SCION Host Context #21
Description
The ScionHostContext is value-type/dataclass which inherits Object and is aggregated onto every SCIONNode in a ScionAS (along with the ‘ScionL3Protocol’) making it a ‘ScionHost’ in effect (just as IPv4/6 does with ‘IpEndHosts’).
Once the ScionStackHelper has finished the configuration of an AS, a subset of the AS’s configuration state is carried-over from build time to runtime, by storing a copy of it on every of the AS’s Nodes, where it is available/accessible for Applications (and kernel protos) living on these Nodes during the simulation.
The ScionHostContext has an interface similar to the SCION Daemon, which can be invoked by Apps at runtime to get AS internal information, paths to particular endpoints and service addresses in the local AS (i.e. getLocal_IA() , getPaths( Ia src_ia, Ia dst_ia ), getSVCAddress(svc_type ) etc ). Notably, the ScionHostContext is not an application itself. While it caches path requests leading to faster response times, it won’t automatically update paths periodically, only because an App requested them some time ago. Similar to the current SCION Daemon, it’ll serve as a shared path-cache for all a Node’s Applications.