SCION Border Router Application

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Border Routers use RawSockets to process incoming SCION packets other than i.e. UdpSockets, they don’t strip-off the L3(and even L4) header, but yield the ‘scion-packet’ to the application as-is including the ScionHeader (only the L2 header is removed). Each BR opens one internal socket to communicate with hosts inside the AS and one for each configured SCION link to a remote AS. The BR processes the ScionHeader and decides the right egress interface for this packet, which will also be a ScionRawSocket. It modifies the packet’s header in-place (i.e. increment CurrentHop pointer field) and writes it to the egress interface socket, which will only add the outer L2 header (but not a second ScionHeader ) and ‘re-use’s the existing ScionHeader. The last BR on a SCION path will select the hosts address (L2 or L3 depending on AS configuration) as destination for the packet and send it via its internal interface to this address.