PCP Working Group M. Boucadair
Internet-Draft France Telecom
Intended status: Standards Track R. Penno
Expires: March 12, 2012 Juniper Networks
D. Wing
Cisco
September 09, 2011
DHCP and DHCPv6 Options for the Port Control Protocol (PCP)
draft-ietf-pcp-dhcp-00
Abstract
This document specifies DHCP (IPv4 and IPv6) options to configure
hosts with Port Control Protocol (PCP) Server addresses. The use of
IPv4 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 March 12, 2012.
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
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
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Consistent NAT and PCP Configuration . . . . . . . . . . . . . 4
5. DHCPv6 PCP Server Option . . . . . . . . . . . . . . . . . . . 5
5.1. Format . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.2. Client Behaviour . . . . . . . . . . . . . . . . . . . . . 5
5.3. Server Behaviour . . . . . . . . . . . . . . . . . . . . . 6
6. IPv4 DHCP PCP Option . . . . . . . . . . . . . . . . . . . . . 6
6.1. Format . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.2. Server Behaviour . . . . . . . . . . . . . . . . . . . . . 8
6.3. Client Behaviour . . . . . . . . . . . . . . . . . . . . . 8
7. Dual-Stack Hosts . . . . . . . . . . . . . . . . . . . . . . . 9
8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
11.1. Normative References . . . . . . . . . . . . . . . . . . . 10
11.2. Informative References . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
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1. Introduction
This document defines IPv4 DHCP [RFC2131] and DHCPv6 [RFC3315]
options which can be used to provision PCP Server [I-D.ietf-pcp-base]
reachability information; more precisely it defines DHCP options to
convey a Fully Qualified Domain Name (FQDN, as per Section 3.1 of
[RFC1035]) of PCP Server(s). In order to make use of these options,
this document assumes appropriate name resolution means (see Section
6.1.1 of [RFC1123]) are available on the host client.
The use of IPv4 DHCP or DHCPv6 depends on the PCP deployment
scenarios.
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 with
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 refers to both IPv4 DHCP [RFC2131] and DHCPv6 [RFC3315].
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].
3. Rationale
Both IP Address and Name 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 Name option
is maintained within this document.
This choice of defining the PCP Name option rather than the IP
address is motivated by operational considerations: In particular,
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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 Carrier Grade NATs (CGNs,
[I-D.ietf-behave-lsn-requirements])) to meet an increase of customer
base. Operations related to the introduction of these new devices
(e.g., addressing, redirection, etc.) are 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 [RFC6146] might be suitable for
load-balancing purposes;
o For the DS-Lite case [RFC6333], if the encapsulation mode is used
to send PCP messages, an IP address may be used since the AFTR
selection is already done via the AFTR_NAME DHCPv6 option
[RFC6334]. 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.
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 transmitted by the host or any terminal
belonging to the same realm (e.g., DHCP client is embedded in a CP
router). 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.
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5. DHCPv6 PCP Server Option
This DHCPv6 option conveys a domain name to be used to retrieve the
IP addresses of PCP Server(s). Appropriate name resolution queries
should be issued to resolve the conveyed name. For instance, in the
context of a DS-Lite architecture [RFC6333], the retrieved address
may be an IPv4 address or an IPv4-mapped IPv6 address [RFC4291], and
in the case of NAT64 [RFC6146] 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 9)
o Option-length: 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 domain name is encoded as specified
in Section 8 of [RFC3315]. Any possible future updates to Section
8 of [RFC3315] also apply to this option.
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 Name option as described in Section 22.7 of [RFC3315] (i.e.,
include OPTION_PCP_SERVER on its OPTION_ORO). 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, only the first instance of that option MUST
be used.
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Upon receipt of an OPTION_PCP_SERVER option, the DHCPv6 client MUST
verify that the option length does not exceed 255 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 included Name is passed to the name resolution library (see
Section 6.1.1 of [RFC1123] or [RFC6055]) to retrieve the
corresponding IP address (IPv4 or IPv6). If more than one IPv6/IPv4
address are retrieved, the PCP Client MUST use the procedure defined
in [I-D.ietf-pcp-base] for address selection.
It is RECOMMENDED to associate a TTL with any address resulting from
resolving the Name 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.
If OPTION_PCP_SERVER option is requested by the DHCPv6 client, the
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 255 octets.
6. IPv4 DHCP PCP Option
6.1. Format
The PCP Server IPv4 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 IPv4 DHCP option codes and in order to
anticipate future PCP-related IPv4 DHCP options, the proposed option
uses a sub-option field.
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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 2: IPv4 DHCP PCP Option
The description of the fields is as follows:
o Code: OPTION_PCP_SERVER (TBA, see Section 9);
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 IPv4 DHCP
option. The format of each sub-option follows the structure shown
in Figure 3.
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 an FQDN of the PCP Server
to be used by the PCP Client when issuing PCP messages.
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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 Section 3.1 of [RFC1035].
A side 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). In such case, it is RECOMMENDED to
use [RFC3396].
6.2. Server Behaviour
IPv4 DHCP server MUST NOT provide this option, unless the client
requested it in Parameter Request List Option.
If OPTION_PCP_SERVER option is requested by the IPv4 DHCP client, the
IPv4 DHCP server MUST NOT send more than one OPTION_PCP_SERVER option
and more than one OPTION_PCP_SERVER_D sub-option in the response.
The IPv4 DHCP server MUST include only one FQDN in a
OPTION_PCP_SERVER_D sub-option.
6.3. Client Behaviour
IPv4 DHCP client expresses the intent to get OPTION_PCP_SERVER by
specifying it in Parameter Request List Option [RFC2132].
If the IPv4 DHCP client receives more than one OPTION_PCP_SERVER
option from the IPv4 DHCP server, only the first instance of that
option MUST be used. If the selected OPTION_PCP_SERVER includes more
than one OPTION_PCP_SERVER_D sub-option, only the first instance of
that option MUST be used.
When the PCP Server Domain Name Sub-option is used, the client
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invokes the underlying name resolution library (see Section 6.1.1 of
[RFC1123] or [RFC6055]) to retrieve the IPv4 address(es) of the PCP
server(s).
7. Dual-Stack Hosts
A PCP Server configured using OPTION_PCP_SERVER over IPv4 DHCP is
likely to be resolved to IPv4 address(es).
A PCP Server configured using OPTION_PCP_SERVER over DHCPv6 may be
resolved to IPv4 address(es) (e.g., DS-Lite [RFC6333]) or IPv6
address(es) (e.g., NAT64 [RFC6146], IPv6 firewall [RFC6092], NPTv6
[RFC6296]).
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.
A Dual-Stack host may receive OPTION_PCP_SERVER via both IPv4 DHCP
and DHCPv6. The content of these OPTION_PCP_SERVER options may refer
to the same or distinct PCP Servers. This is deployment-specific and
as such it is out of scope of this document.
8. Security Considerations
The security considerations in [RFC2131], [RFC3315] and
[I-D.ietf-pcp-base] are to be considered.
9. IANA Considerations
Authors of this document request the following DHCPv6 option code:
OPTION_PCP_SERVER
Authors of this document request the following IPv4 DHCP option code:
OPTION_PCP_SERVER
Authors of this document request also to create a sub-option registry
for OPTION_PCP_SERVER option; a code for the following sub-option is
requested:
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OPTION_PCP_SERVER_D
10. Acknowledgements
Many thanks to B. Volz, C. Jacquenet, R. Maglione, D. Thaler and T.
Mrugalski for their review and comments.
11. References
11.1. Normative References
[I-D.ietf-pcp-base]
Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P.
Selkirk, "Port Control Protocol (PCP)",
draft-ietf-pcp-base-13 (work in progress), July 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.
[RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, 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,
November 2002.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
11.2. Informative References
[I-D.ietf-behave-lsn-requirements]
Perreault, S., Yamagata, I., Miyakawa, S., Nakagawa, A.,
and H. Ashida, "Common requirements for Carrier Grade NAT
(CGN)", draft-ietf-behave-lsn-requirements-03 (work in
progress), August 2011.
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[RFC1123] Braden, R., "Requirements for Internet Hosts - Application
and Support", STD 3, RFC 1123, October 1989.
[RFC6055] Thaler, D., Klensin, J., and S. Cheshire, "IAB Thoughts on
Encodings for Internationalized Domain Names", RFC 6055,
February 2011.
[RFC6092] Woodyatt, J., "Recommended Simple Security Capabilities in
Customer Premises Equipment (CPE) for Providing
Residential IPv6 Internet Service", RFC 6092,
January 2011.
[RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers", RFC 6146, April 2011.
[RFC6296] Wasserman, M. and F. Baker, "IPv6-to-IPv6 Network Prefix
Translation", RFC 6296, June 2011.
[RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
Stack Lite Broadband Deployments Following IPv4
Exhaustion", RFC 6333, August 2011.
[RFC6334] Hankins, D. and T. Mrugalski, "Dynamic Host Configuration
Protocol for IPv6 (DHCPv6) Option for Dual-Stack Lite",
RFC 6334, August 2011.
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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