Expand Configuration and Management Manual (H06.21+, J06.10+)

Expand Modifiers
Expand Configuration and Management Manual — 529522-013
16 - 15
L4RETRIES n
for all lines in a path. The extended packet header format allows increased throughput
over high bandwidth and multi-line paths.
The L4EXTPACKETS_ON modifier is required for the variable packet size and
congestion control features and for Expand line-handler processes that are part of a
multi-CPU path. The L4EXTPACKETS_ON modifier is also required to support the
larger message size of 60K bytes. If the modifier is not set ON, the message size will
be 32K bytes.
The L4EXTPACKETS_OFF modifier specifies that the older 16-byte packet header
format should be used. It can be used to provide performance compatibility with lower-
speed lines.
L4RETRIES n
Default: 3
Units: Not applicable
Range: 1 through 255
This path modifier is applicable to all Expand line types. This modifier specifies the
number of times that the Expand line-handler process will try an end-to-end (Layer 4)
request before reporting an error. You should read the description of Layer 4 retries in
Section 17, Subsystem Description, before using this modifier.
L4SENDWINDOW n
Default: 254
Units: Packets
Range: 187 through 254
This path modifier is applicable to all Expand line types. This modifier specifies the
size, in packets, of the Layer 4 send window. This window determines how many
packets are sent before an acknowledgment is required. The default value allows up to
254 unacknowledged packets in any single end-to-end (Layer 4) connection.
The L4SENDWINDOW modifier value should be reduced from the default of 254 for
p
aths that consist of multiple lines of greatly varying speeds. Using the default value in
this type of configuration can cause the retransmission of many packets during error-
recovery and can increase out-of-sequence (OOS) packet processing.
For example, if a path has two lines, one at a speed o
f 224 Kbps and the other at a
speed of 19.2 Kbps, setting the L4SENDWINDOW modifier to its lower limit of 187 will
help ensure that packets traveling on the faster line are not discarded because they
are too far ahead of packets traveling on the slower line.
Note. The L4RETRIES modifier value should be set to the same value for every Expand line-
handler process on every node in the network.