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Wireless Broadband Router User Manual
157
Appendix A Quality of Service
Furthermore, the Router cannot control the behavior of the ISP, which may not have
proper QoS handling. Unfortunately, this is a common situation. Let’s look at a scenar-
io of downloading a large file and surfing the Internet at the same time. Downloading
the file is distinguished by small requests, followed by very large responses. This may
result in blocking HTML traffic at the ISP. A solution for such a situation is limiting the
bandwidth of low-priority TCP connections (such as the file download).
Differentiated Services Code Point Settings
In order to understand what DSCP is, one must first be familiarized with the
Differentiated Services model.
Differentiated Services (Diffserv) is a Class of Service (CoS) model that enhances
best-effort Internet services by differentiating traffic by users, service requirements,
and other criteria. Packets are specifically marked, allowing network nodes to
provide different levels of service, as appropriate for voice calls, video playback, or
other delay-sensitive applications, via priority queuing or bandwidth allocation, or
by choosing dedicated routes for specific traffic flows.
Diffserv defines a field in IP packet headers referred to as the Differentiated Services
Codepoint (DSCP). Hosts or routers passing traffic to a Diffserv-enabled network
will typically mark each transmitted packet with an appropriate DSCP. The DSCP
markings are used by Diffserv network routers to appropriately classify packets and
to apply particular queue handling or scheduling behavior
The Router provides a table of predefined DSCP values, which are mapped to
802.1p priority marking method. Any of the existing DSCP setting can be edited or
deleted, and new entries can be added.