Transcript Configuration_by Rob_Horn

DICOM Configuration
Robert Horn, Agfa Corporation
HealthCar
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
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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
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Time Synchronization
• For
– Multi-device simultaneous acquisitions
• Cardiac Catheterization laboratory
– Coordination
• Security Logs, Procedure Logs
– Convenience
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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).
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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
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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
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How NTP works
Time Sent (Ta)
Response
Redundant Servers
NTP Server
Query
Query
Time Query Received (Ti)
Time Response Sent (Tj)
Current Time Parameters (TP)
Client Provides
Old Network Parameters
Old Time Parameters
Response
Mathematical Magic happens
Client Sets and Fine Tunes System Clock
NTP Client
SNTP performs only the clock setting
NTP includes the network delay estimation,
optimal estimation mathematics and
fine tuning of the system clock.
NTP clients may utilize redundant servers
NTP clients may utilize instrumentation grade
pulse generators (e.g. Atomic Clocks)
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Typical NTP configurations
Internet
NTP Server
GPS Receiver
Campus
Network
NTP Clients
Switching Hub
Local NTP Server
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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
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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"
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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
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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.
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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
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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
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Pre-configured Installation
– Large network addition
– Multiple vendors
– Reduce coordination and scheduling delays
– Reduce configuration errors
– Reduce staging requirements
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Pre-configured Installation
Vendor A Preparation
LDAP
Prepared
Configurations
LDIF
IT Organization
A
A
DHCP
Network
Planning
A
LDIF
Prepared
Configurations
A
B
B
B
Vendor B preparation
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Add another machine
Get IP, hostname, etc.
DHCP
Install Hardware
Assign Name
Find LDAP Server
DNS
LDAP
Query Configuration
Configure System
Obtain Unique AE Titles
Update Configuration
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Hospital network reconfiguration
Shutdown (DHCP)
DHCP Server
Revise DHCP Configuration
Resume DHCP
Modify network hardware
Clients Resume
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Customer Assisted Maintenance
– Simple device swap
– Remote reconfiguration
– Local reconfiguration