3Com 3031 Command Reference Manual page 376

376 C 4: L L
HAPTER INK AYER
x25 packet-size
P
ROTOCOL
order, like "...2, 3, 4, 5, 6..." "Cyclically" means that the numbering starts again
from the beginning when a certain number (called modulus) is reached. For
example, when the modulus is 8, the numbering goes "...4, 5, 6, 7, 0, 1...".
X.25 defines two numbering modulus: 8 (also called the basic numbering) and
128 (also called extended numbering), and the X.25 of the 3Com series routers
supports both views.
For the related commands, see display interface, x25 call-facility, x25 map, x25
pvc, x25 switch pvc, x25 xot pvc, x25 fr pvc, and x25 window-size.
Example
Set the modulus on the X.25 interface Serial0/0/0 to 128.
[3Com-Serial0/0/0] x25 modulo 128
Syntax
x25 packet-size input-packet output-packet
undo packet-size
View
Interface view
Parameter
input-packet: Maximum input packet length in bytes, its value ranges from 16
to 1024 (including 16 and 1024) and must be the integer power of 2.By
default, the maximum input packet length of X.25 interface is 128 bytes.
output-packet: Maximum output packet length in bytes, its value ranges from
16 to 1024 (including 16 and 1024) and must be the integer power of 2. By
default, the maximum output packet length of X.25 interface is 128 bytes.
Description
Using the x25 packet-size command, you can set the maximum input and output
packet lengths of X.25 interface. Using the undo x25 packet-size command, you
can restore their default values.
Usually, the X.25 packet-switching network has a limitation of the transmission
packet size, and the maximum size of a data packet sent by the DTE shall not
exceed this size (otherwise it will trigger the reset of the VC).In this way, the DTE
devices at sending end and receiving end are required to have datagram
fragmentation and reassembly functions. The DTE device at sending end
fragments the datagram with a length exceeding the maximum transmission
packet length based on the maximum transmission packet length, and sets M bit
in other fragments besides the final fragment. After receiving these fragments, the
DTE at receiving end will reassemble them as a datagram to submit the upper-layer
protocol based on the M bit. Please consult users' ISP about this maximum
receiving packet length.