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BUSINESS SYSTEMS
Systems Development Department

To: Distribution Date: September 20, 1978

From: Hal Murray Org: SDD/SD System Architecture

Subject: Alto Gateway Operation Filed: [Iris] Memos> AltoGateway,bravo

This is my first attempt at modifing Ed Taft's memo titled "Nova Gateway Operation" to describe
how to run the new Alto Gateway/Router program. Comments and such are desired.

This 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.bravo.

I have avoided any details of lhe current network topology since it keeps changing so often these
days. There are two documents that are very helpful when trying to track down network troubles.
111ey are [MAXC) AltoNetwork.press and [MAXC) Pup-Network.txt. I suggest that you
keep a reasonably up to date copy handy.

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 Lo the normal Ethernet. If the Alto asks you to set the date
and time, the trick is to use text such as in "lui" rather than a number for the month. If
you get really frustrated, SIIIFT-SW AT 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 ICw messages about boot tiles, 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 information to be propagated throughout the inter-network, so it may not be
possible for connections to be 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
'111e display is turned off shortly after the Gateway program is started. '111is conserves CPU
cycles, and saves the core that would be needed by the bitmap. Normally the screen wilt be
all black. If you type anything on the Keyboard, it will reappear. If the disk is active, the
screen will switch to all white. 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.
Alto Gateway Operation 2

Whenever any character is typed in, the display will be turned on for 30 seconds. If the
Gateway program is running in debugging mode, the display is turned on for 5 seconds
whenever it prints out an informational 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 EIA board, there are troubles keeping the
clock accurate when the display is on. To avoid sending out inacurate information, 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.

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). 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 rate occurs on a single in-use
line (whose state is "Up"), the line or modem is suspect, whereas if frequent errors
occur on all lincs (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 all other
Gatcways through one or more of the connected lines.

Reset Time

'(be Gateway program maintains the current date and time, which it gives out to
other hosts that request it. '111c date and lime arc obtained from another Gateway
when the Gateway program is started. 'Ibc I~cset Time command causes the local
date and lime to be invalidated so as to tbrce the Gateway program to reset itself
from another Gateway. 'Ibis is necessary if the local time has become incorrect.

Probe for New Directory
A data base of host names and addresses is maintained al Parc and distributed lo aU
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 the net and host number indicated.
If the hop count is greater than 0, then the pup will be forwarded to another
gateway at the indicated address for further processing.
Echo
There is an Echo user program built into the Gateway. It is just like the one in
PupTest. If you are Echoing to your self, the $ 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 with a RETURN.
Toggle Display
'This command toggles a lock on the display. If The display was off, or on
temporatily, it will be turned on, and the 30 second timer will be disabled. If it was
on, it will be turned off.
x
This belches forth reams of statistics that are probably only interesting to
programmers and/or hardware debuggers.
'This is a dummy command that just turns the display on for 30 seconds.
Boot File Table
This just prints the table used by the Boot Server. It includes counters so you can
see which files are really used in case the disk gets full.
Cache for Name Lookup Server
'This prints out the current contents of the cache maintained by the Name Lookup
server.
Quit
Terminates the Gateway program and causes control to return to the Alto Executive,
which responds with an @.

Bugs
If the Gateway program gets into trouble, it will probably print a message on the display
and wait for a person to do something. At this point, there arc two options. [f you have
Alto Gateway Opcration . 4

the Mesa Debugger on your Gateway disk, you can get to it and poke around. Normally
there won't be room for it. In that case, you can only get to SWAT. I think I can do a
reasonable job of diagnosing bugs if you are careful to save SWATEE an the right time. 'The
trick is to be sure the the right information is there, and to avoid clobbering it. If the
Gateway program is waiting for you to hit SWAT, do so. That will write the current core
image into SWATEE. The Alto will then go to either SWAT or the Mesa Debugger. In either
case, reboot it. tK or SHIFf-SWAT will overwrite SWATEE. Then FTP SWATEE away to a safe
place. Remember that FfP only knows how to talk to machines that are connected to the
normal Ethernet board. If you don't have an IFS handy, you can store it on another Alto
until you get the Gateway back up again.
There are three general categories of troubles. The first is a problem during initialization.
Hopefully, the text will be sufficient to solve the problem. The most likely cause is a bug in
GateParamctcr.txt. If you run into a message that is too cryptic, please let me know, and I
will fix it. The second is a uncaught SIGNAL. It will be printed in octal, and a listing of
Gateway.signals (from [IRIS] Gateway.signals