GarrettCom 14E manual Rules-of-thumb Collision Domain Calculations

Magnum14E Media Converters Installation and User Guide (10/02)

(DTEs) which have the longest round trip delay time.

PDV = (sum of cabling delays) + (sum of repeater & media converter delays) + (DTE pair delays) + (safety margin)

PDV is the Path Delay Value of the worst case path. For the network to adhere to IEEE 802.3u standard, this value must be less than 512 BT. The safety margin is specified in BT and may be a value between 0 and 5. This margin can be used to accommodate unexpected delays, such as an extra long patch cable. A safety margin of at least 2 to 4 BT is recommended.

“Rules-of-thumb” Collision Domain Calculations

Rules-of-thumb, while inexact, may be helpful in planning network topology. As a rule-of-thumb, a Class II Repeater has a PDV of about 90 to 95 BTs, and twisted-pair or fiber

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