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Services
Figure 7.138. End-to-end QoS Challenge Areas
The following are the potential bottleneck areas that need be taken into consideration when implementing an endto-end QoS-enabled service.
• The Local Area Network LANs have finite bandwidth, and are typically limited to 100 Mbps. When given
the chance, some applications will consume all available network bandwidth. In business networks, a large
number of network-attached devices can lead to congestion. The need for QoS mechanisms is more apparent
in wireless LANs (802.11a/b/g), where bandwidth is even more limited (typically no more than 20 Mbps on
802.11g networks).
• The Broadband Router All network traffic passes through and is processed by the broadband router. It is
therefore a natural focal point for QoS implementation. Lack of sufficient buffer space, memory or processing
power, and poor integration among system components can result in highly undesirable real-time service
performance. The only way to assure high quality of service is the use of proper and tightly-integrated router
operating system software and applications, which can most effectively handle multiple real-time services
simultaneously.
• The Broadband Connection Typically the most significant bottleneck of the network, this is where the high
speed LAN meets limited broadband bandwidth. Special QoS mechanisms must be built into routers to ensure
that this sudden drop in connectivity speed is taken into account when prioritizing and transmitting real-time
service-related data packets.
• The Internet Internet routers typically have a limited amount of memory and bandwidth available to them,
so that congestions may easily occur when links are over-utilized, and routers attempt to queue packets and
schedule them for retransmission. One must also consider the fact that while Internet backbone routers take
some prioritization into account when making routing decisions, all data packets are treated equally under
congested conditions.
The follwing figure depicts OpenRG's QoS role and architecture in a network. Many of the terms it contains will
become familiar as you read on.
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