1. DICOM Configuration Robert Horn, Agfa Corporation

2. Supplement 67 • Existing Industry Protocols • NTP (Network Time Protocol) • DHCP (Dynamic Host Configuration Protocol) • DNS (Domain Name System) • LDAP (Lightweight Directory Access Protocol) • Existing Configuration Tools • Existing support databases • DICOM specific information model for LDAP databases

3. DICOM Configuration Goals • Support New Functions • Security and Privacy • Synchronized Multi-device Acquisitions • Reduce Operational Costs • Network Administration • AE-Title management • Service location management • Feature location management

4. Time Synchronization • For • Multi-device simultaneous acquisitions • Cardiac Catheterization laboratory • Coordination • Security Logs, Procedure Logs • Convenience

5. Synchronization Specification • Specify error relative to time reference(s) • Acceptable absolute time error (relative to UTC) • o( 1s ) security logs • o( 100s ) cardiac catheterization • Acceptable synchronization error within a Time Source (0018,1801) (relative to local source) • o( 1s ) security logs • o( 10ms) cardiac catheterization (a few percent of one cycle of a rapidly beating heart).

6. NTP - Network Time Protocol • Widely available • Suitable for both low precision time and high precision time synchronization • SNTP (Simple NTP) clients for low precision and limited capability systems. • Extensively documented and explained on www.ntp.org

7. Accuracy capability of NTP • o(1s) Either client (NTP,SNTP), network capable OS, Internet, GPS, or radio connection • o(250ms) NTP client, interrupt driven OS, NTP clock controls • o(100ms) local network topology • o(10ms) OS clock, OS design • o(1 ms) OS/application design, network topology • o(100 us) Hardware assist, OS/application design • o(10 us) Instrumentation clock, custom OS • o(1 us) Atomic clock, extensive hardware assist

8. How NTP works Query Time Sent (Ta) Response Time Query Received (Ti) Time Response Sent (Tj) Current Time Parameters (TP) Redundant Servers NTP Server Client Provides Old Network Parameters Old Time Parameters Query Response Mathematical Magic happens Client Sets and Fine TunesSystem Clock SNTP performs only the clock setting NTP includes the network delay estimation, optimal estimation mathematics and fine tuning of the system clock. NTP Client NTP clients may utilize redundant servers NTP clients may utilize instrumentation grade pulse generators (e.g. Atomic Clocks)

9. Typical NTP configurations Internet NTP Server GPS Receiver Campus Network NTP Clients Switching Hub Local NTP Server

10. Network admin • DHCP (Dynamic Host Configuration Protocol) • Assigns IP address, hostname • Informs DNS of assignment • Provides routing, NTP, DNS, etc. information to client • DNS (Domain Name System) • Provides hostname to IP lookup services • Provides server location lookup services • LDAP (Lightweight Directory Access Protocol) • Provides simple information directory services

11. DHCP • Widely used • Support stable IP allocation (needed for transition and legacy equipment) • Supports dynamic IP allocation • Understood by IT administrators • Documents network IP configuration in file • Devices only need their "name"

12. DNS • Widely used • Provides translation from hostname to IP • DHCP uses DDNS option to maintain coordination with dynamic IP assignments • RR SRV records provide location of LDAP server

13. LDAP • Widely used (known as Active Directory in Windows) • Simple query oriented network database • Simple information model. Schema provided as part of Supplement 67. • Alternatives examined • CIM: very attractive, but a much larger effort to define and implement. Not yet widely used. • SNMP, DMTF: interesting but deal with different aspects of network administration and management.

14. Locate AE-title (internal operation) LDAP Server Where is AE-X AE-X is at hostname, port Database Where is hostname? DNS Server Hostname is x.y.z.w DICOM Traffic

15. Beyond Finding AE-Titles • Installation and Network Configuration oriented • AE Configuration • Obtain new unique AE-Title • SOP Classes supported (SCU/SCP, Transfer Syntaxes) • IHE Actor • Vendor extension • Device Configuration • Description • Vendor extension • Hospital extension

16. Pre-configured Installation • Large network addition • Multiple vendors • Reduce coordination and scheduling delays • Reduce configuration errors • Reduce staging requirements

17. Pre-configured Installation Vendor A Preparation LDAP Prepared Configurations LDIF IT Organization DHCP Network Planning A A LDIF A Prepared Configurations A B B B Vendor B preparation

18. Add another machine Get IP, hostname, etc. DHCP Install Hardware Find LDAP Server Assign Name DNS LDAP Query Configuration Configure System Obtain Unique AE Titles Update Configuration

19. Hospital network reconfiguration DHCP Server Shutdown (DHCP) Revise DHCP Configuration Resume DHCP Modify network hardware Clients Resume

20. Customer Assisted Maintenance • Simple device swap • Remote reconfiguration • Local reconfiguration