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XEROX SDD ARCHIVES
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Reviewer Date
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BUSINESS SYSTEMS
Systems Development Department
To: Distribution Date: October 10, 1978
From: Hal Murray Org: SDD/SD System Architecture
Subject: Alto Gateway Operation Filed: [Iris] AltoGateway.bravo&press
111is memo documents the operation of the Alto Gateway program. You are assumed to be
reasonably familiar with Altos. Familiarity with Mesa will be very helpful. You might also want to
read Ed Taft's memo titled "Nova Gateway Operation". It is stored on
[IVY] GatewayOperation.press.
I have avoided any details of the current network topology since it is changing frequenlly. There
arc two documents that are very helpful when trying to track down network troubles. They are
[MAXC] AltoNetwork.prcss and [MAXC] Pup-Network. txt. I suggest that you keep a
reasonably up to date copy handy.
There is also a one page summary on Iris] AltoGateSummary.bravo&press.
1. Normal Operation
Power Up and such
The only problem with turning a Gateway Alto on and/or off is setting the time if there is
not another Gateway connected to the n011nal Ethernet. If the Alto asks you to set the date
and time, the trick is to use text such as in "Jul" rather than a number for the month. If
you get really frustrated, tC or SIIIFT-SWA'f will also get you past this problem.
Starting the Gateway Program
Type the command Gateway followed by carriage return. The program will, read the
parameter file, print out a few messages about boot files, print a few informational messages,
pause for a while, and finally print the message "Gateway of date-time in operation". At
this point the Gateway program is running. However, it takes approximately one minute for
new routing infonnation to be propagated throughout the inter-network, so it may not be
possible for connections to bt: established through the Gateway during the first minute after
the Gateway program is started. About a minute after the program is started, the display
will get turned off.
The Alto Display
'The display is turned off shortly after the Gateway program is started. This conserves CPU
cycles, and saves the core that would be needed by the bitmap. NOlmally the screen will be
all black. [f you type anything on the Keyboard, the picture will normally reappear. If the
disk is active, the screen will switch to all while. This happens while the Gateway is
sending a boot file, searching the name lookup data base, or receiving a new copy of a file.
If you want to see if the Gateway is alive, watch the cursor, or hit the space bar.
Whenever any character is typed in, the display wilt be turned on for 30 seconds. If the
Gateway program is funning in debugging mode, the display is turned on for 5 seconds
Alto Gateway Operation 2
whenever it prints out an infOlmational message. Normally, it stays off, and the messages
can be found in Mesa.typescript if you are interested.
The cursor will move one step to the right for each Pup that is forwarded, 50 steps left for
each Pup that cannot be forwarded, and one step down for each Pup received by the Echo
server or the Miscellaneous Services server.
If the Gateway has an SLA line driven by an ErA board, there are troubles keeping the
clock accurate when the display is on. To avoid sending out inacurate infol1lJation, the Pup
Time Server is disabled whenever the display is turned on. It is automatically reset when
the display goes off.
Gateway Program Commands
The Gateway program has a simple command interpreter that responds to single-character
commands typed on the keyboard. Whenever a character is typed, the display is turned on
for 30 seconds.
If you are using an EIA board, any command will disable the time server.
The commands are as follows (the "?". or any unrecognized character elicits this list):
Gateway Statistics
Prints out a summary of various operating statistics, including the length of time
Gateway program has been running (hours:minutes:seconds), the number of times
each server has been invoked (explained later in this memo), and a matrix showing
number of packets forwarded from one directly-connected network to another. The
number of discarded packets is also listed. Discard of packets is not cause for
alarm: it is a normal consequence of the great disparity in speed between the
Ethernet and the leased lines, and does not give rise to loss of information in file
transfers or terminal connections.
SLA Statistics
Prints out operating summaries for the Synchronous Line Adaptor (SLA) Le. the EIA
board or the CommProc. For each line, the number of packets successfully sent
and received on that line is printed, followed by the number of instances of three
types of errors: eRe (Cyclical Redundancy Check) errors, Sync errors (bit
synchronization was lost), and Control sequence errors. The total number of errors
should be much less than one percent of the packets successfully received. If a high
error ratt: occurs on a single in-usc line (whose state is "Up"), the line or modem is
suspect, whereas if frequent errors occur on all lines (or particularly on "Looped
back" lines), the SLA interface is suspect.
'This command also prints out the SLA routing table. Under normal circumstances,
the routing table for a particular Gateway should show that it can reach aU other
Gateways through one or more of the connected lines.
Reset Time
The Gateway program maintains the current date and time, which it gives out to
other hosts that request it. The date and time are obtained from another Gateway
when the Gateway program is started. The Reset Time command causes the local
date and time to qe invalidated so as to f()rce the Gateway program to reset itself
from another Gateway. This is necessary if the local lime has become incorrect.
Probe for New Directory
A data base of host names and addresses is maintained at Parc and distributed to all
Alto Gateway Operation 3
Gateways for use in responding to name lookup requests from Altos. The data base
distribution procedure is automatic, with requests for data base update generated
once per hour. The Probe for New Directory command simply forces such an
update to occur immediately.
Local Routing Table
This command prints out the routing table used by the Pup Software to determine
where to send a pup to get it to its final destination. 0 hops means that this
gateway is directly connected to that network by tile net and host number indicated.
If the hop count is greater than 0, then the pup will be forwarded to anoilier
gateway at ilie indicated address for further processing.
Echo
There is an Echo user program built into the Gateway. It is very similar to the one
in PupTest. If you arc Echoing to yourself, ilie $ won't get printed, but the cursor
will move down one step each time a packet gets echoed.
Debug
This command causes control to be given to the Mesa Debugger (if there is one on
the disk). From within the Debugger, the Gateway program is resumed by typing P
(for Proceed) and confirming WiUl a RETURN.
Toggle Display
This command toggles a lock on the display. If The display was off, or on
temporarily, it will be turned on, and the 30 second timer will be disabled. If it was
on, it will be turned off. If you Ulink the display will timeout, but you want to be
sure that it will go off without wailing, hit the T key twice. The first one will lock
the display on, and the second one will turn it off.
x
This belches forth reams of statistics that arc probably only interesting to
programmers and/or hardware debuggers.
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