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 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 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 Boucadair, et al. Expires March 17, 2013 [Page 1] Internet-Draft PCP Server Selection September 2012 (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 include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. 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 Boucadair, et al. Expires March 17, 2013 [Page 2] Internet-Draft PCP Server Selection September 2012 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. Boucadair, et al. Expires March 17, 2013 [Page 3] Internet-Draft PCP Server Selection September 2012 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. Boucadair, et al. Expires March 17, 2013 [Page 4] Internet-Draft PCP Server Selection September 2012 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: Boucadair, et al. Expires March 17, 2013 [Page 5] Internet-Draft PCP Server Selection September 2012 * 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. Boucadair, et al. Expires March 17, 2013 [Page 6] Internet-Draft PCP Server Selection September 2012 [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 Boucadair, et al. Expires March 17, 2013 [Page 7]