ATM on Linux, release 0.33 (alpha)     by Werner Almesberger, EPFL LRC
====================================== werner.almesberger@lrc.di.epfl.ch

This is experimental software. There are known major bugs and certainly
even many more yet unknown problems. Internal and external interfaces are
far from being stable. In fact, they change daily. Use at your own risk.

This package contains a kernel patch for ATM protocol stacks and for ATM
device drivers, source for management and test tools, and this
description.

The following network devices are supported:
  ATM over TCP pseudo device for "dry runs"
  Efficient Networks ENI155p-MF/U5 155 Mbps ATM adapter
  SMC ATM Power 155
  Rolf Fiedler's TNETA1570 board / UniNET1570 (*)
  Zeitnet ZN1221/ZN1225 155 Mbps ATM adapter
  IDT 77901/77903 ("NICStAR", 77201/77211 SAR) 155 and 25 Mbps adapters
  (probably also IDT 77914/77915/77916) (*)

The following connection types are supported:
  constant bit rate (CBR) permanent connections
  best-effort (UBR) permanent connections
  support for UNI 3.0, 3.1, and some 4.0 unicast signaling

The following protocols are supported:
  "raw" unreliable ATM transport without AAL ("AAL0")
  "raw" unreliable ATM transport over AAL5
  IP over ATM (NULL or SNAP encapsulation)
  ATMARP as defined in RFC1577 (client and server)
  LAN Emulation (client and server side) (*)
  Arequipa (Application REQUested IP over ATM) (*)
  ANS (ATM Name Service)

(* Not included in this version, but expected to follow early '98)

The API is based on the Linux ATM API proposed on the linux-atm mailing
list.

For usage and installation instructions, please read the file USAGE or
generate the LaTeX documentation in doc/ The README in that directory
explains how.

For known restrictions and bugs, please read the file BUGS.


Performance (version 0.1)
-----------

THIS SECTION IS VERY VERY VERY OBSOLETE AND BADLY NEEDS TO BE UPDATED. ALSO
NOTE THAT MOST OF THE THROUGHPUT MEASUREMENTS ARE TOO LOW BY 5% BECAUSE OF A
BUG IN TTCP THAT WAS ONLY DISCOVERED MUCH LATER.

- - - - - - - - - - - - - obsolete text follows - - - - - - - - - - - - - -

Note that version 0.10 has some debugging code enabled in the ENI driver.
It is therefore about 10% slower than indicated below.

Platform:

 Pentium 90 MHz, Neptune and Triton PCI board, 32 MB RAM, ENI155p-MF-C
 2048 PDUs, 8192 bytes each, no wait for close
 Directly connected, no switch, max buffers (128kB) allocated on board
 Kernel buffers were only limited by available memory

Results (average of ten ttcp runs):

 Transport		  TX Mbps  RX Mbps  Loss (bytes)
 raw AAL5 (unchecksummed) 128-132      101     0-13%
 UDP, checksummed	  111-127   17- 55    49-76% (*)
 UDP, unchecksummed	  114-128   73- 82    27-41%
 TCP (checksummed)	   63- 67   63- 67	  0%

(* additional slowdown because driver printed warning messages)

For reference, the results with the 0.0 version (average of ten ttcp
runs, only between Neptune-based PCs):

 Transport		  MMU hacks  TX Mbps  RX Mbps  Loss (bytes)
 raw AAL5 (unchecksummed) no	       132	   97	    0%
			  yes	      1607	  129	    0%
 UDP, checksummed	  no	       117         51      56%
 UDP, unchecksummed	  no	       118	   72	   39%
 TCP (checksummed)	  no		38	   38	    0%

Because ttcp does not measure the time spent in the close system call for
datagram protocols, the raw AAL5 TX rate reflects the rate at which data
can be enqueued to the device driver.

The performance measurements are only accurate within about +-5%. Even
marginal changes can lead to a systematic change of 2-3%.

The theoretical limits are 135.367 Mbps for raw AAL5 and 134.580 Mbps
for UDP, assuming data is sent in blocks of 8192 bytes each.

When the Neptune-based PC was the receiving machine, transfers were
always as good or better (in terms of throughput and loss) with version
0.1 than with version 0.0. So it seems that my Triton still needs some
tuning. TCP is now pleasently fast.


Addendum
--------

An early version of the ZN1221 driver yielded:

                            ZN->ENI         ENI->ZN
                        TX Mbps RX Mbps TX Mbps RX Mbps
raw AAL5                 ~118     ~94    ~129    ~103 *
UDP, checksummed         ~120     ~36   too many losses
TCP (checksummed)         ~62     ~62     ~61     ~61
 
* ENI->ZN: RX varies between 98 and 120 Mbps

"ZN" is a ZN1221 in a P90 Neptune, "ENI" is a ENI155p-MF-C in a P90
Triton. Both drivers were compiled with some debugging code.
