removed by the source node. FDDI and Token Ring networks use source stripping, whereas DPT and SRP use destination stripping. Again, consider the previous example of the OC-48c ring. In a source stripping (FDDI or Token Ring) environment, in the event that router A wanted to communicate with router D, the entire network would be taken up while the data was being transmitted because it would have to wait until it completed the loop and got back to router A before it was eliminated. In a destination stripping (DPT and SRP) environment, the data would only be present between router A and Router D and the rest of the network would be free to communicate. SRP Header The SRP header is 16 bits (2 bytes) total. It contains 5 fields. These fields are as follows: Time to Live (TTL), Ring Identifier (R), Priority (PRI), Mode, and Parity (P). The TTL field is 8 bits, its only metric is hop count. The R field is 1 bit (either 0 or 1 designating the inner or outer ring). The PRI field is 3 bits designating the packet priority. The Mode field is 3 bits designating what type of data is contained in the payload. The P field is 1 bit. References RFC2892: Spatial Reuse Protocol Tomsu, Peter; Schmutzer, Christian, "Next Generation Optical Networks" pp. 105-113, Prentice-Hall (c) 2002 Cisco protocols