User guide

QOS QoS implementation for DIFFSERV
iMG/RG Software Reference Manual (Quality of Service)
7-2
Taking into account the QoS related software tools described above, a more detailed view of the gateway archi-
tecture is shown below.
FIGURE 7-1 Gateway Architecture
Note: Note that QoS support is available only for the upstream direction, i.e. in for Ethernet packets that
coming from internal hosts (connected to the Layer2 switch VLANs) need to be routed or bridged to the
ADSL port.
Note: If two-level priority scheduling is required per ATM VC then ATM packet prioritization provides a lower
latency alternative to the Scheduler.
Note: If more than two levels of priority scheduling (or WF2Q+ scheduling) is required then the Scheduler
should be used instead of ATM Packet prioritization.
7.1.3 QoS implementation for DIFFSERV
7.1.3.1 The Classifier
When packet classification is enabled on a transport (only the Ethernet transport named default) every incom-
ing packet is examined by the Classifier. The Classifier never examines outgoing packets.
The Classifier examines incoming packets and assigns a traffic class to them based on user-configured rules that
are stored in a profile. These rules can depend on various IP header fields, or can simply be a function of which
interface the packet arrived on.
TEL 1
TEL 2
CPU
VoIP
Bridge/Router Software
Layer 2 Switch
Meter
Marker
Classifier
Scheduler
LAN 2 LAN 3 LAN 4
ADSL Driver ADSL