Light Weight Access Point Protocol (LWAPP)IETF 57

Pat Calhoun, Airespace

Mobile

AP

AR

Ethernet orUDP

LWAPP

LWAPP Architecture

Why LWAPP?

● At last count, there are at least 6 WLAN switch vendors, plus some of the Ethernet switching incumbents have announced products in this space.

● Most of these products have a proprietary protocol between the AP and the AR (A.K.A WLAN Switch).

● APs are being commoditized, and many AP OEMs see LWAPP as a way to enter the enterprise market - interest is very strong here!

● Standardizing LWAPP would benefit the Internet community by ensuring interoperability between WLAN switches and APs.

LWAPP Goals● Reduction of the amount of protocol code being

executed at the light weight AP.● Centralization of the bridging, forwarding,

authentication, encryption and policy enforcement functions for a WLAN, to apply the capabilities of network processing silicon to the WLAN, as it has already been applied to wired LANs.

● Providing a generic encapsulation and transport mechanism, the protocol may be applied to other access protocols in the future (note: the draft needs work here)

Division of Labor

Mobile

AP

AR

802.11 Control

802.11 Data & Management

Ethernet orUDP

LWAPP Control (signalling) & Data

LWAPP assumes the MAC is split betweenthe AP and the AR, reducing the functionsrequired on the AP.

What does it do?

● LWAPP enables a new architecture for 802.11 infrastructure devices.

● Most of the functionality that is traditionally in the AP can be moved to the centralized AR.

● This gives the AR a greater view of the RF topology, enabling many different types of benefits, such as:– Security. Detecting attacks on a network basis vs. on

a single cell– Mobility. Easier to proactively handle mobility events

LWAPP Components

● LWAPP consists of the following:– Control Channel Management– AR Configuration– Mobile Session Management– Firmware Management– Transport Services– Security

Control Channel Management

● Discovery– The draft currently defines a zero-config dynamic

discovery mechanism for Ethernet and IP (when run in same subnet). The draft proposes different discovery mechanisms, but this area probably needs some work

● AP-AR session establishment– Creates a binding between the AP and the AR. This phase

also includes a key exchange to secure all control messages

● Heatbeat● Key Update

– Periodically update the AP-AR key

AR Configuration

● Configure Response– Allows the AP to securely push its current

configuration to the AR● Configure Update

– Allows the AR to securely push configuration to the AP

● Statistics Update– Allows the AP to send current stats to the AR

● Reset Request– Reboots the AP

Mobile Session Management

● Add Mobile– Pushes a specific rule (and optionally dynamic

TKIP/WEP/AES key) to the AP● Delete Mobile

– Deletes a previous rule (and key)

Firmware Management

● During the AP-AR session establishment phase, the peers exchange firmware versions.

● If the versions are out of sync, this allows the AR to securely download a new image to the AP.

Transport Services

● The LWAPP document includes a transport section, and currently defines two transports:– Ethernet, allows LWAPP to run natively over Layer 2– IP, specifies how LWAPP is run over UDP

● The transport section discusses the following:– Transport specific discovery extensions– Packet Framing– Fragmentation/Reassembly issues

LWAPP Security

● The document currently assumes that all LWAPP peers have a certificate

● During the AP-AR session establishment phase, a session key is exchanged and all control packets are subsequently encrypted using AES-CCM

● A rekey message exists in order to allow the AP (or AR) to create a new session key

Points raised on the mailing list

● Where does encryption occur?● LWAPP discovery over Layer 3● Should LWAPP data messages be secured?● Should we use certificates or shared keys?

LWAPP Mailing List

● The mailing list is accessible at lwapp@frascone.com.