ELSA LANCOM Business 6000, Руководство пользователя

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Connection via 2-Mbit interface
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ELSA LANCOM Business 6000
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46
EN
The choice of E1 mode initially depends on your telecommunications
provider. For providers with an infrastructure relying heavily on multiplexers,
unstructured G.703 is the preferred, if not only connection type. Providers
with an infrastructure based mainly on switching stations also offer G.704
connections.
Even with unstructured G.703–structure thanks to HDLC
A framing protocol is always applied to the data transfer, as unstructured
connections are never sufficient for data communications. In the case of
unstructured G.703 it is applied to the full bandwidth, for G.704 only to the
resulting timeslot blocks.
Data integrity is thus assured, even in the event of varying error rates. A few
additional observations on this topic:
Operational security and Error rate
One important advantage of G.704 connections as opposed to a combination
of G.703 and a self-monitoring layer 2 protocol is its high guaranteed
operational security. Very few providers are willing to guarantee an
operational security higher than 95% for unstructured G.703 connections.
As errors in G.704 lines can be monitored and detected by the line providers,
the providers can easily localize the sources of errors and take corrective
action. In the case of unstructured G.703 connections, errors can only be
detected at the terminal devices, making corrections more difficult.
Multiple fixed connections
An important advantage of G.704 is the flexible structuring of multiple fixed
connections. Individual timeslots can be bundled on a hardware basis by the
exchanges for a variety of fixed connections. Fixed connections to multiple
remote stations are not possible without G.704.
Data throughput
G.704 connections have a lower data throughput by nature, as the timeslots
occupied with protocol data are not available for the transfer of user data. In
the case of a G.704 connection that only occupies TS0, the bandwidth
available for user data is reduced by over 3%. If TS16 is also occupied, the
loss amounts to over 6% as opposed to unstructured G.703.