BS ISO 18427:2013 pdf download

BS ISO 18427:2013 pdf download.Space data and information transfer systems— Spacecraft Onboard Interface Services —Subnetwork Synchronization Service.
2.3 ASSUMPTIONS
The following assumptions have been made in designing the SOIS Suhnetwork Synchronisation Scrvicc:
— The SOIS Suhnetwork Synchronisation Seisee is provided across single suhnctworks.
— The SOIS Subnetssork Synchronisation Service is made available to protocol entities in the Transfer. Application Support, and User Application Layers.
2.4 QUALITY OF SERVICE
The Synchronisation Service operates with a single, Best.effort quality of service. This service makes a single attempt to provide the requested service but cannot ensure that ii will be completed successfully.
Channel and Priority parameters are not provided in the Synchronisation Service. Were a subnctwork to provide channelisation or pnoritisaion to users of other subnetwor& services. it would fall to the subnetwork Management Information Base MlB to set default channel and priority levels to ensure that the Synchronisation Service adhere to an overall suhnetwork prioritisation and resource reservation scheme.
2.5 SECURITY
2.5.1 SECURITY BACKCROUNI)
The SOIS services are intended for use with proocols that operate solely within the confines of an onboard subneL ft is therefore assumed that SOIS services operate in an isolated environment which is protected from external threats. Any external communication is assumed to be protected by services associated with the relevant space-link protocols. The specification of such security services is outside the scope of this document.
2.5.2 SECURITY CONCERNS
At the time of writing there are no identified security concerns. If confidentiality of data is required within a spacecraft it is assumed it is applied at the Application layer. More infonnation regarding the choice of service and where it can be implemented can be found in reference (A21.
2.5.3 POTENTIAL THREATS AN!) ATTACK SCENARIOS
Potential threats and attack scenario typically derive from external communication and are thcrck,rc no the direct conccrn of the SOIS services which make the assumption that the services operate within a safe and secure environment.
4 MANAGEMENT INFORMATION BASE
4.1 OVERVIEW
There is currently no Managcmcnt Infomiaion Base tMIBt associated with (his service. All management items are associated with the protocol providing the service. However, guidance is provided as to MIB contents in 4.3.
4.2 SIKCIHCATIONS
Any protocol claiming to provide this service in a SOIS-compliant manner shall publish its MIB as pail of the protocol specification.
4.3 GUIDANCE
The MIB of the protocol providing the Synchronisation service should consider the following aspects:
— resource allocation per channel:
— Time semantics:
– Event Time semantics;
— Esent IL) semantics; Event Data semantics:
— managed allocation of Synchronisation POUs to:
• priority.
• channel:
– periodicity or causality of unsolicited TIME.lndication primitives.
NOTE – These aspects are not in any way an indIcation of the complete contents of a NUB 11r a protocol providing the Synchronisation service hut are offered as guidance as to those aspects of the MIB which may relate to the Synchronisation service interlace.