Chapter 3 System Features
Multiservice Media Gateway Software Features
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PacketStar
®
PSAX 4500 Multiservice Media Gateway User Guide
, Issue 2
Release 8.0.0
error space of the principal address used for actual transmission. The most
probable error patterns occurring in the address field will simply change the
address to another valid address. This approach maintains independence
from the application layer because it encodes the header address within the
same 10-nibble header space of standard ATM cells. In addition, it avoids the
extra delay (detrimental to CBR traffic) required of multiple header-encoding
schemes.
In practice, to tolerate 2-bit random errors or 5-bit burst errors requires set-
ting up 526 addresses for each channel. This is not a serious constraint
because noisy low-speed links will likely only be used to support a small
number of users.
Finally, given the ability to deliver cells, the payload can now be FEC-pro-
tected on each virtual circuit, depending on the error tolerance of the appli-
cation at the service-specific convergence sublayer (SSCS). Figure 3-9 shows
the LANET frame structure.
The LANET subframe functions in the following ways:
•
The timely arrival of the header patterns is used as a confidence check,
confirming that the system is properly synchronized.
•
In the event of synchronization loss, a Multiservice Media Gateway system
can easily seek and resynchronize to the regular appearance of the simple
header patterns.
Figure 3-9. LANET Frame Structure
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