Cisco Systems manual Cisco uBR10012 Router and Cisco IOS Software, Baud Rate

Chapter 1 Cisco uBR10012 Universal Broadband Router Overview

Cisco uBR10012 Router and Cisco IOS Software

a.Each ASIC decodes the header to determine if the packet is destined for one of the downstream ports on that card. If so, the downstream header is removed and the 802.3 MAC header is saved.

b.The MAC header is processed to determine how to build the DOCSIS MAC header and what operations to perform on the packet. These might include prepending the DOCSIS MAC header, computing the HCS and FCS, performing Packet Header Suppression, and BPI encryption.

8.Once the packet is ready, it is immediately transmitted on the downstream.

Cisco uBR10012 Router and Cisco IOS Software

The Cisco uBR10012 router runs the Cisco IOS software, which is stored on the Type II PCMCIA flash memory disks stored in the two PCMCIA slots in the primary PRE module. A PCMCIA flash memory disk in either slot can store a Cisco IOS image or configuration file.

In addition to the flash memory disks, each PRE module contains onboard flash memory that is used to store a boot loader. The loader executes following a system reset to reload and execute the Cisco IOS software on the flash memory disks.

The PRE module also stores the system configuration in the onboard flash memory. The configuration information read from the flash memory is buffered in operational memory following initialization, and is written to the flash memory device when the configuration is saved.

Each line card also contains onboard flash memory that is used to store a boot loader, similar in function to that used on the PRE module. However, the line card loader executes following a system reset, line card reset, or line card insertion to reload and execute any code that must run on the line card.

Software images may also be stored on an external TFTP server. If the Cisco uBR10012 router is so configured, it then downloads the proper image from the TFTP server and executes it.

DOCSIS and EuroDOCSIS Data Rates and Modulation Schemes

Cisco cable interface line cards can be configured in a number of different upstream combinations based on the card used, your cable network, and the anticipated subscription and service levels. Table 1-1lists the data rates and modulation schemes for both DOCSIS1.1 and EuroDOCSIS 1.1 standards. Table 1-2lists the data rates and modulation schemes for DOCSIS 2.0 and EuroDOCSIS 2.0 standards. Table 1-3lists the downstream data rates.

Table 1-1		DOCSIS and EuroDOCSIS 1.1 Upstream Data Rates
			Modulation Scheme,	Baud Rate,	Raw Bit Rate,	Throughput (Bit Rate - Overhead),
	Upstream Channel Width		bit/symbol	symbol/sec	Mb/sec	Mb/sec
	3.2 MHz		16-QAM (4)	2.56 M	10.24	9.0
			QPSK (2)		5.12	4.6
	1.6 MHz		16-QAM (4)	1.28 M	5.12	4.5
			QPSK (2)		2.56	2.3
	800 kHz		16-QAM (4)	640 K	2.56	2.3
			QPSK (2)		1.28	1.2
	400 kHz		16-QAM (4)	320 K	1.28	1.2
			QPSK (2)		0.64	0.6
	200 kHz		16-QAM (4)	160 K	0.64	0.6
			QPSK (2)		0.32	0.3
				Cisco uBR10012 Universal Broadband Router Hardware Installation Guide
	OL-18259-01						1-5