3
The SPA passes the packet from the SPI4 interface to the POS processor where it is encapsulated in a POS
frame and FCS is added.
4
The POS frame is sent to the SONET/SDH framer where it is placed into the SONET payload.
5
The framer adds the FCS and SONET/SDH overhead.
6
The framer sends the data to the SFP optics for transmission onto the network.
1-Port OC-192c/STM-64 POS/RPR XFP SPA Architecture
The following figure identifies the primary hardware devices that are part of the POS SPA architecture. The
figure shows a single optics transceiver. The 1-Port OC-192c/STM-64 POS/RPR XFP SPA supports XFP
optics.
Figure 8: 1-Port OC-192c/STM-64 POS/RPR XFP SPA Architecture
In POS mode, every incoming and outgoing packet on the OC-192 POS SPAs goes through the SONET/SDH
framer and SPI4.2 interface.
Path of a Packet in the Ingress Direction
The following steps describe the path of an ingress packet through the 1-Port OC-192c/STM-64 POS/RPR
XFP SPA:
1
The framer receives SONET/SDH streams from the XFP optics, extracts clocking and data, and processes
the section, line, and path overhead.
2
The framer extracts the POS frame payload and verifies the frame size and frame check sequence (FCS).
3
The framer passes valid frames to the System Packet Level Interface 4.2 (SPI4.2) interface on the SPA.
4
The SPI4.2 interface transfers frames to the host through the SPI4.2 bus for further processing and switching.
Path of a Packet in the Egress Direction
The following steps describe the path of an egress packet through the 1-Port OC-192c/STM-64 POS/RPR
XFP SPA:
1
The host sends packets to the SPA using the SPI4.2 bus.
2
The SPA stores the data in the appropriate channel
’
s first-in first-out (FIFO) queue.
Cisco ASR 1000 Series Aggregation Services Routers SIP and SPA Software Configuration Guide, Cisco IOS XE
Everest 16.5
OL-14127-17
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Overview of the POS SPAs
1-Port OC-192c/STM-64 POS/RPR XFP SPA Architecture