Furthermore, DOCSIS 1.1??“3.0
provide additional security tools, including
?– A mechanism for the operator to prevent theft of service by requiring that each
modem authenticate itself using a digital certificate
?– A secure method to download new operational software to a modem
?– A way to encrypt high-value ???multicast??? traffic and provide decryption keys only to
those customers who are authorized for the service
Bandwidth Efficiency
Because the bandwidth on the upstream and downstream channels is distributed over a
number of customers, bandwidth usage is much more efficient than the alternative of a
point-to-point dedicated link. Since most communications links are idle for a significant
Hybrid Fiber-Coax 155
portion of time, aggregating and distributing bandwidth allows users with data to send to
take advantage of the otherwise unused capacity available from idle users. For packetized
data services, the term statistical multiplexing is often used to describe the efficiency gains
realized by distributing bandwidth. The advantages of statistical multiplexing increase
as more bandwidth is aggregated. For example, doubling the raw channel capacity can increase
the effective capacity by a factor of 2.
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