draft-ietf-dhc-mac-assign-00.txt   draft-ietf-dhc-mac-assign-01.txt 
Dynamic Host Configuration (DHC) B. Volz Dynamic Host Configuration (DHC) B. Volz
Internet-Draft Cisco Internet-Draft Cisco
Intended status: Standards Track T. Mrugalski Intended status: Standards Track T. Mrugalski
Expires: October 19, 2019 ISC Expires: March 23, 2020 ISC
CJ. Bernardos CJ. Bernardos
UC3M UC3M
April 17, 2019 September 20, 2019
Link-Layer Addresses Assignment Mechanism for DHCPv6 Link-Layer Addresses Assignment Mechanism for DHCPv6
draft-ietf-dhc-mac-assign-00 draft-ietf-dhc-mac-assign-01
Abstract Abstract
In certain environments, e.g. large scale virtualization deployments, In certain environments, e.g. large scale virtualization deployments,
new devices are created in an automated manner. Such devices new devices are created in an automated manner. Such devices
typically have their link-layer (MAC) addresses randomized. With typically have their link-layer (MAC) addresses randomized. With
sufficient scale, the likelihood of collision is not acceptable. sufficient scale, the likelihood of collision is not acceptable.
Therefore an allocation mechanism is required. This draft proposes Therefore an allocation mechanism is required. This draft proposes
an extension to DHCPv6 that allows a scalable approach to link-layer an extension to DHCPv6 that allows a scalable approach to link-layer
address assignments. address assignments.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 19, 2019. This Internet-Draft will expire on March 23, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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4.2. Direct client mode scenario . . . . . . . . . . . . . . . 4 4.2. Direct client mode scenario . . . . . . . . . . . . . . . 4
4.3. Mechanism Overview . . . . . . . . . . . . . . . . . . . 5 4.3. Mechanism Overview . . . . . . . . . . . . . . . . . . . 5
5. Design Assumptions . . . . . . . . . . . . . . . . . . . . . 7 5. Design Assumptions . . . . . . . . . . . . . . . . . . . . . 7
6. Information Encoding . . . . . . . . . . . . . . . . . . . . 8 6. Information Encoding . . . . . . . . . . . . . . . . . . . . 8
7. Requesting Addresses . . . . . . . . . . . . . . . . . . . . 8 7. Requesting Addresses . . . . . . . . . . . . . . . . . . . . 8
8. Renewing Addresses . . . . . . . . . . . . . . . . . . . . . 9 8. Renewing Addresses . . . . . . . . . . . . . . . . . . . . . 9
9. Releasing Addresses . . . . . . . . . . . . . . . . . . . . . 10 9. Releasing Addresses . . . . . . . . . . . . . . . . . . . . . 10
10. Option Definitions . . . . . . . . . . . . . . . . . . . . . 10 10. Option Definitions . . . . . . . . . . . . . . . . . . . . . 10
10.1. Identity Association for Link-Layer Addresses Option . . 10 10.1. Identity Association for Link-Layer Addresses Option . . 10
10.2. Link-Layer Addresses Option . . . . . . . . . . . . . . 12 10.2. Link-Layer Addresses Option . . . . . . . . . . . . . . 12
11. Client Behavior . . . . . . . . . . . . . . . . . . . . . . . 14 11. Selecting Link Layer Addresses for Assignment to an IA_LL . . 14
12. Server Behavior . . . . . . . . . . . . . . . . . . . . . . . 14 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 13. Security Considerations . . . . . . . . . . . . . . . . . . . 15
14. Security Considerations . . . . . . . . . . . . . . . . . . . 15 14. Privacy Considerations . . . . . . . . . . . . . . . . . . . 15
15. Privacy Considerations . . . . . . . . . . . . . . . . . . . 15 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
16. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 15.1. Normative References . . . . . . . . . . . . . . . . . . 15
16.1. Normative References . . . . . . . . . . . . . . . . . . 15 15.2. Informative References . . . . . . . . . . . . . . . . . 16
16.2. Informative References . . . . . . . . . . . . . . . . . 15 Appendix A. IEEE 802c Summary . . . . . . . . . . . . . . . . . 17
Appendix A. IEEE 802c Summary . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction 1. Introduction
There are several new deployment types that deal with a large number There are several new deployment types that deal with a large number
of devices that need to be initialized. One of them is a scenario of devices that need to be initialized. One of them is a scenario
where virtual machines (VMs) are created on a massive scale. where virtual machines (VMs) are created on a massive scale.
Typically the new VM instances are assigned a random link-layer (MAC) Typically the new VM instances are assigned a random link-layer (MAC)
address, but that does not scale well due to the birthday paradox. address, but that does not scale well due to the birthday paradox.
Another use case is IoT devices. Typically there is no need to Another use case is IoT devices. Typically there is no need to
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While this document presents a design that should be usable for any While this document presents a design that should be usable for any
link-layer address type, some of the details are specific to Ethernet link-layer address type, some of the details are specific to Ethernet
/ IEEE 802 48-bit MAC addresses. Future documents may provide / IEEE 802 48-bit MAC addresses. Future documents may provide
specifics for other link-layer address types. specifics for other link-layer address types.
The IEEE originally set aside half of the 48-bit MAC Address space The IEEE originally set aside half of the 48-bit MAC Address space
for local use (where the U/L bit is set to 1). In 2017, the IEEE for local use (where the U/L bit is set to 1). In 2017, the IEEE
specified an optional specification (IEEE 802c) that divides this specified an optional specification (IEEE 802c) that divides this
space into quadrants (Standards Assigned Identifier, Extended Local space into quadrants (Standards Assigned Identifier, Extended Local
Identifier, Administratively Assigned Identifier, and a Reserved Identifier, Administratively Assigned Identifier, and a Reserved
quadrant) - more details are in Appendix A. The IEEE is also working quadrant) - more details are in Appendix A.
to specify protocols and procedures for assignment of locally unique
addresses (IEEE 802.1cq). This work may serve as one such protocol The IEEE is also working to specify protocols and procedures for
for assignment. For additional background, see [IEEE-802-Tutorial]. assignment of locally unique addresses (IEEE 802.1cq). This work may
serve as one such protocol for assignment. For additional
background, see [IEEE-802-Tutorial].
2. Requirements 2. Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
3. Terminology 3. Terminology
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server Software that manages link-layer address allocation and server Software that manages link-layer address allocation and
is able to respond to client queries. It implements is able to respond to client queries. It implements
basic DHCPv6 server functionality as described in basic DHCPv6 server functionality as described in
[RFC8415] and supports the new options (IA_LL and [RFC8415] and supports the new options (IA_LL and
LLADDR) specified in this document. The server may or LLADDR) specified in this document. The server may or
may not support address assignment and prefix may not support address assignment and prefix
delegation as specified in [RFC8415]. delegation as specified in [RFC8415].
address Unless specified otherwise, an address means a link- address Unless specified otherwise, an address means a link-
layer (or MAC) address, as defined in IEEE802. The layer (or MAC) address, as defined in IEEE802. The
address is typically 6 bytes long, but some network address is typically 6 octets long, but some network
architectures may use different lengths. architectures may use different lengths.
address block A number of consecutive link-layer addresses. An address block A number of consecutive link-layer addresses. An
address block is expressed as a first address plus a address block is expressed as a first address plus a
number that designates the number of additional (extra) number that designates the number of additional (extra)
addresses. A single address can be represented by the addresses. A single address can be represented by the
address itself and zero extra addresses. address itself and zero extra addresses.
4. Deployment scenarios and mechanism overview 4. Deployment scenarios and mechanism overview
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4.2. Direct client mode scenario 4.2. Direct client mode scenario
This mode is used when an entity acts as a DHCP client and requests This mode is used when an entity acts as a DHCP client and requests
available DHCP servers to assign one or more MAC addresses (an available DHCP servers to assign one or more MAC addresses (an
address block) for its own use. This usage scenario is related to address block) for its own use. This usage scenario is related to
IoT (Internet of Things). With the emergence of IoT, a new class of IoT (Internet of Things). With the emergence of IoT, a new class of
cheap, sometimes short lived and disposable devices, has emerged. cheap, sometimes short lived and disposable devices, has emerged.
Examples may include various sensors (e.g. medical) and actuators or Examples may include various sensors (e.g. medical) and actuators or
controllable LED lights. Upon first boot, the device uses a controllable LED lights. Upon first boot, the device uses a
temporary MAC address, as described in [IEEE-802.11-02-109r0], to temporary MAC address, as described in [IEEE-802.11-02-109r0], to
send initial DHCP packets to available DHCP servers. Such devices send initial DHCP packets to available DHCP servers. Then, such
will typically request a single MAC address for each available devices would typically request a single MAC address for each
network interface, which typically means one MAC address per device. available network interface, which typically means one MAC address
Once the server assigns a MAC address, the device abandons its per device. Once the server assigns a MAC address, the device
temporary MAC address. abandons its temporary MAC address and uses the assigned (leased) MAC
address.
4.3. Mechanism Overview 4.3. Mechanism Overview
In all scenarios the protocol operates in fundamentally the same way. In all scenarios the protocol operates in fundamentally the same way.
The device requesting an address, acting as a DHCP client, will send The device requesting an address, acting as a DHCP client, will send
a Solicit message with a IA_LL option to all available DHCP servers. a Solicit message with a IA_LL option to all available DHCP servers.
That IA_LL option MUST include a LLADDR option specifying the link- That IA_LL option MUST include a LLADDR option specifying the link-
layer-type and link-layer-len and may specify a specific address or layer-type and link-layer-len and may specify a specific address or
address block as a hint for the server. Each available server address block as a hint for the server. Each available server
responds with an Advertise message with offered link-layer address or responds with an Advertise message with offered link-layer address or
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and two servers for the typical lifecycle of one or more leases and two servers for the typical lifecycle of one or more leases
Confirm, Decline, and Information-Request messages are not used in Confirm, Decline, and Information-Request messages are not used in
link-layer address assignment. link-layer address assignment.
Clients implementing this mechanism SHOULD use the Rapid Commit Clients implementing this mechanism SHOULD use the Rapid Commit
option as specified in Section 5.1 and 18.2.1 of [RFC8415]. option as specified in Section 5.1 and 18.2.1 of [RFC8415].
An administrator may make the address assignment permanent by An administrator may make the address assignment permanent by
specifying use of infinite lifetimes, as defined in Section 7.7 of specifying use of infinite lifetimes, as defined in Section 7.7 of
[RFC8415]. An administrator may also the disable the need for the [RFC8415]. An administrator may also disable the need for the
renewal mechanism by setting the T1 and T2 values to infinity. renewal mechanism by setting the T1 and T2 values to infinity.
Devices supporting this proposal MAY support reconfigure mechanism, Devices supporting this proposal MAY support the reconfigure
as defined in Section 18.2.11 of [RFC8415]. If supported by both mechanism, as defined in Section 18.2.11 of [RFC8415]. If supported
server and client, this mechanism allows the administrator to by both server and client, this mechanism allows the administrator to
immediately notify clients that the configuration has changed and immediately notify clients that the configuration has changed and
triggers retrieval of relevant changes immediately, rather than after triggers retrieval of relevant changes immediately, rather than after
T1 timer elapses. Since this mechanism requires implementation of the T1 timer elapses. Since this mechanism requires implementation
Reconfigure Key Authentication Protocol (See Section 20.4 of of Reconfigure Key Authentication Protocol (See Section 20.4 of
[RFC8415]), small footprint devices may chose to not support it. [RFC8415]), small footprint devices may chose to not support it.
DISCUSSION: A device may send its link-layer address in a LLADDR DISCUSSION: A device may send its link-layer address in a LLADDR
option to ask the server to register that address to the client (if option to ask the server to register that address to the client (if
available), making the assignment permanent for the lease duration. available), making the assignment permanent for the lease duration.
The client MUST be prepared to use a different address if the server The client MUST be prepared to use a different address if the server
choses not to honor its hint. choses not to honor its hint.
5. Design Assumptions 5. Design Assumptions
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link-layer-address Specifies the link-layer address that is being link-layer-address Specifies the link-layer address that is being
requested or a special value to request any address. requested or a special value to request any address.
For a link-layer type of 1 (Ethernet / IEEE 802 For a link-layer type of 1 (Ethernet / IEEE 802
48-bit MAC addresses), see Section 6 for details on 48-bit MAC addresses), see Section 6 for details on
these values. This value can be only sent by a these values. This value can be only sent by a
client that requests a new block. In responses from client that requests a new block. In responses from
a server, this value specifies the first address a server, this value specifies the first address
allocated. allocated.
extra-addresses Number of additional addresses that follow address extra-addresses Number of additional addresses that follow the
specified in link-layer-address. For requesting a address specified in link-layer-address. For
single address, use 0. For example: link-layer- requesting a single address, use 0. For example:
address: 02:04:06:08:0a and extra-addresses 3 link-layer-address: 02:04:06:08:0a and extra-
designates a block of 4 addresses, starting from addresses 3 designates a block of 4 addresses,
02:04:06:08:0a (inclusive) and ending with starting from 02:04:06:08:0a (inclusive) and ending
02:04:06:08:0d (inclusive). In responses from a with 02:04:06:08:0d (inclusive). In responses from a
server, this value specifies the number of additional server, this value specifies the number of additional
addresses allocated. A four octets long field. addresses allocated. A four octets long field.
valid-lifetime The valid lifetime for the address(es) in the option, valid-lifetime The valid lifetime for the address(es) in the option,
expressed in units of seconds. A four octets long expressed in units of seconds. A four octets long
field. field.
LLaddr-options any encapsulated options that are specific to this LLaddr-options Any encapsulated options that are specific to this
particular address block. Currently there are no particular address block. Currently there are no
such options defined, but they may appear in the such options defined, but there may be in the future.
future.
In a message sent by a client to a server, the valid lifetime field In a message sent by a client to a server, the valid lifetime field
SHOULD be set to 0. The server MUST ignore any received value. SHOULD be set to 0. The server MUST ignore any received value.
In a message sent by a server to a client, the client MUST use the In a message sent by a server to a client, the client MUST use the
value in the valid lifetime field for the valid lifetime for the value in the valid lifetime field for the valid lifetime for the
address block. The value in the valid lifetime field is the number address block. The value in the valid lifetime field is the number
of seconds remaining in the lifetime. of seconds remaining in the lifetime.
As per Section 7.7 of [RFC8415], the valid lifetime of 0xffffffff is As per Section 7.7 of [RFC8415], the valid lifetime of 0xffffffff is
taken to mean "infinity" and should be used carefully. taken to mean "infinity" and should be used carefully.
More than one LLADDR option can appear in an IA_LL option. More than one LLADDR option can appear in an IA_LL option.
11. Client Behavior 11. Selecting Link Layer Addresses for Assignment to an IA_LL
TODO: We need start this section by clearly defining what 'client' A server selects link layer addresses to be assigned to an IA_LL
means in this context (either hypervisor acting on behalf of the according to the assignment policies determined by the server
client to be spawned or the IOT device acting on its own behalf). administrator.
12. Server Behavior Link layer addresses are typically specific to a link and the server
SHOULD follow the steps in Section 13.1 of [RFC8415] to determine the
client's link.
TODO: Need to describe server operation. Likely also recommend For Ethernet / IEEE 802 MAC addresses, a server MAY use additional
assigning MAC addresses from an appropriate quadrant (see Appendix). options supplied by a relay agent or client to select the quadrant
(see Appendix A) from which addresses are to be assigned. This MAY
include new options, such as those specified in
[I-D.ietf-dhc-slap-quadrant].
13. IANA Considerations 12. IANA Considerations
IANA is kindly requested to assign new value for options OPTION_LL IANA is kindly requested to assign new value for options OPTION_LL
(tbd1) and OPTION_LLADDR (tbd2) and add those values to the DHCPv6 (tbd1) and OPTION_LLADDR (tbd2) and add those values to the DHCPv6
Option Codes registry maintained at http://www.iana.org/assignments/ Option Codes registry maintained at http://www.iana.org/assignments/
dhcpv6-parameters. dhcpv6-parameters.
14. Security Considerations 13. Security Considerations
See [RFC8415] for the DHCPv6 security considerations. See [RFC8415] for the DHCPv6 security considerations. See [RFC8200]
for the IPv6 security considerations.
TODO: Do we need more? There is a possibility of the same link-layer address being used by
more than one device if not all parties on a link use this mechanism
to obtain a link-layer address from the space assigned to the DHCP
server. It is also possible that a bad actor purposely uses a
device's link-layer address.
15. Privacy Considerations 14. Privacy Considerations
See [RFC8415] for the DHCPv6 privacy considerations. See [RFC8415] for the DHCPv6 privacy considerations.
For a client requesting a link-layer address directly from a server, For a client requesting a link-layer address directly from a server,
as the link-layer address assigned to a client will likely be used by as the link-layer address assigned to a client will likely be used by
the client to communicate on the link, the address will be exposed to the client to communicate on the link, the address will be exposed to
those able to listen in on this communication. For those peers on those able to listen in on this communication. For those peers on
the link that are able to listen in on the DHCPv6 exchange, they the link that are able to listen in on the DHCPv6 exchange, they
would also be able to correlate the client's identity (based on the would also be able to correlate the client's identity (based on the
DUID used) with the assigned address. Additional mechanisms, such as DUID used) with the assigned address. Additional mechanisms, such as
the ones described in [RFC7844] can also be used. the ones described in [RFC7844] can also be used.
TODO: Do we need more? 15. References
16. References
16.1. Normative References 15.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A.,
Richardson, M., Jiang, S., Lemon, T., and T. Winters, Richardson, M., Jiang, S., Lemon, T., and T. Winters,
"Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
RFC 8415, DOI 10.17487/RFC8415, November 2018, RFC 8415, DOI 10.17487/RFC8415, November 2018,
<https://www.rfc-editor.org/info/rfc8415>. <https://www.rfc-editor.org/info/rfc8415>.
16.2. Informative References 15.2. Informative References
[I-D.ietf-dhc-slap-quadrant]
Bernardos, C. and A. Mourad, "SLAP quadrant selection
options for DHCPv6", draft-ietf-dhc-slap-quadrant-01 (work
in progress), July 2019.
[IEEE-802-Tutorial] [IEEE-802-Tutorial]
Thaler, P., "Emerging IEEE 802 Work on MAC Addressing", Thaler, P., "Emerging IEEE 802 Work on MAC Addressing",
<https://datatracker.ietf.org/meeting/96/materials/ <https://datatracker.ietf.org/meeting/96/materials/slides-
slides-96-edu-ieee802work-0/>. 96-edu-ieee802work-0/>.
[IEEE-802.11-02-109r0] [IEEE-802.11-02-109r0]
Edney, J., Haverinen, H., Honkanen, J-P., and P. Orava, Edney, J., Haverinen, H., Honkanen, J-P., and P. Orava,
"Temporary MAC address for anonymity", "Temporary MAC address for anonymity",
<https://mentor.ieee.org/802.11/dcn/02/11-02-0109-00-000i- <https://mentor.ieee.org/802.11/dcn/02/11-02-0109-00-000i-
temporary-mac-address-for-anonymity.ppt>. temporary-mac-address-for-anonymity.ppt>.
[IEEEStd802c-2017] [IEEEStd802c-2017]
IEEE Computer Society, "IEEE Standard for Local and IEEE Computer Society, "IEEE Standard for Local and
Metropolitan Area Networks: Overview and Architecture, Metropolitan Area Networks: Overview and Architecture,
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[RFC5494] Arkko, J. and C. Pignataro, "IANA Allocation Guidelines [RFC5494] Arkko, J. and C. Pignataro, "IANA Allocation Guidelines
for the Address Resolution Protocol (ARP)", RFC 5494, for the Address Resolution Protocol (ARP)", RFC 5494,
DOI 10.17487/RFC5494, April 2009, DOI 10.17487/RFC5494, April 2009,
<https://www.rfc-editor.org/info/rfc5494>. <https://www.rfc-editor.org/info/rfc5494>.
[RFC7844] Huitema, C., Mrugalski, T., and S. Krishnan, "Anonymity [RFC7844] Huitema, C., Mrugalski, T., and S. Krishnan, "Anonymity
Profiles for DHCP Clients", RFC 7844, Profiles for DHCP Clients", RFC 7844,
DOI 10.17487/RFC7844, May 2016, DOI 10.17487/RFC7844, May 2016,
<https://www.rfc-editor.org/info/rfc7844>. <https://www.rfc-editor.org/info/rfc7844>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
Appendix A. IEEE 802c Summary Appendix A. IEEE 802c Summary
This appendix provides a brief summary of IEEE802c from This appendix provides a brief summary of IEEE802c from
[IEEEStd802c-2017]. [IEEEStd802c-2017].
The original IEEE 802 specifications assigned half of the 48-bit MAC The original IEEE 802 specifications assigned half of the 48-bit MAC
address space to local use -- these addresses have the U/L bit set to address space to local use -- these addresses have the U/L bit set to
1 and are locally administered with no imposed structure. 1 and are locally administered with no imposed structure.
In 2017, the IEEE issued the 802c specification which defines a new In 2017, the IEEE issued the 802c specification which defines a new
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