Presentation Context Negotiation#

Consider an acceptor that supports the following abstract syntax/transfer syntaxes:

Verification SOP Class
- Implicit VR Little Endian
- Explicit VR Little Endian
CT Image Storage
- Implicit VR Little Endian
MR Image Storage
- JPEG Baseline

And a requestor that proposes the following presentation contexts:

Context 1: Verification SOP Class
- Implicit VR Little Endian
- Explicit VR Little Endian
- Explicit VR Big Endian
- JPEG Baseline
Context 3: CT Image Storage
- Implicit VR Little Endian
- Explicit VR Little Endian
- Explicit VR Big Endian
Context 5: MR Image Storage
- Implicit VR Little Endian
- Explicit VR Little Endian
Context 7: CR Image Storage
- Implicit VR Little Endian
- Explicit VR Little Endian

Then the outcome of the presentation context negotiation will be:

Context 1: Accepted (with the acceptor choosing either Implicit or Explicit VR Little Endian to use as the transfer syntax)
Context 3: Accepted with Implicit VR Little Endian transfer syntax
Context 5: Rejected (transfer syntax not supported) because the acceptor and requestor have no matching transfer syntax for the context.
Context 7: Rejected (abstract syntax not supported) because the acceptor doesn’t support the CR Image Storage abstract syntax.

Contexts 1 and 3 have been accepted and can be used for sending data while 5 and 7 have been rejected and are not available.

Implementation Note#

When acting as an acceptor, pynetdicom will choose the first matching transfer syntax in PresentationContext.transfer_syntax. For example, if the requestor proposes the following:

Abstract Syntax: Verification SOP Class
Transfer Syntax(es):
    =Implicit VR Little Endian
    =Explicit VR Little Endian
    =Explicit VR Big Endian

While the acceptor supports:

Abstract Syntax: Verification SOP Class
Transfer Syntax(es):
    =Explicit VR Little Endian
    =Implicit VR Little Endian
    =Explicit VR Big Endian

Then the accepted transfer syntax will be Explicit VR Little Endian.