Extensions to the Proxy Mobile IPv6 (PMIPv6) Access Network Identifier Option
updates
- rfc-6757 — Access Network Identifier (ANI) Option for Proxy Mobile IPv6
Extracted elements (24)
Civic location is introduced because in indoor WLAN (AP) deployments it is difficult to determine geospatial coordinates, yet many location-based applications only require a civic address (street address or room number). The existing Geo-Location sub-option from RFC 6757 is insufficient for these deployments.
The ANI Update-Timer sub-option is introduced to handle WLC (Wireless LAN Controller) deployments where the MAG is co-located with the WLC rather than individual APs. In such cases, intra-WLC AP roaming is invisible to the LMA, causing ANI information to go stale. The timer lets the LMA control how frequently it receives ANI refreshes without requiring a PBU per AP transition.
The MAG-Group-Identifier is introduced to allow operators to express AP group affiliation (e.g., floor or small building), which serves as a proxy for coarse location and enables group-level policy (QoS, charging, DPI) to be applied by the LMA for all APs in the group.
If the MAG included ANI sub-options in its PBU but receives a successful PBA without an ANI option, the MAG may log the event and, based on local policy, terminate the mobility session, indicating the LMA does not understand the ANI option.
The MAG-Group-Identifier should be unique within an operator network but is not assumed globally unique. In multi-operator domains, it SHOULD be combined with the Operator-Identifier sub-option (RFC 6757) to ensure uniqueness.
If a received PBU does not include the Access Network Information option, the LMA updates the mobility session to remove any previously stored access network information elements.
If the MAG is configured to support the ANI sub-options defined in this specification, it includes the ANI option with those sub-options in all PBU messages (including lifetime-extension and deregistration PBUs) sent to the LMA.
On receiving a PBU with the ANI option, the LMA MUST process the option and update the corresponding fields in the Binding Cache entry. If the option is not understood, the LMA skips it and processes the PBU without those options.
The civic location field in the Civic-Location sub-option SHALL NOT exceed 253 bytes.
The LMA echoes back accepted ANI sub-options in the PBA. The Civic-Location and MAG-Group-Identifier sub-options SHOULD NOT be altered by the LMA; the LMA MAY change the ANI Update-Timer value.
The Reserved field in the Civic-Location sub-option MUST be set to zero when sending and ignored when received.
When the LMA-provided Update-Timer value in the PBA differs from the value the MAG sent in the PBU, the MAG SHOULD use the LMA-provided value.
When the MAG sends a PBU for any reason before the Update-Timer expires (e.g., for a QoS service request), the MAG MUST reset the Update-Timer.
The Civic-Location sub-option is considered very sensitive as it reveals the physical location of the network to which a mobile node is attached. Care must be taken to secure PMIPv6 signaling carrying this sub-option, and provisioning location at the coarsest acceptable granularity is recommended.
The ANI Update-Timer sub-option allows the LMA to control how frequently the MAG sends ANI updates. The MAG proposes a value in the PBU; the LMA may echo, increase, or decrease it in the PBA. A value of 0 means the MAG sends updates immediately upon detecting ANI changes.
The Civic-Location sub-option carries the civic address (street address or building location) of the mobile node as known to the MAG. Binary Encoding (Format=0) follows RFC 4776 Section 3.1 encoding with the first 3 DHCP-specific octets omitted, starting with a two-letter ISO 3166 country code.
The MAG-Group-Identifier sub-option identifies the group affiliation of the MAG within its PMIPv6 domain. The group identifier is not assumed to be globally unique; operators spanning multiple domains SHOULD use it together with the Operator-Identifier sub-option from RFC 6757.
Three new type values are allocated in the IANA registry 'Access Network Information (ANI) Sub-Option Type Values': Civic-Location (type 4), MAG-Group-Identifier (type 5), and ANI Update-Timer (type 6).
Access-network information elements the MAG sends may be dynamically learned over DHCP or other protocols. Without proper security (IPsec, TLS, or equivalent) on the MAG-to-access-point path, exchanged information can be compromised, leading to incorrect policy enforcement at the LMA.
The Civic-Location sub-option exposes sensitive civic location of the mobile node's attachment point. IPsec ESP with confidentiality and integrity protection SHOULD be used to protect this information in PMIPv6 signaling, as specified in RFC 5213. Operators may also choose to provision location only to coarse granularity (e.g., city or province level).
MAG Update-Timer state machine: when ANI parameters change, if the timer has expired the MAG sends a PBU; if not expired, no PBU is sent. When the timer expires, the MAG checks for changes — if changed since last report it sends a PBU; otherwise it does not and the timer remains expired.
ANI Update-Timer Sub-Option (ANI Type=6): 1-byte ANI Type, 1-byte ANI Length (always 2), and a 16-bit unsigned integer Update-Timer in units of 4 seconds; value 0 means immediate updates on ANI change.
Civic-Location Sub-Option (ANI Type=4): 1-byte ANI Type, 1-byte ANI Length, 1-byte Format (0=Binary Encoding per RFC 4776 Section 3.1, omitting first 3 DHCP octets), 1-byte Reserved, followed by civic location data not exceeding 253 bytes.
MAG-Group-Identifier Sub-Option (ANI Type=5): 1-byte ANI Type, 1-byte ANI Length (always 2), and a 3-octet unsigned integer group identifier assigned to a group of MAGs.