User guide

EDA System Services

1/1551-HSC 901 35/3 Uen C 2005-12-02

Interactive gaming however, is more sensitive to large packets losses and

unacceptably long delays.

Loss of packets is rare within the EDA access network, unless the loss is

caused by capacity limitations. In that case it tends to occur in bursts.

Consequently, in order to provide the transport service required for

Telephony over IP there are two main requirements for the QoS function.

One is to minimize the delay of voice packets, the other to minimize the

influence of capacity limitations on voice packets.

In a network carrying a mixture of real-time applications and data packets,

delays are mainly imposed on voice packets when they have to wait for

transmission of often-longer data packets.

The Quality of Service in EDA is ensured by classifying packets and

handling their transmission through the network according to the

classification of each packet.

6.2.1 Traffic Classification

The classification of the traffic is done by the edge nodes in the network.

The Access nodes (IP DSLAM or POTS line board) tag upstream frames

with classification tags (also called p-bit), determined by the origin of the

frame. A frame generated internally by the Access node is tagged with the

management priority tag. A frame originating from an ATM PVC is tagged

with the priority tag defined for that PVC or the CoS flow within the PVC by

the operator.

The classification tags included in downstream frames may originate from a

voice gateway or a Service Provider’s PoP or it may be a result of a

conversion performed at the edge of the EDA network. Figure 38 on page

52 illustrates the classifying nodes in the network.