Inter-Packet Gap Parameters; Defining An Additional Delay Before Transmitting A Packet Using Lance_Mode And Ipg0; Table 3-4 Read-Write Inter-Packet Gap Parameter Values And Descriptions - Sun Microsystems GigabitEthernet/S 2.0 Installation And User Manual

Inter-Packet Gap Parameters

The GEM ASIC supports the programmable Inter-Packet Gap (IPG) parameters
ipg1 and ipg2. The total IPG is the sum of ipg1 and ipg2. The total IPG is 0.096
microseconds for the link speed of 1000 Mbps.
lists the default values and allowable values for the inter-packet gap (IPG)
TABLE 3-4
parameters, ipg1 and ipg2.
Read-Write Inter-Packet Gap Parameter Values and Descriptions
TABLE 3-4
Parameter
ipg1
ipg2
By default, the driver sets ipg1 to 8-byte time and ipg2 to 4-byte time, which are
the standard values. (Byte time is the time it takes to transmit one byte on the link,
with a link speed of 1000 Mbps.)
If your network has systems that use longer IPG (the sum of ipg1 and ipg2) and if
those machines seem to be slow in accessing the network, increase the values of
ipg1 and ipg2 to match the longer IPGs of other machines.
Defining an Additional Delay Before Transmitting
a Packet Using lance_mode and ipg0
The GEM ASIC supports a programmable mode called lance_mode. The ipg0
parameter is associated with lance_mode.
After a packet is received with lance_mode enabled (default) an additional delay is
added by setting the ipg0 parameter before transmitting the packet. This delay, set
by the ipg0 parameter, is in addition to the delay set by the ipg1 and ipg2
parameters. The additional delay set by ipg0 helps to reduce collisions. Systems
that have lance_mode enabled might not have enough time on the network.
If lance_mode is disabled, the value of ipg0 is ignored and no additional delay is
set. Only the delays set by ipg1 and ipg2 are used. Disable lance_mode if other
systems keep sending a large number of back-to-back packets.
You can add the additional delay by setting the ipg0 parameter from 0 to 31, which
is the media byte time delay.
Values Description
(Byte-time)
0, 255 ipg1 = 8 (default at initialization)
0, 255 ipg2 = 4 (default at initialization)
Chapter 3 Configuring Driver Parameters 17