Alcatel-Lucent 9500 MXC User Manual page 155

DAC GE Priority Mapping
DAC GE Flow Control
DAC GE Disable Address Learning
DAC GE Maximum Frame Size
3DB 23063 ADAA - Rev 004 July 2007
Provides selection of queue-controller operation for the following options. This
selection applies to all ports.
• Port default. Enables the setting of a four-level port priority on each of the four
ingress ports. See DAC GE Basic Port Settings above.
• 802.1p provides prioritization based on the three-bit priority field of the 802.1p
VLAN tag. Each of the possible eight tag priority values are mapped into a
four-level (2-bit) priority level. Mapping is user configurable.
• DiffServ provides prioritization based on the six bits of the IP packet DiffServ
or Type of Service byte. Each of the possible 63 levels are mapped into a
four-level (2-bit) priority level. Mapping is user configurable.
• No priority. Incoming packets are passed transparently.
Flow Control is implemented through use of IEEE 802.3x PAUSE frames, which
tell the terminal node to stop or restart transmission to ensure that the amount of
data in the receive buffer does not exceed a 'high water mark'.
• The receiver signals to the transmitter to stop transmitting until sufficient data
has been read from the buffer, triggered by a 'low water mark', at which point
the receiver signals to the transmitter to resume transmission.
• To be effective, flow control must be established from the originating source
through to the end point, and vice versa, which means the equipment connected
to the DAC GE ports and beyond should also be enabled for flow control.
Address Learning is default implemented to support efficient management of
Ethernet traffic in multi-host situations. The option to disable Address Learning
is for use in a ring network where protection for the Ethernet traffic is provided
by an external RSTP switch. To avoid conflict between the self-learning
functions within the DAC GE and external RSTP switches during path failure
situations, the DAC GE capability must be switched off. Failure to do means that
in the event of an Ethernet path failure, and subsequent re-direction of Ethernet
traffic by the external switch to the alternate path, the DAC GE will prevent
re-direction of current/recent traffic until its address register matures and deletes
unused/un-responsive destination addresses, which may take up to 5 minutes.
Maximum Frame Size sets the largest size frame for the interface, which
determines the largest datagram than can be transmitted without it being broken
down into smaller units (fragmented). The DAC GE supports jumbo-frames to
9600 bytes; configurable range is 64 to 9600 bytes.
9500 MXC User Manual
Vol. II-3-61