TP-Link TL-SG2008 manual Version, Hello Time, Max Age, Forward Delay, TxHold Count, Max Hops

The following entries are displayed on this screen:

¾Global Config

STP:	Select Enable/Disable STP function globally on the switch.
Version:	Select the desired STP version on the switch.
	z STP: Spanning Tree Protocol.
	z	RSTP: Rapid Spanning Tree Protocol.
	z	MSTP: Multiple Spanning Tree Protocol.

¾Parameters Config

CIST Priority:Enter a value from 0 to 61440 to specify the priority of the switch

for comparison in the CIST. CIST priority is an important criterion on determining the root bridge. In the same condition, the switch with the highest priority will be chosen as the root bridge. The lower value has the higher priority. The default value is 32768 and should be exact divisor of 4096.

Hello Time	Enter a value from 1 to 10 in seconds to specify the interval to
	send BPDU packets. It is used to test the links. 2*(Hello Time + 1)
	≤ Max Age. The default value is 2 seconds.
Max Age:	Enter a value from 6 to 40 in seconds to specify the maximum
	time the switch can wait without receiving a BPDU before
	attempting to reconfigure. The default value is 20 seconds.
Forward Delay:	Enter a value from 4 to 30 in seconds to specify the time for the
	port to transit its state after the network topology is changed.
	2*(Forward Delay-1) ≥ Max Age. The default value is 15 seconds.
TxHold Count:	Enter a value from 1 to 20 to set the maximum number of BPDU
	packets transmitted per Hello Time interval. The default value is
	5pps.
Max Hops:	Enter a value from 1 to 40 to set the maximum number of hops
	that occur in a specific region before the BPDU is discarded. The
	default value is 20 hops.
Note:

1.The forward delay parameter and the network diameter are correlated. A too small forward delay parameter may result in temporary loops. A too large forward delay may cause a network unable to resume the normal state in time. The default value is recommended.

2.An adequate hello time parameter can enable the switch to discover the link failures occurred in the network without occupying too much network resources. A too large hello time parameter may result in normal links being regarded as invalid when packets drop occurred in the links, which in turn result in spanning tree being regenerated. A too small hello time parameter may result in duplicated configuration being sent frequently, which increases the network load of the switches and wastes network resources. The default value is recommended.

3.A too small max age parameter may result in the switches regenerating spanning trees frequently and cause network congestions to be falsely regarded as link problems. A too large max age parameter result in the switches unable to find the link problems in time, which in turn handicaps spanning trees being regenerated in time and makes the network less adaptive. The default value is recommended.

4.If the TxHold Count parameter is too large, the number of MSTP packets being sent in each hello time may be increased with occupying too much network resources. The default value is recommended.

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