PCP Working Group M. Boucadair
Internet-Draft France Telecom
Intended status: Standards Track R. Penno
Expires: July 16, 2012 Juniper Networks
D. Wing
Cisco
January 13, 2012
DHCP Options for the Port Control Protocol (PCP)
draft-ietf-pcp-dhcp-02
Abstract
This document specifies DHCP (IPv4 and IPv6) options to configure
hosts with Port Control Protocol (PCP) Server addresses. The use of
DHCPv4 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 16, 2012.
Copyright Notice
Copyright (c) 2012 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. IP Address Selection . . . . . . . . . . . . . . . . . . . . . 5
5.1. Serial Queries . . . . . . . . . . . . . . . . . . . . . . 5
5.2. Parallel Queries . . . . . . . . . . . . . . . . . . . . . 5
6. DHCPv6 PCP Server Option . . . . . . . . . . . . . . . . . . . 5
6.1. Format . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.2. Client Behaviour . . . . . . . . . . . . . . . . . . . . . 6
7. DHCPv4 PCP Option . . . . . . . . . . . . . . . . . . . . . . 7
7.1. Format . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.2. Client Behaviour . . . . . . . . . . . . . . . . . . . . . 8
8. Dual-Stack Hosts . . . . . . . . . . . . . . . . . . . . . . . 8
9. Security Considerations . . . . . . . . . . . . . . . . . . . 9
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
10.1. DHCPv6 Option . . . . . . . . . . . . . . . . . . . . . . 9
10.2. DHCPv4 Option . . . . . . . . . . . . . . . . . . . . . . 9
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
12.1. Normative References . . . . . . . . . . . . . . . . . . . 9
12.2. Informative References . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
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1. Introduction
This document defines DHCPv4 [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 name (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 (e.g., Section 6.1.1 of [RFC1123])
are available on the host client.
The use of DHCPv4 or DHCPv6 depends on the PCP deployment scenarios.
2. Terminology
This document makes use of the following terms:
o PCP Server denotes 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 denotes a PCP software instance responsible for issuing
PCP requests to a PCP Server. Refer to [I-D.ietf-pcp-base].
o DHCPv4 refers to the Dynamic Host Configuration Protocol [RFC2131]
for IPv4.
o DHCP refers to both DHCPv4 [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].
o Name is a domain name (as per Section 3.1 of [RFC1035]) that
contains one or more labels. In particular, a PCP name may be
structured as DNS qualified name or be composed of strings such as
can be passed to getaddrinfo (Section 6.1 of [RFC3493]), including
address literals, etc.
3. Rationale
Both IP Address and Name DHCP options have been considered in early
stages of this specification. 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.
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This document defines an option to carry a name rather than an IP
address. This choice 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 server
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 Name 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 Name would be more convenient.
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. IP Address Selection
Resolving the Name conveyed in DHCP PCP Name options may return a
list of IP addresses. This section specifies the behavior to be
followed by the PCP Client to contact its PCP Server.
1. If only one PCP Name option is returned in DHCP: the PCP Client
follows the procedure specified in Section 5.1 if a list of IP
addresses are returned as a result of resolving the name conveyed
in the PCP Name DHCP option.
2. If several PCP Name options are returned in DHCP: the PCP Client
contacts in parallel all PCP Servers as defined in Section 5.2.
For each PCP Name option occurrence, the PCP Client resolves the
conveyed name; if more than one IP address are returned, the PCP
Client follows the procedure specified in Section 5.1.
5.1. Serial Queries
The PCP Client initializes its retransmission timer, RETRY_TIMER, to
2 seconds. The PCP Client sends its PCP message to the PCP Server
and waits 2 seconds for a response. If no response is received, it
doubles the value of RETRY_TIMER, sends another (identical) PCP
message and waits 2*RETRY_TIMER. This procedure is repeated three
(3) times, doubling the value of RETRY_TIMER each time. If no
response is received after four (4) attempts, the PCP Client tries
with the next IP address in its list of PCP Servers. If it has
exhausted its list, the procedure is repeated every fifteen minutes
until the PCP request is successfully answered. If, when sending PCP
requests the PCP Client receives an ICMP error (e.g., port
unreachable, network unreachable) it SHOULD immediately try the next
IP address in the list. Once the PCP Client has successfully
received a response from a PCP Server on that interface, it sends
subsequent PCP requests to that same server until that PCP Server
becomes non-responsive, which causes the PCP client to attempt to re-
iterate the procedure starting with the first PCP Server on its list.
5.2. Parallel Queries
The PCP Client contacts in parallel all the PCP Servers in the IP
addresses list. For each IP address in the list, the PCP Client
follows the procedure specified in Section 7.1 of
[I-D.ietf-pcp-base].
6. 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
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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.
6.1. 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 Name DHCPv6 Option
The fields of the option shown in Figure 1 are as follows:
o Option-code: OPTION_PCP_SERVER (TBA, see Section 10.1)
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].
6.2. 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, it extracts the Name conveyed in each
OPTION_PCP_SERVER option and proceeds to validating it. If more than
one Name is included in a OPTION_PCP_SERVER option occurrence, only
the first instance MUST be used. Then, the DHCPv6 client MUST verify
that the option length does not exceed 255 octets [RFC1035]). The
DHCPv6 client MUST verify the name is properly encoded as detailed in
Section 8 of [RFC3315].
Once the name conveyed in each OPTION_PCP_SERVER option is validated,
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the included Name is passed to the name resolution library (e.g.,
Section 6.1.1 of [RFC1123] or [RFC6055]) to retrieve the
corresponding IP address(es) (IPv4 or IPv6).
The PCP Client MUST follow the procedure specified in Section 5 to
contact its PCP Server(s).
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.
A host may have multiple network interfaces (e.g, 3G, WiFi, etc.);
each configured differently. Each PCP Server learned MUST be
associated with the interface via which it was learned. When an
application issues a PCP request to a PCP Server, the source address
of the request MUST be among those assigned on the interface to which
the destination PCP Server is bound.
7. DHCPv4 PCP Option
7.1. Format
The PCP Server Name DHCPv4 option can be used to configure a name to
be used by the PCP Client to contact a PCP Server. The format of
this option is illustrated in Figure 2.
Code Length PCP Server Domain Name
+-----+-----+-----+-----+-----+-----+-----+--
| TBA | n | s1 | s2 | s3 | s4 | s5 | ...
+-----+-----+-----+-----+-----+-----+-----+--
The values s1, s2, s3, etc. represent the domain name labels in the
domain name encoding.
Figure 2: PCP Server Name DHCPv4 Option
The description of the fields is as follows:
o Code: OPTION_PCP_SERVER (TBA, see Section 10.2);
o Length: Includes the length of the "PCP Server Domain Name" field
in octets; The maximum length is 255 octets.
o PCP Server Domain Name: The domain name of the PCP Server to be
used by the PCP Client when issuing PCP messages. The encoding of
the domain name is described in Section 3.1 of [RFC1035].
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7.2. Client Behaviour
DHCPv4 client expresses the intent to get OPTION_PCP_SERVER by
specifying it in Parameter Request List Option [RFC2132].
If the DHCPv4 client receives more than one OPTION_PCP_SERVER option
from the DHCPv4 server, it extracts the Name conveyed in each
OPTION_PCP_SERVER option and proceeds to validating it. If more than
one Name is included in a OPTION_PCP_SERVER option occurrence, only
the first instance MUST be used. Then, the DHCPv4 client MUST verify
that the option length does not exceed 255 octets [RFC1035]).
Once the name conveyed in each OPTION_PCP_SERVER option is validated,
the included Name is passed to the name resolution library (e.g.,
Section 6.1.1 of [RFC1123] or [RFC6055]) to retrieve the
corresponding IPv4 address(es).
The PCP Client MUST follow the procedure specified in Section 5 to
contact its PCP Server(s).
It is RECOMMENDED to associate a TTL with any address resulting from
resolving the Name conveyed in a OPTION_PCP_SERVER DHCPv4 option when
stored in a local cache. Considerations on how to flush out a local
cache are out of the scope of this document.
A host may have multiple network interfaces (e.g, 3G, WiFi, etc.);
each configured differently. Each PCP Server learned MUST be
associated with the interface via which it was learned. When an
application issues a PCP request to a PCP Server, the source address
of the request MUST be among those assigned on the interface to which
the destination PCP Server is bound.
8. Dual-Stack Hosts
A PCP Server configured using OPTION_PCP_SERVER over DHCPv4 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.
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A Dual-Stack host may receive OPTION_PCP_SERVER via both DHCPv4 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.
9. Security Considerations
The security considerations in [RFC2131], [RFC3315] and
[I-D.ietf-pcp-base] are to be considered.
10. IANA Considerations
10.1. DHCPv6 Option
Authors of this document request the following DHCPv6 option code:
Option Name Value
----------------- -----
OPTION_PCP_SERVER TBA
10.2. DHCPv4 Option
Authors of this document request the following DHCPv4 option code:
Option Name Value
----------------- -----
OPTION_PCP_SERVER TBA
11. Acknowledgements
Many thanks to B. Volz, C. Jacquenet, R. Maglione, D. Thaler, T.
Mrugalski and T. Lemon for their review and comments.
12. References
12.1. 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-21 (work in progress), January 2012.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
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[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.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
12.2. Informative References
[I-D.ietf-behave-lsn-requirements]
Perreault, S., Yamagata, I., Miyakawa, S., Nakagawa, A.,
and H. Ashida, "Common requirements for Carrier Grade NATs
(CGNs)", draft-ietf-behave-lsn-requirements-05 (work in
progress), November 2011.
[RFC1123] Braden, R., "Requirements for Internet Hosts - Application
and Support", STD 3, RFC 1123, October 1989.
[RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J., and W.
Stevens, "Basic Socket Interface Extensions for IPv6",
RFC 3493, February 2003.
[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-
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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.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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