Cisco Octal-Port DMT ATU-C Line Card Uživatelský manuál stáhnout pdf (Strana 2)

C H A P T E R

Using DSL to Access

a Central Site

This chapter focuses on Digital Subscriber Line (DSL) technology. DSL, like cable modem,

is one of the most popular broadband access methods and will be a new topic on the

CCNP exam.

After completing this chapter, you will understand the basic Asymmetric DSL (ADSL)

technology, Cisco 6160 DSL Access Multiplexer (DSLAM) conﬁguration, and Cisco 6400

Universal Access Concentrator (UAC) conﬁguration. You will also understand different

access architectures and protocols such as Integrated Routing and Bridging (IRB), Routed

Bridge Encapsulation (RBE), Point-to-Point Protocol over ATM (PPPoA), and Point-to-Point

Protocol over Ethernet (PPPoE).

Note that there are different ﬂavors of DSL technologies. This chapter focuses on ADSL

technology.

ADSL Overview

DSL technology introduces a new family of products that can provide high-speed data and

voice service over existing copper pairs. Several ﬂavors of DSL exist, but each type can be

categorized as either SDSL or ADSL. Symmetric DSL (SDSL) provides equal bandwidth

from the customer premises to the service provider (upstream) and from the service

provider to the customer (downstream). ADSL provides higher downstream speeds than

upstream.

Traditionally, ADSL has been used to provide high-speed data service by encoding data

on the local loop by using frequencies (up to 1 MHz) greater than voice (up to 4 kHz) so

that existing telephone service would be preserved and would travel simultaneously with

the data. At the central ofﬁce (CO), the voice would be routed to the public switched

telephone network (PSTN) using a low-pass frequency ﬁlter called a POTS splitter

chassis (PSC).

Figure 8-1 depicts a typical end-to-end ADSL system. Beginning at the customer premises,

the user’s general-purpose computer is connected to the ADSL Terminating Unit-Remote

(ATU-R) over an Ethernet connection.

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Cisco Octal-Port DMT ATU-C Line Card Uživatelský manuál Strana 2