@node Use cases
@unnumbered Use cases
-@table @strong
-
-@item Occasional connection to mail server
+@menu
+* Occasional connection to mail server: UsecaseMail.
+* Lightweight fast POP3/IMAP4 replacement: UsecasePOP.
+* Unreliable/expensive communication link: UsecaseUnreliable.
+* Slow/expensive link for high-volume data, bad QoS: UsecaseQoS.
+* Extreme terrestrial environments, no link: UsecaseNoLink.
+* Private, isolated MitM/Sybil-resistant networks: UsecaseF2F.
+* Highly secure isolated air-gap computers: UsecaseAirgap.
+* Network censorship bypassing, health: UsecaseCensor.
+* Reconnaissance, spying, intelligence, covert agents: UsecaseSpy.
+@end menu
+
+@node UsecaseMail
+@section Occasional connection to mail server
Assume that you have got your own @url{http://www.postfix.org/, Postfix}
SMTP server connected to the Internet. But you read and write emails on
Another possibility is to use POP3/IMAP4 servers, but this is too
overcomplicated and bloated for the simple task. Not an option.
+@url{https://en.wikipedia.org/wiki/KISS_principle, KISS}!
Just tell both of your Postfixes (on the server and notebook) to drop
-email as a mail via NNCP to specified node. Search for @code{uucp}
-related strings in @code{master.cf} and replace command to NNCP ones:
-
-@verbatim
-nncp unix - n n - - pipe
- flags=Fqhu user=nncp argv=nncp-mail -quiet $nexthop $recipient
-@end verbatim
-
-Now, all mail will be stored in NNCP spool, that after exchanging and
-tossing will call local @code{sendmail} command to deliver them just
-that was happened on the same machine.
-
-@item Unreliable/expensive communication link
+email as a mail via NNCP (@ref{nncp-mail}) to specified node. This is
+done similarly as with UUCP and as written in
+@url{http://www.postfix.org/UUCP_README.html, Postfix documentation}.
+
+Look @ref{Postfix, here} for further information. All mail will be
+stored in NNCP @ref{Spool, spool}, that after exchanging and tossing
+will call local @command{sendmail} command to deliver them just like
+that happened on the same machine.
+
+@node UsecasePOP
+@section Lightweight fast POP3/IMAP4 replacement
+
+@ref{nncp-daemon} can be connected with @ref{nncp-caller} for a long
+time -- it can create TCP connection that lasts for many hours. When
+SMTP server receives mail, it will call @ref{nncp-mail} creating an
+outbound encrypted packet. Daemon checks outbound directory each second
+and immediately sends notification about undelivered packets to remote
+side, that also downloads it at once.
+
+There are only dozens of bytes notifying about incoming packets, dozens
+of bytes telling to download those packets. Mail packets are compressed
+(POP3 and IMAP4 as a rule do not). You have lightweight, compressed,
+low-delay, reliable link for the mail with strong encryption and mutual
+sides authentication!
+
+@node UsecaseUnreliable
+@section Unreliable/expensive communication link
Assume that you have got slow modem/radio/cellular link that frequently
disconnects and causes TCP timeouts. Not all HTTP servers support file
download continuation. SMTP does not support resuming at all and heavy
-messages is a problem to retrieve. Moreover, each disconnect leads to
-the same data retransmission again, that can be expensive to afford.
+messages is problematic to retrieve. Moreover, each disconnect leads to
+the same data retransmission again, that can not be afforded sometimes.
-Just send your mail and files through NNCP. You can use either offline
-delivery methods -- read about them below, or you can use included NNCP
-TCP daemon.
+Just send your @ref{nncp-mail, mail} and @ref{nncp-file, files} through
+NNCP. You can use either offline delivery methods -- read about them in
+the next section, or you can use included NNCP @ref{nncp-daemon, TCP
+daemon}.
-The command below:
+The command:
@verbatim
% nncp-file file_i_want_to_send bob:
% nncp-file another_file bob:movie.avi
@end verbatim
-will queue two files for sending to @code{bob} node. Fire and forget!
-Now this is daemon's job (or offline transfer) to send this file part by
-part to remote system when it is available.
+will queue two files for sending to @emph{bob} node. Fire and forget!
+Now this is daemon's job (or offline transfer) to send this files part
+by part to remote system when it is available.
-@item Slow/expensive link for high-volume data
+@node UsecaseQoS
+@section Slow/expensive link for high-volume data, bad QoS
Assume that you can give your relatively cheap 2 TiB removable hard
drive to someone each day at the morning (and take it back at the
evening). This equals to 185 Mbps good quality (without any speed
degradation) link in single direction. What about more and bigger hard
-drives? This type of data transferring is called
+drives? This type of data exchange is called
@url{https://en.wikipedia.org/wiki/Sneakernet, sneakernet}/floppynet.
-@item Extreme terrestrial environments, no link
+NNCP allows traffic @ref{Niceness, prioritizing}: each packet has
+niceness level, that will guarantee that it will be processed earlier or
+later than the other ones. Nearly all commands has corresponding option:
+
+@verbatim
+% nncp-file -nice 32 myfile node:dst
+% nncp-xfer -nice 192 /mnt/shared
+% nncp-call -nice 224 bob
+[...]
+@end verbatim
+
+Huge files could be split on smaller @ref{Chunked, chunks}, giving
+possibility to transfer virtually any volumes using small capacity
+storages.
+
+@node UsecaseNoLink
+@section Extreme terrestrial environments, no link
This is some kind of too slow link. Offline delivery methods is the only
-choice. Just send files as shown above, but use removable media for
-transferring packets to other nodes.
+choice. Just send files as shown in previous section, but use removable
+media for transferring packets to other nodes.
-Assume that you send two files to @code{bob} node. Insert USB storage
-device, mount it and run:
+Assume that you send two files to @emph{bob} node. Insert USB storage
+device, mount it and run @ref{nncp-xfer}:
@verbatim
% nncp-xfer -node bob /media/usbstick
@end verbatim
-to copy all outbound packets related to @code{bob}'s node. Use
-@code{-force} option to forcefully create related directory on USB
-storage if they are missing (for example when running for the first
-time).
+to copy all outbound packets related to @emph{bob}. Use @option{-mkdir}
+option to create related directory on USB storage if they are missing
+(for example when running for the first time).
-If you use single storage device to transfer data both to @code{bob} and
-@code{alice}, then just omit @code{-node} option to copy all existing
-outgoing packets to that storage device.
+If you use single storage device to transfer data both to @emph{bob} and
+@emph{alice}, then just omit @option{-node} option to copy all available
+outgoing packets.
@verbatim
% nncp-xfer /media/usbstick
@end verbatim
-Unmount it and transfer somehow to Bob and Alice. When they will insert
+Unmount it and transfer storage to Bob and Alice. When they will insert
it in their computers, they will use exactly the same command:
@verbatim
@end verbatim
to find all packets related to their node and copy them locally for
-further processing. @code{nncp-xfer} is the only command used with
+further processing. @command{nncp-xfer} is the only command used with
removable devices.
-@item Private, isolated MitM-resistant networks
+@node UsecaseF2F
+@section Private, isolated MitM/Sybil-resistant networks
All Internet connections can be eavesdropped and forged. You
@strong{have to} to use encryption and authentication for securing them.
The most popular cryptographic protocol in Internet is
@url{https://en.wikipedia.org/wiki/Transport_Layer_Security, TLS} that
-is very hard to implement right and hard to configure for mutual
+is very hard to implement correctly and hard to configure for mutual
participants authentication. Not all TLS configurations and related
protocols provide @url{https://en.wikipedia.org/wiki/Forward_secrecy,
forward secrecy} property -- all previously intercepted packets could be
read if private keys are compromised.
Friend-to-friend networks, darknets can mitigate risks related to fake
-and forged nodes. However they are harder to support require more time
-to be done right.
+and forged nodes. However they are harder to support and require more
+time to be done right.
-NNCP's TCP daemon uses @url{http://noiseprotocol.org/, Noise-IK}
-protocol to mutually authenticate peers and provide effective (both
-participants send payload in the very first packet) secure transport
-with forward secrecy property.
+NNCP's @ref{nncp-daemon, TCP daemon} uses
+@url{http://noiseprotocol.org/, Noise-IK} protocol to mutually
+authenticate peers and provide effective (both participants send payload
+in the very first packet) secure transport with forward secrecy
+property.
@verbatim
% nncp-daemon -bind [::]:5400
@verbatim
% nncp-call bob
@end verbatim
-will try to connect to @code{bob}'s node known TCP addresses (taken from
+will try to connect to @emph{bob}'s node known TCP addresses (taken from
configuration file) and send all related outbound packets and retrieve
those the Bob has. All interrupted transfers will be automatically
resumed.
-@item Highly secure isolated air-gap computers
+@node UsecaseAirgap
+@section Highly secure isolated air-gap computers
If you worry much about security, then air-gapped computer could be the
only choice you can afford. Computer without any modems, wired and
via: [bob]
@end verbatim
-That configuration file tells that we have got two known neighbours
-(nodes, peers): @code{bob} and @code{bob-airgap}. @code{bob} can be
-reached via online connection using @code{lan} address.
-@code{bob-airgap} can be reached by sending intermediate relay packet
-through the @code{bob}.
+That @ref{Configuration, configuration file} tells that we have got two
+known neighbours: @emph{bob} and @emph{bob-airgap}. @emph{bob} can be
+reached via online connection using @emph{lan} address.
+@emph{bob-airgap} can be reached by sending intermediate relay packet
+through the @emph{bob}.
-Any command like @code{nncp-file myfile bob-airgap:} will automatically
-create two packets: one for the destination endpoint, other for
-intermediate relaying node.
+Any command like @command{nncp-file myfile bob-airgap:} will
+automatically create an encapsulated packet: one for the destination
+endpoint, and other carrying it for intermediate relaying node.
Pay attention that relaying node knows nothing about the packet inside,
-but just its size and priority. Transition packets are encrypted too.
-@code{bob} can not read @code{bob-airgap}'s packets.
-
-@item Reconnaissance, spying, intelligence, covert agents
+but just its size and priority. Transition packets are encrypted too:
+using well-known @url{https://en.wikipedia.org/wiki/Onion_routing, onion
+routing} technology. @emph{bob} can not read @emph{bob-airgap}'s packets.
+
+@node UsecaseCensor
+@section Network censorship bypassing, health
+
+This is some kind of bad link too. Some governments tend to forbid
+@strong{any} kind of private communication between people, allowing only
+entertainment content delivering and popular social networks access
+(that are already bloated with advertisements, locally executed
+@url{https://www.gnu.org/philosophy/free-sw.html, proprietary}
+JavaScript code (for spying on user activities, collect data on them),
+shamelessly exploiting the very basic human need of communication).
+
+This is their natural wish. But nobody forces you to obey huge
+corporations like Apple, Google or Microsoft. It is your choice to
+create an isolated friend-to-friend network with piles of harmless
+content and private messaging. Only predators silently watch for their
+victims in mammals world -- it harms your health being watched and
+feeling that you are the victim that has already done something wrong.
+
+@node UsecaseSpy
+@section Reconnaissance, spying, intelligence, covert agents
Those guys know how Internet is a dangerous place incompatible with
privacy. They require quick, fast dropping and picking of data. No
possibility of many round-trips -- just drop the data, fire-and-forget.
-It could be either removable media again, or
-@url{https://en.wikipedia.org/wiki/USB_dead_drop, USB dead drops}, or
-@url{https://en.wikipedia.org/wiki/PirateBox, PirateBox}es, or
+It could be either removable media again and/or
+@url{https://en.wikipedia.org/wiki/USB_dead_drop, USB dead drops},
+@url{https://en.wikipedia.org/wiki/PirateBox, PirateBox}es,
@url{https://en.wikipedia.org/wiki/Short-range_agent_communications, SRAC}.
Short lived short range networks like Bluetooth and WiFi can also
be pretty fast, allowing to quickly fire chunks of queued packets.
Very important property is that compromising of those dead drops and
-storages must not be fatal and even dangerous. Packets sent through the
-network and exchanged via those devices are end-to-end encrypted (but
-unfortunately without forward secrecy property). No filenames, mail
-recipients are seen.
-
-All communications are done with so-called spool area: directory
-containing only those unprocessed encrypted packets. After packet
-transfer you still can not read any mail of get files: you have to run
-another stage: tossing. Only that stage involves your private
+storages must be neither fatal nor even dangerous. Packets sent through
+the network and exchanged via those devices are end-to-end
+@ref{Encrypted, encrypted} (but unfortunately lacking forward secrecy).
+No filenames, mail recipients are seen.
+
+All node communications are done with so-called @ref{Spool, spool} area:
+directory containing only those unprocessed encrypted packets. After
+packet transfer you still can not read any of them: you have to run
+another stage: @ref{nncp-toss, tossing}, that involves your private
cryptographic keys. So even if your loose your computer, storage devices
and so on -- it is not so bad, because you are not carrying private keys
-with it, you do not "toss" those packets immediately on the same device.
-
-Tossing (reading those encrypted packets and extracting transferred
-files and mail messages) could and should be done on a separate
-computer.
-
-@end table
+with it (don't you?), you do not "toss" those packets immediately on the
+same device. Tossing (reading those encrypted packets and extracting
+transferred files and mail messages) could and should be done on a
+separate computer (@ref{nncp-cfgmin} command could help creating
+configuration file without private keys for that purpose).