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Motorola Surfboard 4100 + 4200 Series USB Cable Modem mini-HOWTO

Howard Shane


<hshane[AT]austin.rr.com>
Revision History                                                             
Revision 1.0             2003-05-15           Revised by: tmm                
Initial release, reviewed by LDP                                             
Revision 0.02            2003-04-10           Revised by: jhs                
Completed draft.                                                             


 This document was written to assist the Linux user in setting up the
Motorola Surfboard 4000 series of cable modems.

-----------------------------------------------------------------------------
Table of Contents
1. Introduction
    1.1. Copyright Information
    1.2. Disclaimer
    1.3. New Versions
    1.4. Credits
    1.5. Feedback
    1.6. Conventions Used in this Document
   
   
2. Prerequisites
    2.1. Networking and Operating System Support
    2.2. The Modem Device
    2.3. The DHCP Client
   
   
3. Using the USB interface instead of an ethernet card
    3.1. USB CDCEther
   
   
4. Troubleshooting
A. Gnu Free Documentation License

1. Introduction

 This document was written to assist the Linux user in setting up the
Motorola Surfboard 4100 and 4200 series cable modems, and includes
information on configuring a DHCP client, enabling the device with or without
USB support and troubleshooting.
-----------------------------------------------------------------------------

1.1. Copyright Information

 This document is Copyright 2003 by Howard Shane.

 Permission is granted to copy, distribute and/or modify this document under
the terms of the GNU Free Documentation License, Version 1.2 or any later
version published by the Free Software Foundation with no Invariant Sections,
no Front-Cover Texts, and no Back-Cover Texts. A copy of the license can be
found in Appendix A.
-----------------------------------------------------------------------------

1.2. Disclaimer

 No liability for the contents of this document can be accepted. Use the
concepts, examples and other content entirely at your own risk. As this is a
new edition, there may be technical or other inaccuracies that may result in
the loss of irreplaceable data. In any case, proceed with caution, and
realize that although errors are highly unlikely, the author can accept no
responsibility for them.

 All copyrights are held by their by their respective owners, unless
specifically noted otherwise. Use of a term in this document should not be
regarded as affecting the validity of any trademark or service mark.

 Naming of particular products or brands should not be seen as endorsements.
-----------------------------------------------------------------------------

1.3. New Versions

 This is the initial release.

 The latest version number of this document can be found [http://
www.hshanemd.net/docs/HOWTOS/SurfBoard/] here.
-----------------------------------------------------------------------------

1.4. Credits

 I would like to thank Brad Hards, the primary author of the Linux CDCEther
kernel driver for graciously volunteering several useful bits of information.

 Also, I would like to thank Marla, who has cheerily tolerated the time I've
spent sifting through documentation and endless typing while completing this
and other projects. Without you I'm lost.
-----------------------------------------------------------------------------

1.5. Feedback

 Please send any additions or comments pertaining to this document to the
following email address: <hshane[AT]austin.rr.com>. If you have an earlier
(e.g., 3000 series) or later (e.g. 5000) series Surfboard and have it working
in linux, please contact me with any model-specific setup information so we
can update this document!
-----------------------------------------------------------------------------

1.6. Conventions Used in this Document

 The following conventions are used in this document and are outlined here
for those who may not yet have a complete understanding of how to access and
control the underlying operating system in Linux, which is almost always the
bash shell.

 First, filenames are referenced in a paragraph like so: /path/file

 Commands in Linux are executed (or 'called') at the command prompt,
otherwise known as the 'command line.' If you are in the non-graphical
(text-based) environment you will usually be presented the bash shell prompt
which is a dollar sign:

 
$                                                                            

 ...or the hash mark:

 
#                                                                            

 ...if you have logged in as root or have acquired root, or 'superuser'
privileges. You can also access the bash shell in the X window system,
otherwise known as X or X11, with an [http://invisible-island.net/xterm/]
xterm or similar X-terminal-emulator. Commands to be performed at the bash
prompt, but referenced in a paragraph of this document, usually look like
this: do this now

 Commands and/or the resulting output of commands may also be outlined with
screen output in their own paragraph or heading:

 
$ date                                                                       
Sun Jul 27 22:37:11 CDT 2003                                                 

When a command is written in front of the bash prompt (e.g. $ date above), it
is assumed the [Return] or [Enter] key has been depressed after the command,
possibly followed by the output on a new line (e.g., as in the date in the
above example).
-----------------------------------------------------------------------------

2. Prerequisites

2.1. Networking and Operating System Support

 The Motorola Surfboard 4100 and 4200 Cable Modem series are common devices
provided by cable Internet services. They are easily configurable for use
under Linux. For more information about the device not related to Linux
configuration, please see the manufacturer's website [http://
broadband.motorola.com/noflash/surfboard.html] here.

 There are two requirements for using a Motorola Surfboard 4100 and 4200
series USB cable modem (hereafter referred to as a 'Surfboard'). The first is
the appropriate networking support for the device in your kernel; note that
most base installs of Linux distributions come TCP/IP and ethernet enabled
'out of the box,' so there is probably very little most readers will need to
do other than be sure their ethernet card is working. If you know that your
ethernet card is supported and working you can move on to Section 2.2. For
those who like to compile their own kernels (see the [http://www.tldp.org/
HOWTO/Kernel-HOWTO.html] Kernel HOWTO for more information), the following
options are required to get the cable modem to work:

 Under 'Networking options':

��*�  TCP/IP Networking
   

along with ONE of the following:

��*�  Network Device Support: Ethernet (10 or 100Mbit) Support and your
    ethernet card driver
   
��*�  USB Support + USB CDCEther driver support
   

 PPP support is not required per se, as the modem is itself a PPP link.

 Note that there are two possible interfaces on the modem to connect your
computer. One is through ethernet and is probably the default a cable
provider will attempt to use when setting up the Surfboard. The other is to
use the USB interface. The former of these is arguably easiest; the only
requirements other than the above is that you have an ethernet card installed
which is open, i.e. that you can connect to the modem ethernet jack using
ordinary 10BaseT/100BaseT ethernet cable. If you are uncertain about anything
in the last sentence I recommend you read the [http://www.tldp.org/HOWTO/
Ethernet-HOWTO.html] Ethernet HOWTO for proper configuration of your ethernet
card.

I have used my own 4100 model with each interface, and at least on my system
there seems to be little difference in performance using an ethernet card or
the USB port. The drawback of the ethernet method is that your network card
will be tied up.
-----------------------------------------------------------------------------

2.2. The Modem Device

First, plug in and turn on the Surfboard. Connect your ethernet card to the
Surfboard with 10BaseT/100BaseT cable into the non-USB interface, if this was
not already done for you. Be sure the modem isn't on standby mode by checking
the LEDs; you should see some dancing green lights to confirm this. The
standby button is on the top of the device on most models. Your cable
internet provider should be able to tell remotely whether your modem is
connected and functioning properly, which is helpful for differentiating
between hardware and configuration problems on your end. They will also need
the MAC (Media Access Control) hardware address of your modem to allow the
device access to their network. If at any time you substitute one modem for
another you will need to inform them so the MAC address can be updated and
your access to the cable network restored.

Once you connect for the first time, your modem will be assigned an IP
address, which may remain the same or change periodically depending on the IP
address turnover of your ISP's DHCP server, and how long you remain offline
if you disconnect. Should the IP address provided to the modem by your ISP
ever have to be released, for whatever reason, you can do this by resetting
the device. This involves inserting the tip of a sharp pencil or a pin into
the small orifice on the input face. The only time this may be necessary is
if you are having trouble with your connection and you are instructed to try
this maneuver by your ISP's technical support staff. Only do this if you know
what you're doing or are directed to do so by your ISP, as it's generally not
a good idea to go around sticking metal objects into the various openings of
electrical devices.
-----------------------------------------------------------------------------

2.3. The DHCP Client

2.3.1. Installation on a Debian System

 The Surfboard works fine out of the box under Debian once you have installed
and started the DHCP client package. As of this writing there are two
user-space programs for this. In Woody (stable), there is the dhcp-client
package, automatically installed as a part of the base packages as /sbin/
dhclient. For Sarge (testing) and up, this has been replaced by the dhcpcd
package. The latter has its configuration files under /etc/dhcpc, but nothing
really needs to be modified if you are setting up only one ethernet card for
the cable internet service. The dhcpcd daemon is easily installed for those
using testing branch as root, with apt-get install dhcpcd .
-----------------------------------------------------------------------------

2.3.2. Installing on .rpm- or .tgz-Based Systems

 For .rpm- or .tgz-based distributions, I offer the following link that walks
you through the setup of a DHCP client, in the [http://www.tldp.org/HOWTO/
mini/DHCP/x74.html] DHCP mini-HOWTO.

 Just run /sbin/dhclient or whichever client you use to get a dynamic IP
address.
-----------------------------------------------------------------------------

2.3.3. Checking your Configuration

 Once you are plugged into the system you are provided your own IP address,
which doesn't change unless you drop the lease (i.e. go offline) for a while.
To confirm that the DHCP client is working and you have a new IP address,
execute (as root) ifconfig without any other arguments, and you should see
the following:

 
eth0    Link encap:Ethernet  HWaddr 00:D0:09:DE:D4:6F                        
        inet addr:66.190.XXX.XXX  Bcast:255.255.255.255  Mask:255.255.255.0  
        UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1                   
        RX packets:2591777 errors:0 dropped:0 overruns:0 frame:0             
        TX packets:5589 errors:0 dropped:0 overruns:0 carrier:0              
        collisions:0 txqueuelen:100                                          
        RX bytes:168673636 (160.8 MiB)  TX bytes:1752872 (1.6 MiB)           
        Interrupt:12 Base address:0xc400                                     

 
lo      Link encap:Local Loopback                                            
        inet addr:127.0.0.1  Mask:255.0.0.0                                  
        UP LOOPBACK RUNNING  MTU:16436  Metric:1                             
        RX packets:5168 errors:0 dropped:0 overruns:0 frame:0                
        TX packets:5168 errors:0 dropped:0 overruns:0 carrier:0              
        collisions:0 txqueuelen:0                                            
        RX bytes:1695104 (1.6 MiB)  TX bytes:1695104 (1.6 MiB)               

 ...which shows the system loopback device, /dev/lo, and also /dev/eth0, your
ethernet card and the Surfboard, having successfully acquired an IP address
(or 'inet addr') provided by the cable internet service provider.
-----------------------------------------------------------------------------

3. Using the USB interface instead of an ethernet card

3.1. USB CDCEther

 If you wish to use the USB interface to accept data you will need USB
subsystem support in your kernel, whether USB-ohci, USB-ehci, or whichever
USB host controller driver type your system prefers. For a more in-depth
discussion of this, I direct you to the [http://www.linux-usb.org/] Linux-USB
project site.

 Assuming you have USB subsystem support, to find out if your kernel supports
the CDCEther (Communications Device Class Ethernet) driver as a module, in a
shell, issue the command lsmod as root.

 You should see output similar to the following, though a number of entries
have been edited, and you shouldn't worry too much if you don't see the exact
entries displayed here:

 
CDCEther               11040   0  (unused)                                   
usb-ohci               17888   0  (unused)                                   
usbcore                56768   1  [scanner CDCEther usb-ohci]                

 If you don't see CDCEther listed among the modules try loading the module
directly:

 
 #  modprobe CDCEther                                                        

 If all goes well you should see the following message in your system log
files, or with dmesg:

 
Mar  2 11:00:52 K7 kernel: CDCEther.c: 0.98.6 7 Jan 2002 Brad Hards and another  
Mar  2 11:00:52 K7 kernel: usb.c: registered new driver CDCEther                 

 If you don't have it compiled as a module, check the output of dmesg (you
may need to pipe it through 'less' or 'more' like so: dmesg | less); if the
driver loads as a module you will see a message similar to the above at boo-
up. If not, and you want to use the USB conduit of this device, you will need
to recompile your kernel to support it. You will need the 2.4.3 kernel or
later. For detailed instructions on recompiling your kernel, I direct you to
[http://www.tldp.org/HOWTO/Kernel-HOWTO.html] the Kernel-HOWTO. The options
shown next will need to be selected. As an aside, you should be aware that
compiling things as modules, rather than statically within the kernel, gives
you a greater degree of control and greatly simplifies troubleshooting.
-----------------------------------------------------------------------------

3.1.1. Kernel Requirements

 In addition to the 'TCP/IP networking' listed in Section 2, the following
should be compiled in your kernel in the 'USB support' menu (assuming you are
using menuconfig):

 

��*�  USB support
   
��*�  USB Communication Class Ethernet device support
   

-----------------------------------------------------------------------------
3.1.2. Grabbing the Correct Interface

Now we have to select the correct ethernet interface (/dev/ethX) to be the
receipient of the DHCP service. If you run ifconfig as root you get a list of
open devices:

 
eth0 Link encap:Ethernet HWaddr 00:D0:09:DE:D4:6F                              
        inet addr:192.168.1.1                                                  
        Bcast:192.168.1.255 Mask:255.255.255.0                                 
        BROADCAST RUNNING MULTICAST MTU:1500 Metric:1                          
        RX packets:0 errors:0 dropped:0 overruns:0 frame:0                     
        TX packets:0 errors:0 dropped:0 overruns:0 carrier:0                   
        collisions:0 txqueuelen:100                                            
        RX bytes:0 (0.0 b) TX bytes:0 (0.0 b) Interrupt:12 Base address:0xc400 

 
lo Link encap:Local Loopback                                                 
        inet addr:127.0.0.1 Mask:255.0.0.0                                   
        UP LOOPBACK RUNNING MTU:16436 Metric:1                               
        RX packets:5168 errors:0 dropped:0 overruns:0 frame:0                
        TX packets:5168 errors:0 dropped:0 overruns:0 carrier:0              
        collisions:0 txqueuelen:0                                            
        RX bytes:1695104 (1.6 MiB)  TX bytes:1695104 (1.6 MiB)               

...where eth0 is a standard NIC, pre-configured to the IP address
192.168.1.1.

 Note the HWaddr field, or hardware address, on the first line. This is the
same as the MAC, or Media Access Control address, and is how we will specify
the interface for each action. If you are running a Debian system, you can
alter the /etc/network/interfaces file to look like this:

 
        # /etc/network/interfaces -- configuration file for ifup(8), ifdown(8)  
        # The loopback interface                                                
        auto lo                                                                 
        iface lo inet loopback                                                  
        auto eth0                                                               
        iface eth0 inet static                                                  
        address 192.168.1.1                                                     
        netmask 255.255.255.0                                                   
        network 192.168.1.0                                                     
        hwaddress ether 00:D0:09:DE:D4:6F                                       
                                                                                
        auto eth1                                                               
        iface eth1 inet dhcp                                                    
        hwaddress ether 00:04:BD:DE:42:0B                                       

 The auto eth0 and auto eth1 are required to have the interfaces configured
at bootup. Note that some versions of dhcp clients by default always grab
eth0 for the dhcpc interface. So even after doing all the above, unless you
specifically run /sbin/dhcpcd-bin eth1 it won't work. The easy way to do this
at boot-up is to make an init script to load the dhcp address to the correct
interface. For most distributions, such a script is in /etc/rc.d or a similar
location. If you have an rc.local script, as in Slackware, you can simply add
/sbin/dhclient to the end of the file. If you have a model rc.d script (such
as /etc/init.d/skeleton in Debian) you can convert that to such a purpose.
Whatever the case (either at the command line manually or appended to an init
script), the command to run is as follows:

 
# ifconfig ethX hw ether 00:D0:09:DE:D4:6F up                                

You can confirm it worked by calling ifconfig without options after your next
reboot.
-----------------------------------------------------------------------------

4. Troubleshooting

 Q: I get kicked offline about once every 4 days, for no apparent reason, and
get the following error, or something similar, in the kernel log:

 
Feb 20 10:05:12 K7 kernel: CDCEther.c: rx status -110                        
Feb 20 10:05:12 K7 kernel: CDCEther.c: no repsonse in BULK IN                
Feb 20 10:05:12 K7 kernel: CDCEther.c: rx status -110                        
Feb 20 10:05:12 K7 kernel: CDCEther.c: no repsonse in BULK IN                
Feb 20 10:05:12 K7 kernel: CDCEther.c: rx status -110                        
Feb 20 10:05:12 K7 kernel: CDCEther.c: no repsonse in BULK IN                
Feb 20 10:05:12 K7 kernel: CDCEther.c: rx status -110                        

 A: There are a number of reasons this may be happening, and future updates
to the CDCEther driver may solve some of them. A user on the Linux-USB-user
mailing list noticed that on at least one occasion data sent to the modem
from upstream by the cable provider has triggered it. Also, the modem itself
is very sensitive to power interruptions and can lose the connection if this
occurs. The fix is to run ifdown ethX, where ethX is the ethernet interface
(eth0, eth1 etc.) to clear out any remaining settings that are hung, then
remove the module with rmmod CDCEther, reinsert the CDCEther module and then 
ifup ethX . A reboot may be necessary if this doesn't fix the problem. If
none of these work you probably have a real service interruption.

 Q: I get the following messages on boot-up; are they errors?

 
Can't use SetEthernetMulticastFilters request                                
Mar  2 11:00:52 K7 kernel: CDCEther.c: Ethernet information found at         
device configuration.  Trying to use it anyway.                              
Mar  2 11:00:52 K7 kernel: CDCEther.c: Imperfect filtering support -         
need sw hashing                                                              

 A: No. The multicast message is pertaining to Multicast support in the
kernel, which is optional and not necessary for the proper functioning of
this modem. The message about 'Ethernet Information' is a design bug in the
modem and can be ignored. As for the 'Imperfect filtering support,' to quote
Brad Hards:

 " This is a bit difficult to explain - I assume that you know what
multicasting is - when you join a multicast group, this can be handled by the
networking device so that other multicast traffic doesn't cause interrupts.
That is called 'perfect filtering.' However sometimes the number of multicast
addresses exceeds the number of filters that you have. This leads to
'imperfect filtering,' which can cut down the number of interrupts, but you
still need to do some work in the networking stack. Then you get to the
typical cable modem implementation, and there is not filtering at all. Every
multicast packet goes to the host to be filtered. This doesn't normally
matter though, because the cable modem is a point to point link. "

 Q: I'm still having problems, or I'm unusually curious...is there a way that
I can get more information about what the device is up to?

 A: Yes, there is. The manufacturer hard-wired an http server for status and
configuration purposes into the modem itself. It seems to have been designed
for troubleshooting by cable tecnician staff, but you can access the 4100 and
4200 models by directing your web browser to [http://192.168.100.1] http://
192.168.100.1. You will need to kill your firewall if you have one running
prior to doing this. You can see statistics, logs and some other
miscellaneous info at this address.
-----------------------------------------------------------------------------

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its principal authors, if it has fewer than five), unless they release you
from this requirement.

 C. State on the Title page the name of the publisher of the Modified
Version, as the publisher.

 D. Preserve all the copyright notices of the Document.

 E. Add an appropriate copyright notice for your modifications adjacent to
the other copyright notices.

 F. Include, immediately after the copyright notices, a license notice giving
the public permission to use the Modified Version under the terms of this
License, in the form shown in the Addendum below.

 G. Preserve in that license notice the full lists of Invariant Sections and
required Cover Texts given in the Document's license notice.

 H. Include an unaltered copy of this License.

 I. Preserve the section Entitled "History", Preserve its Title, and add to
it an item stating at least the title, year, new authors, and publisher of
the Modified Version as given on the Title Page. If there is no section
Entitled "History" in the Document, create one stating the title, year,
authors, and publisher of the Document as given on its Title Page, then add
an item describing the Modified Version as stated in the previous sentence.

 J. Preserve the network location, if any, given in the Document for public
access to a Transparent copy of the Document, and likewise the network
locations given in the Document for previous versions it was based on. These
may be placed in the "History" section. You may omit a network location for a
work that was published at least four years before the Document itself, or if
the original publisher of the version it refers to gives permission.

 K. For any section Entitled "Acknowledgements" or "Dedications", Preserve
the Title of the section, and preserve in the section all the substance and
tone of each of the contributor acknowledgements and/or dedications given
therein.

 L. Preserve all the Invariant Sections of the Document, unaltered in their
text and in their titles. Section numbers or the equivalent are not
considered part of the section titles.

 M. Delete any section Entitled "Endorsements". Such a section may not be
included in the Modified Version.

 N. Do not retitle any existing section to be Entitled "Endorsements" or to
conflict in title with any Invariant Section.

 O. Preserve any Warranty Disclaimers. If the Modified Version includes new
front-matter sections or appendices that qualify as Secondary Sections and
contain no material copied from the Document, you may at your option
designate some or all of these sections as invariant. To do this, add their
titles to the list of Invariant Sections in the Modified Version's license
notice. These titles must be distinct from any other section titles. You may
add a section Entitled "Endorsements", provided it contains nothing but
endorsements of your Modified Version by various parties--for example,
statements of peer review or that the text has been approved by an
organization as the authoritative definition of a standard.

 You may add a passage of up to five words as a Front-Cover Text, and a
passage of up to 25 words as a Back-Cover Text, to the end of the list of
Cover Texts in the Modified Version. Only one passage of Front-Cover Text and
one of Back-Cover Text may be added by (or through arrangements made by) any
one entity. If the Document already includes a cover text for the same cover,
previously added by you or by arrangement made by the same entity you are
acting on behalf of, you may not add another; but you may replace the old
one, on explicit permission from the previous publisher that added the old
one.

 The author(s) and publisher(s) of the Document do not by this License give
permission to use their names for publicity for or to assert or imply
endorsement of any Modified Version.

 5. COMBINING DOCUMENTS

 You may combine the Document with other documents released under this
License, under the terms defined in section 4 above for modified versions,
provided that you include in the combination all of the Invariant Sections of
all of the original documents, unmodified, and list them all as Invariant
Sections of your combined work in its license notice, and that you preserve
all their Warranty Disclaimers.

 The combined work need only contain one copy of this License, and multiple
identical Invariant Sections may be replaced with a single copy. If there are
multiple Invariant Sections with the same name but different contents, make
the title of each such section unique by adding at the end of it, in
parentheses, the name of the original author or publisher of that section if
known, or else a unique number. Make the same adjustment to the section
titles in the list of Invariant Sections in the license notice of the
combined work.

 In the combination, you must combine any sections Entitled "History" in the
various original documents, forming one section Entitled "History"; likewise
combine any sections Entitled "Acknowledgements", and any sections Entitled
"Dedications". You must delete all sections Entitled "Endorsements".

 6. COLLECTIONS OF DOCUMENTS

 You may make a collection consisting of the Document and other documents
released under this License, and replace the individual copies of this
License in the various documents with a single copy that is included in the
collection, provided that you follow the rules of this License for verbatim
copying of each of the documents in all other respects.

 You may extract a single document from such a collection, and distribute it
individually under this License, provided you insert a copy of this License
into the extracted document, and follow this License in all other respects
regarding verbatim copying of that document.

 7. AGGREGATION WITH INDEPENDENT WORKS

 A compilation of the Document or its derivatives with other separate and
independent documents or works, in or on a volume of a storage or
distribution medium, is called an "aggregate" if the copyright resulting from
the compilation is not used to limit the legal rights of the compilation's
users beyond what the individual works permit. When the Document is included
in an aggregate, this License does not apply to the other works in the
aggregate which are not themselves derivative works of the Document.

 If the Cover Text requirement of section 3 is applicable to these copies of
the Document, then if the Document is less than one half of the entire
aggregate, the Document's Cover Texts may be placed on covers that bracket
the Document within the aggregate, or the electronic equivalent of covers if
the Document is in electronic form. Otherwise they must appear on printed
covers that bracket the whole aggregate.

 8. TRANSLATION

 Translation is considered a kind of modification, so you may distribute
translations of the Document under the terms of section 4. Replacing
Invariant Sections with translations requires special permission from their
copyright holders, but you may include translations of some or all Invariant
Sections in addition to the original versions of these Invariant Sections.
You may include a translation of this License, and all the license notices in
the Document, and any Warranty Disclaimers, provided that you also include
the original English version of this License and the original versions of
those notices and disclaimers. In case of a disagreement between the
translation and the original version of this License or a notice or
disclaimer, the original version will prevail.

 If a section in the Document is Entitled "Acknowledgements", "Dedications",
or "History", the requirement (section 4) to Preserve its Title (section 1)
will typically require changing the actual title.

 9. TERMINATION

 You may not copy, modify, sublicense, or distribute the Document except as
expressly provided for under this License. Any other attempt to copy, modify,
sublicense or distribute the Document is void, and will automatically
terminate your rights under this License. However, parties who have received
copies, or rights, from you under this License will not have their licenses
terminated so long as such parties remain in full compliance.

 10. FUTURE REVISIONS OF THIS LICENSE

 The Free Software Foundation may publish new, revised versions of the GNU
Free Documentation License from time to time. Such new versions will be
similar in spirit to the present version, but may differ in detail to address
new problems or concerns. See http://www.gnu.org/copyleft/.

 Each version of the License is given a distinguishing version number. If the
Document specifies that a particular numbered version of this License "or any
later version" applies to it, you have the option of following the terms and
conditions either of that specified version or of any later version that has
been published (not as a draft) by the Free Software Foundation. If the
Document does not specify a version number of this License, you may choose
any version ever published (not as a draft) by the Free Software Foundation.

 ADDENDUM: How to use this License for your documents

 To use this License in a document you have written, include a copy of the
License in the document and put the following copyright and license notices
just after the title page:

 Copyright (c) YEAR YOUR NAME. Permission is granted to copy, distribute and/
or modify this document under the terms of the GNU Free Documentation
License, Version 1.2 or any later version published by the Free Software
Foundation; with no Invariant Sections, no Front-Cover Texts, and no
Back-Cover Texts. A copy of the license is included in the section entitled
"GNU Free Documentation License".

 If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
replace the "with...Texts." line with this: with the Invariant Sections being
LIST THEIR TITLES, with the Front-Cover Texts being LIST, and with the
Back-Cover Texts being LIST. If you have Invariant Sections without Cover
Texts, or some other combination of the three, merge those two alternatives
to suit the situation.

 If your document contains nontrivial examples of program code, we recommend
releasing these examples in parallel under your choice of free software
license, such as the GNU General Public License, to permit their use in free
software.





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