doc.: IEEE /313r1 Submission March 2004 Beach & Klein, Symbol Technologies, Inc.Slide 1 Typical Access Point Architectures John Klein Symbol Technologies, Inc. Bob Beach Symbol Technologies, Inc.

doc.: IEEE /313r1 Submission March 2004 Beach & Klein, Symbol Technologies, Inc.Slide 2 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 –Distribution of Access Point Functions Questions and Discussion

doc.: IEEE /313r1 Submission March 2004 Beach & Klein, Symbol Technologies, Inc.Slide 3 Part 1 WLAN Architecture and Functional Decomposition

doc.: IEEE /313r1 Submission March 2004 Beach & Klein, Symbol Technologies, Inc.Slide 4 Typical WLAN Topology 802.1Q trunk links Access Switches Distribution Switches

doc.: IEEE /313r1 Submission March 2004 Beach & Klein, Symbol Technologies, Inc.Slide 5 Typical Access Point Hardware Architecture (Dual Radio) D/A A/D RF Circuit Baseband / MAC MAC / PHY Control CPU D/A A/D RF Circuit Baseband / MAC Flash

doc.: IEEE /313r1 Submission March 2004 Beach & Klein, Symbol Technologies, Inc.Slide 6 Radio Driver(s) Typical Access Point Software Architecture (1) Ethernet PHYRadio PHYRS-232 Port TCP / IP / UDP RS 232 Driver Session Manager Authorization, i, WPA TFTP / FTP SNMP / MIB WEB / HTTP QoS BOOTP / DHCP Client Association, Roaming, Session TMO VLANs Control Manager CLI FW Mgmt Key Mgmt 802.1x RTOS / System Services Flash / Config k d f 802.1Q e 802.1p Telnet Client PPP AP Core Upper Level Lower Level + PHY

doc.: IEEE /313r1 Submission March 2004 Beach & Klein, Symbol Technologies, Inc.Slide 7 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 PPPoE interface from the RS-232 port to the CLI in the Control Manager. Access Point Core is discussed in detail later in this presentation.

doc.: IEEE /313r1 Submission March 2004 Beach & Klein, Symbol Technologies, Inc.Slide 8 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

doc.: IEEE /313r1 Submission March 2004 Beach & Klein, Symbol Technologies, Inc.Slide 9 Access Point Functional Decomposition (3) Session Manager: Handles high level session information for each STA. Keeps status and state. Authorization via 802.1x or other means Handles security key management for each client and BC/MC keys per VLAN / SSID Association and roaming processing (in / out) d and f functionality STA timeout and disassociation due to inactivity Future placeholder for k setup information Client / SSID VLAN information and setup for STA QoS information and setup for STA

doc.: IEEE /313r1 Submission March 2004 Beach & Klein, Symbol Technologies, Inc.Slide 10 Access Point Functional Decomposition (4) Control Manager: Handles external command and 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

doc.: IEEE /313r1 Submission March 2004 Beach & Klein, Symbol Technologies, Inc.Slide 11 RF Transmit Scheduler Access Point Core TCP Interface Receive PHY Encrypt / MIC Decrypt / MIC ACL, Filters, LT Rate Scaling, Beacon Prep Packet Classification and Address Recognition Format Packet (.11 /.3) Probe Requests Queue Manager Transmit PHY Buffer Pool Ingress Queues Receive Queues Channel Access PCF, DCF, HCF, SIFS PSP Poll Packet Data Packets Ack from STA Other Mgmt Pkts Probe Resp Instant Rates Fragmentation Ack Beacons Retries Packet Ack Request STA Data Pkt Scheduler 802.1p e PSP Buffering PSP Data Multi ESS/BSS Other Mgmt Pkts Pkts Session Control Reassembly Acks and Probes Beacons, Start Rates, Other Mgmt Packet CRC Transmit Queues Upper Level MAC Lower Level MAC

doc.: IEEE /313r1 Submission March 2004 Beach & Klein, Symbol Technologies, Inc.Slide 12 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.

doc.: IEEE /313r1 Submission March 2004 Beach & Klein, Symbol Technologies, Inc.Slide 13 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 i Buffers and Prioritizes outbound packets per e and 802.1p rules into Transmit Queues. Buffers PSP packets in response to incoming PSP Poll packets received Formats packets from to or to Filters packets based on Type, ACLs and other filtering rules.

doc.: IEEE /313r1 Submission March 2004 Beach & Klein, Symbol Technologies, Inc.Slide 14 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.

doc.: IEEE /313r1 Submission March 2004 Beach & Klein, Symbol Technologies, Inc.Slide 15 Access Point Core Functional Decomposition (4) Channel Access: Handles all access to the airwaves. Handles CCA, PCF, DCF, and HCF per and e rules. Handles RTS / CTS Handles SIFS

doc.: IEEE /313r1 Submission March 2004 Beach & Klein, Symbol Technologies, Inc.Slide 16 Part 2 Distribution

doc.: IEEE /313r1 Submission March 2004 Beach & Klein, Symbol Technologies, Inc.Slide 17 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

doc.: IEEE /313r1 Submission March 2004 Beach & Klein, Symbol Technologies, Inc.Slide 18 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 Upper Level MAC –Association Management –QoS support –Roaming –Authorization –Buffer Management –Installation/configuration –Host integration –Fragmentation/reassembly –Encryption

doc.: IEEE /313r1 Submission March 2004 Beach & Klein, Symbol Technologies, Inc.Slide 19 Distribution of Access Point Functions (3) UL MACL3 / TCPSessions & Mgmt CAPWAP Split Architecture II (WLAN Switch or Controller) L3 / TCPSessions & Mgmt CAPWAP PHYLL MAC RF Point UL MAC A B C PHYLL MACUL MACL3 / TCPSessions & Mgmt Stand Alone AP (FAT) Split Architecture I (WLAN Switch or Controller) PHYLL MACUL MACL3 / TCPSessions & MgmtPHYLL MACUL MACL3 / TCPSessions & MgmtPHYLL MAC RF Point PHYLL MAC RF Point UL MACPHYLL MAC RF Point UL MACPHYLL MAC RF Point PHYLL MAC RF Point Split Architecture III (WLAN Switch or Controller) Sessions & Mgmt CAPWAP D PHYLL MAC RF Point / Access Point UL MACL3 / TCPPHYLL MAC RF Point / Access Point UL MACL3 / TCPPHYLL MAC RF Point / Access Point UL MACL3 / TCP Variations on a distribution theme

doc.: IEEE /313r1 Submission March 2004 Beach & Klein, Symbol Technologies, Inc.Slide 20 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, QoS, Packet Buffering, etc. –All management and control functions –Located in secure location (computer room, closet, etc) –Less PHY specific

doc.: IEEE /313r1 Submission March 2004 Beach & Klein, Symbol Technologies, Inc.Slide 21 Questions and Answers