The
recent evolution of VoD applications, however, seems to bring the ratio into asymmetry
again, with the downstream flow strongly dominating the upstream traffic (see: http://
grouper.ieee.org/groups/802/3/cfi/0306_1/cfi_0306_1.pdf). Data traffic is increasing at an
unprecedented rate, with a sustainable traffic growth rate of over 100 percent per year observed
since 1990 (already quoted: www.ieee802.org/3/hssg/public/mar07/bach_01_0307.
pdf, www.ieee802.org/3/hssg/public/jan07/lee_01_0107.pdf, or www.ieee802.org/3/hssg/
public/sep06/steenman_01_0906.pdf). There were periods when a combination of economic
and technological factors resulted in even greater growth rates, e.g., a 1000 percent increase
per year in 1995 and 1996 [6]. This trend is likely to continue in the future, especially
with the deployment of Voice over IP (VoIP) telephony and with the increasing
Passive Optical Networks (PONs) 175
role of online services, VoD, interactive gaming, and so on. Although the impact of these
technologies is still very limited, they are very likely to spur currently unimaginable traffic
growth in the near future.
Unsatisfied subscribers??™ demand for new services have attracted a new breed of market
players.
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