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Conference netcad::hub_mgnt

Title:	DEChub/HUBwatch/PROBEwatch CONFERENCE
Notice:	Firmware -2, Doc -3, Power -4, HW kits -5, firm load -6&7
Moderator:	NETCAD::COLELLADT

Created:	Wed Nov 13 1991
Last Modified:	Fri Jun 06 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	4455
Total number of notes:	16761

1779.0. "Connected Stations" by KERNEL::EVANSN () Tue Dec 13 1994 10:33

Can anybody explain to me what the mechanism for displaying connected stations 
is ? I have a customer who is seeing inconsistent connected station info on a 
DECrepeater 90T with DECagent 90 v2.1 whilst running HUBwatch VMS V3.1.

What I am after in particular is does the repeater tell the agent what addresses
it has ever seen, or only addresses it has recently seen ? If the latter how 
many addresses can be held by the agent and is there a time when not seeing a
certain address will cause the agent to purge that address out. ?

Also is this reliable ??

Regards

Neal Evans - UK CSC

T.R Title User Personal
Name Date Lines

1779.1 Address information NETCAD::WALTER Fri Dec 16 1994 11:46 47

T.R	Title	User	Personal Name	Date	Lines
1779.1	Address information	NETCAD::WALTER		`Fri Dec 16 1994 11:46`	47
	Neil, The way the address data is collected depends on where the repeater is physically located. If it is in the same hub as the DECagent 90, then the agent gets the information directly from the repeater (through the backplane serial channel). If the repeater is in a remote hub, the agent must request the address info from the DECbridge 90 that services that hub. Case: Repeater in agent hub The agent periodically polls the repeaters in the hub, asking them for the last address seen on a per port basis. Polling is roughly every 30 seconds. The agent can hold up to 256 addresses in its database, each address associated with a particular repeater port. Addresses are aged out every 7 minutes by default, but this number can be changed through the dechub90 mib object da90BackplaneAddr- DbAgingTime (I'm not sure if this is available from Hubwatch). This is not a foolproof scheme; the repeater only reports the last address seen on a port since we asked it. Other addresses may exist on that port, and we hope that through constant polling we pick them all up, but it's a statistical thing. So it's possible that a station will live on a port but we won't pick up its address. We have this limitation because the agent can't see addresses on the ethernet, so it has to "fish around" for what is there. You didn't expound on "inconsistent connected station info", but you should not see a bad address on a port, unless the station had just moved and the entry didn't yet age out. Case: Repeater in remote hub In this case, it is the DECbridge 90 which is accumulating the address information. It does this differently. Being a bridge, it can amass a table of addresses seen on the workgroup side of the bridge. It then polls the repeaters, asking each one "have you seen this address on a port?" So the bridge already knows what addresses to look for, and is more likely to find all known addresses. The bridge has a limit of 200 addresses. I don't know what the poll frequency or age time is, but I can look around for those numbers. I hope this helps. Regards, Dave

Neil,
    
    The way the address data is collected depends on where the repeater is 
physically located. If it is in the same hub as the DECagent 90, then the
agent gets the information directly from the repeater (through the backplane
serial channel). If the repeater is in a remote hub, the agent must request
the address info from the DECbridge 90 that services that hub.

    Case: Repeater in agent hub
	The agent periodically polls the repeaters in the hub, asking them
	for the last address seen on a per port basis. Polling is roughly
	every 30 seconds. The agent can hold up to 256 addresses in its
	database, each address associated with a particular repeater port.
	Addresses are aged out every 7 minutes by default, but this number
	can be changed through the dechub90 mib object da90BackplaneAddr-
	DbAgingTime (I'm not sure if this is available from Hubwatch).

	This is not a foolproof scheme; the repeater only reports the last
	address seen on a port since we asked it. Other addresses may exist
	on that port, and we hope that through constant polling we pick them
	all up, but it's a statistical thing. So it's possible that a station
	will live on a port but we won't pick up its address. We have this
	limitation because the agent can't see addresses on the ethernet, 
	so it has to "fish around" for what is there.

	You didn't expound on "inconsistent connected station info", but
	you should not see a bad address on a port, unless the station
	had just moved and the entry didn't yet age out.

    Case: Repeater in remote hub
	In this case, it is the DECbridge 90 which is accumulating the
	address information. It does this differently. Being a bridge,
	it can amass a table of addresses seen on the workgroup side of
	the bridge. It then polls the repeaters, asking each one "have
	you seen this address on a port?" So the bridge already knows
	what addresses to look for, and is more likely to find all known
	addresses. The bridge has a limit of 200 addresses. I don't know
	what the poll frequency or age time is, but I can look around for
	those numbers.
		

I hope this helps. 

Regards,
Dave