Eicon Networks 1550 - Manual (Page 107)

Web Interface Settings Glossary 107
HDLC Menu (VHSI Tree) (X.25)
Note: The HDLC menu is only accessible through the Protocol page, 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 parameters 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.