Cisco Systems UBR900 specifications Event 1-Wait for the Link to Come Up

Feature Overview

In the following paragraphs, a sample log file is broken down into the chronological sequence of events listed below. Sample comments are also included in the log file.

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Event 1—Wait for the Link to Come Up

Event 2—Scan for a Downstream Channel, then Synchronize

Event 3—Obtain Upstream Parameters

Event 4—Start Ranging for Power Adjustments

Event 5—Establish IP Connectivity

Event 6—Establish the Time of Day

Event 7—Establish Security

Event 8—Transfer Operational Parameters

Event 9—Perform Registration

Event 10—Comply with Baseline Privacy

Event 11—Enter the Maintenance State

Event 1—Wait for the Link to Come Up

When the Cisco uBR900 series cable access router is powered on and begins initialization, the MAC layer first informs the cable access router drivers that it needs to reset. The LINK_DOWN and LINK_UP fields are similar to the shut and no shut conditions on a standard Cisco interface.

uBR924# show controllers cable-modem 0 mac log
528302.040	CMAC_LOG_LINK_DOWN
528302.042	CMAC_LOG_RESET_FROM_DRIVER
528302.044	CMAC_LOG_STATE_CHANGE	wait_for_link_up_state
528302.046	CMAC_LOG_DRIVER_INIT_IDB_SHUTDOWN	0x08098D02
528302.048	CMAC_LOG_LINK_DOWN
528308.428	CMAC_LOG_DRIVER_INIT_IDB_RESET	0x08098E5E
528308.432	CMAC_LOG_LINK_DOWN
528308.434	CMAC_LOG_LINK_UP

Event 2—Scan for a Downstream Channel, then Synchronize

Different geographical regions and different cable plants use different RF frequency bands. A frequency band is a group of adjacent 6 MHz-wide channels. These bands are numbered from 88 to

99.Each band has starting and ending digital carrier frequencies and a 6 MHz step size. For example, a search of EIA channels 95-97 is specified using band 89. The starting frequency of band 89 is

93MHz; the ending frequency is 105 MHz.

The Cisco uBR900 series’ default frequency bands correspond to the North American EIA CATV channel plan for 6 MHz channel slots between 90 and 858 MHz. For example, EIA channel 95 occupies the 90-96 MHz slot. The digital carrier frequency is specified as the center frequency of the slot, which is 93 MHz. Channel 95 is usually specified using the analog video carrier frequency of 91.25 MHz, which lies 1.75 MHz below the center of the slot.

Some CATV systems use alternative frequency plans such as the IRC (Incrementally Related Carrier) plan and HRC (Harmonically Related Carrier) plan. Cisco uBR900 series cable access routers support both of these plans. Most of the IRC channel slots overlap the EIA plan.

The Cisco uBR900 series uses a built-in default frequency scanning feature to find and lock onto a downstream channel. After the cable access router successfully finds a downstream frequency channel, it saves the channel to NVRAM. The router recalls this value the next time it needs to synchronize its frequency.

26Cisco IOS Release 12.0(7)T