Conference netcad::hub_mgnt

879.0. "Repeater90 (C) address discovery mechanism" by BACHUS::VANDENBERGHE () Fri Apr 01 1994 05:58

	Hi,
	
	Is it possible to explain how a DECrepeater 90C or other identifies a 	
	connections.

	I made the following tests:
	
	1. PC connected on one port running LAST/LAT
	   From DOS or Terminal Emulator, connect to a LAT service 
	   (sethost bis6)

	   On the PC the following message is received:

Brussels Datacenter BRSISB VAX 6540 VMS V5.5-2

                     PROPERTY OF DIGITAL EQUIPMENT CORPORATION

                                  INTERNAL USE ONLY

                 UNAUTHORISED ACCESS TO THIS NETWORK IS PROHIBITED

Username:

	Looking at the Repeater summary status, I have 'No Connected Stations' 	
	for that specific port.
	Only after somme exchanges (pressing return � 10 times on the PC), the 	
	hardware address appears on the repeater.

	This correspond to � 100 frames exchanged between the PC and the LAT 	
	server.

	2. Starting DECnet on the PC, the Physical address appears nearly 	
	immediately. (I didn't measured the numers of frames exchanged with that
		protocol).
	
	So the question, how does the repeater/agent decides that a device is 
	connected on a port?

	Another question.
	A Repeater may display several adresses (Hardware and Physical) after a 
	while one address will be removed (I have measured � 7 minutes, is this 
	a default parameter that we can change somewhere (in the Repeater MIB?)
 
	Thanks in advance,
	Robert

    See note 875.
    
    -Bob

	Bob, I don't think this question has anything to do with DECagent 
	and HUBwatch rev levels. It depends more on what is being used to 
	query the DECrepeater 90C - DECbridge, DECagent V2.0, or DEChub 900 
	agent.

	The DECrepeater 90C (and 90T, 90FA, 90FL) captures the last source 
	address to come through on each port. It will report that address 
	if queried on the backplane for the last address.

	Alternatively, the 90C can be given an address and told to report 
	whether a match was found.

	So the answer depends on which module is hub bus master, and how 
	often it polls each slot and port. I'm not sure what the address 
	aging algorithm is that is used by each bus master.

    OOps.  I answered the wrong note.  My answer applies to note
    878 not 879.  Please ignore .1
    
    Bob