March 2004 doc IEEE 802 11 04313 r

March 2004 doc. : IEEE 802. 11 -04/313 r 1 Typical Access Point Architectures John Klein Symbol Technologies, Inc. Jklein@sj. symbol. com Submission Bob Beach Symbol Technologies, Inc. bobb@sj. symbol. com 1 Beach & Klein, Symbol Technologies, Inc.

March 2004 doc. : IEEE 802. 11 -04/313 r 1 Outline of presentation • Part 1 – WLAN Architecture and Functional Decomposition – – – Typical WLAN Topology Typical Access Point Hardware Architecture Typical Access Point Software Architecture Access Point Functional Decomposition Access Point Core Details Access Point Core Functional Decomposition • Part 2 – Distribution of Access Point Functions • Questions and Discussion Submission 2 Beach & Klein, Symbol Technologies, Inc.

March 2004 doc. : IEEE 802. 11 -04/313 r 1 Part 1 WLAN Architecture and Functional Decomposition Submission 3 Beach & Klein, Symbol Technologies, Inc.

March 2004 doc. : IEEE 802. 11 -04/313 r 1 Typical WLAN Topology Distribution Switches 802. 1 Q trunk links Access Switches Submission 4 Beach & Klein, Symbol Technologies, Inc.

March 2004 doc. : IEEE 802. 11 -04/313 r 1 Typical Access Point Hardware Architecture (Dual Radio) RF Circuit D/A A/D 802. 11 Baseband / MAC Flash Submission 802. 3 MAC / PHY Control CPU 5 Beach & Klein, Symbol Technologies, Inc.

March 2004 doc. : IEEE 802. 11 -04/313 r 1 Typical Access Point Software Architecture (1) Association, Roaming, Session TMO VLANs Qo. S TCP / IP / UDP Control Manager Session Manager RTOS / System Services Upper Level Key Mgmt 802. 1 x 802. 11 k 802. 11 d 802. 11 f 802. 1 Q 802. 11 e 802. 1 p Authorization, 802. 11 i, WPA TFTP / FTP WEB / HTTP SNMP / MIB CLI FW Mgmt Flash / Config BOOTP / DHCP Client PPP Telnet Client RS 232 Driver AP Core Lower Level + PHY Submission Ethernet PHY Radio. Driver(s) PHY 6 RS-232 Port Beach & Klein, Symbol Technologies, Inc.

March 2004 doc. : IEEE 802. 11 -04/313 r 1 Access Point Functional Decomposition (1) • PHY: Ethernet PHY, Radio PHY, represent interfaces to • the respective hardware for data path and control of the HW interface. • RS 232 Driver interfaces to the RS 232 port out of the fast path AP Core • PPP provides a PPP or sometimes a PPPo. E interface from the RS-232 port to the CLI in the Control Manager. • Access Point Core is discussed in detail later in this presentation. Submission 7 Beach & Klein, Symbol Technologies, Inc.

March 2004 doc. : IEEE 802. 11 -04/313 r 1 Access Point Functional Decomposition (2) • TCP/ IP / UDP Stack: Standard TCP stack for • handling IP and UDP traffic. Minor changes for some routing functions are possible. • BOOTP / DHCP Client handles DHCP and BOOTP Services from servers. Vendor specific options for FW download, ACL, Filters, and Configuration download. • Telnet Client interfaces the CLI from the Command Manager to the Ethernet interface Submission 8 Beach & Klein, Symbol Technologies, Inc.

March 2004 doc. : IEEE 802. 11 -04/313 r 1 Access Point Functional Decomposition (3) • Session Manager: Handles high level session • information for each STA. Keeps status and state. • Authorization via 802. 1 x or other means • Handles security key management for each client and BC/MC keys per VLAN / SSID • Association and roaming processing (in / out) • 802. 11 d and 802. 11 f functionality • STA timeout and disassociation due to inactivity • Future placeholder for 802. 11 k setup information • Client / SSID VLAN information and setup for STA • Qo. S information and setup for STA Submission 9 Beach & Klein, Symbol Technologies, Inc.

March 2004 doc. : IEEE 802. 11 -04/313 r 1 Access Point Functional Decomposition (4) • Control Manager: Handles external command • control interfaces for the AP. • TFTP / FTP are used for downloading FW, configuration files, ACLs, as well as offloading configurations and debug dumps • WEB / HTTP, SNMP / MIB, and CLI are used to get and set AP configuration parameters and collect runtime information and statistics • FW Mgmt manages burning of new FW into the AP • Flash / Config handles configuration data on the secondary storage device Submission 10 Beach & Klein, Symbol Technologies, Inc.

Access Point Core TCP Interface March 2004 doc. : IEEE 802. 11 -04/313 r 1 Beacons, Start Rates, Other Mgmt Upper Level MAC ACL, Filters, LT Rate Scaling, Beacon Prep 802. 3 Pkts Session Control STA Data Pkt Scheduler Format Packet (. 11 /. 3) 802. 11 Pkts 802. 1 p 802. 11 e PSP Buffering Encrypt / MIC Decrypt / MIC Packet Ack Request Transmit. Queues Transmit Channel Access PCF, DCF, HCF, SIFS Transmit PHY Other Mgmt Beacons PSP Data Fragmentation Instant Rates 11 Multi ESS/BSS Buffer Pool Ack Submission Queue Manager Probe Resp Receive PHY Acks and Probes Retries PSP Poll Packet CRC Probe Requests Ack from STA Reassembly Data Packets Other Mgmt Pkts Lower Level MAC Packet Classification and Address Recognition Ingress Queues Receive RF Transmit Scheduler Beach & Klein, Symbol Technologies, Inc.

March 2004 doc. : IEEE 802. 11 -04/313 r 1 Access Point Core Functional Decomposition (1) • Receive and Transmit queues and Queue Manager / Free buffer pool: Nothing particularly interesting here except that there are multiple queues per ESS/BSS and per STA. • Lower Level Receive Side: handles address recognition and packet classification for inbound packets. Routes packets to the proper target destination based on classification. Reassembles inbound fragments. Received Acks and Probe requests from STAs are immediately sent to the RF Transmit scheduler. Data packets, PSP Polls, and Management packets are pushed up the stack to the Upper Level. Submission 12 Beach & Klein, Symbol Technologies, Inc.

March 2004 doc. : IEEE 802. 11 -04/313 r 1 Access Point Core Functional Decomposition (2) • Upper Level - Various Functions: Handles incoming and outgoing bridging functions. • Keeps Long Term Rate Scaling information and calculates • start rates based on time and historical performance information from the RF TX Scheduler. • Prepares Beacons that include PSP, Load and TIMS per ESS / BSS • Handles Encryption / Decryption and MIC per 802. 11 i • Buffers and Prioritizes outbound packets per 802. 11 e and 802. 1 p rules into Transmit Queues. • Buffers PSP packets in response to incoming PSP Poll packets received • Formats packets from 802. 3 to 802. 11 or 802. 11 to 802. 3 • Filters packets based on Type, ACLs and other filtering rules. Submission 13 Beach & Klein, Symbol Technologies, Inc.

March 2004 doc. : IEEE 802. 11 -04/313 r 1 Access Point Core Functional Decomposition (3) • Lower Level Transmit Side: Handles all outbound per packet traffic. • Uses start rate information and makes instantaneous • Transmit rate changes. Feeds back info to Long Term Rate Calculation Algorithm. • Handles instantaneous packet Acks, multiple Probe Responses per ESS / BSS • Schedules and sends out Beacons per BSS • Sends out PSP data packets to waiting PSP STAs as well as other data packets to proper ESS / BSS as they arrive from packet scheduler. • Handles packet level retries, and back offs per packet. • Fragments large packets into smaller chunks per fragmentation rules. Submission 14 Beach & Klein, Symbol Technologies, Inc.

March 2004 doc. : IEEE 802. 11 -04/313 r 1 Access Point Core Functional Decomposition (4) • Channel Access: Handles all access to the airwaves. • Handles CCA, PCF, DCF, and HCF per 802. 11 and 802. 11 e rules. • • Handles RTS / CTS • Handles SIFS Submission 15 Beach & Klein, Symbol Technologies, Inc.

March 2004 doc. : IEEE 802. 11 -04/313 r 1 Part 2 Distribution Submission 16 Beach & Klein, Symbol Technologies, Inc.

March 2004 doc. : IEEE 802. 11 -04/313 r 1 Distribution of Access Point Functions (1) • PHY Level • Antenna and / or Radio + Antenna • Lower Level MAC functions have strong real time demands • Must be accomplished in micro/milliseconds • Upper Level MAC functions have strong application dependencies • User or STA application determines policy, very loose timing. • AP Control Management functions • Some functions can be placed in either category • Essentially these are implementation choices • AP and STA often mirror one another’s functions • Beacon/TIM (AP) and PSP support (STA) • Roaming: AP supplies data, SAT acts on it • RTS/CTS Submission 17 Beach & Klein, Symbol Technologies, Inc.

March 2004 doc. : IEEE 802. 11 -04/313 r 1 Distribution of Access Point Functions (2) • Lower Level MAC – CRC – Channel Access – Timeout/retransmission – Packet Acknowledgements – Header Processing – Rate Control – RTS/CTS packets – PSP Support – Beacon/TIM Processing – Interface to PHY Submission • Upper Level MAC – Association Management – Qo. S support – Roaming – Authorization – Buffer Management – Installation/configuration – Host integration – Fragmentation/reassembly – Encryption 18 Beach & Klein, Symbol Technologies, Inc.

March 2004 doc. : IEEE 802. 11 -04/313 r 1 Distribution of Access Point Functions (3) Variations on a distribution theme A Split Architecture I (WLAN Switch or Controller) Sessions & Mgmt L 3 / TCP Split Architecture II (WLAN Switch or Controller) Sessions & Mgmt Split Architecture III (WLAN Switch or Controller) Submission CAPWAP D L 3 / TCP UL MAC CAPWAP C Sessions & Mgmt CAPWAP B Sessions & Mgmt L 3 / TCP UL MAC LL MAC PHY Sessions Stand Alone & APMgmt (FAT) L 3 / TCP UL MAC LL MAC PHY RF LL Point RF Point UL MAC LL MAC PHY RF UL Point RF Point L 3 / TCP UL MAC LL MAC PHY / TCP ULPoint MAC LL MAC PHY RF L 3 Point / Access RF Point / Access Point 19 Beach & Klein, Symbol Technologies, Inc.

March 2004 doc. : IEEE 802. 11 -04/313 r 1 Distributing Access Point Functions (4) • AP Functional Distribution can happen in one device or across several devices on the network. – Stand Alone Access Points (FAT APs) – Wireless Switch or Controller with RF Points (Thin APs) • Wireless Switch or Controller – Splits Upper Level MAC and Lower Level MAC between RF Points and Wireless Switch or Controller devices – Devices are connected via wired Ethernet infrastructure • RF Points provide PHY and Lower MAC Functions – provides RF coverage for multiple PHYs – PHY specific, POE • Wireless Switch provides Upper MAC Functions – Plus: Security, Qo. S, Packet Buffering, etc. – All management and control functions – Located in secure location (computer room, closet, etc) – Less PHY specific Submission 20 Beach & Klein, Symbol Technologies, Inc.

March 2004 doc. : IEEE 802. 11 -04/313 r 1 Questions and Answers Submission 21 Beach & Klein, Symbol Technologies, Inc.