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ADSL WAN Connections
ADSL Overview
To separate the ISDN data from the ADSL data, an ISDN splitter is installed at
both the customer’s premises and the CO. This splitter ensures that each type
of traffic is transmitted to the appropriate device at each location. (See
Figure 7-6.)
Figure 7-6. ADSL Network
ADSL Without Splitters
ADSL Lite, or G.lite, was developed to provide a low-cost, no-hassle WAN
connection. Instead of the up to 8 Mbps downstream transmission rate of
ADSL, ADSL Lite provides just 1 Mbps downstream. The upstream rate is only
512 Kbps, rather than the 1.544 Mbps offered by ADSL.
In addition to the low cost, subscribers receive the following advantages:
■ No splitter—No splitter is required at the customer’s premises. Instead,
ADSL Lite uses a microfilter, which is easy to install. Typically, the
microfilter is a small device that is attached on the wire that connects the
DSL modem to the wall jack at the customer’s premises.
■ Easy installation—With ADSL Lite, no modifications need to be made to
the local loop, so the customer does not have to wait for a service call
from the local carrier. After the DSL modem and the microfilter are
plugged in, the installation is complete.
Central Office
Customer’s Premises
WAN router
DSLAM
Local
loop
Splitter
Regional
broadband
network
Splitter
LAN
Internet
Internet core
router
Broadband
switch (ATM)
Broadband
access server
Other
DSLAMs
Voice or
ISDN switch
Voice or ISDN traffic
is sent to the voice or
ISDN switch
ADSL traffic is sent
to the DSLAM
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