This read-only octet string holds the route selection control vector (RSCV, SNA control vector x'2B') used in the direction toward the session's secondary logical unit (SLU) for a session crossing an ISTG at this Extended Border Node. Admins use it, alongside diagnostic tools that decode SNA control vectors, to trace exactly which path an SNA session takes across the network when troubleshooting connectivity or performance issues. For example, comparing this RSCV against the expected topology helps confirm whether a session is taking the intended route toward its destination LU.