PCP Unsupported Family Error
draft-cheshire-pcp-unsupp-family-01

Abstract

The Port Control Protocol allows clients to request mappings in NAT gateways and firewalls. The PCP UNSUPP_FAMILY error code enables PCP servers to inform clients when the requested external address family is not supported.

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

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This Internet-Draft will expire on December 01, 2013.

Copyright Notice

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1. Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in "Key words for use in RFCs to Indicate Requirement Levels" [RFC2119].

2. Introduction

The Port Control Protocol [RFC6887] allows clients to request mappings in NAT gateways and firewalls. A client can request a mapping to an external IPv4 address or to an external IPv6 address. The client signifies which family of external address it desires by the type of address it puts into the Suggested External Address field.

If the client wants an external IPv4 address, then it populates the Suggested External Address field with an IPv4-mapped IPv6 address (the first 80 bits set to zero, the next 16 set to one). This includes the case of the all-zeros IPv4 address (::ffff:0:0).

If the client wants an external IPv6 address, then it populates the Suggested External Address field with a native IPv6 address. This includes the case of the all-zeros IPv6 address (::).

However, some devices may not be able to provide the requested external address family. For example, an IPv4-only NAT cannot provide an external IPv6 address.

Note that while the specific address placed in the Suggested External Address field is merely a suggestion that the PCP server is free to ignore, the address family is not. If the suggested address *family* cannot be provided by this PCP server, then it MUST return a PCP error reply containing the UNSUPP_FAMILY error code.

The ability to provide the requested external address family may depend on the client's internal address. For example, a gateway that supports traditional NAT44, and native IPv6, but not NAT64, is able to provide mappings from an internal IPv4 address to an external IPv4 address, and mappings from an internal IPv6 address to an external IPv6 address, but not mappings from an internal IPv6 address to an external IPv4 address. When such a gateway receives a request to map an internal IPv4 address to an external IPv4 address it MUST return an external IPv4 address, if available, but when it receives a request to map an internal IPv6 address to an external IPv4 address it MUST return an UNSUPP_FAMILY error.

3. IANA Considerations

IANA should allocate the following PCP Result Code:

14

UNSUPP_FAMILY: Unsupported external address family, e.g., IPv6 in a NAT that handles only IPv4. This is a long lifetime error.

4. Security Considerations

This new error code leaks no sensitive information and creates no new security vulnerabilities.

5. Normative References

Author's Address

Table of Contents

• 1. Terminology
• 2. Introduction
• 3. IANA Considerations
• 4. Security Considerations
• 5. Normative References
• Author's Address