Most probably you already know this, but for those who are interested, here is a list of the letter definitions for Cisco IOS release trains. In more human terms, if you have loaded an IOS image like c2900-universalk9-mz.SPA.150-1.M5.bin, what those letters (in this case SPA) mean:
- A = Aggregation/Access Server/Dial technology
- B = Broadband
- C = Core routers (11.1CA, 11.1CT, 11.1CC)
- D = xDSL technology
- E = Enterprise feature set
- F = Feature Specific enhancements (11.2F)
- G = Gigabit Switch Routers (GSR)
- H = SDH/SONET technology (11.3HA)
- J = Wireless Networking technology (Aironet)
- M = Mobile (Restricted to Mobile Wireless BU usage and further reserved for Mainline)
- N = Voice, Multimedia, Conference (11.3NA)
- P = Platform features (11.2P)
- R = Reserved for ROMMON reference
- S = Service Provider
- T = Reserved for Consolidated Technology Train
- W = LAN Switching/Layer 2 routing
- X = A short lived, one-time release (12.0XA)
- Y = A short-lived, one-time release (when Xs are exhausted)
- Z = A short-lived, one-time release (reserved if Ys are exhausted)
Additional information can be found here.
I believe SPA stands for Shared Port Adaptor, and are not flags of S P A and each of those corresponding features.