draft-ietf-dhc-dhcp4o6-saddr-opt-03.txt   draft-ietf-dhc-dhcp4o6-saddr-opt-04.txt 
DHCWG I. Farrer DHCWG I. Farrer
Internet-Draft Deutsche Telekom AG Internet-Draft Deutsche Telekom AG
Updates: 7598 (if approved) Q. Sun Updates: 7598 (if approved) Q. Sun
Intended status: Standards Track Y. Cui Intended status: Standards Track Y. Cui
Expires: September 28, 2018 L. Sun Expires: December 16, 2018 L. Sun
Tsinghua University Tsinghua University
March 27, 2018 June 14, 2018
Softwire Provisioning using DHCPv4 Over DHCPv6 Softwire Provisioning using DHCPv4 Over DHCPv6
draft-ietf-dhc-dhcp4o6-saddr-opt-03 draft-ietf-dhc-dhcp4o6-saddr-opt-04
Abstract Abstract
DHCPv4 over DHCPv6 is a mechanism for dynamically configuring IPv4 DHCPv4 over DHCPv6 (RFC7341) is a mechanism for dynamically
over an IPv6-only network. For DHCPv4 over DHCPv6 to function with configuring IPv4 over an IPv6-only network. For DHCPv4 over DHCPv6
some IPv4-over-IPv6 softwire mechanisms and deployment scenarios, the to function with some IPv4-over-IPv6 softwire mechanisms and
operator needs to know the IPv6 address that the client will use as deployment scenarios, the operator needs to know the IPv6 address
the source of IPv4-in-IPv6 softwire tunnel. This address, in that the client will use as the source of IPv4-in-IPv6 softwire
conjunction with the client's IPv4 address and (in some deployments), tunnel. This address, in conjunction with the client's IPv4 address,
the Port Set ID are used to create a binding table entry in the and (in some deployments) the Port Set ID are used to create a
operator's softwire tunnel concentrator. This memo defines a DHCPv6 binding table entry in the operator's softwire tunnel concentrator.
option to convey IPv6 parameters for establishing the softwire tunnel This memo defines a DHCPv6 option to convey IPv6 parameters for
and a DHCPv4 option (to be used only with DHCP 4o6) to communicate establishing the softwire tunnel and a DHCPv4 option (to be used only
the source tunnel IPv6 address between the DHCP 4o6 client and with DHCP 4o6) to communicate the source tunnel IPv6 address between
server. It is designed to work in conjunction with the IPv4 address the DHCP 4o6 client and server. It is designed to work in
allocation process. This document updates "DHCPv6 Options for conjunction with the IPv4 address allocation process.
Configuration of Softwire Address and Port-Mapped Clients" to allow
the DHCPv6 option OPTION_S46_BR (90) to appear outside of DHCPv6
softwire container options.
This document updates RFC7598, allowing OPTION_S46_BR (90) to be This document updates "DHCPv6 Options for Configuration of Softwire
enumerated in the DHCPv6 client's ORO request and appear directly Address and Port-Mapped Clients" (RFC7598), allowing OPTION_S46_BR
within subsequent messages sent by the DHCPv6 server. (90) to be enumerated in the DHCPv6 client's ORO request and appear
directly within subsequent messages sent by the DHCPv6 server.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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 December 16, 2018.
This Internet-Draft will expire on September 28, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 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
skipping to change at page 2, line 49 skipping to change at page 2, line 46
7.2.1. Changing the Bound IPv6 Softwire Source Address . . . 10 7.2.1. Changing the Bound IPv6 Softwire Source Address . . . 10
7.3. Releasing the IPv4 Address Lease and Softwire 7.3. Releasing the IPv4 Address Lease and Softwire
Source Address . . . . . . . . . . . . . . . . . . . . . 10 Source Address . . . . . . . . . . . . . . . . . . . . . 10
7.4. OPTION_S46_BIND_IPV6_PREFIX Validation Behavior . . . . . 10 7.4. OPTION_S46_BIND_IPV6_PREFIX Validation Behavior . . . . . 10
7.5. Client and Server Softwire Source Address Mismatch . . . 11 7.5. Client and Server Softwire Source Address Mismatch . . . 11
7.6. Use With Dynamic, Shared IPv4 Addresses . . . . . . . . . 11 7.6. Use With Dynamic, Shared IPv4 Addresses . . . . . . . . . 11
8. Server Behavior . . . . . . . . . . . . . . . . . . . . . . . 11 8. Server Behavior . . . . . . . . . . . . . . . . . . . . . . . 11
8.1. Changing the Bound IPv6 Source Address . . . . . . . . . 11 8.1. Changing the Bound IPv6 Source Address . . . . . . . . . 11
9. Security Considerations . . . . . . . . . . . . . . . . . . . 12 9. Security Considerations . . . . . . . . . . . . . . . . . . . 12
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
12.1. Normative References . . . . . . . . . . . . . . . . . . 13 12.1. Normative References . . . . . . . . . . . . . . . . . . 13
12.2. Informative References . . . . . . . . . . . . . . . . . 13 12.2. Informative References . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction 1. Introduction
Deterministic IPv4-over-IPv6 transition technologies require that Deterministic IPv4-over-IPv6 transition technologies require that
elements are pre-configured with binding rules for routing traffic to elements are pre-configured with binding rules for routing traffic to
clients. This places a constraint on the choice of address used as clients. This places a constraint on the choice of address used as
the client's softwire source address: it must use a pre-determined the client's softwire source address: it must use a pre-determined
prefix which is usually configured on the home gateway device. prefix which is usually configured on the home gateway device.
[RFC7597] describes a DHCPv6 based mechanism for provisioning such [RFC7598] describes a DHCPv6 based mechanism for provisioning such
deterministic softwires. deterministic softwires.
A dynamic provisioning model, such as using DHCPv4 over DHCPv6 A dynamic provisioning model, such as using DHCPv4 over DHCPv6
[RFC7341] (DHCP 4o6) allows much more flexibility in the location of [RFC7341] (DHCP 4o6) allows much more flexibility in the location of
the IPv4-over-IPv6 softwire source address. In this model, the IPv6 the IPv4-over-IPv6 softwire source address. In this model, the IPv6
address is dynamically communicated back to the service provider address is dynamically communicated back to the service provider
allowing the corresponding softwire configuration to be created in allowing the corresponding softwire configuration to be created in
the border router (BR). the border router (BR).
The DHCP 4o6 client and softwire client could be run on end devices The DHCP 4o6 client and softwire client could be run on end devices
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
4. Solution Overview 4. Solution Overview
In order to provision a softwire, both IPv6 and IPv4 configuration In order to provision a softwire, both IPv6 and IPv4 configuration
needs to be passed to the client. To map this to the DHCP 4o6 needs to be passed to the client. To map this to the DHCP 4o6
configuration process, the IPv6 configuration is carried in DHCPv6 configuration process, the IPv6 configuration is carried in DHCPv6
options carried inside the DHCPv6 message DHCPV4-RESPONSE (21) sent options [I-D.ietf-dhc-rfc3315bis], carried inside the DHCPv6 message
by the server. OPTION_S46_BR (90) is used to provision the remote DHCPV4-RESPONSE (21) sent by the server. OPTION_S46_BR (90) is used
IPv6 address for the softwire (see Section 4.1 below). to provision the remote IPv6 address for the softwire (see
OPTION_S46_BIND_IPV6_PREFIX (TBD1), is optionally sent by the DHCP Section 4.1 below). OPTION_S46_BIND_IPV6_PREFIX (TBD1), is
4o6 server to indicate to the client a preferred IPv6 prefix for optionally sent by the DHCP 4o6 server to indicate to the client a
binding the received IPv4 configuration and sourcing tunnel traffic. preferred IPv6 prefix for binding the received IPv4 configuration and
This may be necessary if there are multiple IPv6 prefixes in use in sourcing tunnel traffic. This may be necessary if there are multiple
the customer network (e.g. ULAs), or if the specific IPv4-over-IPv6 IPv6 prefixes in use in the customer network (e.g. ULAs), or if the
transition mechanism requires the use of a particular prefix for any specific IPv4-over-IPv6 transition mechanism requires the use of a
reason. particular prefix for any reason.
IPv4 configuration is carried in DHCPv4 messages (inside the DHCP 4o6 IPv4 configuration is carried in DHCPv4 messages [RFC2131], (inside
option OPTION_DHCPV4_MSG (87)) using the mechanism described in the DHCP 4o6 option OPTION_DHCPV4_MSG (87)) using the mechanism
[RFC7341]. described in [RFC7341].
In order for the client to communicate the softwire source address, a In order for the client to communicate the softwire source address, a
new DHCPv4 option OPTION_DHCP4O6_S46_SADDR (TBD2) is defined in this new DHCPv4 option OPTION_DHCP4O6_S46_SADDR (TBD2) is defined in this
document. This is included in DHCPREQUEST messages sent by the document. This is included in DHCPREQUEST messages sent by the
client and is stored by the server for the lifetime of the IPv4 client and is stored by the server for the lifetime of the IPv4
address lease. address lease.
4.1. Updating RFC7598 to Permit the Reuse of OPTION_S46_BR(90) 4.1. Updating RFC7598 to Permit the Reuse of OPTION_S46_BR(90)
Section 4.2 of [RFC7598] defines option OPTION_S46_BR(90) for Section 4.2 of [RFC7598] defines option OPTION_S46_BR(90) for
communicating remote softwire border relay (BR)'s' IPv6 address(es) communicating remote softwire border relay (BR) IPv6 address(es) to a
to a client, but mandates that the option can only be used when client, but mandates that the option can only be used when
encapsulated within one of the softwire container options: encapsulated within one of the softwire container options:
OPTION_S46_CONT_MAPE (94) or OPTION_S46_CONT_LW(96). From Section 3 OPTION_S46_CONT_MAPE (94) or OPTION_S46_CONT_LW(96). From Section 3
of [RFC7598]: of [RFC7598]:
"Softwire46 DHCPv6 clients that receive provisioning options that "Softwire46 DHCPv6 clients that receive provisioning options that
are not encapsulated in container options MUST silently ignore are not encapsulated in container options MUST silently ignore
these options." these options."
This document updates [RFC7598], removing this restriction for This document updates [RFC7598], removing this restriction for
OPTION_S46_BR (90), allowing it to be enumerated in the client's ORO OPTION_S46_BR (90), allowing it to be enumerated in the client's ORO
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Step 1 The client constructs a DHCPv6 'DHCPV4-QUERY(20)' message. Step 1 The client constructs a DHCPv6 'DHCPV4-QUERY(20)' message.
This message contains two options: DHCPv6 OPTION_ORO (6) and This message contains two options: DHCPv6 OPTION_ORO (6) and
OPTION_DHCPV4_MSG (87). OPTION_ORO lists '90' OPTION_DHCPV4_MSG (87). OPTION_ORO lists '90'
(OPTION_S46_BR) and 'TBD1' (OPTION_S46_BIND_IPV6_PREFIX). (OPTION_S46_BR) and 'TBD1' (OPTION_S46_BIND_IPV6_PREFIX).
OPTION_DHCPV4_MSG contains a DHCPv4 DHCPDISCOVER message. OPTION_DHCPV4_MSG contains a DHCPv4 DHCPDISCOVER message.
Step 2 The server responds with a DHCPv6 'DHCPV4-RESPONSE (21)' Step 2 The server responds with a DHCPv6 'DHCPV4-RESPONSE (21)'
message. This message contains OPTION_S46_BR (90) containing message. This message contains OPTION_S46_BR (90) containing
the IPv6 address of the BR for the client's softwire the IPv6 address of the BR for the client's softwire
configuration. The message may also, optionally contain configuration. The message may also optionally contain
OPTION_S46_BIND_IPV6_PREFIX (TBD1). OPTION_DHCPV4_MSG OPTION_S46_BIND_IPV6_PREFIX (TBD1). OPTION_DHCPV4_MSG
contains a DHCPv4 DHCPOFFER message. contains a DHCPv4 DHCPOFFER message.
Step 3 The client sends with a DHCPv6 'DHCPV4-QUERY(20)' message Step 3 The client sends with a DHCPv6 'DHCPV4-QUERY(20)' message
containing a DHCPv4 DHCPREQUEST message with containing a DHCPv4 DHCPREQUEST message with
OPTION_DHCP4O6_S46_SADDR (TBD2) with the IPv6 address which OPTION_DHCP4O6_S46_SADDR (TBD2) with the IPv6 address which
the client will use as its softwire source address. the client will use as its softwire source address.
Step 4 The server sends a DHCPv6 'DHCPV4-RESPONSE(21)' message. Step 4 The server sends a DHCPv6 'DHCPV4-RESPONSE(21)' message.
OPTION_DHCPV4_MSG contains a DHCPv4 DHCPACK message. OPTION_DHCPV4_MSG contains a DHCPv4 DHCPACK message.
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o option-code: OPTION_S46_BIND_IPV6_PREFIX (TBD1) o option-code: OPTION_S46_BIND_IPV6_PREFIX (TBD1)
o option-length: 1 + length of bind-ipv6-prefix, specified in bytes. o option-length: 1 + length of bind-ipv6-prefix, specified in bytes.
o bindprefix6-len: 8-bit field expressing the bit mask length of the o bindprefix6-len: 8-bit field expressing the bit mask length of the
IPv6 prefix specified in bind-ipv6-prefix. Valid values are 0 to IPv6 prefix specified in bind-ipv6-prefix. Valid values are 0 to
128. 128.
o bind-ipv6-prefix: The IPv6 prefix indicating the preferred prefix o bind-ipv6-prefix: The IPv6 prefix indicating the preferred prefix
for the client to bind the received IPv4 configuration to. The for the client to bind the received IPv4 configuration to. The
length is (bindprefix6-len + 7) / 8. The field is padded on the length is (bindprefix6-len + 7) / 8. The field is padded on the
right with zero bits up to the next octet boundary when bind- right with zero bits up to the next octet boundary when bind-
ipv6-prefix is not evenly divisible by 8. ipv6-prefix is not evenly divisible by 8. These padding bits are
ignored by the receiver (see Section 7.4).
OPTION_S46_BIND_IPV6_PREFIX is a singleton. Servers MUST NOT send OPTION_S46_BIND_IPV6_PREFIX is a singleton. Servers MUST NOT send
more than one instance of the OPTION_S46_BIND_IPV6_PREFIX option. more than one instance of the OPTION_S46_BIND_IPV6_PREFIX option.
6.2. DHCPv4 over DHCPv6 Softwire Source Address Option 6.2. DHCPv4 over DHCPv6 Softwire Source Address Option
The format of DHCPv4 over DHCPv6 softwire source address option is as The format of DHCPv4 over DHCPv6 softwire source address option is as
follows: follows:
0 1 0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| option-code (TBD) | option-length | | option-code | option-length |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+ softwire-ipv6-src-address + + softwire-ipv6-src-address +
. (128 bits) . . (128 bits) .
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
Format of OPTION_DHCP4O6_S46_SADDR Format of OPTION_DHCP4O6_S46_SADDR
o option-code: OPTION_DHCP4O6_S46_SADDR (TBD2) o option-code: OPTION_DHCP4O6_S46_SADDR (TBD2)
o option-length: 16. o option-length: 16.
o softwire-ipv6-src-address: 16 bytes long; The IPv6 address that is o softwire-ipv6-src-address: 16 bytes long; The IPv6 address that is
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are required to remain constant throughout the address lease are required to remain constant throughout the address lease
lifetime, they cannot be used with the mechanism described in this lifetime, they cannot be used with the mechanism described in this
document. This is because the client may only be able to construct document. This is because the client may only be able to construct
the IPv6 address to use as the source address after it has received the IPv6 address to use as the source address after it has received
the first DHCPV4-RESPONSE message from the server containing the first DHCPV4-RESPONSE message from the server containing
OPTION_S46_BIND_IPV6_PREFIX. OPTION_S46_BIND_IPV6_PREFIX.
7. Client Behavior 7. Client Behavior
A client requiring dynamic softwire configuration first enables DHCP A client requiring dynamic softwire configuration first enables DHCP
4o6 configuration using the method described in Section 5. of 4o6 configuration using the method described in Section 5 of
[RFC7341]. If OPTION_DHCP4_O_DHCP6_SERVER is received in the [RFC7341]. If OPTION_DHCP4_O_DHCP6_SERVER is received in the
corresponding REPLY message, the client MAY continue with the corresponding REPLY message, the client MAY continue with the
configuration process described below. configuration process described below.
It is also a prerequisite that the client has already learned a It is also a prerequisite that the client has already learned a
suitable IPv6 prefix to use for its local softwire endpoint using suitable IPv6 prefix to use for its local softwire endpoint using
DHCPv6, RA/PIO or another mechanism. DHCPv6, RA/PIO or another mechanism.
7.1. Client Initialization 7.1. Client Initialization
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the 'IPv6 binding prefix' and follows to the process described in the 'IPv6 binding prefix' and follows to the process described in
Section 5.1 of [RFC7596] in order to select an active IPv6 prefix to Section 5.1 of [RFC7596] in order to select an active IPv6 prefix to
construct the softwire. If no match is found, or the client doesn't construct the softwire. If no match is found, or the client doesn't
receive OPTION_S46_BIND_IPV6_PREFIX the client MAY select any valid receive OPTION_S46_BIND_IPV6_PREFIX the client MAY select any valid
IPv6 prefix (of a suitable scope) to use as the tunnel source. IPv6 prefix (of a suitable scope) to use as the tunnel source.
Once the client has selected a suitable prefix, it MAY use either an Once the client has selected a suitable prefix, it MAY use either an
existing IPv6 address that is already configured on an interface, or existing IPv6 address that is already configured on an interface, or
create a new address specifically for use as the softwire source create a new address specifically for use as the softwire source
address (e.g. using an Interface Identifier constructed as per address (e.g. using an Interface Identifier constructed as per
Section 6. of [RFC7597]). If a new address is being created, the Section 6 of [RFC7597]). If a new address is being created, the
client MUST complete configuration of the new address, performing client MUST complete configuration of the new address, performing
duplicate address detection (if required) before proceeding. duplicate address detection (if required) before proceeding.
The client then constructs a DHCPV4-QUERY message containing a DHCPv4 The client then constructs a DHCPV4-QUERY message containing a DHCPv4
DHCPREQUEST message. OPTION_DHCP4O6_S46_SADDR is included in the DHCPREQUEST message. OPTION_DHCP4O6_S46_SADDR is included in the
options field of the DHCPREQUEST message with the IPv6 address of its options field of the DHCPREQUEST message with the IPv6 address of its
softwire source address in the softwire-ipv6-src-address field. softwire source address in the softwire-ipv6-src-address field.
When the client receives a DHCPv4 DHCPACK message from the server, it When the client receives a DHCPv4 DHCPACK message from the server, it
checks the IPv6 address in OPTION_DHCP4O6_S46_SADDR against its checks the IPv6 address in OPTION_DHCP4O6_S46_SADDR against its
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In this situation, the client MUST inform the server of the new In this situation, the client MUST inform the server of the new
address. This is done by sending a DHCPREQUEST message containing address. This is done by sending a DHCPREQUEST message containing
OPTION_DHCP4O6_S46_SADDR with the new IPv6 source address. OPTION_DHCP4O6_S46_SADDR with the new IPv6 source address.
When the client receives a DHCPv4 DHCPACK message from the server, it When the client receives a DHCPv4 DHCPACK message from the server, it
checks the IPv6 address in OPTION_DHCP4O6_S46_SADDR against its checks the IPv6 address in OPTION_DHCP4O6_S46_SADDR against its
active softwire source address. If they match, the allocation active softwire source address. If they match, the allocation
process has concluded. If there is a discrepancy then the process process has concluded. If there is a discrepancy then the process
described in Section 7.5 is followed. described in Section 7.5 is followed.
If the client receives a DHCPv4 DHCPNAK message in repsonse from the If the client receives a DHCPv4 DHCPNAK message in response from the
server, then the change of the bound IPv6 Softwire source address has server, then the change of the bound IPv6 Softwire source address has
been unsuccessful. In this case, the client MUST stop using the new been unsuccessful. In this case, the client MUST stop using the new
IPv6 source address. The client then restarts the process from Step IPv6 source address. The client then restarts the process from Step
1 of Figure 1. 1 of Figure 1.
7.3. Releasing the IPv4 Address Lease and Softwire Source Address 7.3. Releasing the IPv4 Address Lease and Softwire Source Address
When the client no longer requires the IPv4 resource, it sends a When the client no longer requires the IPv4 resource, it sends a
DHCPv4 DHCPRELEASE message to the server. As the options field is DHCPv4 DHCPRELEASE message to the server. As the options field is
unused in this message type, OPTION_DHCP4O6_S46_SADDR is not unused in this message type, OPTION_DHCP4O6_S46_SADDR is not
included. included.
7.4. OPTION_S46_BIND_IPV6_PREFIX Validation Behavior 7.4. OPTION_S46_BIND_IPV6_PREFIX Validation Behavior
On receipt of the OPTION_S46_BIND_IPV6_PREFIX option, the client On receipt of the OPTION_S46_BIND_IPV6_PREFIX option, the client
makes the following validation checks: makes the following validation checks:
o The received bindprefix6-len value is not larger than 128. o The received bindprefix6-len value is not larger than 128.
o The received bindprefix6-len value is not larger than the number o The received bindprefix6-len value is not larger than the number
of bytes sent in the bind-ipv6-prefix field. (e.g. the of bytes, divided by 8, received in the bind-ipv6-prefix field.
bindprefix6-len is 128 but the bind-ipv6-prefix has only 8 bytes). (e.g. the bindprefix6-len is 128 but the bind-ipv6-prefix field is
only 8 bytes long).
For either of these cases the receiver MAY either discard the option For either of these cases, the receiver discards the invalid option
and proceed to attempt configuration as if the option had not been and proceeds to attempt configuration as if the option had not been
received, or attempt to use the received values for the longest received.
prefix match anyway.
The receiver MUST only use bits from the bind-ipv6-prefix field up to The receiver MUST only use bits from the bind-ipv6-prefix field up to
the value specified in the bindprefix6-len when performing the the value specified in the bindprefix6-len when performing the
longest prefix match. bind-ipv6-prefix bits beyond this value MUST be longest prefix match. bind-ipv6-prefix bits beyond this value MUST be
ignored. ignored.
7.5. Client and Server Softwire Source Address Mismatch 7.5. Client and Server Softwire Source Address Mismatch
If the client receives a DHCPACK message with an If the client receives a DHCPACK message with an
OPTION_DHCP4O6_S46_SADDR containing an IPv6 address which differs OPTION_DHCP4O6_S46_SADDR containing an IPv6 address which differs
from its active softwire source address, the client MAY either: from its active softwire source address, the client SHOULD wait for a
randomised time interval and then resend the DHCPREQUEST message with
the correct softwire source address. [RFC2131] Section 4.1 descibes
the retransmission backoff interval process.
o Wait for a randomised time interval and then resend a DHCPREQUEST If, after a number of re-tries, the retransmission process does not
message with the correct softwire source address, OR return a DHCPACK message with the correct bound IPv6 address, a
o Send a DHCPRELEASE message and re-start the process described in client MAY send a DHCPRELEASE message and re-start the process
Section 7. described in Section 7. The number of re-tries should be
configurable and aligned with any server policy defining the minimum
time interval for client address updates as described in Section 8.1.
7.6. Use With Dynamic, Shared IPv4 Addresses 7.6. Use With Dynamic, Shared IPv4 Addresses
[RFC7618]describes a mechanism for using DHCPv4 to distribute [RFC7618] describes a mechanism for using DHCPv4 to distribute
dynamic, shared IPv4 addresses to clients. The mechanism described dynamic, shared IPv4 addresses to clients. The mechanism described
in this document is compatible with IPv4 address sharing, and can be in this document is compatible with IPv4 address sharing, and can be
enabled by following the process described in Section 6 of [RFC7618]. enabled by following the process described in Section 6 of [RFC7618].
8. Server Behavior 8. Server Behavior
Beyond the normal DHCP 4o6 functionality defined in [RFC7341], the Beyond the normal DHCP 4o6 functionality defined in [RFC7341], the
server MUST also store the IPv6 softwire source address of the client server MUST also store the IPv6 softwire source address of the client
in the leasing address database, alongside the IPv4 address and in the leasing address database, alongside the IPv4 address and
client identifier. An OPTION_DHCP4O6_S46_SADDR containing the bound client identifier. An OPTION_DHCP4O6_S46_SADDR containing the bound
skipping to change at page 12, line 7 skipping to change at page 12, line 12
server updates the stored softwire source address with the new server updates the stored softwire source address with the new
address supplied by the client, and sends a DHCPACK message address supplied by the client, and sends a DHCPACK message
containing the updated softwire source address in containing the updated softwire source address in
OPTION_DHCP4O6_S46_SADDR. OPTION_DHCP4O6_S46_SADDR.
The server MAY implement a policy enforcing a minimum time interval The server MAY implement a policy enforcing a minimum time interval
between a client updating its softwire source IPv6 address. If a between a client updating its softwire source IPv6 address. If a
client attempts to update the softwire source IPv6 address before the client attempts to update the softwire source IPv6 address before the
minimum time has expired, the server can either silently drop the minimum time has expired, the server can either silently drop the
client's message or send back a DHCPACK message containing the client's message or send back a DHCPACK message containing the
exisiting IPv6 address binding in OPTION_DHCP4O6_S46_SADDR. existing IPv6 address binding in OPTION_DHCP4O6_S46_SADDR.
9. Security Considerations 9. Security Considerations
Security considerations which are applicable to [RFC7341] are also Security considerations which are applicable to [RFC7341] are also
applicable here. applicable here.
10. IANA Considerations A rogue client could attempt to use the mechanism described in
Section 7.2.1 to redirect IPv4 traffic intended for another client to
itself. This would be performed by sending a DHCPREQUEST message for
another client's active IPv4 lease containing the attacker's softwire
IPv6 address in OPTION_DHCP4O6_S46_SADDR.
IANA is requested to assign the OPTION_DHCP4O6_S46_SADDR option code For such an attack to be effective, the attacker would need to know
from the "BOOTP Vendor Extensions and DHCP Options" registry both the client identifier and active IPv4 address lease currently in
maintained at http://www.iana.org/assignments/bootp-dhcp-parameters. use by another client. The risk of this can be reduced by using a
client identifier format which is not easily guessable, e.g. by
including a time component for when the client identifier was
generated (see [I-D.ietf-dhc-rfc3315bis] Section 11.2).
IANA is requested to assign the OPTION_S46_BIND_IPV6_PREFIX option A client may attempt to overload the server by sending multiple
code from the DHCPv6 "Option Codes" registry maintained at source address update messages (see Section 7.2.1) in a short time
frame. This risk can be reduced by implementing a server policy
enforcing a minimum time interval between client address changes as
described in Section 8.1.
10. IANA Considerations
IANA is requested to assign the OPTION_S46_BIND_IPV6_PREFIX (TBD1)
option code from the DHCPv6 "Option Codes" registry maintained at
http://www.iana.org/assignments/dhcpv6-parameters. http://www.iana.org/assignments/dhcpv6-parameters.
IANA is requested to assign the OPTION_DHCP4O6_S46_SADDR (TBD2)
option code from the "BOOTP Vendor Extensions and DHCP Options"
registry maintained at http://www.iana.org/assignments/bootp-dhcp-
parameters.
IANA is requested to update the entry for DHCPv6 Option S46_BR (90) IANA is requested to update the entry for DHCPv6 Option S46_BR (90)
in the table at https://www.iana.org/assignments/dhcpv6-parameters as in the table at https://www.iana.org/assignments/dhcpv6-parameters as
follows: follows:
Old entry: Old entry:
| 90 | S46_BR | No | No | | 90 | S46_BR | No | No |
New entry: New entry:
| 90 | S46_BR | Yes | No | | 90 | S46_BR | Yes | No |
IANA is also requested to make a new entry for IANA is also requested to make a new entry for
OPTION_S46_BIND_IPV6_PREFIX TBD1) in the table at OPTION_S46_BIND_IPV6_PREFIX (TBD1) in the table at
https://www.iana.org/assignments/dhcpv6-parameters: https://www.iana.org/assignments/dhcpv6-parameters:
| TBD1 |OPTION_S46_BIND_IPV6_PREFIX| Yes | Yes | | TBD1 |OPTION_S46_BIND_IPV6_PREFIX| Yes | Yes |
11. Acknowledgements 11. Acknowledgements
The authors would like to thank Ted Lemon, Lishan Li, Tatuya Jinmei, The authors would like to thank Ted Lemon, Lishan Li, Tatuya Jinmei,
Jonas Gorski and Razvan Becheriu for their contributions and Jonas Gorski and Razvan Becheriu for their contributions and
comments. comments.
12. References 12. References
12.1. Normative References 12.1. Normative References
[I-D.ietf-dhc-rfc3315bis]
Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A.,
Richardson, M., Jiang, S., Lemon, T., and T. Winters,
"Dynamic Host Configuration Protocol for IPv6 (DHCPv6)
bis", draft-ietf-dhc-rfc3315bis-13 (work in progress),
April 2018.
[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>.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, DOI 10.17487/RFC2131, March 1997,
<https://www.rfc-editor.org/info/rfc2131>.
[RFC7341] Sun, Q., Cui, Y., Siodelski, M., Krishnan, S., and I. [RFC7341] Sun, Q., Cui, Y., Siodelski, M., Krishnan, S., and I.
Farrer, "DHCPv4-over-DHCPv6 (DHCP 4o6) Transport", Farrer, "DHCPv4-over-DHCPv6 (DHCP 4o6) Transport",
RFC 7341, DOI 10.17487/RFC7341, August 2014, RFC 7341, DOI 10.17487/RFC7341, August 2014,
<https://www.rfc-editor.org/info/rfc7341>. <https://www.rfc-editor.org/info/rfc7341>.
[RFC7598] Mrugalski, T., Troan, O., Farrer, I., Perreault, S., Dec,
W., Bao, C., Yeh, L., and X. Deng, "DHCPv6 Options for
Configuration of Softwire Address and Port-Mapped
Clients", RFC 7598, DOI 10.17487/RFC7598, July 2015,
<https://www.rfc-editor.org/info/rfc7598>.
12.2. Informative References 12.2. Informative References
[RFC7596] Cui, Y., Sun, Q., Boucadair, M., Tsou, T., Lee, Y., and I. [RFC7596] Cui, Y., Sun, Q., Boucadair, M., Tsou, T., Lee, Y., and I.
Farrer, "Lightweight 4over6: An Extension to the Dual- Farrer, "Lightweight 4over6: An Extension to the Dual-
Stack Lite Architecture", RFC 7596, DOI 10.17487/RFC7596, Stack Lite Architecture", RFC 7596, DOI 10.17487/RFC7596,
July 2015, <https://www.rfc-editor.org/info/rfc7596>. July 2015, <https://www.rfc-editor.org/info/rfc7596>.
[RFC7597] Troan, O., Ed., Dec, W., Li, X., Bao, C., Matsushima, S., [RFC7597] Troan, O., Ed., Dec, W., Li, X., Bao, C., Matsushima, S.,
Murakami, T., and T. Taylor, Ed., "Mapping of Address and Murakami, T., and T. Taylor, Ed., "Mapping of Address and
Port with Encapsulation (MAP-E)", RFC 7597, Port with Encapsulation (MAP-E)", RFC 7597,
DOI 10.17487/RFC7597, July 2015, DOI 10.17487/RFC7597, July 2015,
<https://www.rfc-editor.org/info/rfc7597>. <https://www.rfc-editor.org/info/rfc7597>.
[RFC7598] Mrugalski, T., Troan, O., Farrer, I., Perreault, S., Dec,
W., Bao, C., Yeh, L., and X. Deng, "DHCPv6 Options for
Configuration of Softwire Address and Port-Mapped
Clients", RFC 7598, DOI 10.17487/RFC7598, July 2015,
<https://www.rfc-editor.org/info/rfc7598>.
[RFC7618] Cui, Y., Sun, Q., Farrer, I., Lee, Y., Sun, Q., and M. [RFC7618] Cui, Y., Sun, Q., Farrer, I., Lee, Y., Sun, Q., and M.
Boucadair, "Dynamic Allocation of Shared IPv4 Addresses", Boucadair, "Dynamic Allocation of Shared IPv4 Addresses",
RFC 7618, DOI 10.17487/RFC7618, August 2015, RFC 7618, DOI 10.17487/RFC7618, August 2015,
<https://www.rfc-editor.org/info/rfc7618>. <https://www.rfc-editor.org/info/rfc7618>.
Authors' Addresses Authors' Addresses
Ian Farrer Ian Farrer
Deutsche Telekom AG Deutsche Telekom AG
CTO-ATI, Landgrabenweg 151 CTO-ATI, Landgrabenweg 151
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