Dod/Pritchard Communications
Efficient University Technical Track Copy
-- Draft 4: September 5, 2001--
Efficient Networks Router and Gateway Service Compatibility
5851 SDSL Business Class Router
The 5851 is designed for Symmetric DSL (SDSL) service. SDSL has equal upload (customer to Internet) and
download (Internet to customer) speeds, is typically used for business, and requires installation of a separate,
dedicated service line.
SDSL data transmission speeds vary from 160 thousand bits per second (160 kbps) to 2.3 million bits per second
(2.3 Mbps), depending on the distance between the customer site and the telephone company’s “central office”
(usually, the “CO” is the location at which subscriber lines are connected to the telephone network). The maximum
customer-to-CO distance for SDSL is about 22,000 feet in line length (about 4.1 miles), a little farther than ADSL
(see below).
5861 ADSL Business Class Router
The 5861 works with Asymmetric DSL (ADSL). ADSL is very popular in both business and residential
applications, as it can be delivered over an existing telephone line without affecting standard telephone operation.
The term “asymmetric DSL” comes from the service’s different upload and download speeds. The download speed
of a typical ADSL service may be up to 10 times higher than its upload speed. This works well for many
applications, as the amount of downloaded data often exceeds the amount uploaded.
The fastest available ADSL download speed is 8 Mbps (more than 125 times faster than a dial-up connection). The
top upload speed ranges between 640 kbps and 1 Mbps, depending on specific service offerings. ADSL works at
line-length distances up to 18,000 feet (about 3.4 miles) from the CO, the shortest distance of the three DSL services
described here.
5871 IDSL Business Class Router
The 5871 works with DSL based on the Integrated Systems Digital Network (ISDN) standard. IDSL offers an
always-on alternative to ISDN’s digital dial-up connections. Like SDSL, IDSL features equal upload and download
speeds, but at a slower rate of 144 kbps (nearly three times the speed available to dial-up 56k modem connections,
however).
Although it does not provide speeds as high as ADSL or SDSL, IDSL has the advantage of extending to greater
distances from the CO. The maximum distance allowed from the customer site to the CO for IDSL is approximately
35,000 feet in line length (about 6.6 miles).
IDSL is often used to reach homes and businesses that are too far from a CO for ADSL or SDSL but still need an
always-on, fast connection. Like SDSL, IDSL requires installation of a separate dedicated service line and does not
support simultaneous voice communication over that same line.
5950 SHDSL Business Gateway
The Efficient Networks 5950 works with a DSL variant called SHDSL, for Symmetric High-density Digital
Subscriber Line. The SHDSL standard improves on the bandwidth and reach capabilities of other DSL
implementations and employs their best features to provide up to two symmetric channels operating at 2.3 Mbps
each (for a possible total throughput of 4.6 Mbps).
The maximum customer-to-CO distance for SHDSL is 20,000 feet (about 3.8 miles), but it can be extended
substantially though the use of in-line repeaters. This means SHDSL can deliver high-speed connectivity to many
customers previously deemed unreachable by DSL technology.
SHDSL is especially well suited for businesses as it easily addresses the needs of small and mid-size businesses,
enterprise branches, and teleworkers. SHDSL also supports a range of applications with the flexibility to allow for
tailored solutions.
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