Cisco UBR904 Manuale utente

CHAPTER

Product Overview 1-1

Product Overview

This chapter provides physical and functional overviews of the Cisco uBR904 cable

modem. It contains physical descriptions of the cable modem hardware and functional

descriptions of hardware-related features.

The Cisco uBR904 cable modem is a part of a new class of Cisco data-over-cable products.

The Cisco uBR904 cable modem is a compact, easy-to-install device that can receive and

transmit digital data over hybrid fiber coaxial (HFC) cable; the same cable that brings

television broadcast transmissions into a cable television (CATV) subscriber’s home.

With a Cisco uBR904 cable modem, a personal computer can be connected to the HFC

cable network for high-speed access to the Internet. The link that enables the transmission

of two-way digital data from the HFC network to the Internet is provided by the

Cisco uBR7246 universal broadband router installed at the cable headend.

The Cisco data-over-cable products, the Cisco uBR904 cable modem and the

Cisco uBR7246 universal broadband router, are based on the Multimedia Cable Network

Partners, Ltd. (MCNS) Data Over Cable Service Interface Specification (DOCIS)

standards-based specifications. MCNS is a consortium of cable television companies

whose goal is to create standards for interoperable data-over-cable systems.

The Cisco uBR904 cable modem operates with one external AC-input power supply.

The Cisco uBR904 cable modem provides the following features:

•High-speed access to the Internet—Downstream (receive) connection speeds of up to

36 Mbps, and upstream (send) connection speeds of up to 2 Mbps

•Multicast messages—Multiple users can receive important information at the same time

Cable Modem Terminology

Cisco uBR904 Cable Modem Installation and Configuration Guide

1-2

•User data privacy—Upstream and downstream data is encrypted to provide data privacy

protection

•Downloadable software—Software and configuration information is downloaded from

the cable headend to the cable modem

Note Data-over-cable systems are capable of providing access speeds up to 36 Mbps.

That bandwidth, however, is shared by several subscribers because there are very few

computers today that can connect to a network at such high speeds. Typical connection

speeds to be expected are 5 Mbps downstream and 1 Mbps upstream.

To compare data-over-cable speeds with other Internet access technologies available

today, a file that would take eight minutes to download over standard telephone lines

with a 28.8 kbps modem would take two minutes to download over ISDN. The same file

would take approximately eight seconds to download over a data-over-cable system.

Cable Modem Terminology

CATV Originally stood for Community Antenna Television. Now refers to any cable

(coaxial/fiber) based system that provides television services.

Cable modem Any device that modulates and demodulates digital data onto a CATV plant.

Cable router A modular chassis-based router optimized for the data over CATV HFC

application.

Channel A specific frequency allocation and bandwidth. Downstream channels used for

television in the U.S. are 6 MHz wide.

CM Cable modem.

Downstream The set of frequencies used to send data from a headend to a subscriber.

Headend Central distribution point for a CATV system. Video signals are received here

from satellite (either co-located or remote), frequency converted to the

appropriate channels, combined with locally originated signals, and rebroadcast

onto the HFC plant. For a CATV data system, the headend is the typical place to

link between the HFC system and any external data networks.

Product Overview 1-3

Cable Modem Terminology

HFC Hybrid fiber-coaxial (cable). Older CATV systems were provisioned using only

coaxial cable. Modern systems use fiber transport from the headend to an optical

node located in neighborhood to reduce system noise. Coax runs from the node to

the subscriber. The fiber plant is generally a star configuration with all optical

node fibers terminating at a headend. The coaxial cable part of the system is

generally a trunk-and-branch configuration.

Host Any end-user computer system that connects to a network. In this guide, the term

host refers to computer systems connected to the LAN interface of the cable

modem.

Host Device See Host for details.

MCNS Multimedia Cable Network System Partners Ltd., a consortium of cable

companies representing the majority of homes in the U.S. and Canada who have

decided to drive a standard with the goal of having interoperable cable modems.

QAM Modulation scheme mostly used in the downstream direction (QAM-64,

QAM-256). QAM-16 is expected to be usable in the upstream direction.

Numbers indicate number of code points per symbol. Number of bits per symbol

can be computed by 2^(number of bits/symbol) = number of code points.

QPSK Modulation scheme used in the upstream direction. Supports two data bits per

symbol.

Subscriber Unit (SU) A term used for cable modems. See Cable Modem for a description.

Upstream The set of frequencies used to send data from a subscriber to the headend.

Physical Description

Cisco uBR904 Cable Modem Installation and Configuration Guide

1-4

Physical Description

The front of the Cisco uBR904 cable modem (see Figure 1-1) provides a basic operating

status display using 16 LEDs. For a description of the LEDs, see the section,

“Troubleshooting the Power Subsystem Using LEDs” in the chapter, “Troubleshooting the

Installation.”

Figure 1-1 Cisco uBR904 Cable Modem—Front View

The rear of the Cisco uBR904 cable modem (see Figure 1-2) provides the receptacles to

connect the unit to the CATV network, a console device, and a personal computer.

Figure 1-2 Cisco uBR904 Cable Modem—Rear View

The Cisco uBR904 cable modem operates as a desktop device. Place it on a sturdy desktop

or platform near the personal computer to which it will be connected.

11578

12051

Cable F-connector

Reset

switch

Power

receptacle

Ethernet 10BaseT

(RJ-45)

Console

(RJ-45)

Product Overview 1-5

Physical Description

System Specifications

Table 1-1 lists the Cisco uBR904 cable modem physical specifications and power

requirements.

Table 1-1 Cisco uBR904 Cable Modem Physical Specifications

Description Specification

Dimensions (H x W x D) 2.30 x 13.50 x 9.30 in. (5.08cm x 34.29cm x 24.77cm)

Weight ~ 4.5 lb (~ 2.04 kg) for the Cisco uBR904

~ 0.5 lb (~ 0.23 kg) for the AC-input external power supply

AC-input voltage 120 to 240 VAC1wide input with power factor correction

1. VAC = volts alternating current.

AC-input current rating 1.2A2maximum at 120 VAC and 0.6A maximum at 240 VAC

2. A = ampere.

AC-input cable 18 AWG3three-wire cable, with a three-lead receptacle on the power supply end, and a

North American (NEMA 5-15P) plug on the power source end

3. AWG = American Wire Gauge.

Power dissipation 12 to 15W

Frequency 50/60 Hz4

4. Hz = hertz.

Temperature 23 to 113°F (0 to 40°C) operating; -13 to 95°F (-25 to 70°C) nonoperating

Humidity 5 to 95% noncondensing

Noise level 38 dBa5maximum at desktop, 43 dBa maximum in an office

5. dBa = adjusted decibels.

Software requirement Cisco uBR904 Cable Modem software and Cisco IOS Release 11.3(7) NA or later.

Agency approvals Safety: UL 1950, CSA 22.2 No. 950, EN60950

EMI: FCC Class A, FCC Class B, CSA Class A, EN60555-2, EN55022 Class B,

VCC1 Class 2, AS/NZS 3548 Class A

Immunity: IEC-1000-4-2, IEC-1000-4-3, IEC-1000-4-4, IEC-1000-4-5, IEC-1000-4-6,

IEC-1000-4-11, IEC-1000-3-2, IEC 60950, AS3260, TS001

See also the Regulatory Compliance and Safety Information for the Cisco uBR904

document.

Physical Description

Cisco uBR904 Cable Modem Installation and Configuration Guide

1-6

Note For footprint information and additional dimensions, refer to the section “Site

Requirements” in the chapter “Preparing for Installation.”

Power Supply

The Cisco uBR904 cable modem uses one external AC-input power supply. The OK

(power) LED on the front of the cable modem indicates that the power supply is supplying

power to the unit. Table 1-1 lists the AC-input power supply power specifications, including

input voltage and operating frequency ranges.

The bottom, sides, and rear of the cable modem must remain unobstructed to ensure

adequate airflow and prevent overheating inside the unit. The rubber feet on the bottom of

the cable modem provide enough clearance when the unit is placed on a flat, hard surface.

Do not place the cable modem on an uneven or soft surface. We recommend at least

3 inches of clearance at the rear of the cable modem. (See the section “Site Requirements”

in the chapter “Preparing for Installation.”)

Compliance with U.S. Export Laws and Regulations Regarding

Encryption

Cisco cable modem cards perform encryption and are regulated for export by the U.S.

Government. Following is specific information regarding compliance with U.S. export laws

and regulations for encryption products:

•Cisco cable modem cards are not authorized for use by persons located outside the

United States and Canada that do not have export license authority from the U.S.

Government.

•Cisco cable modem cards may not be exported outside the U.S. and Canada either by

physical or electronic means without the prior written approval of the U.S. Government.

•Persons outside the U.S. and Canada may not reexport, resell, or transfer Cisco cable

modem cards by either physical or electronic means without prior written approval of

the U.S. Government.

Product Overview 1-7

Functional Overview

This section provides a functional overview of the Cisco uBR904 cable modem. It describes

the cable modem Media Access Control (MAC) address, connection, and configuration.

These descriptions will help you become familiar with the functions of the Cisco uBR904

cable modem.

MAC-Layer Address

All local-area network (LAN) devices, such as cable modems, require unique MAC-layer

addresses, also known as hardware addresses. The MAC address of a Cisco uBR904 cable

modem is stored in the unit. You should record the MAC address on the site installation

sheet provided in the chapter, “Preparing for Installation.”

Cisco uBR904 Cable Modem Cable Connections

The Cisco uBR904 cable modem is connected to CATV coaxial cable and to an Ethernet

port on a personal computer. The personal computer must have an Ethernet network card

installed; either an internal card installed in the computer chassis, or a PCMCIA adapter

card and cable installed on a laptop computer.

The coaxial cable connection uses standard connectors at both ends of the coaxial cable,

and an F-connector on the back of the cable modem. The F-connector is labeled

“Cable TV In.” The Ethernet connections use straight-through Ethernet cables with RJ-45

connectors at both ends, and RJ-45 receptacles on the back of the cable modem. The

RJ-45 connectors are labeled 1X, 2X, 3X, and 4X.

Note One straight-through Ethernet cable with RJ-45 connectors has been included with

your Cisco uBR904 cable modem. Additional RJ-45 cables are also available from outside

commercial cable vendors.

Functional Overview

Cisco uBR904 Cable Modem Installation and Configuration Guide

1-8

If you are connecting the Cisco uBR904 cable modem to a hub at the installation site (to

provide access to the cable modem from multiple computers), you need to use a crossover

Ethernet cable with RJ-45 connectors.

Note Crossover Ethernet cables are not available from Cisco Systems; they are available

from Cisco and outside commercial cable vendors. Optionally, you can use a straight-

through Ethernet cable and connect to the uplink port on your hub (often labeled Uplink or

MDI).

Airflow and Cooling

To keep the Cisco uBR904 cable modem operating at optimal internal temperature, keep

the bottom, sides, and rear of the cable modem clear of obstructions and away from the

exhaust of other equipment.

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