 It clearly enjoys lower overhead than ATM. Users see a 20 to 30 percent increase in capacity when ATM is removed. PoS preserves the exist- ing investments in SONET infrastructure while enabling the deployment of IP-based video and voice applications and other broadband applications. Figure 3-70 depicts a typical application of PoS technology. Figure 3-71 depicts the PoS encapsulation process. PoS provides limited quality of service (QoS) to IP without the overhead of ATM and has faster recovery from failure than Ethernet-based systems (compared to both the Spanning Tree Algorithm and Rapid Spanning Tree Algorithm). Some see PoS as an interim technology for moving from ATM. The next step is transporting packets directly on the physical layer (IP over Chapter 3 Figure 3-68 communications protocol stacks. GbE MAC 10GbE MAC RPR MAC DS0/DS1/DS3 10GbE WAN PHY SONET GbE LAN PHY 10GbE LAN PHY Fiber Traditional SONET Next-gen SONET Ethernet-based core architectures Figure 3-69 PoS stack. Network Layer PPP in Byte Synchronous Data Link Layer HDLC Framing SONET/SDH Physical Layer Traditional SONET Architectures Location A Figure 3-70 PoS example. Location C Location B POS (OC-3) (intranet) OC-48 SONET SONET SONET/SDH (OC-3) SONET Protected Ring (intranet) SONET (intranet) T1/T3 (Internet) Voice Firewall Switch Backbone Rotor Internet Location D SONET/SDH (intranet) Chapter 3 PPP in HDLC-like Framing (RFC 1662): Figure 3-71 PoS encapsulation Address Control PPP Packet process. 16/32 PPP encapsulation over SONET/SDH (RFC 2615): Mapping, Sonet/SDH Generation Stuffing Scrambling Framing Point-to-Point 1+X^43 Self Bellcore GR-253 Protocol, IETF RFC Synchronous ITU-T G.957 Scrambler, IETF RFC ITU-T G.958 PPP in HDLC-like Framing, IETF RFC 1662 Table 3-5 STATUS IETF RFCs PPP over SONET/SDH Standard protocol The Point-to-Point Protocol (PPP) Standard protocol PPP in High-Level Data Link Control Standard protocol (HDLC) framing PPP over SONET/SDH Proposed standard protocol optics). IEEE 802.17 Resilient Packet Ring (RPR) is viewed 