1. LUMP: Location-to-URL mapping draft-schulzrinne-ecrit-lump
Henning Schulzrinne
Columbia University
Dept. of Computer Science
ECRIT interim meeting - Washington, DC - Feb. 2006

2. LUMP: Mapping service URNs + locations to URLs
Common problem:
{geo or civic location, service}  set of URLs
e.g., {Broadway/NY, “911”} 
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

3. LUMP: Location-to-URL Mapping
VSP1
cluster serving VSP1
replicate
root information
cluster
serves VSP2
123 Broad Ave
Leonia
Bergen County
NJ US
root
nodes NJ US NY US
search
referral
Bergen County
NJ US
Leonia
NJ US
ECRIT interim meeting - Washington, DC - Feb. 2006

4. LUMP architecture G G G G G T2 (.de) T3 T1 (.dk) (.us) tree guide
T1: .us
T2: .de
broadcast (gossip) G
resolver T2
(.de)
seeker
313 Westview
Leonia, NJ US T3
(.dk) T1
(.us)
ECRIT interim meeting - Washington, DC - Feb. 2006
Leonia, NJ 

5. ECRIT interim meeting - Washington, DC - Feb. 2006
Caching
Generally, UA caches lookup results
query: “I’m at (X,Y), what’s my PSAP?”
answer: “Your PSAP is 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

6. ECRIT interim meeting - Washington, DC - Feb. 2006
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

7. 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