Internet DRAFT - draft-ietf-softwire-map-dhcp
draft-ietf-softwire-map-dhcp
Softwire WG T. Mrugalski
Internet-Draft ISC
Intended status: Standards Track O. Troan
Expires: September 10, 2015 Cisco
I. Farrer
Deutsche Telekom AG
S. Perreault
Viagenie
W. Dec
Cisco
C. Bao
Tsinghua University
L. Yeh
CNNIC
X. Deng
March 09, 2015
DHCPv6 Options for configuration of Softwire Address and Port Mapped
Clients
draft-ietf-softwire-map-dhcp-12
Abstract
This document specifies DHCPv6 options, termed Softwire46 options,
for the provisioning of Softwire46 Customer Edge (CE) devices.
Softwire46 is a collective term used to refer to architectures based
on the notion of IPv4 Address+Port (A+P) for providing IPv4
connectivity across an IPv6 network.
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 http://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 September 10, 2015.
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Copyright Notice
Copyright (c) 2015 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
(http://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
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Softwire46 Overview . . . . . . . . . . . . . . . . . . . . . 3
4. Common Softwire46 DHCPv6 Options . . . . . . . . . . . . . . 4
4.1. S46 Rule Option . . . . . . . . . . . . . . . . . . . . . 5
4.2. S46 BR Option . . . . . . . . . . . . . . . . . . . . . . 7
4.3. S46 DMR Option . . . . . . . . . . . . . . . . . . . . . 7
4.4. S46 IPv4/IPv6 Address Binding Option . . . . . . . . . . 8
4.5. S46 Port Parameters Option . . . . . . . . . . . . . . . 9
5. Softwire46 Containers . . . . . . . . . . . . . . . . . . . . 10
5.1. Softwire46 MAP-E Container Option . . . . . . . . . . . . 10
5.2. Softwire46 MAP-T Container Option . . . . . . . . . . . . 11
5.3. Softwire46 LightWeight 46 Container Option . . . . . . . 11
6. Softwire46 Options Formatting . . . . . . . . . . . . . . . . 12
7. DHCPv6 Server Behavior . . . . . . . . . . . . . . . . . . . 13
8. DHCPv6 Client Behavior . . . . . . . . . . . . . . . . . . . 13
9. Security Considerations . . . . . . . . . . . . . . . . . . . 14
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
12.1. Normative References . . . . . . . . . . . . . . . . . . 15
12.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction
A number of architectural solution proposals discussed in the IETF
Softwire Working Group use Address and Port (A+P) as their technology
base for providing IPv4 connectivity to end users using CE devices
across a Service Provider's IPv6 network, while allowing for shared
or dedicated IPv4 addressing of CEs.
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An example is Mapping of Address and Port (MAP) defined in
[I-D.ietf-softwire-map]. The MAP solution consists of one or more
MAP Border Relay (BR) routers, responsible for stateless forwarding
between a MAP IPv6 domain and an IPv4 network, and one or more MAP
Customer Edge (CE) routers, responsible for forwarding between a
user's IPv4 network and the MAP IPv6 network domain. Collectively,
the MAP CE and BR form a domain when configured with common service
parameters. This characteristic is common to all of the Softwire46
mechanisms.
To function in such a domain, a CE needs to be provisioned with the
appropriate A+P service parameters for that domain. These consist
primarily of the CE's IPv4 address and transport layer port-range(s).
Furthermore, the IPv6 transport mode (i.e. encapsulation or
translation) needs to be specified. Provisioning of other IPv4
configuration information not derived directly from the A+P service
parameters is not covered in this document. It is expected that
provisioning of other IPv4 configuration will continue to use DHCPv4
[RFC2131].
This memo specifies a set of DHCPv6 [RFC3315] options to provision
Softwire46 information to CE routers. Although the focus is to
deliver IPv4 service to an end-user network (such as a residential
home network), it can equally be applied to an individual host acting
as a CE. Configuration of the BR is out of scope of this document.
2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
3. Softwire46 Overview
This document describes a set of common DHCPv6 options for
configuring the MAP-E [I-D.ietf-softwire-map], MAP-T
[I-D.ietf-softwire-map-t] and Lightweight 4over6
[I-D.ietf-softwire-lw4over6] mechanisms. For definition of the
terminology used in this document please see the relevant terminology
sections in the above references.
MAP-E, MAP-T and Lightweight 4over6 are essentially providing the
same functionality: IPv4 service to a CE router over an IPv6 only
access network. MAP-E and MAP-T may embed parts of the IPv4 address
in IPv6 prefixes, thereby supporting many clients with a fixed set of
mapping rules and mesh mode (direct CE to CE communication). MAP-E
and MAP-T CEs may also be provisioned in hub and spoke mode, and in
1:1 mode (with no embedded address bits). The difference between
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MAP-E and MAP-T is that they use different means to connect to the
IPv6 domain. MAP-E uses [RFC2473] IPv4 over IPv6 tunnelling, while
MAP-T uses NAT64 [RFC6145] based translation. Lightweight 4over6 is
a hub and spoke IPv4 over IPv6 tunneling mechanism, with complete
independence of IPv4 and IPv6 addressing (zero embedded address
bits).
The DHCP options described here tie the provisioning parameters, and
hence the IPv4 service itself, to the End-user IPv6 prefix lifetime.
The validity of a Softwire46's IPv4 address, prefix or shared IPv4
address, port set and any authorization and accounting are tied to
the lifetime of its associated End-user IPv6 prefix.
To support more than one mechanism at a time and to allow for a
possibility of transition between them, the DHCPv6 Option Request
Option [RFC3315] is used. Each mechanism has a corresponding DHCPv6
container option. A DHCPv6 client can request a particular mechanism
by including the option code for a particular container option in its
ORO option. The provisioning parameters for that mechanism are
expressed by embedding the common format options within the
respective container option.
This approach implies that all of the provisioning options MUST
appear only within the container options. The client MUST NOT
request any of the provisioning options directly within an ORO. MAP-
DHCP clients that receive provisioning options that are not
encapsulated in container options MUST silently ignore these options.
DHCP server administrators are advised to ensure that DHCP servers
are configured to send these options in the proper encapsulation.
The document is organized with the common sub-options described
first, followed by the three container options. Some sub-options are
mandatory in some containers, some are optional and some are not
permitted at all. This is shown in Table 1.
4. Common Softwire46 DHCPv6 Options
The DHCPv6 protocol is used for Softwire46 CE provisioning following
regular DHCPv6 notions, with the CE assuming the role of a DHCPv6
client, and the DHCPv6 server providing options following DHCPv6
server side policies. The format and usage of the options are
defined in the following sub-sections.
Each CE needs to be provisioned with enough information to calculate
its IPv4 address, IPv4 prefix or shared IPv4 address. MAP-E and
MAP-T use the OPTION_S46_RULE, while Lightweight 4over6 uses the
OPTION_S46_V4V6BIND option. A CE that needs to communicate outside
of the A+P domain also needs the address or prefix of the BR. MAP-E
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and Lightweight 4over6 use the OPTION_S46_BR option to communicate
the IPv6 address of the BR. MAP-T forms an IPv6 destination address
by embedding an IPv4 destination address into the BR's IPv6 prefix
conveyed via the OPTION_S46_DMR option. Optionally, all mechanisms
can include OPTION_S46_PORTPARAMS to specify parameters and port sets
for the port range algorithm.
Softwire46 options use addresses rather than FQDNs. For rationale
behind this design choice, see Section 8 of [RFC7227].
4.1. S46 Rule Option
Figure 1 shows the format of the S46 Rule option (OPTION_S46_RULE)
used for conveying the Basic Mapping Rule (BMR) and Forwarding
Mapping Rule (FMR).
This option follows behavior described in Sections 17.1.1 and 18.1.1
of [RFC3315]. Clients can insert those options with specific values
as hints for the server. Depending on the server configuration and
policy, it may accept or ignore the hints. Client MUST be able to
process received values that are different than the hints it sent
earlier.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_S46_RULE | option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| flags | ea-len | prefix4-len | ipv4-prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (continued) | prefix6-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ipv6-prefix |
| (variable length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. S46_RULE-options .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: S46 Rule Option
o option-code: OPTION_S46_RULE (TBD1)
o option-length: length of the option, excluding option-code and
option-length fields, including length of all encapsulated
options, expressed in bytes.
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o flags: 8 bits long field carrying flags applicable to the rule.
The meaning of specific bits are explained in Figure 2.
o ea-len: 8 bits long field that specifies the Embedded-Address (EA)
bit length. Allowed values range from 0 to 48.
o prefix4-len: 8 bits long field expressing the prefix length of the
IPv4 prefix specified in the rule-ipv4-prefix field. Valid values
0 to 32.
o ipv4-prefix: a fixed length 32 bit field that specifies the IPv4
prefix for the S46 rule. The bits in the prefix after prefix4-len
number of bits are reserved and MUST be initialized to zero by the
sender and ignored by the receiver.
o prefix6-len: 8 bits long field expressing the length of the IPv6
prefix specified in the rule-ipv6-prefix field.
o ipv6-prefix: a variable length field that specifies the IPv6
domain prefix for the S46 rule. The field is padded on the right
with zero bits up to the nearest octet boundary when prefix6-len
is not evenly divisible by 8.
o S46_RULE-options: a variable field that may contain zero or more
options that specify additional parameters for this S46 rule.
This document specifies one such option, OPTION_S46_PORTPARAMS.
The Format of the S46 Rule Flags field is:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|Reserved |F|
+-+-+-+-+-+-+-+-+
Figure 2: S46 Rule Flags
o Reserved: 7-bits reserved for future use as flags.
o F-Flag: 1 bit field that specifies whether the rule is to be used
for forwarding (FMR). If set, this rule is used as a FMR, if not
set this rule is a BMR only and MUST NOT be used for forwarding.
Note: A BMR can also be used as an FMR for forwarding if the
F-flag is set. The BMR rule is determined by a longest-prefix
match of the Rule-IPv6-prefix against the End-User IPv6
prefix(es).
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It is expected that in a typical mesh deployment scenario, there will
be a single BMR, which could also be designated as an FMR using the
F-Flag.
4.2. S46 BR Option
The S46 BR Option (OPTION_S46_BR) is used to convey the IPv6 address
of the Border Relay. Figure 4 shows the format of the OPTION_S46_BR
option.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_S46_BR | option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| br-ipv6-address |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: S46 BR Option
o option-code: OPTION_S46_BR (TBD2)
o option-length: 16
o br-ipv6-address: a fixed length field of 16 octets that specifies
the IPv6 address for the S46 BR.
BR redundancy can be implemented by using an anycast address for the
BR IPv6 address. Multiple OPTION_S46_BR options MAY be included in
the container; this document does not further explore the use of
multiple BR IPv6 addresses.
4.3. S46 DMR Option
The S46 DMR Option (OPTION_S46_DMR) is used to convey values for the
Default Mapping Rule (DMR). Figure 4 shows the format of the
OPTION_S46_DMR option used for conveying a DMR.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_S46_DMR | option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|dmr-prefix6-len| dmr-ipv6-prefix |
+-+-+-+-+-+-+-+-+ (variable length) |
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. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: S46 DMR Option
o option-code: OPTION_S46_DMR (TBD3)
o option-length: 1 + length of dmr-ipv6-prefix specified in bytes.
o dmr-prefix6-len: 8 bits long field expressing the bit mask length
of the IPv6 prefix specified in the dmr-ipv6-prefix field.
o dmr-ipv6-prefix: a variable length field specifying the IPv6
prefix or address for the BR. This field is right padded with
zeros to the nearest octet boundary when dmr-prefix6-len is not
divisible by 8.
4.4. S46 IPv4/IPv6 Address Binding Option
The IPv4 address Option (OPTION_S46_V4V6BIND) MAY be used to specify
the full or shared IPv4 address of the CE. The IPv6 prefix field is
used by the CE to identify the correct prefix to use for the tunnel
source.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_S46_V4V6BIND | option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ipv4-address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|bindprefix6-len| bind-ipv6-prefix |
+-+-+-+-+-+-+-+-+ (variable length) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. S46_V4V6BIND-options .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: S46 IPv4/IPv6 Address Binding Option
o option-code: OPTION_S46_V4V6BIND (TBD4)
o option-length: length of the option, excluding option-code and
option-length fields, including length of all encapsulated
options, expressed in bytes.
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o ipv4-address: A fixed field of 4 octets specifying an IPv4
address.
o bindprefix6-len: 8 bits long field expressing the bit mask length
of the IPv6 prefix specified in the bind-ipv6-prefix field.
o bind-ipv6-prefix: a variable length field specifying the IPv6
prefix or address for the S46 CE. This field is right padded with
zeros to the nearest octet boundary when bindprefix6-len is not
divisible by 8.
o S46_V4V6BIND-options: a variable field that may contain zero or
more options that specify additional parameters. This document
specifies one such option, OPTION_S46_PORTPARAMS.
4.5. S46 Port Parameters Option
The Port Parameters Option (OPTION_S46_PORTPARAMS) specifies optional
Port Set information that MAY be provided to CEs.
See [I-D.ietf-softwire-map], Section 5.1 for a description of MAP
algorithm, explaining all of the parameters in detail.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_S46_PORTPARAMS | option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| offset | PSID-len | PSID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: S46 Port Parameters Option
o option-code: OPTION_S46_PORTPARAMS (TBD5)
o option-length: 4
o offset: (PSID offset) 8 bits long field that specifies the numeric
value for the S46 algorithm's excluded port range/offset bits
(a-bits), as per section 5.1.1 of [I-D.ietf-softwire-map].
Allowed values are between 0 and 15. Default values for this
field are specific to the softwire mechanism being implemented and
are defined in the relevant specification document.
o PSID-len: Bit length value of the number of significant bits in
the PSID field. (also known as 'k'). When set to 0, the PSID
field is to be ignored. After the first 'a' bits, there are k
bits in the port number representing the value of the Port Set
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Identifier (PSID). Consequently, the address sharing ratio would
be 2^k.
o PSID: Explicit 16-bit (unsigned word) PSID value. The PSID value
algorithmically identifies a set of ports assigned to a CE. The
first k bits on the left of this field contain the PSID value.
The remaining (16-k) bits on the right are padding zeros.
When receiving the OPTION_S46_PORTPARAMS option with an explicit
PSID, the client MUST use this explicit PSID in configuring its
softwire interface. The OPTION_S46_PORTPARAMS option with an
explicit PSID MUST be discarded if the S46 CE isn't configured with a
full IPv4 address (e.g. IPv4 prefix).
The OPTION_S46_PORTPARAMS option with an explicit PSID MUST be
discarded if the S46 CE isn't configured with a full IPv4 address
(e.g. IPv4 prefix).
The OPTION_S46_PORTPARAMS option is contained within an
OPTION_S46_RULE option or an OPTION_S46_V4V6BIND option.
5. Softwire46 Containers
5.1. Softwire46 MAP-E Container Option
The MAP-E Container Option (OPTION_S46_CONT_MAPE) specifies the
container used to group all rules and optional port parameters for a
specified domain.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_S46_CONT_MAPE | option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. encapsulated-options (variable length) .
. .
+---------------------------------------------------------------+
Figure 7: MAP-E Container Option
o option-code: OPTION_S46_CONT_MAPE (TBD6)
o option-length: Length of encapsulated options
o encapsulated-options: options associated with this Softwire46
MAP-E domain.
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The encapsulated options field conveys options specific to the
OPTION_S46_CONT_MAPE. Currently there are two sub-options specified,
OPTION_S46_RULE and OPTION_S46_BR. There MUST be at least one
OPTION_S46_RULE option and at least one OPTION_S46_BR option.
Other options applicable to a domain may be defined in the future. A
DHCP message MAY include multiple OPTION_S46_CONT_MAPE options
(representing multiple domains).
5.2. Softwire46 MAP-T Container Option
The MAP-T Container option (OPTION_S46_CONT_MAPT) specifies the
container used to group all rules and optional port parameters for a
specified domain.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_S46_CONT_MAPT | option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. encapsulated-options (variable length) .
. .
+---------------------------------------------------------------+
Figure 8: MAP-E Container Option
o option-code: OPTION_S46_CONT_MAPT (TBD7)
o option-length: Length of encapsulated options
o encapsulated-options: options associated with this Softwire46
MAP-T domain.
The encapsulated options field conveys options specific to the
OPTION_S46_CONT_MAPT option. Currently there are two options
specified, the OPTION_S46_RULE and OPTION_S46_DMR options. There
MUST be at least one OPTION_S46_RULE option and exactly one
OPTION_S46_DMR option.
5.3. Softwire46 LightWeight 46 Container Option
The LW46 Container option (OPTION_S46_CONT_LW) specifies the
container used to group all rules and optional port parameters for a
specified domain.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_S46_CONT_LW | option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ encapsulated-options (variable length) .
. .
+---------------------------------------------------------------+
Figure 9: LW46 Container Option
o option-code: OPTION_S46_CONT_LW (TBD8)
o option-length: Length of encapsulated options
o encapsulated-options: options associated with this Softwire46
domain.
The encapsulated options field conveys options specific to the
OPTION_S46_CONT_LW option. Currently there are two options
specified, OPTION_S46_V4V6BIND and OPTION_S46_BR. There MUST be at
most one OPTION_S46_V4V6BIND option and at least one OPTION_S46_BR
option.
6. Softwire46 Options Formatting
The below table shows which sub-options are mandatory, optional or
not permitted for each defined container option.
+-----------------------+-------+-------+--------------------+
| Option | MAP-E | MAP-T | Lightweight 4over6 |
+-----------------------+-------+-------+--------------------+
| OPTION_S46_RULE | M | M | N/A |
| | | | |
| OPTION_S46_BR | M | N/A | M |
| | | | |
| OPTION_S46_PORTPARAMS | O | O | O |
| | | | |
| OPTION_S46_DMR | N/A | M | N/A |
| | | | |
| OPTION_S46_V4V6BIND | N/A | N/A | O |
+-----------------------+-------+-------+--------------------+
M - Mandatory, O - Optional, N/A - Not Applicable
Table 1: Option to Container Mappings
MAP-DHCP clients that receive container options that violate any of
the above rules MUST silently ignore such container options.
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7. DHCPv6 Server Behavior
[RFC3315] Section 17.2.2 describes how a DHCPv6 client and server
negotiate configuration values using the ORO. As a convenience to
the reader, we mention here that by default, a server will not reply
with a Softwire46 Container Option if the client has not explicitly
enumerated one in its Option Request Option.
A CE router may support several (or all) of the mechanisms mentioned
here. In the case where a client requests multiple mechanisms in its
ORO option, the server will reply with the corresponding Softwire46
Container options for which it has configuration information.
8. DHCPv6 Client Behavior
An S46 CE acting as DHCPv6 client will request S46 configuration
parameters from the DHCPv6 server located in the IPv6 network. Such
a client MUST request the S46 Container option(s) that it is
configured for in its ORO in SOLICIT, REQUEST, RENEW, REBIND and
INFORMATION-REQUEST messages.
When processing received S46 container options the following
behaviour is expected:
o A client MUST support processing multiple received OPTION_S46_RULE
options in a container OPTION_S46_CONT_MAPE or
OPTION_S46_CONT_MAPT option
o A client receiving an unsupported S46 option, or an invalid
parameter value SHOULD discard that S46 Container option and log
the event.
The behavior of a client supporting multiple Softwire46 mechanisms,
is out of scope of this document. [I-D.ietf-softwire-unified-cpe]
describes client behaviour for the prioritization and handling of
multiple mechanisms simultaneously.
Note that system implementing CE functionality may have multiple
network interfaces, and these interfaces may be configured
differently; some may be connected to networks using a Softwire46
mechanism, and some may be connected to networks that are using
normal dual stack or other means. The CE should approach this
specification on an interface-by-interface basis. For example, if
the CE system is MAP-E capable and is attached to multiple networks
that provide the OPTION_S46_CONT_MAPE option, then the CE MUST
configure MAP-E for each interface separately.
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Failure modes are out of scope for this document. Failure recovery
mechanisms may be defined in the future. See Section 5 of
[I-D.ietf-softwire-map] for discussion on valid MAP rule
combinations. See Section 11 of [RFC7227], Sections 18.1.3, 18.1.4
and 19.1 of [RFC3315] for parameters update mechanisms in DHCPv6 that
can be leveraged to update configuration after a failure.
9. Security Considerations
Section 23 of [RFC3315] discusses DHCPv6-related security issues.
As with all DHCPv6-derived configuration state, it is possible that
configuration is actually being delivered by a third party (Man In
The Middle). As such, there is no basis on which access over MAP or
lw4o6 can be trusted. Therefore, softwires should not bypass any
security mechanisms such as IP firewalls.
In IPv6-only networks that lack any IPv4 firewalls, a device
supporting MAP could be tricked into enabling its IPv4 stack and
direct IPv4 traffic to the attacker, thus exposing itself to
previously infeasible IPv4 attack vectors.
Section 11 of [I-D.ietf-softwire-map] discusses security issues of
the MAP mechanism.
Readers concerned with security of MAP provisioning over DHCPv6 are
encouraged to read [I-D.ietf-dhc-sedhcpv6].
10. IANA Considerations
IANA is kindly requested to allocate the following DHCPv6 option
codes:
TBD1 for OPTION_S46_RULE
TBD2 for OPTION_S46_BR
TBD3 for OPTION_S46_DMR
TBD4 for OPTION_S46_V4V6BIND
TBD5 for OPTION_S46_PORTPARAMS
TBD6 for OPTION_S46_CONT_MAPE
TBD7 for OPTION_S46_CONT_MAPT
TBD8 for OPTION_S46_CONT_LW
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All values should be added to the DHCPv6 option code space defined in
Section 24.3 of [RFC3315].
11. Acknowledgements
This document was created as a product of a MAP design team.
Following people were members of that team: Congxiao Bao, Mohamed
Boucadair, Gang Chen, Maoke Chen, Wojciech Dec, Xiaohong Deng, Jouni
Korhonen, Xing Li, Satoru Matsushima, Tomasz Mrugalski, Tetsuya
Murakami, Jacni Qin, Necj Scoberne, Qiong Sun, Tina Tsou, Dan Wing,
Leaf Yeh and Jan Zorz.
The authors would like to thank Bernie Volz and Tom Taylor for their
insightful comments and suggestions.
12. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
and M. Carney, "Dynamic Host Configuration Protocol for
IPv6 (DHCPv6)", RFC 3315, July 2003.
12.2. Informative References
[I-D.ietf-dhc-sedhcpv6]
Jiang, S., Shen, S., Zhang, D., and T. Jinmei, "Secure
DHCPv6 with Public Key", draft-ietf-dhc-sedhcpv6-03 (work
in progress), June 2014.
[I-D.ietf-softwire-lw4over6]
Cui, Y., Qiong, Q., Boucadair, M., Tsou, T., Lee, Y., and
I. Farrer, "Lightweight 4over6: An Extension to the DS-
Lite Architecture", draft-ietf-softwire-lw4over6-03 (work
in progress), November 2013.
[I-D.ietf-softwire-map-t]
Li, X., Bao, C., Dec, W., Troan, O., Matsushima, S., and
T. Murakami, "Mapping of Address and Port using
Translation (MAP-T)", draft-ietf-softwire-map-t-04 (work
in progress), September 2013.
[I-D.ietf-softwire-map]
Troan, O., Dec, W., Li, X., Bao, C., Matsushima, S.,
Murakami, T., and T. Taylor, "Mapping of Address and Port
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with Encapsulation (MAP)", draft-ietf-softwire-map-08
(work in progress), August 2013.
[I-D.ietf-softwire-unified-cpe]
Boucadair, M., Farrer, I., Perreault, S., and S.
Sivakumar, "Unified IPv4-in-IPv6 Softwire CPE", draft-
ietf-softwire-unified-cpe-01 (work in progress), May 2013.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC
2131, March 1997.
[RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in
IPv6 Specification", RFC 2473, December 1998.
[RFC6145] Li, X., Bao, C., and F. Baker, "IP/ICMP Translation
Algorithm", RFC 6145, April 2011.
[RFC7227] Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and
S. Krishnan, "Guidelines for Creating New DHCPv6 Options",
BCP 187, RFC 7227, May 2014.
Authors' Addresses
Tomasz Mrugalski
Internet Systems Consortium, Inc.
950 Charter Street
Redwood City, CA 94063
USA
Phone: +1 650 423 1345
Email: tomasz.mrugalski@gmail.com
URI: http://www.isc.org/
Ole Troan
Cisco Systems, Inc.
Philip Pedersens vei 1
Lysaker 1366
Norway
Email: ot@cisco.com
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Ian Farrer
Deutsche Telekom AG
CTO-ATI, Landgrabenweg 151
Bonn, NRW 53227
Germany
Email: ian.farrer@telekom.de
Simon Perreault
Viagenie
246 Aberdeen
Quebec, QC G1R 2E1
Canada
Phone: +1 418 656 9254
Email: simon.perreault@viagenie.ca
Wojciech Dec
Cisco Systems, Inc.
The Netherlands
Email: wdec@cisco.com
URI: http://cisco.com
Congxiao Bao
CERNET Center/Tsinghua University
Room 225, Main Building, Tsinghua University
Beijing 100084
CN
Phone: +86 10-62785983
Email: congxiao@cernet.edu.cn
Leaf Y. Yeh
CNNIC
4, South 4th Street, Zhong_Guan_Cun
Beijing 100190
P. R. China
Email: leaf.yeh.sdo@gmail.com
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Xiaohong Deng
6 Floor, C Block, DaCheng International Center Chaoyang District
Beijing 100124
China
Phone: +61 3858 3128
Email: dxhbupt@gmail.com
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