Networking over Bluetooth

m s s s Networking over Bluetooth: overview and issues Pravin Bhagwat Mobile Networking Group IBM T. J. Watson Research http://www.research.ibm.com/people/p/pravin pravinb@us.ibm.com IAB Wireless Workshop Feb 29 - March 2, 2000 Sunnyvale, CA Bluetooth  A cable replacement technology  1 Mb/s symbol rate  Range 10+ meters  Single chip radio + baseband Why not use Wireless LANs? - power - cost  at low power & low price point 02/29/00 P. Bhagwat (IBM Research) 2 Value proposition of Bluetooth Cordless headset mouse Cell phone Data access point Cable replacement Internet access Ad hoc networking 02/29/00 P. Bhagwat (IBM Research) 3 Bluetooth working group history  February 1998: The Bluetooth SIG is formed  promoter company group: Ericsson, IBM, Intel, Nokia, Toshiba  May 1998: The Bluetooth SIG goes “public”  July 1999: 1.0A spec (>1,500 pages) is published  December 1999: ver. 1.0B is released  December 1999: The promoter group increases to 9  3Com, Lucent, Microsoft, Motorola  February 2000: There are 1,500+ adopters  adopters "enjoy" royalty free use of the Bluetooth technology  products must pass Bluetooth certification 02/29/00 P. Bhagwat (IBM Research) 4 New Applications 02/29/00 P. Bhagwat (IBM Research) 5 Synchronization User benefits  Automatic synchronization of calendars, address books, business cards  Push button synchronization  Proximity operation 02/29/00 P. Bhagwat (IBM Research) 6 Cordless Headset Cordless headset User benefits  Multiple device access  Cordless phone benefits  Hand’s free operation 02/29/00 P. Bhagwat (IBM Research) 7 Usage scenarios examples  Data Access Points  Synchronization  Headset  Conference Table  Cordless Computer  Business Card Exchange  Instant Postcard  Computer Speakerphone 02/29/00 P. Bhagwat (IBM Research) 8 Bluetooth Specifications 02/29/00 P. Bhagwat (IBM Research) 9 Bluetooth Stack Applications SDP IP RFCOMM Data Audio L2CAP Link Manager Single chip with RS-232, USB, or PC card interface Baseband RF  A hardware/software/protocol description  An application framework 02/29/00 P. Bhagwat (IBM Research) 10 Interoperability & Profiles  A profile represents a default solution for a usage model  Vertical slice through the protocol stack  Basis for interoperability and logo requirements  Each Bluetooth device supports one or more profiles 02/29/00 P. Bhagwat (IBM Research) 11 Technical Overview 02/29/00 P. Bhagwat (IBM Research) 12 Bluetooth Radio Specification Applications SDP IP RFCOMM Data Audio L2CAP Link Manager Baseband RF 02/29/00 P. Bhagwat (IBM Research) 13 Radio  Low Cost  Single chip radio (minimize external components)  Today’s technology  Time divison duplex  Low Power  Standby modes  Low voltage RF Sniff, Hold, Park  Robust Operation  Fast frequency hopping  Strong interference protection  Fast ARQ  Robust access code  Forward header correction 1600 hops/sec 02/29/00 P. Bhagwat (IBM Research) 14 Radio 0 dBm Tx power -20 Rx power @ 10 cm  Allow low cost low IF  Trade sensitivity for integration  One chip radio is possible -70 -91 Rx power @ 10m Noise floor C/I = 21 dB 02/29/00 P. Bhagwat (IBM Research) 15 Baseband Applications SDP IP RFCOMM Data Audio L2CAP Link Manager Baseband RF 02/29/00 P. Bhagwat (IBM Research) 16 Connection Setup  Inquiry - scan protocol  to lean about the clock offset and device address of other nodes in proximity 02/29/00 P. Bhagwat (IBM Research) 17 Piconet formation  Page - scan protocol  to establish links with nodes in proximity Master Active Slave Parked Slave Standby 02/29/00 P. Bhagwat (IBM Research) 18 Addressing  Bluetooth device address (BD_ADDR)  48 bit IEEE MAC address  Active Member address (AM_ADDR)  3 bits active slave address  all zero broadcast address  Parked Member address (PM_ADDR)  8 bit parked slave address 02/29/00 P. Bhagwat (IBM Research) 19 Piconet channel FH/TDD f1 f2 f3 f4 f5 f6 m s1 s2 625 sec 1600 hops/sec 02/29/00 P. Bhagwat (IBM Research) 20 Multi slot packets FH/TDD f1 f4 f5 f6 m s1 s2 625 sec Data rate depends on type of packet 02/29/00 P. Bhagwat (IBM Research) 21 Packet Format 72 bits 54 bits 0 - 2745 bits Access code Header Payload Synchronization identification Filtering Address Packet Type Flow control ARQ SEQN HEC Error correction 1/3 rate FEC 2/3 rate FEC ARQ scheme for the data Smaller than an ATM cell ! Notice that there is no protocol type field 02/29/00 P. Bhagwat (IBM Research) 22 Physical Link Types  Synchronous Connection Oriented (SCO) Link  slot reservation at fixed intervals  No ARQ, No CRC  FEC (optional)  64 Kbps  Asynchronous Connection-less (ACL) Link  Polling access method  ARQ, CRC  FEC (optional)  Symmetric data rate 108 - 433 Kbps  Asymmetric data rate up to 723 Kbps 02/29/00 P. Bhagwat (IBM Research) 23 Mixed Link Example m SCO ACL ACL SCO ACL ACL SCO ACL ACL s1 s2 02/29/00 P. Bhagwat (IBM Research) 24 Inter piconet communication Cordless headset mouse Cordless headset Cell phone Cell phone Cell phone Cordless headset 25 02/29/00 P. Bhagwat (IBM Research) Scatternet 02/29/00 P. Bhagwat (IBM Research) 26 Scatternet, scenario 2 How to schedule presence in two piconets? Forwarding delay ? Missed traffic? 02/29/00 P. Bhagwat (IBM Research) 27 Link Manager Protocol Applications SDP IP RFCOMM Setup and Management of Baseband connections Data Audio L2CAP LMP • Piconet Management • Link Configuration • Security Link Manager Baseband RF 02/29/00 P. Bhagwat (IBM Research) 28 Link Manager Protocol  Piconet Management  Attach and detach slaves  Master-slave switch  Establishing SCO and ACL links  Handling of low power modes ( Sniff, Hold, Park)  Link Configuration  packet type negotiation  power control  Security functions  Authentication  Encryption 02/29/00 P. Bhagwat (IBM Research) 29 L2CAP Applications SDP IP RFCOMM Logical Link Control and Adaptation Protocol Data • L2CAP provides Audio L2CAP • Protocol multiplexing • Segmentation and Re-assembly • Quality of service negotiation • Group abstraction Link Manager Baseband RF 02/29/00 P. Bhagwat (IBM Research) 30 L2CAP Packet Format (CO) 15 bits 16 bits Length 0 - 64K bytes Payload DCID Baseband packets 02/29/00 Minimum MTU is 48 bytes ! default is 672 bytes ! P. Bhagwat (IBM Research) 31 L2CAP Packet Format (CL) 15 bits 16 bits Length 0 - 64K bytes PSM Payload DCID Baseband packets 02/29/00 P. Bhagwat (IBM Research) 32 Serial Port Emulation using RFCOMM Applications SDP IP RFCOMM Data Audio L2CAP Link Manager Baseband RF Serial Port emulation on top of a packet oriented link • Similar to HDLC • For supporting legacy apps 02/29/00 P. Bhagwat (IBM Research) 33 Bluetooth Service Discovery Protocol Applications SDP IP RFCOMM Data Audio L2CAP Link Manager Baseband RF 02/29/00 P. Bhagwat (IBM Research) 34 Example usage of SDP  Establish L2CAP connection to remote device  Query for services  search for specific class of service, or  browse for services  Retrieve attributes that detail how to connect to the service  Establish a separate (non-SDP) connection to user the service 02/29/00 P. Bhagwat (IBM Research) 35 IP over Bluetooth V 1.0 Applications SDP IP RFCOMM GOALS Data Audio L2CAP Link Manager  Internet access using cell phones  Connect PDA devices & laptop computers to the Internet via LAN access points Baseband RF 02/29/00 P. Bhagwat (IBM Research) 36 LAN access point profile IP Access Point PPP Why use PPP? Security Authentication Access control Efficiency header and data compression Auto-configuration Lower barrier for deployment RFCOMM L2CAP LMP Baseband 37 02/29/00 P. Bhagwat (IBM Research) Inefficiency of layering Palmtop IP PPP rfc 1662 RFCOMM LAN access point IP PPP rfc 1662 RFCOMM packet oriented byte oriented packet oriented Bluetooth Bluetooth  Emulation of RS-232 over the Bluetooth radio link could be eliminated 02/29/00 P. Bhagwat (IBM Research) 38 Terminate PPP at LAN access point Palmtop Access Point IP PPP RFCOMM IP PPP RFCOMM ethernet Bluetooth Bluetooth  PPP server function at each access point  management of user name/password is an issue  roaming is not seamless 02/29/00 P. Bhagwat (IBM Research) 39 L2TP style tunneling Palmtop IP PPP Access Point PPP server IP PPP UDP UDP IP ethernet RFCOMM radio link RFCOMM radio link IP ethernet  Tunneling PPP traffic from access points to the PPP server  1) centralized management of user name/password  2) reduction of processing and state maintenance at each access point  3) seamless roaming 02/29/00 P. Bhagwat (IBM Research) 40 IP over Bluetooth Next steps IP based network connectivity IP over wireless media peer-to-peer connectivity Decentralized techniques for link formulation, naming, addressing, and routing Internet connectivity for non-PC devices Investigation of the right design point for running IP over toasters, light switches, & fire alarms 02/29/00 P. Bhagwat (IBM Research) 41 Research challenges Internet cable modem keyboard mouse Plug-n-play applications Resource Discovery Routing over scatternets Techniques for link formation head set m m s s s Cordless base Palmpilot s PC s m cell phone s Will the current solutions for each layer work in this environment? 02/29/00 P. Bhagwat (IBM Research) 42 What is different in this scenario ? cable modem keyboard mouse PC m m s head set Connection oriented, lowpower link technology Small, multi-hop networks Simple devices s cordless s base s cell phone Palmpilot s s m Isolated network Dynamic network Applications ---> services ----> routing ----> link creation 02/29/00 P. Bhagwat (IBM Research) 43 Link Formation The problem does not exist in most wired/wireless networks x1 x2 y1 x5 y2 Proximity  Link x4 x3 x6 x7 x8 Low power modes require careful use of broadcast Maintaining connectivity in absence of application traffic seems wasteful Hints from higher layer are needed 02/29/00 P. Bhagwat (IBM Research) 44 Routing over Scatternets Nodes must co-operate to forward packets (MANET style protocols) x1 x2 y1 x4 x3 x5 y2 x6 x7 x8 Forwarding at Layer 2 or Layer 3? Bridging or routing ? What interface should be exported to the above layer? Better coupling with the service discovery layer is needed 02/29/00 P. Bhagwat (IBM Research) 45 Service discovery cable modem keyboard mouse PC m m s Need solutions for address allocation, name resolution, service discovery Existing solutions in the Internet depend on infrastructure Judicious use of Multicast/broadcast is needed head set s cordless s base s cell phone Palmpilot s s m These goals are similar to what Zero-conf WG is already working on 02/29/00 P. Bhagwat (IBM Research) 46 Point to ponder Will Zero-conf on top of MANET on top of scatternet construction algorithm solve our problem? Layered and simple, but potential inefficiencies Cross-layer optimizations are worth considering Zero-conf r m r s r s r s r s r m r s MANET Scatternet formation 02/29/00 P. Bhagwat (IBM Research) 47 Final Remarks • Zero-conf and Bluetooth can benefit from each other MANET and Bluetooth can also benefit from • Similarly, each other • A new working group in IETF for IP over Bluetooth ? • Multi-hop wireless networks will force us to reevaluate our assumptions about network layering. Should IRTF start looking into those issues? http://www.research.ibm.com/people/p/pravin 02/29/00 P. Bhagwat (IBM Research) 48