Specifications

Installation and Operation Manual Chapter 1 Introduction
FCD-E1LC Ver. 1.0 Functional Description 1-13
• In the full-duplex mode, the standard flow control method defined in IEEE
802.3x is used. This method is based on
pause frames and enables stopping
and restoring the transmission from the remote node. However, this method
can only be used when auto-negotiation is enabled on the port, and the node
attached to the port supports
pause frames.
Forwarding Algorithms
The Ethernet switch operates as a MAC bridge that automatically learns the MAC
addresses located on the local LAN.
The Ethernet switch LAN table can store up to 2048 MAC addresses. Only active
MAC addresses are actually stored: after a user-defined aging interval, inactive
addresses are removed from the switch memory.
VLAN and QoS Support
The Ethernet switch can use the priority information carried in the VLAN tag or
the type of service (ToS) precedence for frames carrying IP packets to select the
priority with which traffic will be forwarded:
• If the frame is tagged, the switch uses the priority value carried by the VLAN
tag to determine the output queue to which the frame is transferred
• If the frame is not tagged but carries an IP packet, the switch uses the
precedence value carried in the ToS field to determine the output queue to
which the frame is transferred
• Other untagged frames are transferred to the low-priority queue.
Table 1-2 lists the queuing priorities.
Table 1-2. Output Queuing Priorities
Priority in VLAN Tag
(Tagged Frames)
Precedence in ToS Filed
(Untagged Frames)
Output Queue
7, 6, 5, 4 7, 6, 5, 4 High priority
3, 2, 1, 0 3, 2, 1, 0 Low priority
The switch uses the weighted fair queue scheduling mode: 2:1 weighting is
applied to the two priorities, that is, when the output queues are full, 2 frames
are egressed from the high priority queue for each frame in the low priority
queue. This approach prevents the lower priority frames from being starved out
with only a slightly increased delay to the higher priority frames.
Timing
Multiple clock source selection provides maximum system timing flexibility, and
supports hierarchical dissemination of timing information.