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<html xmlns="http://www.w3.org/1999/xhtml"><head><title>Compressions des sessions TCP/IP avec des outils de type SSH</title><link rel="stylesheet" type="text/css" href="style.css"/><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"/><meta name="description" content="Ce guide pratique explique pas à pas comment compresser ses connexions en utilisant SSH. Compresser les connexions permet, d'une part, de limiter la bande passante utilisée et, d'autre part, d'accélérer les connexions à faible débit (modem, GSM, RNIS)."/></head><body><div xml:lang="fr" class="article"><div class="titlepage"><div><div><h2 class="title"><a id="d0e1"/>
    Compressions des sessions TCP/IP avec des outils de type SSH
</h2></div><div><h3 class="subtitle"><em>
    Version française du <span class="foreignphrase"><em class="foreignphrase">Compressed TCP/IP-Sessions using 
    SSH-like tools</em></span>
</em></h3></div><div><div class="author"><h3 class="author"><span class="firstname">Sebastian</span> <span class="surname">Schreiber</span></h3><div class="affiliation"><div class="address"><p><code class="email">&lt;<a class="email" href="mailto:Schreib CHEZ SySS POINT de">Schreib CHEZ SySS POINT de</a>&gt;</code></p></div></div></div></div><div><p class="othercredit"><span class="contrib">Adaptation française</span> : <span class="firstname">Vincent</span> <span class="surname">Chartier</span></p><div class="affiliation"><div class="address"><p><code class="email">&lt;<a class="email" href="mailto:vchartier CHEZ kyxar POINT fr">vchartier CHEZ kyxar POINT fr</a>&gt;</code></p></div></div></div><div><p class="othercredit"><span class="contrib">Relecture de la version française</span> : <span class="firstname">Claude</span> <span class="surname">Thomassin</span></p><div class="affiliation"><div class="address"><p><code class="email">&lt;<a class="email" href="mailto:cthomassin CHEZ waika9 POINT com">cthomassin CHEZ waika9 POINT com</a>&gt;</code></p></div></div></div><div><p class="othercredit"><span class="contrib">Préparation de la publication de la v.f.</span> : <span class="firstname">Jean-Philippe</span> <span class="surname">Guérard</span></p><div class="affiliation"><div class="address"><p><code class="email">&lt;<a class="email" href="mailto:jean TIRET philippe POINT guerard CHEZ tigreraye POINT org">jean TIRET philippe POINT guerard CHEZ tigreraye POINT org</a>&gt;</code></p></div></div></div><div><p class="releaseinfo">Version : 2000-02-02.fr.1.0</p></div><div><p class="pubdate">2003-12-31</p></div><div><div class="revhistory"><table summary="Historique des versions"><tr><th align="left" valign="top" colspan="3"><strong>Historique des versions</strong></th></tr><tr><td align="left">Version v2000-02-02.fr.1.0</td><td align="left">2003-07-23</td><td align="left">VC,CT,JPG</td></tr><tr><td align="left">Version v2000-02-02</td><td align="left">2000-02-02</td><td align="left">SS</td></tr></table></div></div><div><div class="abstract"><p class="title"><strong>Résumé</strong></p><p>

Ce guide pratique explique pas à pas comment compresser ses connexions
en utilisant SSH. Compresser les connexions permet, d'une part, de
limiter la bande passante utilisée et, d'autre part, d'accélérer les
connexions à faible débit (modem, GSM, RNIS).

</p></div></div></div><hr/></div><div class="toc"><p><strong>Table des matières</strong></p><dl class="toc"><dt><span class="section"><a href="#d0e85">1. Introduction</a></span></dt><dt><span class="section"><a href="#d0e102">2. Compresser HTTP, FTP…
 </a></span></dt><dt><span class="section"><a href="#d0e146">3. Compression du courrier électronique
 </a></span></dt><dd><dl><dt><span class="section"><a href="#d0e149">3.1. Courrier entrant (POP3, IMAP4)
 </a></span></dt><dt><span class="section"><a href="#d0e195">3.2. Courrier sortant (SMTP)
 </a></span></dt></dl></dd><dt><span class="section"><a href="#d0e229">4. Notes sur les performances
 </a></span></dt><dt><span class="section"><a href="#d0e238">5. Remerciements
 </a></span></dt><dt><span class="section"><a href="#d0e252">6. Droits d'utilisation</a></span></dt><dt><span class="appendix"><a href="#gfdl">A. GNU Free Documentation License</a></span></dt><dd><dl><dt><span class="section"><a href="#gfdl-0">1. PREAMBLE</a></span></dt><dt><span class="section"><a href="#gfdl-1">2. APPLICABILITY AND DEFINITIONS</a></span></dt><dt><span class="section"><a href="#gfdl-2">3. VERBATIM COPYING</a></span></dt><dt><span class="section"><a href="#gfdl-3">4. COPYING IN QUANTITY</a></span></dt><dt><span class="section"><a href="#gfdl-4">5. MODIFICATIONS</a></span></dt><dt><span class="section"><a href="#gfdl-5">6. COMBINING DOCUMENTS</a></span></dt><dt><span class="section"><a href="#gfdl-6">7. COLLECTIONS OF DOCUMENTS</a></span></dt><dt><span class="section"><a href="#gfdl-7">8. AGGREGATION WITH INDEPENDENT WORKS</a></span></dt><dt><span class="section"><a href="#gfdl-8">9. TRANSLATION</a></span></dt><dt><span class="section"><a href="#gfdl-9">10. TERMINATION</a></span></dt><dt><span class="section"><a href="#gfdl-10">11. FUTURE REVISIONS OF THIS LICENSE</a></span></dt><dt><span class="section"><a href="#gfdl-addendum">12. ADDENDUM: How to use this License for
  your documents</a></span></dt></dl></dd></dl></div><div class="section"><div class="titlepage"><div><div><h2 class="title"><a id="d0e85"/>1. Introduction</h2></div></div></div><p>
Dans le passé, nous avions l'habitude de compresser les fichiers
pour économiser de l'espace disque. Aujourd'hui, l'espace disque est
peu onéreux mais la bande passante est limitée. En compressant les flux
de données réseau, vous atteindrez deux objectifs :
</p><p>

</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>

Vous économiserez la bande passante et le volume transféré (ce
qui est important si vous devez payer le trafic ou si votre réseau est
chargé).

</p></li><li class="listitem"><p>

Vous accélérez les connexions à faible bande passante (Modem, 
GSM, RNIS).

</p></li></ol></div><p>

</p><p>

Ce guide va vous expliquer comment économiser la bande passante et le
temps de connexion en utilisant des outils comme SSH1, SSH2, OpenSSH ou
LSH.

</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title"><a id="d0e102"/>2. Compresser HTTP, FTP…
 </h2></div></div></div><p>

Mon bureau est connecté à internet par une ligne RNIS à 64 kbit/s.
Le taux de transfert maximum de cette ligne est donc d'environ
7 ko/s. Il est possible d'accélérer le débit de cette connexion en
compressant les données échangées : quand je télécharge des
fichiers, Netscape affiche un taux de transfert allant jusqu'à
40 ko/s (Il est possible de compresser les fichiers d'historique
par un facteur de 15). SSH est un outil principalement conçu pour la
mise en place de connexions sécurisées au travers de réseaux
non-sécurisés. De plus, SSH est capable de compresser les données
échangées et de faire suivre des ports (comme le font rinetd ou redir).
C'est donc l'outil approprié pour compresser n'importe quelle connexion
TCP simple. « Simple » signifie que seule une connexion TCP
est ouverte. Une connexion FTP ou la connexion entre les produits
Microsoft Outlook et Exchange ne sera pas simple puisque qu'elle
impliquera la mise en place de plusieurs connexions. SSH utilise
l'algorithme de compression Lempel-Ziv (LZ77) — donc vous
atteindrez les mêmes importants taux de compression que winzip et pkzip.
Pour compresser toutes les connexions HTTP provenant de mon intranet
vers internet, il me suffit d'exécuter une commande sur ma
machine :

</p><pre class="screen">
ssh -C -L8080:mandataire:80 -f identifiant@nom_d_hote "sleep 10000"
</pre><p>

<code class="literal">nom_d_hote</code> = la machine
hébergée par le fournisseur d'accès internet (FAI). Un accès via SSH à
cette machine est nécessaire.

</p><p>
<code class="literal">identifiant</code> = mon nom d'utilisateur sur
<code class="literal">nom_d_hote</code>.
</p><p>
<code class="literal">mandataire</code> = le serveur mandataire (<span class="foreignphrase"><em class="foreignphrase">proxy</em></span>)
de mon FAI.
</p><p>
Le navigateur de mon PC est configuré pour utiliser
<code class="literal">localhost:8080</code> comme serveur mandataire (<code class="literal">localhost</code>
étant le nom d'hôte par défaut permettant de se connecter à la machine
locale). Mon portable se connecte lui aussi sur le port <code class="literal">8080</code>
de mon PC (en utilisant l'adresse IP de mon PC au lieu de
<code class="literal">localhost</code>). La connexion est compressée et redirigée vers le
véritable serveur mandataire via SSH. L'infrastructure ressemble à
celle-ci :
</p><pre class="screen">
              64 kbit/s RNIS
Mon PC ----------------------------- Un PC
Client SSH      compressé     (Unix/Linux/Win-NT)
Port 8080                        chez mon FAI
 |                               Serveur SSH
 |                                 Port 22
 |                                    |
 |                                    |
 |                                    |
 | Ethernet 10 mbit/s                 | 100 mbit/s
 | non compressé                      | non compressé
 |                                    |
 |                                    |
Mon second PC                Serveur mandataire (proxy)
avec Netscape,...                 de mon FAI
(portable)                         Port 80
</pre></div><div class="section"><div class="titlepage"><div><div><h2 class="title"><a id="d0e146"/>3. Compression du courrier électronique
 </h2></div></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="d0e149"/>3.1. Courrier entrant (POP3, IMAP4)
 </h3></div></div></div><p>
La plupart des internautes rapatrient leur courrier électronique à
partir de leur serveur de messagerie via le protocole POP3. Ce
protocole présente de nombreux inconvénients :
</p><p>

</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
POP3 fait transiter le mot de passe en clair (des versions de
POP et d'IMAP utilisant SSL ont été développées et un mécanisme
d'authentification via un protocole de type défi-réponse est défini
dans les RFC 2095 et 2195).
  
</p></li><li class="listitem"><p>
POP3 est un protocole très bavard : le client doit tout
d'abord demander un message. Puis le serveur lui envoie le message.
Ensuite, le client demande la suppression du message transféré. Le
serveur lui confirme la suppression. Une fois cela fait, le serveur
est prêt à passer au message suivant. Cela nécessite donc 4
transactions par courrier électronique.

  
</p></li><li class="listitem"><p>
POP3 transfère les courriers électroniques sans aucune
compression, bien que les courriers électroniques soient hautement
compressible (d'un facteur de 3,5).

</p></li></ol></div><p>

</p><p>
Vous pourriez compresser les connexions POP3 en redirigeant le port
110 de la machine locale (<code class="literal">localhost:110</code>) via une connexion
compressée vers le serveur POP3 de votre fournisseur d'accès. Après
cela, il suffirait de configurer votre client de messagerie pour qu'il
se connecte sur l'adresse <code class="literal">localhost:110</code> afin de télécharger le
courrier électronique. Ce qui permettrait de sécuriser et d'accélérer
la connexion — mais le temps de téléchargement reste inhérent à
la surcharge due au protocole POP3.
</p><p>
Il est intéressant de substituer au protocole POP3 un protocole plus
efficace. L'idée est de télécharger la boîte aux lettres toute entière
en une seule fois sans avoir à supporter la surcharge due au protocole. 
De plus, il est intéressant de compresser cette connexion. L'outil
approprié offrant ces deux caractéristiques est SCP. Vous pouvez
télécharger votre fichier boîte aux lettres de la manière
suivante :
</p><pre class="screen">
scp -C identifiant@serveur-de-messagerie:/var/spool/mail/identifiant \
       /tmp/nouveau_courrier
</pre><p>
Mais il y a un problème : que se passe-t-il si un nouveau
courrier arrive sur le serveur pendant que vous téléchargez votre boîte
aux lettres ? Le nouveau courrier serait perdu. On a plutôt
intérêt à utiliser les commandes suivantes :
</p><pre class="screen">
ssh identifiant@serveur-de-messagerie \
    "mv /var/spool/mail/identifiant /tmp/identifiant_a_rapatrier"
scp -C identifiant@serveur-de-messagerie:/tmp/identifiant_a_rapatrier \
       /tmp/nouveau_courrier
</pre><p>
Un déplacement de fichier (mv) est une opération élémentaire, donc
vous n'aurez pas de problème si vous recevez de nouveaux courriers
durant l'exécution des commandes. Cependant si les répertoires /tmp et
/var/spool/mail/ du serveur de messagerie ne sont pas sur le même
disque, vous pourriez avoir des problèmes. Une solution est de créer un
fichier de verrouillage sur le serveur avant d'exécuter la commande de
déplacement :
</p><pre class="screen">
touch /var/spool/mail/identifiant.lock
</pre><p>
Vous devrez le supprimer après coup. Une meilleure solution est de 
déplacer le fichier identifiant dans le même répertoire :
</p><pre class="screen">
ssh identifiant@serveur-de-messagerie \
    "mv /var/spool/mail/identifiant /var/spool/mail/identifiant_a_rapatrier"
</pre><p>
Après cela, vous pourrez utiliser formail à la place de procmail
pour filtrer /tmp/nouveau_courrier dans les répertoires
correspondants :
</p><pre class="screen">
formail -s procmail &lt; /tmp/nouveau_courrier
</pre></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="d0e195"/>3.2. Courrier sortant (SMTP)
 </h3></div></div></div><p>
Envoyez des courriers électroniques au travers de connexions SSH
compressées et chiffrées, permet de :
</p><p>

</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
Économiser du trafic réseau.
  
</p></li><li class="listitem"><p>
Sécuriser la connexion (cela n'a pas d'intérêt si le courrier
électronique transite par des réseaux non sécurisés par la suite).
  
</p></li><li class="listitem"><p>
Authentifier l'émetteur. Beaucoup de serveurs de messagerie
n'autorisent pas le transit des courriers pour éviter les abus. Si
vous envoyez un courrier au travers d'une connexion SSH, le serveur de 
messagerie distant (par exemple Sendmail ou MS Exchange) pensera
être connecté localement, et acceptera donc de faire transiter le 
message.

</p></li></ul></div><p>

</p><p>
Si vous avez un accès SSH au serveur de messagerie, vous aurez 
besoin de la commande suivante :
</p><pre class="screen">
ssh -C -L2525:serveur_de_messagerie:25 identifiant@serveur_de_messagerie
</pre><p>
Si vous n'avez pas d'accès SSH au serveur de messagerie, mais que
vous avez un accès SSH à un serveur autorisé à utiliser le serveur de
messagerie comme relais, la commande sera la suivante :
</p><pre class="screen">
ssh -C -L2525:serveur_de_messagerie:25 identifiant@autre_server
</pre><p>
Après cela, vous pourrez configurer votre client de messagerie local
(ou le serveur de messagerie, recherchez de la documentation sur les
relais de messagerie (<span class="foreignphrase"><em class="foreignphrase">smarthosts</em></span>)) pour envoyer les messages
sortants vers le port 2525 de la machine locale (<code class="literal">localhost</code>).
</p></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title"><a id="d0e229"/>4. Notes sur les performances
 </h2></div></div></div><p>
Bien sûr, la compression et le chiffrement utilisent du temps
processeur. Il a été calculé qu'un vieux Pentium-133 peut chiffrer et
compresser environ 1 Go / heure — ce qui est assez
important. Si vous compilez SSH avec l'option « --with-none »
vous indiquerez à SSH de ne pas utiliser de chiffrement. Cela permet
d'augmenter un peu les performances. Voici une évaluation de 
</p><p>
le compromis entre
différentes méthodes de téléchargement (pendant le test, un fichier non
compressé de 6 Mo est transféré à partir d'un Pentium à
133 MHz vers un portable équipé d'un Pentium 2 à 233 MHz
et ceci sur un segment Ethernet à 10 Mbit/s sans autre charge).
</p><pre class="screen">
+--------------------------+---------+---------+-----------+-----------+
|                          |  FTP    | chiffré | compressé | compressé |
|                          |         |         |           | &amp; chiffré |
+--------------------------+---------+---------+-----------+-----------+
+--------------------------+---------+---------+-----------+-----------+
|     Temps écoulé (s)     |   7.6   |    26   |      9    |     23    |
+--------------------------+---------+---------+-----------+-----------+
| Taux de transfert (ko/s) |   790   |   232   |    320    |    264    |
+--------------------------+---------+---------+-----------+-----------+
|   Facteur compression    |     1   |     1   |    3.8    |    3.8    |
+--------------------------+---------+---------+-----------+-----------+
</pre></div><div class="section"><div class="titlepage"><div><div><h2 class="title"><a id="d0e238"/>5. Remerciements
 </h2></div></div></div><p>
Merci à Harald König
<code class="email">&lt;<a class="email" href="mailto:koenig CHEZ tat POINT physik POINT uni TIRET tuebingen POINT de">koenig CHEZ tat POINT physik POINT uni TIRET tuebingen POINT de</a>&gt;</code>,
qui a utilisé rcp pour télécharger les boîtes aux lettres complètes. La 
dernière version de ce guide pratique en version originale est 
disponible à l'adresse suivante :
<a class="ulink" href="http://www.tldp.org/HOWTO/Compressed-TCP.html" target="_top">http://www.tldp.org/HOWTO/Compressed-TCP.html</a>.
</p><p>

La dernière version française de ce document est toujours disponible à
l'adresse <a class="ulink" href="http://www.traduc.org/docs/howto/lecture/Compressed-TCP.html" target="_top">http://www.traduc.org/docs/howto/lecture/Compressed-TCP.html</a>.

</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title"><a id="d0e252"/>6. Droits d'utilisation</h2></div></div></div><p>

Copyright © 2002 Sebastian Schreiber pour la version originale.

</p><p>

Copyright © 2003-2004 Vincent Chartier, Claude Thomassin et
Jean-Philippe Guérard pour la version française.

</p><p>

Vous est autorisé de copier, distribuer ou modifier la version originale
de ce document selon les termes de la licence de documentation libre GNU
(GFDL), version 1.2 ou ultérieure, telle que publiée par la Free
Software Foundation ; sans section inaltérable, ni texte de
première de couverture, ni texte de quatrième de couverture. Une copie
de cette licence est incluse dans la section intitulée « GNU Free
Documentation License ».

</p><p>

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For works in formats which do not have any title page as such, "Title
Page" means the text near the most prominent appearance of the work's
title, preceding the beginning of the body of the text.</p><p><a id="gfdl-entitled"/>A section "Entitled XYZ" means a named subunit
of the Document whose title either is precisely XYZ or contains XYZ in
parentheses following text that translates XYZ in another language.
(Here XYZ stands for a specific section name mentioned below, such as
"Acknowledgements", "Dedications", "Endorsements", or "History".)  To
"Preserve the Title" of such a section when you modify the Document
means that it remains a section "Entitled XYZ" according to this
definition.</p><p>The Document may include Warranty Disclaimers next to the notice
which states that this License applies to the Document.  These Warranty
Disclaimers are considered to be included by reference in this License,
but only as regards disclaiming warranties: any other implication that
these Warranty Disclaimers may have is void and has no effect on the
meaning of this License.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="gfdl-2"/>3. VERBATIM COPYING</h3></div></div></div><p>

You may copy and distribute the Document in any medium, either
commercially or noncommercially, provided that this License, the
copyright notices, and the license notice saying this License applies to
the Document are reproduced in all copies, and that you add no other
conditions whatsoever to those of this License.  You may not use
technical measures to obstruct or control the reading or further copying
of the copies you make or distribute.  However, you may accept
compensation in exchange for copies.  If you distribute a large enough
number of copies you must also follow the conditions in section <a class="xref" href="#gfdl-3" title="4. COPYING IN QUANTITY">Section 4, « COPYING IN QUANTITY »</a>.

</p><p>You may also lend copies, under the same conditions stated above,
and you may publicly display copies.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="gfdl-3"/>4. COPYING IN QUANTITY</h3></div></div></div><p>If you publish printed copies (or copies in media that commonly
have printed covers) of the Document, numbering more than 100, and the
Document's license notice requires Cover Texts, you must enclose the
copies in covers that carry, clearly and legibly, all these Cover Texts:
Front-Cover Texts on the front cover, and Back-Cover Texts on the back
cover.  Both covers must also clearly and legibly identify you as the
publisher of these copies.  The front cover must present the full title
with all words of the title equally prominent and visible.  You may add
other material on the covers in addition.  Copying with changes limited
to the covers, as long as they preserve the title of the Document and
satisfy these conditions, can be treated as verbatim copying in other
respects.</p><p>If the required texts for either cover are too voluminous to fit
legibly, you should put the first ones listed (as many as fit
reasonably) on the actual cover, and continue the rest onto adjacent
pages.</p><p>If you publish or distribute Opaque copies of the Document
numbering more than 100, you must either include a machine-readable
Transparent copy along with each Opaque copy, or state in or with each
Opaque copy a computer-network location from which the general
network-using public has access to download using public-standard
network protocols a complete Transparent copy of the Document, free of
added material.  If you use the latter option, you must take reasonably
prudent steps, when you begin distribution of Opaque copies in quantity,
to ensure that this Transparent copy will remain thus accessible at the
stated location until at least one year after the last time you
distribute an Opaque copy (directly or through your agents or retailers)
of that edition to the public.</p><p>It is requested, but not required, that you contact the authors of
the Document well before redistributing any large number of copies, to
give them a chance to provide you with an updated version of the
Document.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="gfdl-4"/>5. MODIFICATIONS</h3></div></div></div><p>You may copy and distribute a Modified Version of the Document
under the conditions of sections 2 and 3 above, provided that you
release the Modified Version under precisely this License, with the
Modified Version filling the role of the Document, thus licensing
distribution and modification of the Modified Version to whoever
possesses a copy of it.  In addition, you must do these things in the
Modified Version:</p><div class="orderedlist"><a id="gfdl-modif-cond"/><ol class="orderedlist" type="A"><li class="listitem">Use in the Title Page (and on the covers, if any) a
  title distinct from that of the Document, and from those of previous
  versions (which should, if there were any, be listed in the History
  section of the Document).  You may use the same title as a previous
  version if the original publisher of that version gives permission.
</li><li class="listitem">List on the Title Page, as authors, one or more
  persons or entities responsible for authorship of the modifications in
  the Modified Version, together with at least five of the principal
  authors of the Document (all of its principal authors, if it has fewer
  than five), unless they release you from this requirement.
</li><li class="listitem">State on the Title page the name of the publisher of
  the Modified Version, as the publisher.</li><li class="listitem">Preserve all the copyright notices of the Document.
</li><li class="listitem">Add an appropriate copyright notice for your
  modifications adjacent to the other copyright notices.
</li><li class="listitem">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
  <a class="link" href="#gfdl-addendum" title="12. ADDENDUM: How to use this License for your documents">Addendum</a> below.
</li><li class="listitem">Preserve in that license notice the full lists of
  Invariant Sections and required Cover Texts given in the Document's
  license notice.</li><li class="listitem">Include an unaltered copy of this License.
</li><li class="listitem">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.
</li><li class="listitem">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.
</li><li class="listitem">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.
</li><li class="listitem">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.
</li><li class="listitem">Delete any section Entitled "Endorsements".
  Such a section may not be included in the Modified Version.
</li><li class="listitem">Do not retitle any existing section to be Entitled
  "Endorsements" or to conflict in title with any Invariant Section.
</li><li class="listitem">Preserve any Warranty Disclaimers.
</li></ol></div><p>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.</p><p>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.</p><p>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.</p><p>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.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="gfdl-5"/>6. COMBINING DOCUMENTS</h3></div></div></div><p>You may combine the Document with other documents released under
this License, under the terms defined in <a class="link" href="#gfdl-4" title="5. MODIFICATIONS">section
4</a> 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.</p><p>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.</p><p>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".</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="gfdl-6"/>7. COLLECTIONS OF DOCUMENTS</h3></div></div></div><p>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.</p><p>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.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="gfdl-7"/>8. AGGREGATION WITH INDEPENDENT WORKS</h3></div></div></div><p>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.</p><p>

If the Cover Text requirement of section <a class="xref" href="#gfdl-3" title="4. COPYING IN QUANTITY">Section 4, « COPYING IN QUANTITY »</a> 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.

</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="gfdl-8"/>9. TRANSLATION</h3></div></div></div><p>

Translation is considered a kind of modification, so you may distribute
translations of the Document under the terms of section <a class="xref" href="#gfdl-4" title="5. MODIFICATIONS">Section 5, « MODIFICATIONS »</a>. 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.

</p><p>

If a section in the Document is Entitled "Acknowledgements",
"Dedications", or "History", the requirement (section <a class="xref" href="#gfdl-4" title="5. MODIFICATIONS">Section 5, « MODIFICATIONS »</a>) to Preserve its Title
(section <a class="xref" href="#gfdl-1" title="2. APPLICABILITY AND DEFINITIONS">Section 2, « APPLICABILITY AND DEFINITIONS »</a>) will
typically require changing the actual title.

</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="gfdl-9"/>10. TERMINATION</h3></div></div></div><p>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.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="gfdl-10"/>11. FUTURE REVISIONS OF THIS LICENSE</h3></div></div></div><p>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/.</p><p>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.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="gfdl-addendum"/>12. ADDENDUM: How to use this License for
  your documents</h3></div></div></div><p>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:</p><div class="blockquote"><a id="copyright-sample"/><blockquote class="blockquote"><p>
    Copyright ©  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".
</p></blockquote></div><p>If you have Invariant Sections, Front-Cover Texts and Back-Cover
Texts, replace the "with...Texts." line with this:</p><div class="blockquote"><a id="inv-cover-sample"/><blockquote class="blockquote"><p>
    with the Invariant Sections being LIST THEIR TITLES, with the
    Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
</p></blockquote></div><p>If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.</p><p>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.</p></div></div></div></body></html>
doc-linux-fr-html 2013.01-2 / usr / share / doc / HOWTO / fr-html / Compressed-TCP.html
