The State of SIP Application Development Brian Schwarz VP – Engineering RedSky Technologies, Inc.

3 Agenda What is a SIP Application? Survey of standards applying to presence and location Case study – A SIP Application that supports NG911 (SIP calls with location) Challenges we encountered and how we resolved these

4 What is a SIP Application? Leverages the capabilities of SIP, but provides value-added services beyond the delivery of the call Examples: –Call Recording –Unified Communications (UC) –UC with presence and location –Call Center control

5 RedSky’s SIP Application Receives a SIP call without any location data Uses the content of the SIP INVITE to determine the location of the calling device Adds location information either by reference (through a URI) or by value (in a PIDF-LO) to the SIP INVITE Sends the call out, now with embedded location data that can be used to route the call to the appropriate PSAP (911 call center)

6 Presence Standards SIMPLE (SIP Extensions for Presence) –Supported by Microsoft (and others) – –Tight integration with SIP, so presence additions are “seamless” to the existing voice protocols XMPP (Jabber) –Supported by Google (and others) – –Better for “chat only” messaging

7 Location Standards MLP –Mobile Location Protocol –Widely used in existing mobile wireless infrastructure –Supported by OMG (Object Management Group) –XML-based, only allows geo-coded location HELD/PIDF-LO –“HTTP Enabled Location Delivery” & “Presence Information Data Format-Location Object” –Supported by the IETF (Internet Engineering Task Force) –Allows geo-located and civic addressing schemes

8 Case Study – NG911

9 Challenges to SIP Apps: B2BUA vs Proxy Proxy is simpler to develop and test than a B2BUA “Real” function of the RedSky LIS is as a proxy – we’re not changing the original SIP content Only way to implement additions to the INVITE body is through a B2BUA The B2BUA takes on additional requirements in terms of callback routing –Standards say that the FROM address out of the B2BUA should be the address of the B2BUA. How do we route a dropped call back to the originating device?

10 Challenge: Choosing the right SIP stack Roll your own –Longer development time and interop requirements –“Flexibility” in implementing the standards with regard to content Open Source (i.e. JAIN) –Better development time, but still requires “app” infrastructure SipServlets (i.e. GlassFish, BEA) –Fast development, focusing only on the application content –Reduced control over the SIP content

11 Challenge: SIP capabilities abstract data SIP abstracts the actual device making the call –Location Determination – loss of MAC address Port-level discovery uses SNMP queries to the BRIDGE MIB on network switches, matching the MAC address to a port SIP doesn’t communicate the MAC address – how to do port- level discovery? –Shared line Multiple devices can share the same SIP URI When dialing 911 – which device made the call?

12 Challenge: SIP Data Even if SIP entities (i.e. clients, proxies and B2BUAs) can interoperate, the content of the SIP data can be crucial to an application Requires careful design of the data content within the SIP messaging to ensure the application will function properly

13 Questions?