The POS shared port adapters (SPAs) are available on high-end Cisco Systems routing platforms offering the benefits of network scalability with lower initial costs and ease of upgrades. The Cisco SPA/SIP portfolio continues the Cisco focus on investment protection along with consistent feature support, broad interface availability, and the latest technology. The Cisco SPA/SIP portfolio allows different interfaces (Packet over SONET/SDH [POS], ATM, Ethernet, and so on) to be deployed on the same interface processor.A key feature of these SPAs is the multirate operating mode support. This allows ports to be configured at OC-3 or OC-12 speeds. This gives the flexibility to configure some ports to run at OC-3 speeds, while the rest can run at OC-12 speeds. This requires different optics for different modes. The Cisco POS SPAs provide support for Small Form-Factor Pluggable (SFP) interfaces.