Ericsson EFN324, Руководство пользователя, Страница: 32 / 176

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The ingress port switching described above is based on VLAN ID (or on VLAN
ID and IP destination address), including when the packet is un­tagged or has
double VLAN IDs (if QinQ is used). However, the
egress port switching
domain switching is based on destination address. See Figure 14 on page 28.
Figure 14 Switching domain switching
The EFN324 has optional functions in addition to the basic Layer 2 switching,
in order to increase the security. These additional features are described under
the concept Forced Forwarding, in section 8.1 on page 60.
The final processing is done at the egress port. The packet is placed in one of
four priority queues and sent in the order decided by the scheduling algorithm.
Capacity limits are checked at the egress ports and, to a certain extent, at the
ingress port switching. Capacity limits are either configured bandwidth limits or
physical link and buffer capacities. Violation of capacity restrictions is one
reason why the switch can discard a packet.
In summary, switching consists of these three main steps:
1. At the ingress port, find an ingress connection and a switching domain.
2. At the switching domain, find an egress connection. For multicast and
broadcast, find the egress connections.
3. At the egress port, find the right opportunity and send the packet.
Ethernet
port
Incoming
packet
VLAN ID = x
dest. addr
= y
Switching
domain
? ?
Is there an
egress
connection with
dest. addr. = y
? ?