Vivotek FD8154 User Manual download pdf (Page 74)

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74 - User's Manual

Network>QoS(QualityofService)

Quality of Service refers to a resource reservation control mechanism, which guarantees a certain

quality to different services on the network. Quality of service guarantees are important if the

network capacity is insufcient, especially for real-time streaming multimedia applications. Quality

can be dened as, for instance, a maintained level of bit rate, low latency, no packet dropping, etc.

The following are the main benets of a QoS-aware network:

■

The ability to prioritize trafc and guarantee a certain level of performance to the data ow.

■

The ability to control the amount of bandwidth each application may use, and thus provide higher

reliability and stability on the network.

Requirements for QoS

To utilize QoS in a network environment, the following requirements must be met:

■

All network switches and routers in the network must include support for QoS.

■

The network video devices used in the network must be QoS-enabled.

QoS models

CoS (the VLAN 802.1p model)

IEEE802.1p denes a QoS model at OSI Layer 2 (Data Link Layer), which is called CoS, Class of

Service. It adds a 3-bit value to the VLAN MAC header, which indicates the frame priority level from

0 (lowest) to 7 (highest). The priority is set up on the network switches, which then use different

queuing disciplines to forward the packets.

Below is the setting column for CoS. Enter the VLANID of your switch (0~4095) and choose the

priority for each application (0~7).

If you assign Video the highest level, the switch will handle video packets rst.

► A VLAN Switch (802.1p) is required. Web browsing may fail if the CoS setting is incorrect.

►The Class of Service technologies do not guarantee a level of service in terms of bandwidth

and delivery time; they offer a "best-effort." Users can think of CoS as "coarsely-grained" trafc

control and QoS as "nely-grained" trafc control.

► Although CoS is simple to manage, it lacks scalability and does not offer end-to-end guarantees

since it is based on L2 protocol.

NOTE:

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Vivotek FD8154 User Manual Page 74