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The POSIP (Packet OC-3 Interface Processor) (see the following figure) provides a single 155.520 Mbps, OC-3 single-mode or multimode fiber-optical network interface for Cisco 7000 series and 7500 series routers. It operates on any Cisco 7500 series router or any Cisco 7000 series router equipped with an RSP7000 processor.
Packet data is transported using Point-to-Point Protocol (PPP) and is mapped into the STS-3c/STM-1 frame. The Packet OC-3 interface is compliant with RFC 1619, "PPP over SONET/SDH," and RFC 1662, "PPP in HDLC-like Framing." The encapsulations used add approximately half of the number of bytes of transport overhead as that involved with ATM using ATM adaptation Layer 5 (AAL5) and line card control (LCC) Subnetwork Access Protocol (SNAP) encapsulations.
The POSIP comes configured with 32 MB of DRAM and 2 MB of SRAM as the factory default memory configurations.
The network interfaces reside on the POSIP and provide a direct connection between the high-speed Cisco Extended Bus (CxBus or CyBus) and external networks. The physical layer interface on the POSIP is OC-3. There are no restrictions on slot locations or sequence; you can install a POSIP in any available interface processor slot.
The POSIP supports the following features:
Standards-compliant SONET/SDH interface; SONET/STS-3c and SDH/STM-1 framing and signaling overhead
Full-duplex operation at 155 Mbps
Intermediate reach optical interface with single-mode fiber
Optical interface with multimode fiber
Online insertion and removal (OIR), enabling you to remove, add, or replace POSIPs on line
32 MB of onboard packet and program DRAM to support transmit and receive buffering
2 MB of onboard SRAM
Figure 17-54: Packet OC-3 Interface Processor
