ISO 22646:2005

ISO 22646:2005 pdf free.Space data and information transfer systems一Space packet protocol.
The Space Packet Protocol is designed to meet the requirements of space missions to efficiently transfer space application data of various types and characteristics over a network that involves a ground-to-space or space-to-space communications link (hereafter called space link).
Figure 2-1 illustrates where the Space Packet Protocol is located in the protocol stack. The Space Packet Protocol provides a unidirectional data transfer service from a single source user application to one or more destination user applications through one or more subnetworks. The path from the source user application to the destination user application(s) through the subnetwork(s) is called a Logical Data Path (LDP).
As the data traverse the subnetworks of the LDP, they are carried by subnetwork-specific mechanisms using protocols provided by the subnetworks. The selection of protocols used in the subnetworks is determined independently for each subnetwork and may not be the same through the entire LDP.
The LDP is configured by a service of a management system before actual data transfer occurs, and can only be reconfigured through the management system. Every LDP is uniquely identified by a Path Identifier (Path ID). Each LDP consists of a single source end system, one or more destination end systems, one or more subnetworks, and, if multiple subneiworks are involved, one or niore intermediate systems that interconnect the subnetworks. An LDP involves only one subnetwork only if the source and destination end systems are on the same subnetwork.
Figure 2-2 shows an example of an LDP from a single source user application to a single destination user application. In this example, the source and destination end systems are connected via three suhnetworks interconnected by two intermediate systems.
I For typical configurations of LDPs, see reference (B5).
2 In some implementations. the functions of the source or destination Space Packet Protocol entity depicted in figure 2-2 may be performed by the user application itself. In such cases, the portion of the user application that performs the functions described in this Recommendation should he regarded as the Space Packet Protocol entity.
The Space Packet Protocol provides the users with services to transfer space application data through an LDP. The major function performed by this protocol is the routing of application data along the LDP through underlying subnetworks.
The protocol data units employed by this protocol are Space Packets (unless otherwise stated, the term Packet’ in this document refers to the Space Packet). They are variable in length (or may be fixed at the discretion of the user) and are transmitted at variable intervals. Aside from a header that identifies the Packet, the internal data content of Space Packets is completely under the control of the user application. Each user application can define the organization and content of Packets independently of other user applications and with a minimum of constraints imposed by the transmission mechanisms of the underlying subnetworks.
The Space Packet Protocol entity at the source end system either generates Space Packets from service data units supplied by the source user application, or validates Space Packets provided as service data units by the source user application. At the source and intermediate systems, the Space Packet Protocol entity examines the Path ID of incoming Space Packets and routes them through appropriate suhnetworks using the mechanisms provided by the subnetworks. Routing information (i.e., mapping from Path IDs to subnetwork addresses) is provided to the Space Packet Protocol entities by management. If there are multiple destinations for an LDP, multicasting of Space Packets may he performed by one or more Space Packet Protocol entities at the source end system and/or intermediate system(s).
Each LDP is uniquely identified by a Path ID. A Path ID consists of an Application Process Identifier (APID) and an optional APID Qualifier.
An APID Qualifier identifies a naming domain for APIDs and APIDs are unique only in a single naming domain. An APID naming domain usually corresponds to a spacecraft (or an element of a constellation of cooperating space vehicles). Each space project shall establish APID naming domains to he used in their project. The assignment of APIDs to LDPs within a naming domain is controlled by the space project that owns the naming domain. If a system (or a suhnetwork) handles only Space Packets associated with a single naming domain, the APID Qualifier need not be used in the system (or the subnetwork).ISO 22646 pdf download.

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