Cisco ASR 1000 Configuration Guide

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Cisco ASR 1000 Series Aggregation Services Routers SIP and SPA Software Configuration Guide
OL-14127-08
Chapter 12 Overview of the POS SPAs
SPA Architecture
4. The framer accepts the data and stores it in the appropriate channel queue.
5. The framer adds the FCS and SONET/SDH overhead.
The framer sends the data to the SFP optics for transmission onto the network.
2-Port OC-48c/STM-16 POS SPA Architecture
Figure 2 identifies the primary hardware devices that are part of the 2-Port OC-48c/STM-16 POS SPA
architecture.
Figure 22-Port OC-48c/STM-16 POS SPA Architecture
Path of a Packet in the Ingress Direction
The following steps describe the path of an ingress packet through the 2-Port OC-48c/STM-16 POS
SPA:
1. The framer receives SONET/SDH streams from the SFP optics, extracts clocking and data, and
processes the section, line, and path overhead.
2. The framer detects Loss of Signal (LOS), Loss of Frame (LOF), Severely Errored Frame (SEF), Line
Alarm Indication Signal (AIS-L), Loss of Pointer (LOP), Line Remote Defect Indication Signal
(Enhanced RDI-L), Path Alarm Indication Signal (AIS-P), Standard and Enhanced Path Remote
Defect Indication Signal (RDI-P), Path Remote Error Indication (Enhanced REI-P). The framer
extracts or inserts DCC bytes.
3. The framer processes the S1 synchronization status byte, the pointer action bytes (per Telcordia
GR-253-CORE), and extracts or inserts DCC bytes.
4. The POS processor extracts the POS frame payload and verifies the frame size and frame check
sequence (FCS).
5. The POS processor supports PPP, Frame Relay, or HDLC modes and optionally performs payload
scrambling.
6. The POS processor passes valid frames to the System Packet Level Interface 4.2 (SPI4.2) interface
on the SPA.
7. The SPI4.2 interface transfers frames to the host through the SPI4.2 bus for further processing and
switching.
SONET/SDH
Framer
SONET/SDH
Streams
138848
POS
Processor
Ring
MAC
External
SDRAM
Optics
Transceivers
SONET/SDH
Streams
Host
To
From
SPA
Connector
Packets/
SPI4.2 Bus

Cisco ASR 1000 Specifications

General

Brand	Cisco
Model	ASR 1000
Category	Network Router
Language	English