Qsim/Hsim/Fam Performance At Small Frame Sizes - 3Com 3C63100-AC-C - PathBuilder S600 Bridge/router Reference Manual

Terminal Timing Source—This parameter applies only when the attached cable
is DCE type cable. The setting for the Terminal Timing depends on the nature and
speed of the device application, but the typical configuration is Internal—the
PathBuilder S600 provides the clock for the device application. In any case, the
Terminal Timing Source setting for the PathBuilder S600 QSIM port must be the
opposite of that for the device. For example, if the Terminal Timing Source for the
router is set to Internal, then you must set the Terminal Timing Source for the
QSIM port to External.
Internal—The terminal receives clocking over DCE cable from the PathBuilder
S600. In other words, the PathBuilder S600 provides the clock to clock in the
data traffic from a router or other data device.
External—The terminal provides port clocking over the DCE cable to the
PathBuilder S600. In other words, The PathBuilder S600 accepts the clock for
data from the router or other data device.
Receive Timing Phase—Receive timing phase control. This parameter applies
only when the attached cable is DCE type cable. Depending on the speed of the
device application and the clock phases, particularly those of the return clock, you
may have to set Receive Timing Phase to Inverted (invert the clock) to ensure
correct clock and data phase. This option is used most often to correct for cable
length delays when Terminal Timing is set to Internal.
Normal—The receive timing from the remote endpoint (node) is normal
clocking.
Inverted—The receive timing from the remote endpoint (node) is inverted
clocking.
Data Rate—The data rate supported by the port: 64K, 128K, 256K, 512K, 1M,
6M, or 8M for the QSIM; 1.5M to 20M for the HSIM; 64K to 1.5M for the FAM.
This parameter applies only when the attached cable is DCE type cable. The Data
Rate setting also allows you to optimize the entire WAN ATM application by traffic
engineering your ATM access applications so as to maintain traffic flow across the
network.
Min. Flag Bytes—The minimum number of flag bytes required to distinguish a
frame. Select 1 (1 byte) or 2 (2 bytes). This parameter is valid only for HDLC/SDLC
data.
FCS Size—The number of bytes to use for FCS (Frame Check Sequence)
calculation for each frame. FRC is the CRC remainder sent at the end of a frame.
Select 1 (2 bytes) or 2 (4 bytes). This parameter is valid only for HDLC/SDLC data.
Admin Status—Administrative status: Out of Service or In Service.

QSIM/HSIM/FAM Performance at Small Frame Sizes

Note that this section pertains to QSIM, HSIM, and FAM performance with traffic
running at small frame sizes. Table 32, Table 33, and Table 34 describe the
configurations supported when the QSIM, HSIM, and FAM, respectively, are
running at small frame sizes.
Configuring the QSIM/HSIM/FAM Modules 165