Alcatel-Lucent 9500 MXC, Руководство пользователя

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9500 MXC User Manual
3DB 23063 ADAA - Rev 004 July 2007 Vol. IV-7-53
• Ports with a higher priority have their traffic accepted by the queue
controller ahead of traffic from lower priority ports on a 8:4:2:1
weighted basis where, for example, 8 high priority packets will be sent
for every one low priority packet. Refer to Step 10, Priority Mapping,
for more information on traffic prioritization.
5.6 Port Up
: An arrow indicates detection of valid Ethernet framing at the
local port connection. Unconnected ports or ports with invalid framing
are red-flagged. This status indicator is derived from the auto-negotiation
process.
5.7 Resolved
: A tick in a resolved box indicates that the DAC ES module
has determined the presence of valid Ethernet data from the locally
connected equipment. It also indicates that auto-negotiation has
configured the port for Duplex-Speed and/or Mdi/MdiX where auto is
selected for these options. If the port is not connected or is physically
connected but not resolved, the tick box will be empty and the associated
Port Up arrow will normally be red-flagged. Until resolved, the port is
not traffic-accepting. This auto-negotiation process only acts and reports
on data sensed from the locally connected equipment, it does not respond
to data received from the other end of the DAC ES link.
6.
Maximum Frame Size
sets the maximum frame size for the interface, which
determines the largest datagram (packet) than can be transmitted without it
being broken down into smaller units (fragmented)
3
. A setable range from 64
to 1536 bytes is indicated, but if the value selected is less than or equal to
1522, the maximum frame size is set to 1522, otherwise it is set to 1536. For
a typical 1500 byte packet the frame size for an untagged frame is 1518 bytes.
If the frame is VLAN tagged the frame size increases by four bytes to 1522.
The default setting is 1522 bytes.
7.
Enable Flow Control
: Flow control is applicable to full-duplex links only. It
is implemented by the IEEE 802.3x pause frame mechanism, which tells the
remote 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 ES / IDU ES ports and beyond must also be enabled
for flow control.
8.
Address Learning
: Address Learning is default implemented to support
efficient management of Ethernet traffic in multi-host situations. The option
3
The setting only supports this interface. Some other link/interface in the path may have a smaller MTU,
at which point the datagram will be fragmented if its size is greater.