Mobile Access Gateway (MAG) Multipath Options
Extracted elements (20)
The MAG Identifier option is required alongside the MAG Multipath Binding option in PBU requests so the LMA can uniquely identify the MAG across multiple access paths, which is necessary when the MAG registers CoAs from different access networks (e.g., LTE and WLAN).
The MAG Multipath Binding option carries an Interface Label (If-Label) to identify WAN interface types, allowing both MAG and LMA to consistently mark bindings/tunnels and generate matching application-routing rules (e.g., route HTTP over label '9', fall back to label '11').
This specification deliberately does not define any specific traffic distribution scheme, but identifies per-flow and per-packet distribution as two well-known implementation approaches, noting that per-packet distribution requires care due to reordering, buffering, and application performance impacts from asymmetric link characteristics.
A legacy LMA that does not support this specification will skip the MAG Multipath Binding option and MAG-NAI option and process the rest of the PBU per base PMIPv6 (RFC 5213), and will not include these options in the PBA response.
If the LMA supports multipath capability and enables it for a mobile node's session, the LMA MUST include the Multipath Binding option (without the MAG-NAI option) in the corresponding PBA reply.
If the MAG is not aware of the LMA's multipath capability, it SHOULD first discover that capability by sending PBU packets with multipath on only one path, to prevent the LMA from overwriting a binding from one path with another.
Reserved fields in both the MAG Multipath Binding option and MAG Identifier option MUST be set to zero by the sender and MUST be ignored by the receiver.
The Bulk Re-registration Flag (B) MUST NOT be set to 1 if the Registration Overwrite Flag (O) is set to 1, and vice versa. The O flag MUST be set to 0 in De-Registration requests.
The LMA SHOULD use the CANNOT_SUPPORT_MULTIPATH_BINDING status code when rejecting a PBU from a MAG requesting multipath binding that the LMA cannot support.
The MAG MUST include the MAG Multipath Binding option in each PBU message sent through different WAN interfaces when requesting multipath support, and the MAG Identifier option MUST also be present in the PBU message.
Upon receiving a PBA without the MAG Multipath Binding option (e.g., from a legacy LMA), the MAG SHOULD disable multipath support for the mobile node.
When rejecting a PBU for multipath due to lack of authorization (CANNOT_SUPPORT_MULTIPATH_BINDING), the LMA MUST echo the MAG Multipath Binding option (without the MAG-NAI option) in the PBA message.
A new PBA status code CANNOT_SUPPORT_MULTIPATH_BINDING (value 180) is defined, used by the LMA to reject a PBU from a MAG requesting multipath binding when the LMA does not support multipath binding.
The MAG Identifier option is a new mobility header option (Type 64) used in PBU and PBA messages to convey the MAG's identity. It contains a Subtype field referencing the 'Mobile Node Identifier Option Subtypes' registry and a variable-length Identifier field.
The MAG Multipath Binding (MMB) option is a new mobility header option (Type 63) used in PBU and PBA messages to request multipath support, registering the current CoA as one of multiple CoAs for the MAG, and carrying access network information associated with the CoA.
A new status code CANNOT_SUPPORT_MULTIPATH_BINDING (value 180) is allocated in the IANA 'Status Codes' registry for use in PBA messages, as described in Section 4.3.
Two new entries are allocated in the IANA 'Mobility Options' registry: MAG Multipath Binding (Type 63) defined in Section 4.1, and MAG Identifier (Type 64) defined in Section 4.2.
The multipath capability has no impact on PMIPv6 protocol security. The new mobility header options (MAG Multipath Binding and MAG Identifier) are carried like any other mobility header option per RFC 5213, inheriting its security guidelines. This specification does not weaken PMIPv6 security or introduce new vulnerabilities.
The MAG Identifier option has fields: Type (8-bit, value 64), Length (8-bit), Subtype (8-bit, from 'Mobile Node Identifier Option Subtypes' registry), Reserved (8-bit, must be zero), and Identifier (variable-length, type indicated by Subtype).
The MAG Multipath Binding option is 8 octets (excluding Type and Length fields) with fields: Type (8-bit, value 63), Length (8-bit), If-ATT (8-bit access technology type), If-Label (8-bit interface label), Binding ID (8-bit, values 1-254), Bulk Re-registration Flag B (1-bit), Registration Overwrite Flag O (1-bit), and Reserved (22-bit, must be zero).