Problem Statement of Multi-requirement Extensions for Dynamic Host Configuration Protocol for IPv6 (DHCPv6)
draft-ietf-dhc-problem-statement-of-mredhcpv6-00
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| Authors | Ren Gang , Lin He , Ying Liu | ||
| Last updated | 2019-05-30 (Latest revision 2019-05-23) | ||
| Replaces | draft-ren-dhc-problem-statement-of-mredhcpv6 | ||
| Replaced by | draft-rhl-dhc-dhcpv6-extensions | ||
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draft-ietf-dhc-problem-statement-of-mredhcpv6-00
Dynamic Host Configuration (DHC) G. Ren
Internet-Draft L. He
Intended status: Informational Y. Liu
Expires: November 24, 2019 Tsinghua University
May 23, 2019
Problem Statement of Multi-requirement Extensions for Dynamic Host
Configuration Protocol for IPv6 (DHCPv6)
draft-ietf-dhc-problem-statement-of-mredhcpv6-00
Abstract
The manageability, security, privacy protection, and traceability of
networks can be supported by extending DHCPv6 protocol according to
requirements. This document analyzes current extension practices and
typical DHCP server software on extensions, defines a DHCP general
model, discusses some extension points, and present 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 November 24, 2019.
Copyright Notice
Copyright (c) 2019 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 extracted from this document must
include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Current Extension Practices . . . . . . . . . . . . . . . . . 3
3.1. Standardized and Non-standardized DHCPv6 Extension Cases 3
3.2. Current DHCPv6 Server Software Cases . . . . . . . . . . 4
3.2.1. Cisco Prime Network Registrar DHCP Server Extension
APIs . . . . . . . . . . . . . . . . . . . . . . . . 4
3.2.2. Kea DHCP Hook Mechanisms . . . . . . . . . . . . . . 4
4. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 5
4.1. DHCP General Model . . . . . . . . . . . . . . . . . . . 5
4.2. Extension Discussion . . . . . . . . . . . . . . . . . . 5
4.2.1. DHCP Messages . . . . . . . . . . . . . . . . . . . . 5
4.2.2. Options . . . . . . . . . . . . . . . . . . . . . . . 6
4.2.3. Message Processing Functions . . . . . . . . . . . . 6
4.2.4. Address Generation Mechanisms . . . . . . . . . . . . 6
4.2.5. Extension Principles . . . . . . . . . . . . . . . . 7
5. Extension Cases . . . . . . . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
9. Normative References . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
The IP address plays a significant role in the communication of the
Internet. IP address generation is also closely related to the
manageability, security, privacy protection, and traceability of
networks. 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. Actually, DHCPv6 continues to be extended
and improved through new options, protocols or message processing
mechanisms.
Although DHCPv6 provides more and more comprehensive functionalities
and DHCPv6 server software also provides extension interfaces to
allow administrators to alter and customize the way how they handle
and respond to DHCPv6 messages, there is still a lack of a general
insight into where and how to conduct extensions in DHCPv6
effectively. The extensions to DHCPv6 can be various according to
multiple requirements. Therefore, a detailed analysis is required to
clarify the problems, design principles, and extract and unify the
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design specifications to help better solve the multi-requirement
extension problems.
In summary, multi-requirement extensions for DHCPv6 can be conducted
to support the administrator's self-defined functionalities. As
DHCPv6 is an important and useful protocol related to IPv6 addresses
generation, it can provide more extended and flexible functionalities
to meet administrators' requirements. According to well-designed
principles, extended interfaces can be defined to support more self-
defined multi-requirement extensions without sacrificing the
stability of DHCPv6.
Some people would suggest administrators modify the open-source DHCP
servers to solve their problems. However, a great amount of time
will be taken to understand the open source DHCP server codes, not to
say the consuming time debugging the bugs, failures or system crash
caused by modifying the complicated modules. Another problem is that
as the open source software evolves, the source codes of the server
software may change (new functionalities or fixing bugs). Users may
need to re-write their codes once the new version of open-source
server software comes out [kea_dhcp_hook_developers_guide] . Hence,
the multi-requirement extensions for DHCPv6 to solve administrators'
specific problems are very necessary and significant.
This document describes current extension practices and typical DHCP
server software on extensions and provides a problem statement by
defining a DHCP general model, discussing the extension problems, and
presenting extension cases.
2. Terminology
Familiarity with DHCPv6 and its terminology, as defined in [RFC8415],
is assumed.
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.
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Extended messages Some documents define new protocols that aim to
achieve specific goals, e.g., active leasequery
[RFC7653], GAGMS [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 DHCP servers exist, including
Cisco Prime Network Registrar [CPNR], Microsoft DHCP
[Microsoft_DHCP], VitalQIP [VitalQIP], Nominum DHCP [Nominum_DHCP],
ISC DHCP [ISC_DHCP], Kea DHCP [Kea_DHCP], FreeRADIUS DHCP
[FreeRADIUS_DHCP], WIDE DHCPv6 [WIDE_DHCPv6], and DHCP Broadband
[DHCP_Broadband]. Commercial and open source DHCPv6 software often
considers the extensions of DHCPv6 servers because they cannot always
meet the requirements that the administrators want. In this section,
we introduce two typical DHCPv6 servers: Cisco Prime Network
Registrar and Kea DHCP.
3.2.1. Cisco Prime Network Registrar DHCP Server Extension APIs
Cisco Prime Network Registrar (CPNR) [CPNR] is an appliance which
provides integrated Domain Name Server, DHCP, and IP Address
Management services for IPv4 and IPv6. At the same time, 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 just 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.
3.2.2. Kea DHCP Hook Mechanisms
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. A network operator can use
several well-defined framework functions to load and initialize a
library and write specific callout functions to attach to the hook
points. After building and configuring the hooks library, the server
runs as the network operator requires. Additionally, Kea DHCP allows
the network operator to use logging in the hooks library.
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4. Problem Statement
This section elaborates the problem statement of multi-requirement
extensions for DHCPv6. Section 4.1 describes the general model of
DHCP, while Section 4.2 analyzes the extension points and
requirements, suggesting possible future work.
4.1. DHCP General Model
Figure 1 summarizes the DHCP general model and its possible
extensions: DHCP messages, options, message processing functions, and
address generation mechanisms.
+-------------------+ +------------------+
| DHCPv6 client | | DHCPv6 relay |
| +---------------+ | DHCP messages with options| +--------------+ |
| | Message | |<------------------------->| | Message | |
| | processing | | | | relaying | |
| | functions | | | | functions | |
| +---------------+ | | +--------------+ |
+-------------------+ +------------------+
^
|
DHCP messages with options |
|
V
+------------------+
| DHCPv6 server |
+------------+ | +--------------+ |
| Address | | | Message | |
| generation |<-----------------------------+-| processing | |
| mechanisms | | | functions | |
+------------+ | +--------------+ |
+------------------+
Figure 1: DHCP general model and its possible extensions.
4.2. Extension Discussion
4.2.1. DHCP Messages
In fact, new messages can be designed and added to DHCPv6 protocol,
e.g., active leasequery [RFC7653]. But currently, people are
concerned about the security and privacy issues of DHCP protocol.
[RFC7819] and [RFC7824] describe the privacy issues associated with
the use of DHCPv4 and DHCPv6, respectively. DHCPv6 does not provide
the privacy protection on messages and options. That is to say,
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other nodes can see the options transmitted in the DHCPv6 messages
between DHCPv6 clients and servers.
4.2.2. Options
DHCPv6 allows defining options for common requirements, e.g., DNS and
NTP. In other cases, network operators may require DHCP messages to
transmit some self-defined options between clients and servers.
Currently, vendor-specific information option allows clients and
servers to exchange vendor-specific information. Therefore,
administrative domains can define and use sub-options of vendor-
specific 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 information, which is
currently merely supported. The second one is that DHCPv6 relays
obtain such information and add it into 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 DHCP server software
provides comprehensive functionalities, they still cannot meet all
customers' requirements of processing DHCP requests. Therefore, they
will provide interfaces that customers can use to write their
specific extensions to affect the way how DHCP servers handle and
respond to DHCP requests. For example, not all networks prefer to
use DHCPv6 servers to assign the privacy-preserving random-form
addresses generated by some fixed address generation mechanism to
DHCPv6 clients. 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. The many types of IPv6 address
generation mechanisms available have brought about flexibility and
diversity. Thus, network operators may alter their DHCPv6 servers
through the given extensions to use their own preferred address
generation mechanisms to assign addresses to DHCPv6 clients.
However, not all DHCP 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
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mechanisms. Corresponding interfaces could be open and defined to
allow other address generation mechanisms to be configured.
4.2.5. Extension Principles
The principles used to conduct multi-requirement extensions for
DHCPv6 are summarized as follows:
1) Do not change the current DHCP general model.
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 DHCP software, option definition and server
modification, and message definition between DHCP entities and third-
party entities.
Currently, many DHCP 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. Client classification is often used to
differentiate between different types of clients and treat them
accordingly in certain cases.
To meet specific requirements, more complicated extensions of DHCPv6
are needed. For example, considering such a requirement that DHCP
servers assign IP 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.
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. In fact, the authentication in [RFC7037] can be also 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
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requires the definition of messages communicated between DHCP
entities and third-party entities, e.g., active leasequery [RFC7653].
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.
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 [draft-ren-dhc-mredhcpv6]. Some ideas and thoughts of
[draft-ren-dhc-mredhcpv6] are contained in this document.
9. Normative References
[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>.
[draft-ren-dhc-mredhcpv6]
Ren, G., He, L., and Y. Liu, "Multi-requirement Extensions
for Dynamic Host Configuration Protocol for IPv6
(DHCPv6)", March 2017.
[FreeRADIUS_DHCP]
FreeRADIUS, "FreeRADIUS DHCP", 2017,
<https://wiki.freeradius.org/features/DHCP>.
[GAGMS] Liu, Y., He, L., and G. Ren, "GAGMS: A Requirement-Driven
General Address Generation and Management System",
November 2017.
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[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>.
[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/>.
[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>.
[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>.
[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>.
[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>.
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[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>.
[RFC7819] Jiang, S., Krishnan, S., and T. Mrugalski, "Privacy
Considerations for DHCP", RFC 7819, DOI 10.17487/RFC7819,
April 2016, <https://www.rfc-editor.org/info/rfc7819>.
[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>.
[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>.
[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 100084
P.R.China
Phone: +86-010 6260 3227
Email: rengang@cernet.edu.cn
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Lin He
Tsinghua University
Beijing 100084
P.R.China
Email: he-l14@mails.tsinghua.edu.cn
Ying Liu
Tsinghua University
Beijing 100084
P.R.China
Email: liuying@cernet.edu.cn
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