User's Manual

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System Configuration Introduction – p. 13
There are different configuration requirements for each layer and different
software tools accomplish this task. The configuration of the RF link is typically
unique to each installation with the particular downstream and upstream
frequencies, modulations and bandwidths being the critical parameters that must
be set on the modem and XMTS.
Whereas there is no set standard for implementing an RF link, DOCSIS is a fully
specified protocol as are the upper layers (IP, E1/T1 or PSTN). The following
sections will describe the currently available system components (equipment)
then detail how to configure each of them in turn.
1.2 Equipment Capabilities
There are several different modems available, the simplest being the DOCSIS
modems with IP-only capability. All of the other modems use these as their
foundation.
The XMTS used at the head end is the other major component. There is only one
basic configuration, which is augmented with additional plug-in cards to
accommodate E1/T1 and PSTN capabilities.
NOTE: The term XMTS was originally conceived as
“extended” CMTS for use in a cable plant, hence the “X”.
This was followed by WMTS in which the “W” indicates a
“wireless” CMTS. For practical purposes these terms are
interchangeable and in some places the software uses
the term “WMTS” when referring to any one of these
systems.
1.3 XMTS
The basic XMTS is a chassis with a power supply and a mid-plane PCI bus that
accommodates plug-in cards at the front and rear. Two redundant power supply
cards are provided at the right end of the front of the chassis.
The minimum required hardware configuration for an IP-only system consists of
one "HOST" card and three "Universal" cards. One Universal card acts as a
"Control and Forward" (C&F) card, one as the "Upstream" digital card and one as
the "Downstream" digital card. These latter two cards are attached to RF cards
in the rear slots. The E1/T1 capability is added by requires the Master4 card
(which replaces the older HOST card), and adding one or two E1/T1 interface
cards in the rear slots to provide 12 or 24 E1/T1 ports, respectively.
The HOST or Master4 card serves as the PCI bus arbiter and provides the
system clock and timing. When the XMTS boots, the Master4 card initializes,
then identifies the C&F card. The C&F card then directs the configuration and
downloading of relevant application software. The C&F card is connected
through a 100 BaseT Full Duplex connection to the switch or router and used to
transport data (including management packets) through the system.
All Universal cards are the physically identical: the card attached to them in the
rear slots and the application downloaded during initial startup determine the
function of the card (Upstream, Downstream or Control & Forward).