Chapter 3 System Features
PSAX 20 Software Features
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PacketStar
™
PSAX 20 Access Concentrator User Guide
, Issue 1
Release 6.3.0
Inverse Multiplexing over ATM (IMA)
Inverse multiplexing over ATM (IMA) creates virtual access pipes that are
faster than E-1, but not nearly as expensive as a T-3/E-3 line. This allows for
ATM capabilities without the costs associated with broadband access. The
DS1 IMA and E1 IMA I/O modules support the ATM IMA interface.
LANET Protocol
The LANET (Limitless ATM Network) protocol, coupled with a simple error-
tolerant addressing scheme, addresses the fundamental problem of noise in
adapting ATM to low-speed environments. LANET permits application-
dependent payload protection, allowing selective implementation of
bandwidth-costly, forward-error-correction techniques. It is designed to
identify and extract ATM cells at bit error rates as high as 10
-2
. A simple,
robust addressing scheme facilitates reliable delivery of ATM cells in a noisy
environment. By maintaining the cell extraction capabilities and
strengthening the cell-header error protection, LANET brings the advantages
of the ATM protocol to noisy, low-speed links.
The main features of LANET include the following:
•
Regular framing-bit patterns that enhance cell delineation in high-noise
environments
•
Compatibility with traditional link enhancement schemes such as
forward error correction (FEC) and bit interleaving
•
Consistent interface to the higher layer of the protocol stack (that is, the
ATM layer)
•
Transmission rate and media independence
•
Natural synchronization with a standard 8-kHz telecommunication clock
The LANET solution permits both application-dependent payload protection
and link-quality-dependent header protection, while maintaining maximum
compatibility with ATM standards. Figure 3-6 shows the relationship
between LANET and the Open Systems Interconnection (OSI) model.
Summary of Contents for PacketStar PSAX 20
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