PCP Working Group M. Boucadair
Internet-Draft France Telecom
Intended status: Standards Track R. Penno
Expires: July 11, 2011 Juniper Networks
D. Wing
Cisco
January 7, 2011
DHCP and DHCPv6 Options for Port Control Protocol (PCP)
draft-bpw-pcp-dhcp-01
Abstract
This document specifies DHCP (IPv4 and IPv6) options to provision
Port Control Protocol (PCP) Servers. The use of DHCP or DHCPv6
depends on the PCP deployment scenario.
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
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 July 11, 2011.
Copyright Notice
Copyright (c) 2011 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. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Consistent NAT and PCP Configuration . . . . . . . . . . . . . 5
5. DHCPv6 PCP Server Option . . . . . . . . . . . . . . . . . . . 5
5.1. Format . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.2. Client Behaviour . . . . . . . . . . . . . . . . . . . . . 6
5.3. Server Behaviour . . . . . . . . . . . . . . . . . . . . . 6
6. DHCP PCP Option . . . . . . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
10.1. Normative References . . . . . . . . . . . . . . . . . . . 9
10.2. Informative References . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
This document defines DHCP [RFC2131] and DHCPv6 [RFC3315] options
which can be used to provision a PCP Server [I-D.ietf-pcp-base]
reachability information; more precisely it defines DHCP options to
convey a FQDN (as per Section 3.1 of [RFC1035]) of a PCP Server. In
order to make use of these options, this document assumes that a DNS
server is configured on the host client by DHCP or other means.
The use of DHCP or DHCPv6 depends on the PCP deployment scenarios.
This document does not make any assumption on the IP address to be
used to reach a PCP Server. In particular, this document does not
prevent to configure the IANA-to-be-assigned IP address
[I-D.ietf-pcp-base] to be returned when resolving the FQDN carried 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, a plain IPv4 address or an IPv4-mapped IPv6 address can be
configured to reach the PCP Server. 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. Terminology
This document makes use of the following terms:
o PCP Server: A functional element which receives and processes PCP
requests from a PCP Client. A PCP Server can be co-located or be
separated from the function (e.g., NAT, Firewall) it controls.
Refer to [I-D.ietf-pcp-base].
o PCP Client: a PCP software instance responsible for issuing PCP
requests to a PCP Server. Refer to [I-D.ietf-pcp-base].
o DHCP client (or client) denotes a node that initiates requests to
obtain configuration parameters from one or more DHCP servers
[RFC3315].
o DHCP server (or server) refers to a node that responds to requests
from DHCP clients [RFC3315].
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3. Rationale
[[Note: May be removed in future version of the I-D.]]
Both IP address and FQDN DHCP options have been defined in previous
versions of this document. This flexibility aims to let service
providers to make their own engineering choices and use the
convenient option according to their deployment context.
Nevertheless, DHC WG's position is this flexibility have some
drawbacks such as inducing errors. Therefore, only the FQDN option
is maintained in this updated version.
This choice of defining the FQDN option rather than the IP address is
motivated by operational considerations: In particular, some service
providers are considering two levels of redirection: (1) The first
level is national-wise is undertaken by DHCP: a regional-specific
FQDN will be returned; (2) The second level is done during the
resolution of the regional-specific FQDN to redirect the customer to
a regional PCP Servers among a pool deployed regionally. Distinct
operational teams are responsible for each of the above mentioned
levels. A clear separation between the functional perimeter of each
team is a sensitive task for the maintenance of the offered services.
Regional teams will require to introduce new resources (e.g., new
PCP-controlled devices such as CGNs) to meet an increase of customer
base. The introduction of these new devices (addressing,
redirection, etc.) is implemented locally. Having this regional
separation provides flexibility to manage portions of network
operated by dedicated teams. This two-level redirection can not be
met by the IP Address option.
In addition to the operational considerations:
o The use of the FQDN for NAT64 might be suitable for load-balancing
purposes;
o For the DS-Lite case, if the encapsulation mode is used to send
PCP messages, an IP address may be used (the ipv4-mapped IPv6
address) since the AFTR selection is already done via the
AFTR_NAME DHCPv6 option. Of course, this assumes that the PCP
Server is co-located with the AFTR function. If these functions
are not co-located, conveying the FQDN would be more convenient.
If the PCP Server is located in a LAN, a simple FQDN such as "pcp-
server.local" can be used.
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4. Consistent NAT and PCP Configuration
The PCP Server discovered through DHCP MUST be able to install
mappings on the appropriate upstream PCP-controlled device 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 FQDN of a PCP Server, an operator
SHOULD configure appropriately 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.
5. DHCPv6 PCP Server Option
This DHCPv6 option conveys a domain name to be used to retrieve the
IP address of a PCP Server. Appropriate DNS queries should be issued
to resolve the conveyed FQDN. In the context of a DS-Lite
architecture [I-D.ietf-softwire-dual-stack-lite], the retrieved
address may be an IPv4 address or an IPv4-mapped IPv6 address
[RFC4291] of a PCP Server, and in the case of NAT64
[I-D.ietf-behave-v6v4-xlate-stateful] an IPv6 address can be
retrieved.
5.1. Format
The format of the DHCPv6 PCP Server option is shown in Figure 1.
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 | Option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: PCP Server Domain Name :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: PCP Server FQDN DHCPv6 Option
The fields of the option shown in Figure 1 are as follows:
o Option-code: OPTION_PCP_SERVER (TBA, see Section 8)
o Option-length: Length of the 'PCP Server Domain Name' field in
octets.
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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 Section 8 of [RFC3315].
5.2. Client Behaviour
To discover a PCP Server [I-D.ietf-pcp-base], the DHCPv6 client MUST
include an Option Request Option (ORO) requesting the DHCPv6 PCP
Server FQDN option (i.e., include OPTION_PCP_SERVER on its
OPTION_ORO) as described in Section 22.7 of [RFC3315]. A client MAY
also include the OPTION_DNS_SERVERS option on its OPTION_ORO to
retrieve a DNS servers list.
If the DHCPv6 client receives more than one OPTION_PCP_SERVER option
from the DHCPv6 server, it MUST discard all instances of that option.
Upon receipt of an OPTION_PCP_SERVER option, the DHCPv6 client MUST
verify that the option length (including the Option-length octet))
does not exceed 256 octets [RFC1035]). The DHCPv6 client MUST verify
the FQDN is a properly encoded as detailed in Section 8 of [RFC3315].
Once the FQDN conveyed in a OPTION_PCP_SERVER option is validated,
the DHCPv6 client issues appropriate DNS Query messages using the
provided FQDN to resolve a AAAA Resource Record or A RR Resource
Record. AAAA and A Queries may be issued in parallel or sequentially
(e.g., using [RFC3484] selection process).
[Ed. Is there a value to consider a level of indirection (e.g.,
SRV)? (1) to use an arbitrary port number for PCP Server instead
of the default port, (2) detect whether a security channel is in
use (using the transport protocol)]
If the DNS response contains more than one IPv6/IPv4 address, the PCP
Client MUST use the procedure defined in [I-D.ietf-pcp-base] for the
address selection. The PCP Client MUST NOT send PCP requests to more
than one IP address at the same time.
It is RECOMMENDED to associate a TTL with any address resulting from
resolving the FQDN conveyed in a OPTION_PCP_SERVER DHCPv6 option when
stored in a local cache. Considerations on how to flush out a local
cache are out of the scope of this document.
5.3. Server Behaviour
A DHCPv6 server MUST NOT reply with a value for the OPTION_PCP_SERVER
if the DHCPv6 client has not explicitly included OPTION_PCP_SERVER in
its OPTION_ORO.
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If OPTION_PCP_SERVER option is requested by the DHCPv6 client, DHCPv6
server MUST NOT send more than one OPTION_PCP_SERVER option in the
response. The DHCPv6 server MUST include only one FQDN in a
OPTION_PCP_SERVER option. The DHCPv6 server MUST NOT include an FQDN
having a length exceeding 256 octets.
6. DHCP PCP Option
The PCP Server DHCP option can be used to configure a FQDN to be used
by the PCP Client to contact a PCP Server. The generic format of
this option is illustrated in Figure 2.
Because of the depletion of DHCP option codes and in order to
anticipate future PCP-related DHCP options, the proposed option uses
a sub-option field.
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 2: DHCP PCP Option
The description of the fields is as follows:
o Code: OPTION_PCP_SERVER (TBA, see Section 8);
o Length: Includes the length of included sub-options in octets; The
maximum length is 255 octets.
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 3.
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Sub-option
Code Len Data
+-----+-----+-----...---+
| code| n | Data |
+-----+-----+-----...---+
Figure 3: PCP Server sub-option
Only one sub-option is defined in this document:
1: PCP Server Domain Name Sub-option (OPTION_PCP_SERVER_D
(Figure 4)). This sub-option includes a FQDN of the PCP Server to
be used by the PCP Client when issuing PCP messages.
Sub-option
Code Len FQDN of PCP Server
+-----+-----+-----+-----+-----+-----+-----+--
| 1 | n | s1 | s2 | s3 | s4 | s5 | ...
+-----+-----+-----+-----+-----+-----+-----+--
Figure 4: PCP Server FQDN DHCP Sub-option
The fields of the PCP Server Domain Name sub-option shown in Figure 4
are:
o Sub-option Code: 1.
o Len: Length of the "PCP Server Domain Name" field in octets.
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 in [RFC2131].
When the PCP Server Domain Name Sub-option is used, the client issues
a DNS A record query to retrieve the IPv4 address(es) of the PCP
server(s).
[[Note: aside effect of having the sub-option format is the risk
to have a large option exceeding the maximum permissible within a
single option (254 octets+the length octets). A solution would be
to recommend [RFC3396]?]]
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7. Security Considerations
The security considerations in [RFC2131], [RFC3315] and
[I-D.ietf-pcp-base] are to be considered.
8. IANA Considerations
This document requests the following codes:
DHCPv6 option code:
o OPTION_PCP_SERVER
DHCP option code:
o OPTION_PCP_SERVER
9. Acknowledgements
Many thanks to B. Volz and C. Jacquenet for their review and
comments.
10. References
10.1. Normative References
[I-D.ietf-pcp-base]
Wing, D., "Port Control Protocol (PCP)",
draft-ietf-pcp-base-02 (work in progress), January 2011.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[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.
[RFC3396] Lemon, T. and S. Cheshire, "Encoding Long Options in the
Dynamic Host Configuration Protocol (DHCPv4)", RFC 3396,
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November 2002.
[RFC3484] Draves, R., "Default Address Selection for Internet
Protocol version 6 (IPv6)", RFC 3484, February 2003.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
10.2. 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-12 (work in
progress), July 2010.
[I-D.ietf-softwire-dual-stack-lite]
Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
Stack Lite Broadband Deployments Following IPv4
Exhaustion", draft-ietf-softwire-dual-stack-lite-06 (work
in progress), August 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.
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
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Dan Wing
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, California 95134
USA
Email: dwing@cisco.com
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