NETGEAR GS728TPP, GS752TP manual Differentiated Services DiffServ, Class

GS752TP, GS728TP, and GS728TPP Gigabit Smart Switches

Differentiated Services (DiffServ)

Standard IP-based networks are designed to provide best effort data delivery service. Best effort service implies that the network delivers the data in a timely fashion, although there is no guarantee that it will. During times of congestion, packets might be delayed, sent sporadically, or dropped. For typical Internet applications, such as email and file transfer, a slight degradation in service is acceptable and in many cases unnoticeable. However, any degradation of service has undesirable effects on applications with strict timing requirements, such as voice or multimedia.

Quality of Service (QoS) can provide consistent, predictable data delivery by distinguishing between packets that have strict timing requirements from those that are more tolerant of delay. Packets with strict timing requirements are given special treatment in a QoS-capable network. For this reason, all elements of the network must be QoS-capable. If one node is unable to meet the necessary timing requirements, this creates a deficiency in the network path and the performance of the entire packet flow is compromised.

There are two basic types of QoS:

•Integrated Services. Network resources are apportioned based on request and are reserved (resource reservation) according to network management policy (RSVP, for example).

•Differentiated Services. Network resources are apportioned based on traffic classification and priority, giving preferential treatment to data with strict timing requirements.

The switch support DiffServ.

The DiffServ feature contains a number of conceptual QoS building blocks you can use to construct a differentiated service network. Use these same blocks in various ways to build other types of QoS architectures.

There are three key QoS building blocks needed to configure DiffServ:

•Class

•Policy

•Service (that is, the assignment of a policy to a directional interface)

Class

You can classify incoming packets at Layers 2, 3, and 4 by inspecting the following information for a packet:

•Source and destination MAC addresses

•EtherType

•Class of Service (802.1 p priority) value (first or only VLAN tag)

•VLAN ID range (first or only VLAN tag)

•IP service type octet (also known as: ToS bits, precedence value, DSCP value)

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