Transcript iecrit-2

LUMP: Location-to-URL mapping
draft-schulzrinne-ecrit-lump
Henning Schulzrinne
Columbia University
Dept. of Computer Science
ECRIT interim meeting Washington, DC - Feb. 2006
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LUMP: Mapping service URNs
+ locations to URLs
•
Common problem:
– {geo or civic location, service}  set of URLs
– e.g., {Broadway/NY, “911”}  [email protected]
– also applies to anything from AAA to pizza delivery
•
Service providers don’t trust each other (fully)
– e.g., who gets to include Jerusalem in its map
– service may depend which warlord you belong to 
– can’t wait for UN (or ICANN) to create global emergency
services database
•
Suggested approach: new distributed mapping protocol
– LUMP: location-to-URL mapping protocol
– uses SOAP, but special service URLs
ECRIT interim meeting Washington, DC - Feb. 2006
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LUMP: Location-to-URL Mapping
VSP1
cluster serving VSP1
replicate
root information
cluster
serves VSP2
123 Broad Ave
Leonia
Bergen County
NJ US
NJ
US
sip:[email protected]
root
NY
US
nodes
search
referral
Bergen County
NJ US
Leonia
NJ US
ECRIT interim meeting Washington, DC - Feb. 2006
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LUMP Garchitecture
tree guide
G
G
G
T1: .us
G
broadcast (gossip)
T2: .de
resolver
seeker
313 Westview
Leonia, NJ US
T2
(.de)
T1
T3
(.dk)
(.us)
ECRIT interim meeting Washington, DC - Feb. 2006
Leonia, NJ  sip:[email protected]
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Caching
• Generally, UA caches lookup results
– query: “I’m at (X,Y), what’s my PSAP?”
– answer: “Your PSAP is sip:[email protected] as long as you stay in
polygon (X1,Y1; X2, Y2; …); this is valid for 12 hours”
• almost no impact of node mobility on query frequency
– same for civic: “as long as you stay on Main Street, your town”
• civic only relevant for nomadic users
– actual PSAP coverage area may be larger  just an optimization
• Almost always avoids query during emergency call
– MAY re-query during call
– load distribution via DNS
• given frequency of calls for one resolver, likely to be no DNS caching
anyway
• Further optimization: query with timestamp (or etag) of last answer
– answer: “still the same, thanks for asking”
ECRIT interim meeting Washington, DC - Feb. 2006
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Performance notes
• Use TCP (or TCP/TLS) for reliability
• Expect 1-2 queries/day/client
• Typical: >> 100 queries/second/server
– almost all rows will be cached in memory
• only about 6,000 rows
– one server  8,640,000 queries
– probably N+1 spared
– data center cost: $300/month/server 
$0.0003/user/month (1Mq/day)
ECRIT interim meeting Washington, DC - Feb. 2006
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Implementation status
• Prototype implementation
– includes referrals
– both geo and civic coordinates
– from draft WSDL (with minor fixes)
• Server
– Axis (Apache) SOAP server
– Postgres SQL geo database
• does polygon intersection
• Client
– Java servlet (web page)
– Tcl (for our SIP client)
ECRIT interim meeting Washington, DC - Feb. 2006
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