Introduction to ESA SLE Gateway
The SLE Gateway performs the mapping between SLE and ESA services. The mapping applied onby the gateway comprises the following services:
- RAF to ODD/IDA services of the TMP4
- RCF to ODD/IDA services of the TMP4
- CLTU to POCC-Physical Layer (PLIS) service of the TCE
Figure 1 shows the overall context and major building blocks of the SLE Gateway. The (external) Mission Control System communicates with the ESA SLE Gateway based on the CCSDS SLE protocol for transfer services onabove TCP/IP. The gateway performs the mapping in the bridge modules and serves the interface to the ESA ground station equipment. The figure shows the involved units. Grey shaded boxes represent processes running on the SLE Gateway. This includes the SLE API communication server, which is needed on SLE provider systems for distribution of incoming BIND invocations and other SLE operations to the correct service instance.
Figure 1: ESA SLE GATEWAY
SLE services apply the concept of service instances. In the figure this is indicated by displaying one bridge module for one service instance of a specific service type as follows:
- the CLTU/TC bridge performs the mapping between the SLE CLTU service and the PLIS service as specified in reference 
- the RAF/ODD-IDA bridge performs the mapping between the SLE RAF and the ODD for the online-timely delivery mode and IDA for the delivery modes online-complete and offline.
- the RCF/ODD-IDA bridge performs the mapping between the SLE RCF and the ODD for the online-timely delivery mode and IDA for the delivery modes online-complete and offline.
When a service instance is loaded, the appropriate SLE/ESA Service Bridge is started and launches the corresponding GS I/F process that communicates with the ground station equipment. The actual connection to the ground station is established when a BIND invocation is received from the user and accepted by the Service Instance residing in the Service Bridge. SLE operations received from the SLE API are mapped to the corresponding GS I/F requests and are forwarded to the corresponding GS I/F process, which are
- the PLIS service interface to the TCE on the ground station and
- the ODD and IDA service interfaces to the TMP4 on the ground station.
The ESA SLE API is integrated in the SLE/ESA service bridges and communicates with the SLE API Communication Server, which is a separate process belonging to the SLE API that distributes SLE service requests to the process containing the service instance the request belongs to.