D-Link DI-1750 Reference Manual page 461

12.2 About QoS
12.2.1 What is QoS
Quality of Service (QoS) refers to the capability of a network to provide better service to select ed
network traffic over various technologies. Network transfer can be controlled with QoS. QoS also
provides services based on various policies and provides various services for different operations such
as voice, video, etc.
1. End-to-End QoS Module
Service model refers to a series of end-to-end QoS functions. QoS software supports three kinds of
service model: Best-Effort service, Integrated service (Intserv), Differentiated service (Diffserv).
2. Best-Effort Service
Best effort is a single service model in which an application sends data whenever it must, in any
quantity, and without requesting permission or first informing the network. For best-effort service, the
network delivers data if it can, without any assurance of reliability, delay bounds, or throughput. The
D-Link QoS feature that implements best-effort service is first-in, first-out (FIFO) queueing.
3. Integrated Service
Integrated service is a multiple service model that can accommodate multiple QoS requirements. In this
model the application requests a specific kind of service from the network before it sends data. Explicit
signalling makes the request. The application informs the network of its traffic profile and requests a
particular kind of service that can encompass its bandwidth and delay requirements. The application is
expected to send data only after it gets a confirmation from the network. It is also expected to send data
that lies within its described traffic profile.
The network performs admission control, based on information from the application and available
network resources. It also commits to meeting the QoS requirements of the application as long as the
traffic remains within the profile specifications. The network fulfills its commitment by maintaining
per-flow state and then performing packet classification, policing, and intelligent queueing based on
that state.
D-Link QoS provide Controlled Load Service and Guaranteed Rate Service by Resource Reservation
Protocol (RSVP). Controlled Load Service allow to apply lower delay and higher throughput even at the
crowded period of network. D-Link QoS provide Weighted Fair Queuing to implement this target.
4. Differentiated Service
Differentiated service is a multiple service model that can satisfy differing QoS requirements. However,
unlike the integrated service model, an application using differentiated service does not explicitly signal
the router before sending data.
For differentiated service, the network tries to deliver a particular kind of service based on the QoS
specified by each packet. This specification occurs in different ways, for example, while using the IP
Precedence bit settings in IP packets or source and destination addresses. The network uses the QoS
specification to classify, mark, shape, and police traffic, and to perform intelligent queueing. D-Link QoS
provides Weighted Random Early Detection, Custom Queue, and Priority Queue that use for transmit
differentiated service.
12.2.2 QoS Signalling
D-Link QoS signalling provides a way for an end station or network node to communicate with, or signal,
its neighbors to request special handling of certain traffic. QoS signalling is useful for coordinating the
traffic handling techniques provided by other QoS features. It plays a key role in configuring successful
overall end-to-end QoS service across your network. QoS signalling fully takes advantage of the
Internet Protocol (IP). Either in-band (IP Precedence) or out-of-band (RSVP) signalling is used to
indicate that a particular QoS service is desired for a particular traffic classification.
Model Name
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