This code system http://hl7.org/fhir/endpoint-connection-type defines the following codes:

CodeDisplayDefinition
ihe-xcpdIHE XCPDIHE Cross Community Patient Discovery Profile (XCPD) - http://wiki.ihe.net/index.php/Cross-Community_Patient_Discovery
ihe-xcaIHE XCAIHE Cross Community Access Profile (XCA) - http://wiki.ihe.net/index.php/Cross-Community_Access
ihe-xdrIHE XDRIHE Cross-Enterprise Document Reliable Exchange (XDR) - http://wiki.ihe.net/index.php/Cross-enterprise_Document_Reliable_Interchange
ihe-xdsIHE XDSIHE Cross-Enterprise Document Sharing (XDS) - http://wiki.ihe.net/index.php/Cross-Enterprise_Document_Sharing
ihe-iidIHE IIDIHE Invoke Image Display (IID) - http://wiki.ihe.net/index.php/Invoke_Image_Display
dicom-wado-rsDICOM WADO-RSDICOMweb RESTful Image Retrieve - http://dicom.nema.org/medical/dicom/current/output/chtml/part18/sect_6.5.html
dicom-qido-rsDICOM QIDO-RSDICOMweb RESTful Image query - http://dicom.nema.org/medical/dicom/current/output/chtml/part18/sect_6.7.html
dicom-stow-rsDICOM STOW-RSDICOMweb RESTful image sending and storage - http://dicom.nema.org/medical/dicom/current/output/chtml/part18/sect_6.6.html
dicom-wado-uriDICOM WADO-URIDICOMweb Image Retrieve - http://dicom.nema.org/dicom/2013/output/chtml/part18/sect_6.3.html
hl7-fhir-restHL7 FHIRInteract with the server interface using FHIR's RESTful interface. For details on its version/capabilities you should connect the the value in Endpoint.address and retrieve the FHIR CapabilityStatement.
hl7-fhir-msgHL7 FHIR MessagingUse the servers FHIR Messaging interface. Details can be found on the messaging.html page in the FHIR Specification. The FHIR server's base address is specified in the Endpoint.address property.
hl7v2-mllpHL7 v2 MLLPHL7v2 messages over an LLP TCP connection
secure-emailSecure emailEmail delivery using a digital certificate to encrypt the content using the public key, receiver must have the private key to decrypt the content
direct-projectDirect ProjectDirect Project information - http://wiki.directproject.org/