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EDA 1200 Services

Figure 23 Differentiated Services in an Ethernet Switch

When a frame is received, the mapping and queuing process determines by

examining the header, the destination port and the queue in which the frame

will wait to be sent. The decision of which queue to use is based on the

classification of the frame.

The scheduling process submits the queued frames for transmission. Different

algorithms can be used for emptying the different queues.

Within routed parts of the network, that is, when EDA 1200 traverses an IP

network in order to reach a remote Service Provider’s PoP, differentiated

services are used on the IP level. The principle of the forwarding process of a

router is similar to the process in an Ethernet switch.

Within IP networks various standards for priority tag indication exist, using

DiffServ Code Point (DSCP) fields within the IP header. The tags used to

indicate specific services within these fields also differ from network to network.

Therefore mapping must be performed within the edge nodes in order to adapt

to the priority tags used in the specific network.

3.3 Multicasting

IP Multicasting is the ability to transmit a single data stream to multiple

End-users at the same time. IP multicasting reduces the total traffic load in the

network by eliminating unnecessary traffic:

• Only requested multicast data streams are transmitted downstream

• Only one downstream transmission to several listeners

Note: Multicast is only supported for single tagged traffic. However, EDN312

and EDN612 are able to forward double tagged frames (based on IGMP

snooping) with a multicast group destination. Such forwarding is limited

to downstream traffic towards a single End-user line per Service VLAN.

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APC IP DSLAM Betriebsanweisung Seite 37