TECHNICAL BULLETIN                            PERFORM
LANtastic Performance Issues                  08.07.91
                                              Page 1 of 5


The following information is based on in-house testing of
LANtastic.  If you are not a registered LANtastic owner, your
questions should be directed to our technical sales staff at (602)
293-6363.  Any questions or comments on this bulletin may be
forwarded by FAX (602) 293-8065 or mailed to : Artisoft Inc., 575
East River Road, Tucson, AZ., 85704, ATTN: Technical Support.

                   GENERAL HINTS AND TIPS 
          INCREASING PERFORMANCE OF LANTASTIC NETWORKS


"What can I do to speed up my LAN?" A very common question, and one
to which there is unfortunately, no cut and dried answer. Network
performance depends on many things: to get the best performance out
of your particular installation may require a little
experimentation. This bulletin presents a discussion of some of the
major factors that affect performance, and a few general
suggestions for improvement.

Choosing your Hardware

When you're choosing the hardware for your LAN, keep in mind that
the things that make a fast computer are also the basic ingredients
of a fast network. A fast processor, fast memory and a fast disk
drive all help to provide better network speed. For best
performance, you should choose fast, well balanced components. The
two biggest factors are CPU speed and hard disk speed. 

It's fairly easy to find fast computers and fast disk drives out
there in the marketplace, but for the best results make sure that
the components you buy are well matched. If you install a high
performance disk drive in a 4.77 Mhz XT, your network will be slow
because the computer's CPU won't be able to move data around fast
enough to keep up with the drive, let alone the rest of the
network. Similarly, if you install an old 20mb MFM drive in your
386-33, the fast processor will spend a lot of time waiting around
for the old drive, as will the rest of your network users.

The transmission speed of the adapter cards you choose will also
make a difference. With reasonably fast machines, upgrading from a
LANtastic 2mbps adapter to a new Artisoft Ethernet adapter can
approximately double the throughput of the network. Again, balance
is vital. If you have a slow processor, switching to Ethernet may
not make much difference -- the 2mbps adapter has a coprocessor
that handles all the low level NetBIOS processing, whereas the
Ethernet adapter relies on the computer to handle everything.  

Optimizing Software Performance

Now that we've dealt with hardware selection -- the easy stuff --
let's see what can be done to improve the performance of existing
installations. First, let's tie down what we mean by the "speed" of
the LAN. There are really two things at issue here, the physical
transmission speed of the hardware, and the effective throughput,
or how fast data gets from one place to another on the LAN.
Assuming for now that the hardware is fixed and immutable, here are
some suggestions for getting the best throughput with your
particular application.

General Improvements

One thing that can improve performance on most networks is running
the DOS FASTOPEN command on the server if you have DOS 3.3 or 4.01.
FASTOPEN tracks the location of frequently used files and
directories and greatly decreases the amount of time it takes to
open files. (We have received reports of a problem in MS DOS 5.0
FASTOPEN.)

Another change to improve performance on networks running NOS 3.0x
is eliminating the I from each disk resources Access Control List. 
With the I ACL in place each time a file is opened the NOS checks
to see if the file is an indirect file.  If you are not using
indirect files eliminating this ACL will save time when a file is
opened.

You can reduce the load on heavily used networks by disabling the
Send Server ID selection in NET_MGR, Server Startup Parameters. 
With this selection enabled the server sends out a message once
every retry period (55ms x retry_period setting), this message is
just that the machine is a server and available.  If your system is
using batch files this message is not needed.

Adding a disk cache to the server also helps performance in almost
all situations. Disk caching programs work by storing frequently
requested information in memory. This reduces the number of
physical accesses to the disk. Since accessing memory is almost
always faster than accessing the disk drive, caching can greatly
improve the disk performance of your network. 

The LANtastic disk caching program LANcache, is specifically
designed to work with LANtastic networks. It caches disk writes as
well as disk reads and when it actually does have to write to the
disk, it does so as a background operation so that CPU operations
can continue. 

Choosing the Best Buffer Settings

Beyond these general speedups, getting the best performance out of
your specific application is a matter of fine tuning several
parameters. LANtastic has four sets of buffers, each of which can
affect performance in specific situations. 
Redir Buffers

It takes the network about the same amount of time to send 1 byte
of data as it does to send 256 bytes of data. Every packet sent
over the network takes time to construct and time to process. Given
this, it makes sense to include as much data as possible in each
packet -- it keeps the overhead's impact to a minimum and reduces
network traffic. The REDIR program accomplishes this by buffering
network requests at each machine. Here's an example of REDIR's
buffering in action: 

You are creating a file of customer names on the server and adding
data to it. You type in the names one at a time and your program
writes the names to the data file one at a time. Rather than issue
a network send for each name, the data gets stored in the local
REDIR buffer until you close the file or fill the buffer. At that
point, REDIR issues a single request to send the entire buffer.

REDIR buffers read requests similarly. If you request an amount of
data smaller than the REDIR buffer, REDIR requests one buffer full
of data from the server. Then, if you request the next sequential
piece of data, REDIR can supply it to your program without even
making a network request.

If you read or write blocks of data larger than the REDIR buffer,
the network software bypasses it and deals directly with the
NetBIOS. The ideal REDIR buffer size then, would be about the
average size of the packets that your network typically sends and
receives. You can set the size of the REDIR buffers with the SIZE=
command line switch.

The number of REDIR buffers can also affect the performance of many
applications. If you allocate multiple REDIR buffers using the
BUFFERS= command line switch, the network tries to associate each
one with a file handle. Network printers are handled just like
other files. Ideally, you should have a buffer available for each
open network file. If you have more files than available buffers,
the network flushes the least recently used buffer and assigns it
to the new request.

WordPerfect is a good example of a program that is affected by the
number of buffers. If you have only one buffer allocated, printing
can be very slow because WP has to read the document and send data
to the printer with the same buffer. The poor buffer gets
continually filled and flushed, back and forth, with printer data
and document data. In this situation, allocating just one more
buffer allows WP to use one buffer for document reading and another
for printing. 

Server Buffers and Tasks

A server buffer is at the other end of a REDIR buffer. When, for
example, a workstation makes a read request, the server reads one
server buffer full of data, beginning with the information
requested. If the workstation then asks for the next piece of the
same information, the server can get it from the buffer instead of
physically reading the hard disk.

The server buffer size can be changed from the Server Startup
Parameters option in the NET_MGR program. Be aware that bigger
isn't necessarily better -- as with REDIR buffers, the optimal size
is somewhere around the average size of the packets that will be
transferred across the network by your application. One server
buffer of whatever size you select is allocated for each network
task.

When a workstation submits a request to a server, the server will
work on the request for a while, then switch to work on the next
task for a while, and so on, in a round-robin fashion. If the
server is set up with only one network task, instead of switching,
the server will run the request to completion and other incoming
tasks will be queued up behind it. From the user's standpoint, the
station that submitted the first request will get very good
performance, and everyone else will be kept waiting. In general,
allowing more than one network tasks will ensure that everyone's
requests get processed and will result in "smoother" network
performance.

If you're a using network adapter with a coprocessor, like our
Enhanced 2mbps adapter, increasing the number of network tasks
(with the Server Startup Parameters option of NET_MGR) will give
you a big performance boost. While the coprocessor is busy working
on one task, the server's CPU can work on another. This advantage
is multiplied if you have more than one coprocessor equipped
adapter in a server. In fact, with three or four 2mbps boards in a
dedicated server and a corresponding number of network tasks, you
can achieve a continuous throughput comparable to that of an
Ethernet network with an equal number of stations. As a plus,
you've got built-in redundancy -- the workstations connected to
each adapter will function as separate networks. If one segment
fails because of cabling or adapter problems, the rest will still
operate.

During testing at Artisoft, it was discovered that performance was
at it's optimum with NOS 3.0, 3.03 or 4.00 running on Artisoft's
ethernet adapters when Network Tasks were set to 3 in Server
Startup Parameters.  Artisoft is currently investigating why these
setting are optimum and it is currently unknown if the same results
would be found when testing with Artisoft's Enhanced 2Mbps adapters
or other vendor's adapters with LANtastic AI.

Printer Buffers

As with REDIR and server buffers, increasing the size of your
printer buffers can improve printing speed. If your server has more
than one printer attached, increasing the number of printer tasks
will allow it to print to more than one printer simultaneously. 
NetBIOS Buffers and Adapter Memory 
If your network is very active, try increasing the number of
buffers used by your adapter's NetBIOS. This will decrease the size
of the packet of data that your adapter will send and can increase
the speed with which your network handles user requests. With
LANBIOS or LANBIOS2, you can do this with the BUFFERS= command line
switch. With AE-2, NE-3 and other Ethernet drivers for AI-LANBIOS,
use the PACKET_SIZE= switch. If your network doesn't have a lot of
contention, you can decrease the number of NetBIOS buffers so that
the server can process larger blocks of data. 

With our AE-2 card, there's an easy way to get a performance boost
on heavily loaded networks. You can upgrade the adapter from its
default 16K configuration to a full 64K of RAM. The chips can be
purchased direct from Artisoft, or you can use chips that meet the
specifications in the AE-2 manual.

Effects of Changing Buffer Sizes

Keep in mind that on systems with only two or three stations,
changing the buffer configuration may not have any measurable
impact on speed. In any case, increasing the size and number of
REDIR and SERVER buffers uses memory and can slow down programs
running on the server. If your application performance is critical,
consider setting up a dedicated server for your most used
application programs and printers.

Running applications on the server

To get the best performance out of your network when you run
applications on a server, you should always use the server as
though it was a remote workstation: log in and access the
application through network drives. Using the server locally,
without logging in, places you in contention with the rest of the
users and network performance can suffer. If you log in, the server
will schedule you along with the rest of the network users and
everyone will get good performance.  

Increasing print speed

One of the slowest things about printing to a network printer is
spooling to the hard disk. With LANtastic NOS 3.0 and above you can
easily increase the print spooling speed by spooling to a RAM disk.
To change the spooler's location, use the Change Spool Location
option of NET_MGR's Queue Maintenance function.  

Several programs when run on a server will seriously effect the
print speed, Windows 3.0, Clipper 5.0, and Autocad are prime
examples. If you notice slow printing when running one of these
programs on a print server you can increase print speed by setting
printer tasks to 1 and setting cps in the printer descriptor to
9600.

ARTISOFT, Inc. makes no warranties as to the completeness or
accuracy of this document.  LANtastic is a registered trademark of
ARTISOFT, Inc.  Brand names and product names are trademarks or
registered trademarks of their respective companies.
Network Performance Issues