Automatic DICOM Forwarding IP Address

What is Automatic DICOM Call Forwarding IP Address?


You are probably familiar with telephone call forwarding. Let's say you have two homes, one in the city and one by the beach, and if you go to the house in the beach on every weekend, you may want to forward the home number to the beach house so you give only one number to your parents and grandparents who do not need to remember two different numbers to call you. They do not need to "know" you have "moved" to another location.

Well, on most Imorgon production sites have two servers. One is the Primary server which is used most of the time, but when the Primary Server fails to operate then the Secondary server comes alive and services, thereby virtually eliminating a downtime to do a hardware failure.

Then the question would arise, what happens when this switch-over occurs. You might ask "Do I need to send DICOM images to the secondary server?"

That's when our Automatic DICOM Call Forwarding IP Address come in.

With this feature enabled and implemented (on most networks) the servers will perform automatic "call forwarding" as the server role changes, so like in the beach house example, the Ultrasound machines continue to send the image to the same IP address. This means that there is no need to re-configure the DICOM destinations. Ultrasound machines do not need to "know" the DICOM destination has "moved" to another server.

The Imorgon workstations are even more sophisticated. They are configured to know two IP addresses to contact so in the event it cannot contact the primary server, it can contact the Secondary server automatically. 

One Limitation of Automatic DICOM Call Forwarding IP Address


This forwarding can only be implemented that all servers are on the same subnetwork. Please consult your network engineers if your Imorgon Servers are going to be configured on the same subnetwork. Using the phone example, it is something like we are telling you that this feature will work only if two of your homes are within the same area code otherwise you need give two numbers to your parents and grandparents.

The Imorgon servers do not require the automatic DICOM call forwarding to be enabled. In this case, you can still manually switch the destination IP address for the DICOM sending from ultrasound machines.

Example


This will work.

You have a subnet of 10.1.1.0/24 with effective addresses of 10.1.1.2 through 10.1.1.254. You have extended the 10.1.1.0 VLAN in two separate server locations.
  • Imorgon Server 1: 10.1.1.10  Netmask 255.255.255.0
  • Imorgon Server 2: 10.1.1.11  Netmask 255.255.255.0
  • Forwarding IP:       10.1.1.12 Netmask 255.255.255.0
This will not work:

You have a subnet of 10.1.1.0/24 on the main hospital VLAN and you have located the secondary server at 172.1.1.0/24 subnet located at a another data room on the other hospital campus building to protect the server from environmental failures.
  • Imorgon Server 1: 10.1.1.10  Netmask 255.255.255.0
  • Imorgon Server 2: 172.1.1.11  Netmask 255.255.255.0  (Not in the same 10.1.1.0/24 network!)
  • Forwarding IP:       10.1.1.12 Netmask 255.255.255.0


What If Automatic DICOM Call Forwarding IP Address Cannot Be Used?


Most ultrasound machines have an ability to configure multiple destinations. We ask that you pre-configure two destinations such as "Imorgon Primary" and "Imorgon Secondary" and provide instructions and training to switch these destinations.

Please also note that both the Primary and Secondary servers are accepting DICOM inputs under normal operating condition and you can send images to either and images are replicated between two servers automatically and so delivered to the workstations immediately. It is when the network or the server is down, an explicit destination choice must be made.


Technical Details


The imorgon server pairs monitor the SQL server roles periodically and when the sever role changes from Principal to Mirror or vise versa the Imorgon Server Monitor service performs the multi-homed IP address changes. In essence it does the equivalent of removing the forwarding IP address (we used to call this a Virtual IP) from the Ethernet control panel and then assigning it on the server holding a principal role again on the Ethernet control panel all under the software control.



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