march 2006ietf65 - ecrit1 emergency service identifiers draft-ietf-ecrit-service-urn-01 henning...
TRANSCRIPT
March 2006 IETF65 - ECRIT 1
Emergency Service Identifiersdraft-ietf-ecrit-service-urn-01
Henning Schulzrinne
Columbia [email protected]
March 2006 IETF65 - ECRIT 2
Open Issues
• Identifying the call post-resolution
• Server resolution
March 2006 IETF65 - ECRIT 3
UA recognition & UA resolution
INVITE sip:[email protected]: urn:service:sosAccept-Contact: *;sip.service="urn:service:sos"
<location>
9-1-1(dial string)
mapping
INVITE sip:[email protected]: urn:service:sosAccept-Contact: *;sip.service="urn:service:sos"
<location>
leonianj.gov
mapping may recurse
location information
DHCPLLDP-MED
March 2006 IETF65 - ECRIT 4
UA recognition & proxy resolution
9-1-1
mapping
INVITE urn:service:sosTo: urn:service:sosAccept-Contact: *;sip.service="urn:service:sos"
<location>
INVITE sip:[email protected]: urn:service:sosAccept-Contact: *;sip.service="urn:service:sos"
<location>
provider.com
March 2006 IETF65 - ECRIT 5
UA recognition & proxy resolution(proxy location determination)
9-1-1
mapping
INVITE urn:service:sosTo: urn:service:sosAccept-Contact: *;sip.service="urn:service:sos"
INVITE sip:[email protected]: urn:service:sosLocation: <location>Accept-Contact: *;sip.service="urn:service:sos"
provider.com
March 2006 IETF65 - ECRIT 6
Proxy recognition & proxy resolution
9-1-1
mapping
INVITE sip:[email protected];user=phoneTo: sip:[email protected];user=phone
INVITE sip:[email protected]: sip:[email protected];user=phoneLocation: <location>Accept-Contact: *;sip.service="urn:service:sos"
provider.com
March 2006 IETF65 - ECRIT 7
Problems with approach
• No authentication call [email protected], mark as emergency call get free call– assumes that IP calls are charged– unlikely that providers will just gateway to E.164
PSAP numbers– if mapping done by outbound proxy, next entity will be
PSAP URL anyway• no home routing for emergency services! (visited service in
IMS) only problem for UA rec/res
– thus, could we punt?
March 2006 IETF65 - ECRIT 8
Call identification alternatives• only trust Accept-Contact from same
trust domain– see P-Asserted-Identity model (RFC
3325) brittle– or use Identity model signed by
outbound proxy• unfortunately, not covered by
– doesn’t help with UA rec/res model!• creating a new header likely to have
similar issues• re-do mapping and ensure that URL
matches– server can learn list of “legal” URLs
after a while– can fail if mapping is dynamic
(advertisement changes)• then just replaces URL
– forces each outbound proxy to do mapping
• check external source that URL is indeed a PSAP
– use draft-ietf-sipping-certs for destination URL, but would need to have a role-based cert “this is a bona-fide PSAP”
• easy to posit, harder to deploy globally• can incur significant delay• but only needed when there’s service
differentiation
• new TLD for PSAPs only
March 2006 IETF65 - ECRIT 9
Resolution: DDDS
• (Most) URNs have a resolution mechanism DDDS1. Extract service part, e.g., “sos.fire”2. Get domain D from local source:
1. DHCP ISP as service provider2. domain part of AOR VSP as service provider3. SIP configuration
3. Resolve NAPTR record for D: example.com.
; order pref flags service regexp replacement IN NAPTR 50 50 "u" "LOST+D2T" "!urn:service:(.*)!http://example.com/map/\1!i" .
March 2006 IETF65 - ECRIT 10
Summary
• Only two (known) open issues:– marking can be separated, if needed– DDDS needs NAPTR expert advice