COS - Lingo
1. Class of service. Indication of how an upper-layer protocol requires that a lower-layer protocol treat its messages. In SNA subarea routing, COS definitions are used by subarea nodes to determine the optimal route to establish to given session. A COS definition comprises a virtual route number and a transmission priority field. Also called TOS (type of service). 2. Corporation for Open Systems. Organization that promulgates the use of OSI protocols through conformance testing, certification, and related activities.