will appear to provide a variable bandwidth connection to the Internet
Full-time connections
Cable LAN bandwidth is allocated dynamically to a subscriber only
when he has traffic to send. When he is not transferring traffic, he does
not consume transmission resources. Consequently, he can always be
connected to the Internet Point of Presence without requiring an
expensive dedication of transmission resources.
4.2 Internet Access Via Telephone Company
In contrast to the shared-bus architecture of a cable LAN, the telephone
network requires the residential Internet provider to maintain multiple
connection ports in order to serve multiple customers simultaneously.
Thus, the residential Internet provider faces problems of multiplexing
and concentration of individual subscriber lines very similar to those
faced in telephone Central Offices.
The point-to-point telephone network gives the residential Internet
provider an architecture to work with that is fundamentally different
from the cable plant. Instead of multiplexing the use of LAN
transmission bandwidth as it is needed, subscribers multiplex the use of
dedicated connections to the Internet provider over much longer time
intervals. As with ordinary phone calls, subscribers are allocated fixed
amounts of bandwidth for the duration of the connection. Each
subscriber that succeeds in becoming active (i.e. getting connected to
the residential Internet provider instead of getting a busy signal) is
guaranteed a particular level of bandwidth until hanging up the call.
Bandwidth
Although the predictability of this connection-oriented approach is
appealing, its major disadvantage is the limited level of bandwidth that
can be economically dedicated to each customer. At most, an ISDN
line can deliver 144 Kbps to a subscriber, roughly four times the
bandwidth available with POTS. This rate is both the average and the
peak data rate. A subscriber needing to burst data quickly, for example
to transfer a large file or engage in a video conference, may prefer a
shared-bandwidth architecture, such as a cable LAN, that allows a
higher peak data rate for each individual subscriber. A subscriber who
needs a full-time connection requires a dedicated port on a terminal
server. This is an expensive waste of resources when the subscriber is
connected but not transferring data.