The Internet Real-Time Laboratory Henning Schulzrinne April 2002 .
ORBIT: Location- based services Henning Schulzrinne Columbia University.
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Transcript of ORBIT: Location- based services Henning Schulzrinne Columbia University.
![Page 1: ORBIT: Location- based services Henning Schulzrinne Columbia University.](https://reader035.fdocuments.net/reader035/viewer/2022062309/5697bfe31a28abf838cb5423/html5/thumbnails/1.jpg)
ORBIT: Location-based services
Henning Schulzrinne
Columbia University
![Page 2: ORBIT: Location- based services Henning Schulzrinne Columbia University.](https://reader035.fdocuments.net/reader035/viewer/2022062309/5697bfe31a28abf838cb5423/html5/thumbnails/2.jpg)
Location-based services Finding services based on location
physical services (stores, restaurants, ATMs, …) electronic services (media I/O, printer, display, …) not covered here
Using location to improve (network) services communication
incoming communications changes based on where I am configuration
devices in room adapt to their current users awareness
others are (selectively) made aware of my location security
proximity grants temporary access Privacy rules for access to context data
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Location-based services & SIP We’re using SIP (and SIMPLE) as generic protocols
for effecting change (“actuators”)
send MESSAGE to devices distributing event information (“sensors”)
Advantages: people and rooms identified by URIs
sip:[email protected] sip:[email protected]
cross-domain, with extensive security mechanisms domains don’t need to trust each other
scalable to global system many other systems are mostly local
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Location-based services Presence-based approach:
UA publishes location to presence agent (PA) becomes part of general user context other users (human and machines) subscribe to context
call handling and direction location-based anycast (“anybody in the room”) location-based service directory
Languages for location-based services building on experience with our XML-based service
creation languages CPL for user-location services LESS for end system services
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Location information
geospatial longitude, latitude, altitude
civil time zone, country, city, street, room, …
categorical type of location properties of location
privacy (“no audio privacy”) suitability for different communication media
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Determining location
GPS may not be practical (cost, power, topology)
Add location beacons extrapolate based on distance moved
odometer, pedometer, time-since-sighting idea: meet other mobile location beacons
estimate location based on third-party information
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PA
devicecontroller
SUBSCRIBEto each room
SUBSCRIBE to configurationfor users currently in rooms
1. discover room URI2. REGISTER as contact for room URI
tftp
HTTP
Example: user-adaptive device configuration
SLP
“all devices that are in the building”RFC 3082?
802.11 signal strength
location
REGISTERTo: 815cepsrContact: alice@cs
SIP
room 815
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Architectures for (geo) information access Claim: all using protocols fall into one of these categories Presence or event notification
“circuit-switched” model subscription: binary decision
Messaging email, SMS basically, event notification without (explicit) subscription but often out-of-band subscription (mailing list)
Request-response RPC, HTTP; also DNS, LDAP typically, already has session-level access control (if any at all)
Presence is superset of other two
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Presence/Event notification Three places for policy enforcement
subscription binary only policy, no geo information subscriber may provide filter could reject based on filter
(“sorry, you only get county-level information”) greatly improves scaling since no event-level checks needed
notification content filtering, suppression only policy, no geo information
third-party notification e.g., event aggregator can convert models: gateway subscribes to event source,
distributes by email both policy and geo data
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Presence model
subscriptionpolicy
event generatorpolicy
subscriberfilter
rate limiter
change to previousnotification?
for eachwatcher
subscriber (watcher)
SUBSCRIBE
NOTIFY
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Policy rules
There is no sharp geospatial boundary Presence contains other sensitive data
(activity, icons, …) and others may be added Example: future extensions to personal
medical data “only my cardiologist may see heart rate, but
notify everybody in building if heart rate = 0” Thus, generic policies are necessary
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Processing models
Sequential model: for each subscriber, apply rules to new data doesn’t scale well to large groups
Relational database model: re-use indexing and other query optimizations well-defined query and matching semantics e.g., mySQL and PostGres have geo extensions At time of subscription:
SELECT address FROM policies WHERE person=$subscriber (AND now() between(starttime,endtime) OR starttime is null) AND (a3=$a3 or a3 is null) …