Concept of peer in Orthanc

Google Groups archive
1

Hello,

Could you explain the concept of peer in Orthanc.
What is the difference between a peer or a modality (apart from the use of Orthanc REST API) ?
I’m not sure I understand this concept.

Thank you.

Stephane

2

Hello,

A “peer” is another instance of Orthanc, possibly running on another computer.

Contrarily to a “modality”, it is possible to communicate with a peer through the HTTP/HTTPS protocol (i.e. the REST API of Orthanc), and not through the DICOM protocol. This implies a much easier configuration: It is only required to know the URL, the username and the password to communicate with an Orthanc peer. Indeed, as you might know, the setup of DICOM query/retrieve is quite complex and involves a lot of pitfalls [1] that can be bypassed if using HTTP.

Furthermore, as HTTP(S) communications are generally not blocked by firewalls (contrarily to the DICOM protocol that is inherently an Intranet protocol and that often requires the setup of VPN tunnels), it is much easier to setup communications of medical images through the Internet with Orthanc peers.

HTH,
Sébastien-

[1] https://code.google.com/p/orthanc/wiki/FAQ#Troubleshooting_DICOM_communications

3

Thank you Sébastien for this quick and complete answer.
Stéphane