PCP Working Group M. Boucadair
Internet-Draft France Telecom
Intended status: Standards Track R. Penno
Expires: March 17, 2013 D. Wing
Cisco
September 13, 2012
PCP Server Selection
draft-boucadair-pcp-server-selection-00
Abstract
This document specifies the behavior to be followed by the PCP Client
to contact its PCP Server(s) when one or several PCP Names are
configured. Multiple Names may be configured to a PCP Client in some
deployment contexts such as multi-homing.
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
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This Internet-Draft will expire on March 17, 2013.
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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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Name Resolution . . . . . . . . . . . . . . . . . . . . . . . . 3
4. IP Address Selection . . . . . . . . . . . . . . . . . . . . . 4
4.1. Serial Queries . . . . . . . . . . . . . . . . . . . . . . 4
5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5.1. Example 1 . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.2. Example 2 . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.3. Example 3 . . . . . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
9.1. Normative References . . . . . . . . . . . . . . . . . . . 6
9.2. Informative References . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
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1. Introduction
This document specifies the behavior to be followed by the PCP Client
[I-D.ietf-pcp-base] to contact its PCP Server(s) [I-D.ietf-pcp-base]
when receiving one or several PCP Names (e.g., DHCP
[I-D.ietf-pcp-dhcp]). This document is not specific to DHCP; it is
applicable to any mechanism that configures server names.
Multiple Names may be configured to a PCP Client in some deployment
contexts such as multi-homing. It is out of scope of this document
to enumerate all deployment scenarios which require multiple Names to
be configured.
This document assumes appropriate name resolution means (e.g.,
Section 6.1.1 of [RFC1123]) are available on the host client.
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 Name is a domain name 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. Name Resolution
Each configured 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). Then, the PCP Client
MUST follow the procedure specified in Section 4 to contact its PCP
Server(s).
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.
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4. IP Address Selection
This section specifies the behavior to be followed by the PCP Client
to contact its PCP Server(s) when receiving one or several PCP Names:
1. If only one PCP Name is configured: if a list of IP addresses is
returned as a result of resolving the PCP Server Name, the PCP
Client follows the procedure specified in Section 4.1.
2. If several PCP Names are configured: each Name is treated as a
separate PCP Server. Moreover, each Name may be resolved into
one IP address or a list of IP addresses. The PCP Client
contacts in parallel the first IP address of each Name and
follows the procedure specified in Section 4.1 for the list of IP
addresses returned for each Name. Section 5 provides some
examples to illustrate this procedure.
The discovery procedure may result in a PCP Client instantiating
multiple mappings maintained by distinct PCP Servers. The decision
to use all these mappings or delete some of them is deployment-
specific. Only the client can decide whether all the mappings are
needed or only a subset of them.
4.1. 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 Server addresses. 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 address on that interface, it
sends subsequent PCP requests to that same server address 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 address on its list.
5. Examples
The following sub-sections provide three examples to illustrate the
procedure.
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For all these examples, let's suppose pcpserver-x, pcpserver-y and
pcpserver-z are configured as PCP Names.
5.1. Example 1
Let's also suppose:
* IPx1 and IPx2 are returned for pcpserver-x; IPx1 is not reachable.
* IPy1 and IPy2 are returned for pcpserver-y; IPy1 is reachable
* IPz1 and IPz2 are returned for pcpserver-z; IPz1 is reachable
The procedure to contact the PCP Servers is as follows:
* Send PCP requests to all servers: IPx1, IPy1 and IPz1
* Responses are received from IPy1 and IPz1 but not from IPx1
- The request is re-sent to IPx1
- If no response is received after four attempts, the request
is sent to IPx2
5.2. Example 2
Now, if the following conditions are made:
* IPx1 and IPx2 are returned for pcpserver-x; IPx1 is not reachable.
* IPy1 and IPy2 are returned for pcpserver-y; IPy1 is reachable
* IPz1 and IPz2 are returned for pcpserver-z; IPz1 is not reachable
The procedure to contact the PCP Servers lead to the following:
* Send PCP requests to all servers: IPx1, IPy1 and IPz1
* A response is received from IPy1 but not from IPx1 and IPz1
- the requests are re-sent to IPx1 and IPz1
- If no response is received after four attempts, the request
is then sent to IPx2 and IPz2
5.3. Example 3
Let's suppose now that:
* IPx1 and IPx2 are returned for pcpserver-x; IPx1 is not reachable.
* IPy1 and IPy2 are returned for pcpserver-y; IPy1 is not reachable
* IPz1 and IPz2 are returned for pcpserver-z; IPz1 is not reachable
The procedure to contact the PCP Servers is as follows:
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* Send PCP requests to all servers: IPx1, IPy1 and IPz1
* No answer is received for all requests
- the requests are re-sent to IPx1, IPy1 and IPz1
- If no response is received after four attempts, the request
is then sent to IPx2, IPy2 and IPz2
6. Security Considerations
The security considerations in [I-D.ietf-pcp-base] are to be
considered.
7. IANA Considerations
This document does not request any action from IANA.
8. Acknowledgements
TBC.
9. References
9.1. 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-26 (work in progress), June 2012.
[I-D.ietf-pcp-dhcp]
Boucadair, M., Penno, R., and D. Wing, "DHCP Options for
the Port Control Protocol (PCP)", draft-ietf-pcp-dhcp-04
(work in progress), August 2012.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
9.2. Informative References
[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.
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[RFC6055] Thaler, D., Klensin, J., and S. Cheshire, "IAB Thoughts on
Encodings for Internationalized Domain Names", RFC 6055,
February 2011.
Authors' Addresses
Mohamed Boucadair
France Telecom
Rennes, 35000
France
Email: mohamed.boucadair@orange.com
Reinaldo Penno
Cisco
USA
Email: repenno@cisco.com
Dan Wing
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, California 95134
USA
Email: dwing@cisco.com
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