3Com MSR 50 Series Configuration Manual page 289

cannot perform traffic control effectively and correctly unless correctly configured.
Any inappropriate configuration will cause CLEAR and RESET events of X.25. As
most public X.25 packet networks use the default window size and maximum
packet size specified in ITU-T X.25 Recommendation, the device also adopts the
same default values. Therefore, you need not set the two parameters unless
requested by the access service providers.
After the default window size and the default maximum packet size are set, the
SVC, which can be established only via calling, will use these default values if
related parameters are not negotiated in the call process. (Parameter negotiation
will be described in the later sections). The PVC, which can be established directly
without calling, will also use these default values if no window size or packet size
option is appended when it is specified. (Refer to
X.25 over FR" on page
An X.25 sender will fragment the oversize data packets at the upper layer based
on the maximum packet size, and mark the final fragment packet (M bit not set).
After the packets reach the receiver, X.25 will reassemble the fragment packets,
and determine whether a piece of complete upper layer packet is received based
on the M bit flag. Therefore, too small value of the maximum packet size will
consume too much router resources on message fragmenting and reassembling,
thus lowering efficiency.
Note that:
The maximum packet size < 8*MTU < N1 of LAPB
■
Reset interface using the shutdown and undo shutdown commands to
■
make new configuration take effect
Configuration procedure
To configure X.25 interface parameters, use the following commands:
To do...
Enter system view
Enter interface view
Configure the link layer
protocol as X.25
Set an X.121 address
for the interface
Set X.25 VC range
311).
Use the command...
system-view
interface interface-type
interface-number
link-protocol x25 [ dce |dte ]
[ ietf | nonstandard ]
x25 x121-address
x.121-address
x25 vc-range { bi-channel ltc
htc [ out-channel loc hoc ] |
in-channel lic hic
[ bi-channel ltc htc ]
[ out-channel loc hoc ] |
out-channel loc hoc }
Configuring X.25
"Configuring PVC Application of
Remarks
-
-
Required
The default link layer protocol is
PPP by default. With X.25 enabled,
the default operation mode is DTE
IETF.
Optional
If the device is used for the purpose
of X.25 switching, this task can be
skipped. If it is connected to X.25
public packet network, you must
set an X.121 address for the
connected X.25 interface.
Optional
By default, lower and upper limits
of two-way channel are 1 and
1024, of incoming-only channel are
both 0, of outgoing-only channel
are both 0
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