Negotiation for IPv6 Datagram Compression Using IPv6 Control Protocol
obsoletes
- rfc-2472 — IP Version 6 over PPP
Extracted elements (11)
IPv6 compression negotiated via IPV6CP is specific to IPv6 datagrams and must not be confused with compression negotiated via the PPP Compression Control Protocol (CCP), which potentially affects all datagrams. This separation keeps IPv6-specific compression distinct from link-layer compression.
This document, together with RFC 5072, obsoletes RFC 2472. However, no protocol changes have been introduced over RFC 2472; the split separates the Interface Identifier parameter (RFC 5072) from the compression parameter (RFC 5172).
Each end of the PPP link MUST separately request the IPv6-Compression-Protocol option if bidirectional compression is desired. By default, compression is not enabled.
IPV6CP uses the same Configuration Option format as defined for LCP (RFC 1661) but with a separate set of options. If a Configuration Option is not included in a Configure-Request packet, the default value for that option is assumed.
The IPv6-Compression-Protocol field values are always the same as the PPP Data Link Layer Protocol field values for the same compression protocol. Assigned values include 0061 for IP Header Compression and 0003 for Robust Header Compression (ROHC).
The IPv6-Compression-Protocol is the only IPV6CP Configuration Option defined in this document. It has Type field value 2 and provides a way to negotiate the use of a specific IPv6 packet compression protocol. It is used to indicate the ability to receive compressed packets.
The registry 'IPv6-Compression-Protocol Types' contains assigned values for IPv6 compression protocols. Future allocations require IETF Consensus per RFC 3818. The RFC reference for this registry has been updated to RFC 5172.
The registry 'PPP IPV6CP CONFIGURATION OPTIONS' maintained by IANA includes the IPv6-Compression-Protocol option with Type value 2. The RFC reference for this entry has been updated to RFC 5172.
Lack of proper link security such as authentication prior to data transfers may enable man-in-the-middle attacks resulting in loss of data integrity and confidentiality. Recommended mitigations include Access Control Lists, an authentication protocol (e.g., EAP with MD5), and an encryption control protocol for negotiating cipher suites.
Use of the MD5 authentication method exposes the link to replay attacks, where an attacker could intercept and replay a station's identity and password hash to gain network access. Implementers are advised to consult RFC 3748 for a generic threat model and framework for selecting appropriate authentication methods.
The IPv6-Compression-Protocol Configuration Option has a Type field (1 octet, value 2), a Length field (1 octet, minimum value 4), a 2-octet IPv6-Compression-Protocol field indicating the desired compression protocol, and a variable-length Data field containing protocol-specific additional data.