.ren-dhc-mredhcpv6]
              Ren, G.R., He, L.H., and Y.L. Liu, "Multi-requirement
              Extensions for Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", March 2017.

   [ISC_DHCP] Internet System Consortium, "ISC DHCP", 2018,
              <http://www.isc.org/downloads/dhcp/>.

   [Kea_DHCP] Internet System Consortium, "Kea DHCP", 2018,
              <https://www.isc.org/kea/>.

   [kea_dhcp_hook_developers_guide]
              Internet Systems Consortium, "Hook Developer's Guide",
              2018, <https://jenkins.isc.org/job/Kea_doc/doxygen/df/d46/
              hooksdgDevelopersGuide.html>.

   [Microsoft]
              Microsoft, "IPv6 interface identifiers", 2013, <https://ww
              w.microsoft.com/resources/documentation/windows/xp/all/
              proddocs/en-us/sag_ip_v6_imp_addr7.mspx?mfr=true>.




Ren, et al.               Expires 23 June 2022                 [Page 11]


Internet-Draft       problem statement of mredhcpv6        December 2021


   [Microsoft_DHCP]
              Microsoft, "Microsoft DHCP", 2008,
              <https://technet.microsoft.com/en-us/library/
              cc896553(v=ws.10).aspx>.

   [Nominum_DHCP]
              Nominum, "Nominum DHCP", 2012,
              <https://www.nominum.com/press_item/nominum-releases-new-
              version-of-carrier-grade-dhcp-software-for-telecom-
              providers/>.

   [PAVI]     He, L.H., Ren, G.R., Liu, Y.L., and J.Y. Yang, "PAVI:
              Bootstrapping Accountability and Privacy to IPv6
              Internet", April 2021.

   [RFC2464]  Crawford, M., "Transmission of IPv6 Packets over Ethernet
              Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998,
              <https://www.rfc-editor.org/info/rfc2464>.

   [RFC3646]  Droms, R., Ed., "DNS Configuration options for Dynamic
              Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3646,
              DOI 10.17487/RFC3646, December 2003,
              <https://www.rfc-editor.org/info/rfc3646>.

   [RFC3898]  Kalusivalingam, V., "Network Information Service (NIS)
              Configuration Options for Dynamic Host Configuration
              Protocol for IPv6 (DHCPv6)", RFC 3898,
              DOI 10.17487/RFC3898, October 2004,
              <https://www.rfc-editor.org/info/rfc3898>.

   [RFC4075]  Kalusivalingam, V., "Simple Network Time Protocol (SNTP)
              Configuration Option for DHCPv6", RFC 4075,
              DOI 10.17487/RFC4075, May 2005,
              <https://www.rfc-editor.org/info/rfc4075>.

   [RFC4580]  Volz, B., "Dynamic Host Configuration Protocol for IPv6
              (DHCPv6) Relay Agent Subscriber-ID Option", RFC 4580,
              DOI 10.17487/RFC4580, June 2006,
              <https://www.rfc-editor.org/info/rfc4580>.

   [RFC4649]  Volz, B., "Dynamic Host Configuration Protocol for IPv6
              (DHCPv6) Relay Agent Remote-ID Option", RFC 4649,
              DOI 10.17487/RFC4649, August 2006,
              <https://www.rfc-editor.org/info/rfc4649>.







Ren, et al.               Expires 23 June 2022                 [Page 12]


Internet-Draft       problem statement of mredhcpv6        December 2021


   [RFC4704]  Volz, B., "The Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6) Client Fully Qualified Domain Name (FQDN)
              Option", RFC 4704, DOI 10.17487/RFC4704, October 2006,
              <https://www.rfc-editor.org/info/rfc4704>.

   [RFC4941]  Narten, T., Draves, R., and S. Krishnan, "Privacy
              Extensions for Stateless Address Autoconfiguration in
              IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007,
              <https://www.rfc-editor.org/info/rfc4941>.

   [RFC4994]  Zeng, S., Volz, B., Kinnear, K., and J. Brzozowski,
              "DHCPv6 Relay Agent Echo Request Option", RFC 4994,
              DOI 10.17487/RFC4994, September 2007,
              <https://www.rfc-editor.org/info/rfc4994>.

   [RFC5007]  Brzozowski, J., Kinnear, K., Volz, B., and S. Zeng,
              "DHCPv6 Leasequery", RFC 5007, DOI 10.17487/RFC5007,
              September 2007, <https://www.rfc-editor.org/info/rfc5007>.

   [RFC5460]  Stapp, M., "DHCPv6 Bulk Leasequery", RFC 5460,
              DOI 10.17487/RFC5460, February 2009,
              <https://www.rfc-editor.org/info/rfc5460>.

   [RFC5970]  Huth, T., Freimann, J., Zimmer, V., and D. Thaler, "DHCPv6
              Options for Network Boot", RFC 5970, DOI 10.17487/RFC5970,
              September 2010, <https://www.rfc-editor.org/info/rfc5970>.

   [RFC6422]  Lemon, T. and Q. Wu, "Relay-Supplied DHCP Options",
              RFC 6422, DOI 10.17487/RFC6422, December 2011,
              <https://www.rfc-editor.org/info/rfc6422>.

   [RFC6607]  Kinnear, K., Johnson, R., and M. Stapp, "Virtual Subnet
              Selection Options for DHCPv4 and DHCPv6", RFC 6607,
              DOI 10.17487/RFC6607, April 2012,
              <https://www.rfc-editor.org/info/rfc6607>.

   [RFC6939]  Halwasia, G., Bhandari, S., and W. Dec, "Client Link-Layer
              Address Option in DHCPv6", RFC 6939, DOI 10.17487/RFC6939,
              May 2013, <https://www.rfc-editor.org/info/rfc6939>.

   [RFC7037]  Yeh, L. and M. Boucadair, "RADIUS Option for the DHCPv6
              Relay Agent", RFC 7037, DOI 10.17487/RFC7037, October
              2013, <https://www.rfc-editor.org/info/rfc7037>.








Ren, et al.               Expires 23 June 2022                 [Page 13]


Internet-Draft       problem statement of mredhcpv6        December 2021


   [RFC7217]  Gont, F., "A Method for Generating Semantically Opaque
              Interface Identifiers with IPv6 Stateless Address
              Autoconfiguration (SLAAC)", RFC 7217,
              DOI 10.17487/RFC7217, April 2014,
              <https://www.rfc-editor.org/info/rfc7217>.

   [RFC7653]  Raghuvanshi, D., Kinnear, K., and D. Kukrety, "DHCPv6
              Active Leasequery", RFC 7653, DOI 10.17487/RFC7653,
              October 2015, <https://www.rfc-editor.org/info/rfc7653>.

   [RFC7824]  Krishnan, S., Mrugalski, T., and S. Jiang, "Privacy
              Considerations for DHCPv6", RFC 7824,
              DOI 10.17487/RFC7824, May 2016,
              <https://www.rfc-editor.org/info/rfc7824>.

   [RFC7943]  Gont, F. and W. Liu, "A Method for Generating Semantically
              Opaque Interface Identifiers (IIDs) with the Dynamic Host
              Configuration Protocol for IPv6 (DHCPv6)", RFC 7943,
              DOI 10.17487/RFC7943, September 2016,
              <https://www.rfc-editor.org/info/rfc7943>.

   [RFC8156]  Mrugalski, T. and K. Kinnear, "DHCPv6 Failover Protocol",
              RFC 8156, DOI 10.17487/RFC8156, June 2017,
              <https://www.rfc-editor.org/info/rfc8156>.

   [RFC8539]  Farrer, I., Sun, Q., Cui, Y., and L. Sun, "Softwire
              Provisioning Using DHCPv4 over DHCPv6", RFC 8539,
              DOI 10.17487/RFC8539, March 2019,
              <https://www.rfc-editor.org/info/rfc8539>.

   [VitalQIP] Nokia, "Nokia VitalQIP", 2017,
              <https://networks.nokia.com/products/vitalqip-ip-address-
              management>.

   [WIDE_DHCPv6]
              KAME project, "WIDE DHCPv6", 2008,
              <http://ipv6int.net/software/wide_dhcpv6.html>.

Authors' Addresses

   Gang Ren
   Tsinghua University
   Beijing

   Phone: +86-010 6260 3227
   Email: rengang@cernet.edu.cn





Ren, et al.               Expires 23 June 2022                 [Page 14]


Internet-Draft       problem statement of mredhcpv6        December 2021


   Lin He
   Tsinghua University
   Beijing

   Email: he-lin@tsinghua.edu.cn


   Ying Liu
   Tsinghua University
   Beijing

   Email: liuying@cernet.edu.cn







































Ren, et al.               Expires 23 June 2022                 [Page 15]