Westell Inc. ULS3-C ユーザーズマニュアル

 

 
03/24/09 - DRAFT 
 
 

030-300554 Rev. C 

161 

    March 2009 

 

 

 
If you click the Quality of Service link in the Advanced screen and then click Traffic Shaping in the left submenu, 
the following screen appears.  
 
Traffic Shaping is the solution for managing and avoiding congestion where the network meets limited broadband 
bandwidth. Typical networks use a 100 Mbps Ethernet LAN with a 100 Mbps WAN interface router. This is where 
most bottlenecks occur. A traffic shaper is essentially a regulated queue that accepts uneven and/or bursty flows of 
packets and transmits them in a steady, predictable stream so that the network is not overwhelmed with traffic. 
While traffic priority allows basic prioritization of packets, traffic shaping provides more sophisticated definitions, 
such as: 
 

•  Bandwidth limit for each device 
•  Bandwidth limit for classes of rules 
•  Prioritization policy 
•  TCP serialization on a device 

 
Additionally, QoS traffic shaping rules can be defined for a default device. These rules will be used on a device that 
has no definitions of its own. This enables the definition of QoS rules on the default WAN, for example, and their 
maintenance even if the PPP or bridge device over the WAN is removed.
 
The matching of packets by rules is connection-based, known as Stateful Packet Inspection (SPI ), using the 
Router’s firewall mechanism. Once a packet matches a rule, all subsequent packets with the same attributes receive 
the same QoS parameters, both inbound and outbound. Connection-based QoS also allows inheriting QoS 
parameters by some of the applications that open subsequent connections. For instance, QoS rules can be defined on 
SIP, and the rules will apply to both control and data ports (even if the data ports are unknown). Applications that 
support such inheritance have an application-level gateway (ALG) in the firewall.  
 
To add a traffic shaping rule, click the New Entry link.