Proxy Mobile IPv6 Extensions to Support Flow Mobility
updates
- rfc-5213 — Proxy Mobile IPv6
Extracted elements (25)
Flow-level information exchange between LMA and MAG is not mandated; the specification only requires the LMA to maintain per-flow state (FMC). Flow-level signaling is defined as optional for cases where the MAG needs to associate flows with QoS paths or inform the MN.
FMI/FMA messages are introduced as separate message types (reusing UPN/UPA from RFC 7077) because the LMA cannot send a PBA without first receiving a PBU; this asymmetry prevents the LMA from proactively signaling flow mobility events to MAGs using the standard PBU/PBA exchange.
When all MN interfaces share a common prefix set, no inter-LMA/MAG signaling is required for flow movement because each MAG already has full routing knowledge for all prefixes; FMI signaling is only needed when different prefix sets are assigned per interface and a flow must be forwarded via a MAG that does not anchor the relevant prefix.
This document updates RFC 5213 (Proxy Mobile IPv6) by extending Section 5.4.1 BCE processing rules to handle the new HI value 6, and requires implementation of RFC 7077 UPN/UPA messages for FMI/FMA; no other aspects of RFC 7077 are required.
Both the MN and the LMA MUST have local policies in place to ensure that packets are forwarded coherently for unidirectional and bidirectional communications during flow mobility.
Each LMA MUST maintain a Flow Mobility Cache (FMC) as a conceptual list of entries separate from the binding cache, containing an entry for each registered flow.
If the LMA wants to convey flow-level information to the MAG, it MUST include a Flow Identification Mobility Option in the FMI (or PBA) for all flows the MAG needs to handle at flow granularity, and each such option MUST include a Traffic Selector Sub-Option.
The decision on IP flow mobility MUST be taken either by the MN or the LMA, but it MUST NOT be taken by both simultaneously in a given scenario and MN.
The FMI message MUST be sent to the new target MAG (the one selected for forwarding the flow), not to the current MAG.
The MAG and the LMA MUST use the IPsec security mechanism mandated by Proxy Mobile IPv6 (RFC 5213) to secure the FMI/FMA signaling defined in this document.
The MN MUST be able to enforce uplink policies to select the correct outgoing interface when simultaneously attached to multiple MAGs.
The Mobility Options field of an FMI MUST contain the MN-ID followed by one or more Home Network Prefix Options; prefixes not present in the message MUST be removed from the set of flow-mobility-enabled prefixes.
When a prefix is moved to a new MAG via FMI and that prefix is not anchored by the target MAG, the MAG MUST NOT advertise the off-link prefix on the MAG-MN point-to-point link.
When flow mobility is triggered by a new MN interface attachment, the LMA MUST include a Home Network Prefix Option with the off-link bit (L) set to one in the PBA for each prefix that needs flow mobility support on the new MAG.
When the FMA Status Code is 0 (Success), the Mobility Options field MUST contain the MN-ID followed by one or more Home Network Prefix Options.
When the MAG sends a PBU with Handoff Indicator value 6 ('Attachment over a new interface sharing prefixes') and the BCE ATT/MN-LL-Identifier does not match, the LMA MUST treat the request as creating a new mobility session sharing the same HNPs as the existing BCE.
The Flow Mobility Acknowledgement (FMA) message is the UPA (Update Notification Ack) message from RFC 7077, sent by the MAG in reply to an FMI, with Status Code 0 (Success), 131 (Reason unspecified), or 132 (MN not attached).
The Flow Mobility Cache (FMC) is a conceptual data structure maintained by each LMA, containing per-flow entries with fields: FID-PRI, FID, Traffic Selector, BID(s), Action (Forward/Drop), and Active/Inactive status; reuses the flow-binding list format from RFC 6089.
The Flow Mobility Initiate (FMI) message is the UPN (Update Notification) message from RFC 7077, sent by the LMA to the MAG with Notification Reason FLOW-MOBILITY (8), carrying Home Network Prefix Options and optionally Flow Identification Mobility Options.
The LMA Binding Cache is extended to allow multiple Proxy Care-of Address (Proxy-CoA) registrations per MN, associating each entry with a BID, BID-PRI, MN-ID, ATT, HNP(s), and Proxy-CoA; reuses RFC 5648 multiple care-of address registration extensions.
New value assigned in the IANA 'Handoff Indicator Option type values' registry: value 6 = 'Attachment over a new interface sharing prefixes', used in PBU to signal that the LMA must assign the same prefix set as existing attachments.
New value assigned in the IANA 'Update Notification Reasons Registry': value 8 = 'FLOW-MOBILITY', used as the Notification Reason in FMI messages to request adding or refreshing flow-mobility-enabled prefixes at a MAG.
New values assigned in the IANA 'Update Notification Acknowledgement Status Registry': 131 = 'Reason unspecified' and 132 = 'MN not attached', used in FMA responses to indicate failure conditions.
The protocol signaling extensions defined in this document share the same security concerns as PMIPv6 (RFC 5213) and RFC 7077 and do not introduce additional security threats beyond those already identified in those specifications; IPsec is mandated for all FMI/FMA signaling.
The Home Network Prefix Option is extended with a new Off-link flag (L) in the Reserved field. When L=1, the MAG treats the conveyed HNP as off-link (not hosted on the MAG-MN interface) but adds it to the routing table for flow mobility; when L=0, the prefix is hosted on-link. The rest of the format is unchanged from RFC 5213.