DEC DECrepeater 90T, Руководство пользователя

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Management Details 49
Annotating the Bridge Address Table
The DECbridge 90 SHOW ADDRESS command will list the DECrepeater
slot number and port number for every station in the work group that
is connected to the same DEChub via a DECrepeater. However, there is
some time lag between when the time changes are made to the network
topology, and the reflection of that information in the DECbridge 90
address table. The algorithm for creating this information proceeds as
follows:
For every station in the work group
Tell the repeaters to wait for a message from this station.
Wait (up to 90 seconds) for the station to transmit a message.
Ask the repeaters what port it came from.
The algorithm will wait up to 90 seconds for a station to transmit a
message, before it gives up and proceeds onto the next station. In a
typical network situation, this information will be complete in a matter
of minutes. After a bridge is newly installed or reset, you can expect
this information to be complete after about 10 minutes of operation.
However, if there are stations in the work group that do not often
transmit messages, the DECbridge may hang on those stations for as
long as 90 seconds each before giving up and going on to the next one. If
you add a station, or move it to another port, you can expect it to take
about 10 minutes before SHOW ADDRESS will recognize this move. If
you remove a station from the network entirely, it will take a full address
age time (default is 30 minutes) for the DECbridge 90 to notice. If you
remove many stations at once, the DECbridge 90 will hang on each of
these stations for 90 seconds at a time, until they age out of the bridge
address database. In this case, it will usually take the full address age
time (30 minutes) before the port number annotations are complete.
As a worst case example, if it takes 60 seconds for each of the allowed
200 stations to transmit a message, it could take 200 minutes to complete
the address database annotations. However, the DECbridge will try
to hurry things along. If after 30 seconds of waiting for a message,
the station remains quiet, the DECbridge 90 will attempt to generate
a response via the IEEE XID request. If that doesn’t work, it will try a
MOP System-ID request. Because of this, it will never hang for more than
30 seconds on an IEEE conforming station, nor more than 60 seconds on
any DIGITAL station that predates the IEEE specifications. If you are
monitoring messages and protocols on your work group Ethernet, you will
occasionally see these messages.
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