Network Working Group M. Boucadair
Internet-Draft France Telecom
Intended status: Standards Track R. Penno
Expires: November 11, 2010 Juniper Networks
D. Wing
Cisco
May 10, 2010
DHCP and DHCPv6 Options for Port Control Protocol (PCP)
draft-bpw-softwire-pcp-dhcp-01
Abstract
This document specifies DHCP (IPv4 and IPv6) Options to convey the IP
address or a FQDN of a PCP Server. A dedicated option to prevent
overloading PCP Servers is also specified.
Requirements Language
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].
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
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and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 11, 2010.
Copyright Notice
Copyright (c) 2010 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
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(http://trustee.ietf.org/license-info) in effect on the date of
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Consistent NAT and PCP Configuration . . . . . . . . . . . . . 3
3. DHCPv6 Options . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. PCP Server Address DHCPv6 Option . . . . . . . . . . . . . 4
3.2. PCP Server FQDN DHCPv6 Option . . . . . . . . . . . . . . 5
3.3. PCP Service Time Wait DHCPv6 Option . . . . . . . . . . . 6
3.4. Requirements . . . . . . . . . . . . . . . . . . . . . . . 7
4. DHCP PCP Option . . . . . . . . . . . . . . . . . . . . . . . 7
4.1. PCP Server Address Sub-Option . . . . . . . . . . . . . . 9
4.2. PCP Server FQDN Sub-Option . . . . . . . . . . . . . . . . 9
4.3. PCP Service Time Wait DHCP Sub-Option . . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.1. Normative References . . . . . . . . . . . . . . . . . . . 12
8.2. Informative References . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
[I-D.wing-softwire-port-control-protocol] recommends the use of DHCP
as one of the mechanisms to discover a PCP Server. To that aim, this
document defines DHCP [RFC2131] and DHCPv6 [RFC3315] Options which
can be used to provision a PCP Server reachability information (IP
address, FQDN) to a PCP Client. The use of DHCP or DHCPv6 depends on
the PCP deployment scenarios.
For flexibility reasons, this document defines both IP address and
FQDN Options. It is up to Service Providers to decide which option
is convenient for them according to their engineering policies.
This document does not make any assumption on the IP address to be
conveyed in a DHCP/DHCPv6 Option. In particular, this document does
not prevent Service Providers to use the IANA-to-be-assigned IP
address [I-D.wing-softwire-port-control-protocol] to be conveyed in
DHCP/DHCPv6 Options.
In some deployment contexts, the PCP Server may be reachable with an
IPv4 address but DHCPv6 is used to provision the PCP Client. In such
scenarios, this document suggests to include IPv4-mapped IPv6
addresses (see Section 3.1) as a reachability information of the PCP
Server (or use the domain name option). As described in Section 3.1
of [I-D.wing-behave-dns64-config], dual-stack hosts can issue IPv4
datagrams successfully to that IP address.
2. Consistent NAT and PCP Configuration
The PCP Server discovered through DHCP MUST be able to install
mappings on the NAT that will be crossed by packets issued by the
host or any terminal belonging to the same realm (e.g., DHCP client
is embedded in a CP router). If DHCP is used to provision the
reachability information of a PCP Server, Service Providers SHOULD
configure appropriately their DHCP servers to meet this requirement.
In case this prerequisite is not met, customers would experience
service troubles and their service(s) won't be delivered
appropriately.
Note that this constraint is implicitly met in scenarios where only
one single PCP-controlled device is deployed in the network.
3. DHCPv6 Options
Two DHCPv6 Options defined in the following sub-sections are used to
convey the PCP Server reachability information. The first option
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(i.e., OPTION_PCP_SERVER_A) can be used to include an IPv6 address or
an IPv4-mapped IPv6 address. The second option (i.e.,
OPTION_PCP_SERVER_D) conveys a domain name to be used to retrieve the
IP address of the PCP Server.
For example, in the context of a DS-Lite architecture
[I-D.ietf-softwire-dual-stack-lite] DHCPv6 can be used to include the
IPv4-mapped IPv6 address [RFC2373] of a PCP Server (a PCP Client can
use an IPv4-mapped IPv6 address to send IPv4 PCP messages), and in
the case of NAT64 [I-D.ietf-behave-v6v4-xlate-stateful] to provision
the IPv6 address of the PCP Server.
A third option (OPTION_PCP_SERVICE_T) is defined to convey a timer
used to prevent overload events.
3.1. PCP Server Address DHCPv6 Option
This option specifies an IP address of the PCP Server to be used by
the PCP Client to send PCP messages.
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_PCP_SERVER_A | Option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| PCP Server (IP address) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| PCP Server (IP address) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: .... :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: PCP Server IP Address DHCPv6 Option
The description of the fields of the option shown in Figure 1 is
described below:
o Option-code: OPTION_PCP_SERVER_A (TBA, see Section 6)
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o Option-length: MUST be a multiple of 16.
o PCP Server: One or a list of IP address(es) of PCP Server(s) to be
used by a PCP Client. In particular, IPv4-mapped IPv6 addresses
can be included in this field when the PCP Server is reachable
over IPv4 (e.g., in a DS-Lite architecture, the PCP Server can be
reachable over IPv4 (i.e., PCP messages will be encapsulated in
IPv6). An IPv4-mapped IPv6 address can be used to provision the
PCP Client with the reachability information of the PCP Server).
If several IP addresses are included in the option, these addresses
MUST be listed in the order of preference. A PCP Client MUST use a
reachable address with higher preference order.
In case several addresses are to be conveyed in a DHCPv6 option, it
is RECOMMENDED to use OPTION_PCP_SERVER_D DHCPv6 option.
3.2. PCP Server FQDN DHCPv6 Option
This option includes a FQDN of the PCP Server to be used by the PCP
Client. In order to exploit this option, this document assumes that
a DNS server is configured on the host client by DHCP or other means.
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_PCP_SERVER_D | Option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: PCP Server Domain Name :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: PCP Server FQDN DHCPv6 Option
The fields of the option shown in Figure 2 are:
o Option-code: OPTION_PCP_SERVER_D (TBA, see Section 6)
o Option-length: Length of the 'PCP Server Domain Name' field in
octets. This length is variable.
o PCP Server Domain Name: The domain name of the PCP Server to be
used by the PCP Client. The domain name is encoded as specified
in [RFC3315].
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3.3. PCP Service Time Wait DHCPv6 Option
[NOTE: This section will be removed if the avalanche restart concern
is handled by a generic initiative such as HomeGate. See for example
[RFC3435] how this issue is covered for MGCP.]
In order to avoid overload phenomena (e.g., power outage event in a
big city), the following option (Figure 3) is used to ask a PCP
Client to wait N seconds before sending its first PCP message. If no
overload control mechanism is supported, avalanche restart phenomena
would lead to a huge amount of requests to the PCP Server which would
impact the serviceability of the PCP-controlled device and would even
induce a service outage for a large number of customers serviced by
the same CGN device. Distributing all PCP requests in a random or a
pre-defined manner will avoid experiencing load bursts.
This option SHOULD be used only with a non-null TimeWait value.
The format of the OPTION_PCP_SERVICE_T option is shown in Figure 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_PCP_SERVICE_T | Option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Method | TimeWait |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This option can be generalized to all services (e.g., SIP, PCP, NTP,
etc.) by including a field which specifies the associated service.
Figure 3: PCP Service TimeWait DHCPv6 Option
The description of the fields of this option is as follows:
o Option-code: OPTION_PCP_SERVICE_T (TBA, see Section 6)
o Option-length: 4.
o Method: This field specifies the method to apply on the TimeWait.
Two methods MUST be supported by any OPTION_PCP_SERVICE_T
implementation:
0: Basic. When this method is used, the PCP Client MUST wait
until the expiry of TimeWait seconds before issuing a PCP
message.
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1: Random. When this method is indicated, a RAND() function
MUST be used to generate a value between 0 and TimeWait. The
PCP Client MUST wait until the expiry of the generated value
before issuing a PCP message to a PCP Server.
o TimeWait: This field specifies a number of seconds to be used when
applying the function indicated in the Method field.
3.4. Requirements
If OPTION_PCP_SERVER_D is used to configure the PCP Server, the
client MUST issue a AAAA DNS query to resolve an IPv6 address, if the
query has failed the PCP Client MUST issue an A DNS query. [[Note:
In order to avoid the delay, a field can be added to the option to
inform the client about the type of the DNS query to be issued]]].
OPTION_PCP_SERVER_D and OPTION_PCP_SERVER_A DHCPv6 option MUST be
supported. OPTION_PCP_SERVICE_T DHPCv6 option MAY (SHOULD?) be
supported.
4. DHCP PCP Option
The PCP Server DHCP Option can be used to configure an IPv4 address
or a DNS FQDN to be used by the PCP Client to contact a PCP Server.
It can also be used to indicate a timer to constraint emitting PCP
messages. The generic format of this option is illustrated in
Figure 4.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: Sub-option 1 :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: ... :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: Sub-option n :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: DHCP PCP Option
o Code: OPTION_PCP_SERVER (TBA, see Section 6);
o Length: Includes the length of included sub-options;
o One or several sub-options can be included in a PCP DHCP option.
The format of each sub-option follows the structure shown in
Figure 5.
Sub-option
Code Len Data
+-----+-----+-----...---+
| code| n | Data |
+-----+-----+-----...---+
Figure 5: PCP Server sub-option
Three sub-options are defined in this document:
1: PCP Server Address Sub-option (Section 4.1);
2: PCP Domain Name Sub-option (Section 4.2);
3: PCP Service Time Wait Sub-option (Section 4.3).
Both PCP Server Address and PCP Domain Name Sub-options MUST be
supported. PCP Service Time Wait Sub-option MAY (SHOULD?) be
supported.
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PCP Server Address Sub-option and PCP Domain Name Sub-option are
exclusive.
PCP Service Time Wait Sub-option MAY be jointly included in the same
DHCP message carrying PCP Server Address Sub-option or PCP Domain
Name Sub-option.
When a PCP Domain Name Sub-option is used, the PCP client MUST issue
A DNS queries to retrieve an IPv4 address.
4.1. PCP Server Address Sub-Option
This sub-option specifies one or a list of IPv4 addresses of the PCP
Server to be used by the PCP Client to send PCP messages.
Sub-option
Code Len PCP Server IP Address PCP Server IP Address
+-----+-----+-----+-----+-----+-----+-----+-----+--
| 1 | n | a1 | a2 | a3 | a4 | a1 | a2 | ...
+-----+-----+-----+-----+-----+-----+-----+-----+--
This format assumes that an IPv4 address is encoded as a1.a2.a3.a4.
Figure 6: PCP Server IPv4 Address DHCP Sub-Option
The fields of the sub-option shown in Figure 6 are:
o Sub-option Code: 1.
o Len: Must be a multiple of 4.
o PCP Server IP Address: contains one or several IPv4 addresses of a
PCP Server to be used by a PCP Client. If several addresses are
included, they are included in the preference order. A client
MUST use the reachable address with the highest preference order.
Instead of including several addresses in the DHCP option, it is
RECOMMENDED to use PCP Server FQDN Sub-option.
4.2. PCP Server FQDN Sub-Option
This sub-option includes a FQDN of the PCP Server to be used by the
PCP Client to send PCP messages. In order to exploit this option,
this document assumes that a DNS server is configured on the host
client by DHCP or other means.
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Sub-option
Code Len FQDN of PCP Server
+-----+-----+-----+-----+-----+-----+-----+--
| 2 | n | s1 | s2 | s3 | s4 | s5 | ...
+-----+-----+-----+-----+-----+-----+-----+--
Figure 7: PCP Server FQDN DHCP Sub-option
The fields of the sub-option shown in Figure 7 are:
o Sub-option Code: 2.
o Len: Length of the "PCP Server Domain Name" field in octets. This
length is variable.
o PCP Server Domain Name: The domain name of the PCP Server to be
used by the PCP Client. The encoding of the domain name is
described [RFC2131].
4.3. PCP Service Time Wait DHCP Sub-Option
[NOTE: This section will be removed if the avalanche restart concern
is handled by a generic initiative such as HomeGate]
This sub-option is used to indicate to a host, the time to wait
before issuing a PCP message. The purpose of this option is to
prevent overload phenomena. This sub-option SHOULD be used only with
a non-null TimeWait value.
The format of the PCP Service Time Wait DHCP Sub-option is shown in
Figure 8.
Sub-option
Code Len Method TimeWait
+-----+-----+-----+-----+-----+
| 3 | 3 | M | TimeWait |
+-----+-----+-----+-----+-----+
Figure 8: PCP Service TimeWait DHCP Sub-option
The fields of this sub-option are:
o Sub-option Code: 3.
o Len: 3.
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o Method: This field specifies the method to apply on the TimeWait.
Two methods MUST be supported:
0: Basic. When this method is indicated, the PCP Client MUST
wait until the expiry of TimeWait seconds before issuing a PCP
message.
1: Random. When this method is indicated, a RAND() function
MUST be used to generate a value between 0 and TimeWait. The
PCP Client MUST wait until the expiry of the generated value
before issuing a PCP message to a PCP Server.
o TimeWait: This field specifies a number of seconds to be used when
applying the function indicated in the Method field.
5. Security Considerations
The security considerations in [RFC2131], [RFC3315] and
[I-D.wing-softwire-port-control-protocol] are to be considered.
6. IANA Considerations
This document request three DHCPv6 Option codes and one DHCP Option
code.
DHCPv6 Option codes:
1. OPTION_PCP_SERVER_A
2. OPTION_PCP_SERVER_D
3. OPTION_PCP_SERVICE_T
DHCP Option code:
1. OPTION_PCP_SERVER
7. Acknowledgements
Many thanks to B. Volz and C. Jacquenet for their review and
comments.
8. References
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8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, 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.
8.2. Informative References
[I-D.ietf-behave-v6v4-xlate-stateful]
Bagnulo, M., Matthews, P., and I. Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers",
draft-ietf-behave-v6v4-xlate-stateful-11 (work in
progress), March 2010.
[I-D.ietf-softwire-dual-stack-lite]
Durand, A., Droms, R., Haberman, B., Woodyatt, J., Lee,
Y., and R. Bush, "Dual-Stack Lite Broadband Deployments
Following IPv4 Exhaustion",
draft-ietf-softwire-dual-stack-lite-04 (work in progress),
March 2010.
[I-D.wing-behave-dns64-config]
Wing, D., "DNS64 Resolvers and Dual-Stack Hosts",
draft-wing-behave-dns64-config-02 (work in progress),
February 2010.
[I-D.wing-softwire-port-control-protocol]
Wing, D., Penno, R., and M. Boucadair, "Port Control
Protocol (PCP)",
draft-wing-softwire-port-control-protocol-01 (work in
progress), March 2010.
[RFC2373] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 2373, July 1998.
[RFC3435] Andreasen, F. and B. Foster, "Media Gateway Control
Protocol (MGCP) Version 1.0", RFC 3435, January 2003.
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Authors' Addresses
Mohamed Boucadair
France Telecom
Rennes, 35000
France
Email: mohamed.boucadair@orange-ftgroup.com
Reinaldo Penno
Juniper Networks
1194 N Mathilda Avenue
Sunnyvale, California 94089
USA
Email: rpenno@juniper.net
Dan Wing
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, California 95134
USA
Email: dwing@cisco.com
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