LevelOne GTL-2691 - Manual (Page 162)

C HAPTER 5 | Interface Configuration
Port Configuration
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◆ When using auto-negotiation, the optimal settings will be negotiated
between the link partners based on their advertised capabilities. To set
the speed, duplex mode, or flow control under auto-negotiation, the
required operation modes must be specified in the capabilities list for
an interface.
◆ The 1000BASE-T and 10GBASE-T standard does not support forced
mode. Auto-negotiation should always be used to establish a
connection over any 1000BASE-T or 10GBASE-T port or trunk. If not
used, the success of the link process cannot be guaranteed when
connecting to other types of switches.
◆ The Speed/Duplex mode is fixed at 1000full on the Gigabit SFP ports,
and at 10Gfull on the 10 Gigabit ports. When auto-negotiation is
enabled, the only attributes which can be advertised include flow
control and symmetric pause frames.
Using Jumbo Frames
◆ Use the jumbo frame attribute on the System > Capability page to
enable or disable jumbo frames for all Gigabit and 10 Gigabit Ethernet
ports. Then specify the required MTU size for a specific interface on the
port configuration page.
◆ The comparison of packet size against the configured port MTU
considers only the incoming packet size, and is not affected by the fact
that an ingress port is a tagged port or a QinQ ingress port. In other
words, any additional size (for example, a tagged field of 4 bytes added
by the chip) will not be considered when comparing the egress packet’s
size against the configured MTU.
◆ When pinging the switch from an external device, information added for
the Ethernet header can increase the packet size by at least 42 bytes
for an untagged packet, and 46 bytes for a tagged packet. If the
adjusted frame size exceeds the configured port MTU, the switch will
not respond to the ping message.
◆ For other traffic types, calculation of overall frame size is basically the
same, including the additional header fields SA(6) + DA(6) + Type(2) +
VLAN-Tag(4) (for tagged packets, for untaqged packets, the 4-byte
field will not be added by switch), and the payload. This should all be
less than the configured port MTU, including the CRC at the end of the
frame.
◆ For QinQ, the overall frame size is still calculated as described above,
and does not add the length of the second tag to the frame.
P ARAMETERS
These parameters are displayed:
◆ Port – Port identifier.
◆ Type – Indicates the port type. (1000BASE-T, 1000BASE SFP,
10GBASE-T, 10GBASE XFP)