Web Interface Settings Glossary 90
HDLC Menu (VHSI/Protocol Tree) (when protocol is set to X.25)These parameters are only available when the protocol is set to X.25.
Maximum Frame Size N1
Defines the maximum frame size.
This parameter can generally be determined by adding 5 to the Maximum Packet Size.
However, if your Maximum Packet Size is less than 256, and you are using the Fast Select
feature, then find the size, in bytes, of the following para meters and add them together:
• Direct Header (1)
• HDLC Packet Header (2, or 3 for extended sequence)
• X.25 Packet Header (3, or 4 for extended sequence)
• DTE Address Length (1)
• DTE Address (0 to 15)
• Facility Length (1)
• Facilities (0-63)
• User Data (0-16)
•Fast Select
• Client Data (0-128)
If the exact value cannot be calculated, this parameter can be set to a higher value than needed.
For example, if set to 261, it will accommodate any packet size up to 256 bytes.
Connections using the X.25 protocol use the HDLC protocol at a lower level. As a result, the
valid ranges and default values may vary as follows:
HDLC only:
• Range: 1-8194.
• Default: 1504.
X.25 over HDLC:
• Range: (X.25 Max Packet Size + 5) - 1029.
• Default: 144.
Maximum Window Size K
Defines the Maximum Window Size, which is the number of frames that are to be sent before
the Eicon 1530 waits for an acknowledgment from the remote device. In certain situations, you
may wish to define a large window size (with satellite networks that have significant
transmission delays, for example). The maximum window size can never be exceeded, and it
must match on both sides of the link.
Range: 1-7, or 1-127 if Extended Sequence Mode is enabled. Default: 7
Extended Sequence Mode is defined with the ‘Sequence’ parameter.