NetWare(R) Link/PPP(TM) Data Compression Software

Introduction

The NetWare Link/PPP Data Compression product must be used in conjunction 
with the NetWare MultiProtocol Router Plus(TM) 2.1 software. 

README File

Please read the NetWare Link/PPP Data Compression README file that is 
included with the product. The information in the README file can assist you 
in configuring and troubleshooting the WAN connections.

Installing the Software

Before installing the NetWare Link/PPP Data Compression product, you must 
first have the NetWare 3.11 or NetWare Runtime(TM) 3.11 software installed 
on your server or router. You must also have the NetWare MultiProtocol Router 
Plus 2.1 software installed. Refer to the NetWare documentation for 
installation instructions. If you are also installing any other Novell(R) 
products, do so before installing the NetWare Link/PPP Data Compression 
product.

Use the following procedure to install the software on your machine:

  1.    Insert the first NetWare Link/PPP Data Compression diskette (that 
        you made from the NetWire(R) electronic bulletin board) into the 
        disk drive.

  2.    At the server or router console prompt, type:

                LOAD INSTALL <Enter>

        The Installation Options menu appears.

  3.    Select System Options, then press <Enter>.

  4.    Select Edit STARTUP.NCF File, then press <Enter>.

        Warning: Be sure you select Edit, and not Create, because a 
        STARTUP.NCF file already exists. If you select Create, all 
        information in your existing file is lost.

        A new window displays the full path name of STARTUP.NCF.

  5.    Press <Enter> to view the contents of the file.

        Add the following line (with the appropriate value) to the end of 
        the file:

                SET MAXIMUM PHYSICAL RECEIVE PACKET SIZE=<value>

        The value of this parameter should be set to the largest value used 
        by your LAN media or the largest value used by your applications, 
        whichever is less. Typical minimum values for different media types 
        are shown in Table 1. To use a value greater than 4202, you must 
        apply the MPRPSFIX.EXE file to your SERVER.EXE file. See the README 
        file for more information. 

Table 1 
Minimum Values for the Maximum Physical Receive Packet Size
---------------------------------
Media Type              Value
Ethernet                1514
4 MB token ring         4530    
16 MB token ring        4530
FDDI                    4530
ARCnet*                 4202
LocalTalk*              600
----------------------------------

  6.    Press <Esc> and select Yes to save your changes.

  7.    Press <Esc> to return to the main menu.

  8.    Select Product Options and press <Enter>.

        A new window displays the currently installed products.

  9.    Press <Ins> to insert a new product.

        A new window displays a prompt with drive A: as the default.

  10.   If you are installing the software from drive A:, just press 
        <Enter>. If you are installing the software from drive B:, replace 
        "A:" with "B:," then press <Enter>.

        The Installed Product menu appears after a few moments.

  11.   Select Install on this Server and press <Enter>.

  12.   Insert the remaining diskettes into the drive as prompted; press 
        <Esc> after you insert each diskette.

        All product options contained on the diskettes are installed. The 
        screen displays each filename as it is copied to the hard disk.

  13.   When the installation is complete, select No to return to the 
        Product Options menu; or select Yes to view the INSTALL.LOG file.

        If you chose to view the INSTALL.LOG file, press <Esc> to continue.

  14.   Press <Esc> until you exit INSTALL.

        The software is installed.

  15.   Type the following command at the server prompt: 

                LOAD INETCFG <Enter> 

  16.   Enable your NetWare Link/PPP Data Compression software by configuring 
        the appropriate Enable/Disable parameter in the NetWare Link/PPP 
        Expert Port Configuration screen of INETCFG. 

        Enabling the data compression option allows negotiation of 
        compression with the remote peer. Data compression is used only if
        both the local and remote peers support a common technique 
        appropriate for the link speed. You can disable compression on a 
        given link if the data to be transferred is not of a compressible 
        nature, such as previously compressed archive files or encrypted 
        data.

        For information about configuring the other parameters for PP WAN 
        connections, see the NetWare WAN Connectivity Supervisor's Guide 
        Version 2.1. 

NetWare Link/PPP Data Compression

Support for data compression is provided in the NetWare Link/PPP Data 
Compression software as a user-configurable option of the NetWare Link/PPP 
component. Data compression reduces the amount of information transferred 
over a communications link by replacing previously observed data sequences 
with more compact sequences. This increases the apparent speed of the link, 
at the cost of some additional NetWare MultiProtocol Router CPU load. 

This support allows more effective PPP link utilization when routing or 
bridging between remote LANs. Note that data compression is only necessary 
over the PPP link connecting two LANs, because this is the slowest portion 
of the end-to-end network traffic.

Proper operation of most data compression algorithms requires that no data 
corruption be permitted on the communications link, because each bit of the 
compressed data is much more significant than the uncompressed data. One 
incorrect bit can result in thousands of bytes of incorrect output. This, in 
turn, results in retransmission requests and lower overall throughput.
 
NetWare Link/PPP is, by default, an unreliable or "best effort" data link 
that does not guarantee data integrity. Retransmission of lost or corrupted 
data is the responsibility of higher-level protocols. Therefore, when data 
compression is successfully negotiated by the PPP Link Control Protocol, the 
unreliable PPP data link is replaced with a reliable data-link protocol to 
ensure data integrity of the compressed data exchange. This reliable 
data-link protocol is CCITT Link Access Protocol-Balanced (LAPB). LAPB 
significantly increases the reliability of the communications link when used 
in conjunction with rigorous error checking after the receive data is 
uncompressed. 

Data compression is performed on network data only. NetWare Link/PPP Link 
Control Protocol and Network Control Protocol data is passed uncompressed. 
Link Control Protocol and Network Control Protocol data exchanges are used 
for connection management and configuration negotiation. They are typically 
only used during the connection establishment and termination operations.
These protocol exchanges have their own error recovery mechanisms and, as 
such, do not benefit from the LAPB reliable data-link services.

The current NetWare Link/PPP data compression implementation supports a 
pattern prediction algorithm. This implementation is proprietary to Novell 
and does not interoperate with other vendors' data compression 
implementations. This compression algorithm provides useful data compression 
over a wide range of interface speeds, from 1,200 baud through E1 data 
rates. Future versions of the NetWare Link/PPP product might include 
additional compression algorithms tailored to provide higher compression at 
specific interface speeds. 

As currently implemented in NetWare Link/PPP, the data compression 
capability permits a "best case" 8:1 compression ratio with highly 
compressible data. A realistic figure for a typical mix of graphic, text, 
and binary data is on the order of a 2:1 compression ratio. This increases 
the apparent throughput of a 56 Kbps link, for example, to almost 112 Kbps.

Generally, as the communications link speed increases, the percentage of 
throughput improvement provided by data compression decreases, due to the 
additional CPU overhead of the compression processing. So, although data 
compression provides some benefit at speeds up to E1 (2.048 Mbps), the 
performance improvement is not as great as on a lower speed 56 Kbps link.
Refer to Tables 4 and 5 for a comparison of typical compression improvements 
at 56 Kbps and T1 (1.536 Mbps).

Actual results, of course, vary depending on a number of factors, including 
the type of data being transferred, the type of PC systems NetWare Link/PPP 
runs on, and the speed of the communications link.

Maximizing Performance

NetWare Link/PPP data compression works best when a constant supply of 
transmit data is available at the interface. This allows the compression 
logic to maximize the replacement of data sequences with the more compact 
sequences. Therefore, when using IPX with NetWare Link/PPP data compression, 
the IPX Packet Burst(TM) protocol and the Large Internet Packet (LIP) 
protocol should also be used. The Packet Burst protocol enhances IPX by 
allowing larger data transactions, composed of multiple IPX packets, to be 
transmitted as a single burst (or logical operation). Acknowledgments are 
issued for the complete burst rather than for individual IPX packets. For 
best results, the Packet Burst protocol and the LIP protocol can be enabled 
on each client and server end node system. Although the LIP protocol is 
included in the Packet Burst software for NetWare servers, it can be 
independently enabled or disabled on each client.

Packet Burst protocol support is provided for IPX client workstations by the 
latest version of the Virtual Loadable Module(TM) (VLM(TM)) update. Packet 
Burst protocol support is provided for NetWare 3.11 servers by PBURST.NLM. 
In NetWare 3.12 and NetWare 4.01, Packet Burst protocol support is included 
in SERVER.EXE. Refer to the NetWare Link/PPP Data Compression README file 
for information about obtaining the latest versions of the client 
workstation and server Packet Burst support.

Caution:    The current version of the IPX client workstation Packet Burst 
protocol support is provided by the client VLM files. The IPX client 
workstation support provided by NETX.COM and BNETX.COM is out of date and 
must not be used. 

Statistics

The NetWare Monitor NLM provides real-time statistics indicating the 
Interface Speed, Send Compression Throughput, Send Compression Ratio, LAPB 
Retransmissions, and Compression Resets, as shown next:

        Line 1 Interface Speed (bits/second):                   56,000
        Line 1 Send Comp Throughput (bits/second):              128,500
        Line 1 Send Comp Ratio (1000 * uncomp/comp):            2,295
        Line 1 LAPB Retransmissions:                            0
        Line 1 Compress Resets:                                 0

  o     Interface Speed-is the actual bits-per-second speed of the interface 
        measured during initialization. This is the maximum physical 
        bandwidth of the interface. If the interface speed changes after 
        initialization, for example by changing the speed of a fractional T1 
        DSU/CSU, the Interface Speed statistic does not reflect the speed 
        change until the interface is reinitialized. Changes to interface 
        speed also affect Send Comp Throughput.

  o     Send Comp Throughput-is an eight-second running average of the 
        bits-per-second speed at which uncompressed transmit data, excluding 
        the reliable data-link overhead, is being transmitted on this 
        interface. When compression is operational, Send Comp Throughput 
        might exceed the interface speed. In the preceding example, Send Comp 
        Throughput is twice the interface speed (the maximum physical 
        bandwidth of the interface). When no data is being transmitted, or 
        compression is disabled, Send Comp Throughput reads zero.

  o     Send Comp Ratio-is an eight-second running average of send 
        characters input to the compressor versus characters output by the 
        compressor. The compression ratio is displayed with four significant 
        figures, and should be read as if the comma were a decimal
        separator. In the preceding example, the compression ratio is 
        5.743:1, or for every 5,743 bytes of input data, 1,000 bytes of 
        compressed data are sent over the link. When no data is being 
        transmitted, or compression is disabled, Send Comp Ratio reads zero.

  o     LAPB Retransmissions-is the number of information frames the LAPB 
        reliable data link has re-sent since interface initialization. 
        Excessive LAPB Retransmissions are an indication of poor line 
        quality, and affect the overall Send Comp Throughput. 
        
  o     Compress Resets-is the number of times the data compression 
        subsystem lost synchronization with the remote peer. This can be 
        caused by LAPB failures resulting in data-link reinitialization or 
        receive data decompression failures. Regular LAPB Compression Resets 
        are an indication of poor line quality. 

To access these statistics:

  1.    At the server prompt, type:

                Load MONITOR <Enter>

  2.    Select LAN Information from the main Monitor menu.

  3.    Select the desired PPP interface from the LAN Driver Information 
        list.
 
  4.    Scroll to the desired PPP line group in the Custom Statistics area. 

Typical Performance

The values of Send Comp Throughput and Send Comp Ratio vary depending on the 
amount and type of data being sent. For example, encrypted data does not 
compress at all (and might even increase the amount of data sent), while 
ASCII text documents might compress significantly.

Data compression can significantly increase the apparent link speed of all 
protocols supported by the NetWare Link/PPP Data Compression software, 
including the Novell IPX protocol. Data compression is of greater value if 
the link is already busy; for example, when many workstations are using a 
remote server. 

Table 2 and Table 3 graph the performance of NetWare Link/PPP Data 
Compression, as tested with the PERFORM3 network test program using 
AST* 486/33E servers and workstations running the IPX Packet Burst protocol 
and the Large Internet Packet protocol. The test program was run using the
following command:

PERFORM3 <filename> 12 128 4096 1024

The typical performance data shown in Table 4 and Table 5 is expressed in 
Kbps. Actual performance will vary depending on interface speed, PC hardware 
type, and data content.

Table 2 
Compression Performance for 56 Kbps Links
------------------------------------------------------------------
Scenario                                        Performance (Kbps)
One workstation, without compression            47.76
One workstation, with compression               147.68
Five workstations, without compression          50.56
Five workstations, with compression             173.92
-------------------------------------------------------------------

Table 3 
Compression Performance for T1 (1.5 Mbps) Links
------------------------------------------------------------------
Scenario                                        Performance (Kbps)
One workstation, without compression            888.64
One workstation, with compression               1123.68
Five workstations, without compression          1309.44
Five workstations, with compression             2335.68
------------------------------------------------------------------


Novell, NetWare, the N-Design, and the NetWare Logotype (teeth logo) are 
registered trademarks and Internetwork Packet Exchange, IPX, 
NetWare Link/PPP, NetWare Loadable Module, NetWare MultiProtocol Router, 
NetWare MultiProtocol Router Plus, NetWare Runtime, NLM, Packet Burst, 
Virtual Loadable Module, and VLM are trademarks of Novell, Inc. LocalTalk is 
a registered trademark of Apple Computer, Inc. AST is a registered trademark 
of AST Research, Inc. ARCnet is a registered trademark of Datapoint 
Corporation. 

Published: October 1993. Copyright  1993 Novell, Inc. All rights reserved.

Novell, Inc.
F6-91-2 
2180 Fortune Dr.        
San Jose, CA 95131      


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