@node Use cases
@unnumbered Use cases
+See also this page @ref{Сценарии, on russian}.
+
@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-resistant networks: UsecaseF2F.
+* One-way broadcasting communications: UsecaseBroadcast.
+* Satellite links: UsecaseSatelliteLinks.
+* Private, isolated MitM/Sybil-resistant networks: UsecaseF2F.
* Highly secure isolated air-gap computers: UsecaseAirgap.
-* Network censorship bypassing: UsecaseCensor.
+* Network censorship bypassing, health: UsecaseCensor.
* Reconnaissance, spying, intelligence, covert agents: UsecaseSpy.
+* Cheap night transfers: UsecaseCaller.
@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
-your notebook, that is connected to it just from time to time. How can
-you flush buffered mail queues when your notebook is connected?
+Assume that you have got your own @url{http://www.postfix.org/,
+Postfix}/@url{http://www.exim.org/, Exim} SMTP server connected to the
+Internet. But you read and write emails on your notebook, that is
+connected to it just from time to time. How can you flush buffered mail
+queues when your notebook is connected?
One possibility is to log in and run something like @command{postqueue
-f}, but by default you have got only several days so and sender will
yet. Also you must have secure link (SSH, VPN, etc).
Another possibility is to use POP3/IMAP4 servers, but this is too
-overcomplicated and bloated for the simple task. Not an option. KISS!
+overcomplicated and bloated for the simple task. Not an option.
+@url{https://en.wikipedia.org/wiki/KISS_principle, KISS}!
+
+Just tell both of your Postfix/Exim (on the server and notebook) to drop
+email as a mail via NNCP (@ref{nncp-exec}) to specified node.
+
+More information for Postfix is @ref{Postfix, here} and for Exim is
+@ref{Exim, here}. 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
-Just tell both of your Postfixes (on the server and notebook) to drop
-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}.
+@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-exec} 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.
-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.
+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
messages is problematic to retrieve. Moreover, each disconnect leads to
the same data retransmission again, that can not be afforded sometimes.
-Just send your @ref{nncp-mail, mail} and @ref{nncp-file, files} through
+Just send your @ref{nncp-exec, 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:
-@verbatim
-% nncp-file file_i_want_to_send bob:
-% nncp-file another_file bob:movie.avi
-@end verbatim
+@example
+$ nncp-file file_i_want_to_send bob:
+$ nncp-file another_file bob:movie.avi
+@end example
-will queue two files for sending to @code{emph} 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.
@node UsecaseQoS
@section Slow/expensive link for high-volume data, bad QoS
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
+@example
+$ nncp-file -nice FLASH myfile node:dst
+$ nncp-xfer -nice PRIORITY /mnt/shared
+$ nncp-call -nice NORMAL bob
[...]
-@end verbatim
+@end example
+
+Huge files could be split on smaller @ref{Chunked, chunks}, giving
+possibility to transfer virtually any volumes using small capacity
+storages.
+
+You can also use CD-ROM and tape drives:
+
+@example
+$ nncp-bundle -tx bob | cdrecord -tao -
+$ nncp-bundle -tx bob | dd of=/dev/sa0 bs=10240
+@end example
@node UsecaseNoLink
@section Extreme terrestrial environments, no link
media for transferring packets to other nodes.
Assume that you send two files to @emph{bob} node. Insert USB storage
-device, mount it and run @ref{nncp-xfer}:
+device (SD is preferable!), mount it and run @ref{nncp-xfer}:
-@verbatim
-% nncp-xfer -node bob /media/usbstick
-@end verbatim
+@example
+$ nncp-xfer -node bob /media/usbstick
+@end example
-to copy all outbound packets related to @emph{bob}'s node. Use
-@option{-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/SD storage if they are missing
+(for example when running for the first time).
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 existing
-outgoing packets to that storage device.
+@emph{alice}, then just omit @option{-node} option to copy all available
+outgoing packets.
-@verbatim
-% nncp-xfer /media/usbstick
-@end verbatim
+@example
+$ nncp-xfer /media/usbstick
+@end example
-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
-% nncp-xfer /media/usbstick
-@end verbatim
+@example
+$ nncp-xfer /media/usbstick
+@end example
to find all packets related to their node and copy them locally for
-further processing. nncp-xfer is the only command used with removable
-devices.
+further processing. @command{nncp-xfer} is the only command used with
+removable devices.
+
+@node UsecaseBroadcast
+@section One-way broadcasting communications
+
+Sometimes you have got high-bandwidth but unidirectional link, for
+example, satellite's broadcasting signal. You are not able to use online
+@ref{Sync, synchronization protocol} because it requires mutual interaction.
+
+You can use @ref{Bundles, bundles} and stream them above. They are just
+a sequence of @ref{Encrypted, encrypted packets} you can catch on.
+
+@example
+$ nncp-bundle -tx alice bob eve ... | command to send broadcast
+$ command to receive broadcast | nncp-bundle -rx
+@end example
+
+With built-in packet duplicates detection ability, you can retransmit
+your broadcasts from time to time, to increase chances the recipient
+will catch them by regular stream listening.
+
+@node UsecaseSatelliteLinks
+@section Satellite links
+
+Satellite links have @strong{very} high delays together with high
+bandwidths. You can send several megabits of data per second, but they
+will reach the remote side only after half a second!
+Most file sharing protocols like
+@url{https://en.wikipedia.org/wiki/Files_transferred_over_shell_protocol, FISH},
+@url{https://en.wikipedia.org/wiki/FTP, FTP},
+@url{https://en.wikipedia.org/wiki/Secure_copy, scp},
+@url{https://en.wikipedia.org/wiki/XMODEM, XMODEM}
+will perform very badly because of round-trips quantity. Each file
+transmission explicitly generates request and acknowledgement packets
+that are send over the link. Remote side won't do anything until it
+receives them. Moreover not all protocols allow duplex data
+transmission (when both sides are sending data simultaneously).
+
+NNCP's @ref{Sync, synchronization protocol} (SP) tries to mitigate all
+that issues by reducing number of round-trips, number of packets passing
+through. All file lists, file download requests are grouped together
+(pipelined) in one huge packet. Only transmission halt and successful
+file download acknowledgements are sent explicitly. SP could be asked
+only either to upload or download packets for our node. SP could ignore
+files with low priority. Full files listing is passing even during the
+handshake procedure.
@node UsecaseF2F
-@section Private, isolated MitM-resistant networks
+@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
in the very first packet) secure transport with forward secrecy
property.
-@verbatim
-% nncp-daemon -bind [::]:5400
-@end verbatim
+@example
+$ nncp-daemon -bind "[::]":5400
+@end example
+
will start TCP daemon listening on all interfaces for incoming
connections.
-@verbatim
-% nncp-call bob
-@end verbatim
+@example
+$ nncp-call bob
+@end example
+
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
only choice you can afford. Computer without any modems, wired and
wireless networks. Obviously the only possibility to exchange mail and
files is to use physically removable storage devices like CD-ROM, hard
-drive, tape and USB flash drives (worst choice, due to those devices
-complexity).
+drive, SD, tape and USB flash drives (@strong{worst} choice, due to
+those devices complexity).
Presumably you have got another own hop before that computer: another
intermediate node which performs basic verification of retrieved storage
NNCP supports packets relying (transitioning) out-of-box.
@verbatim
-neigh:
- bob:
+neigh: {
+ bob: {
[...]
- addrs:
- lan: [fe80::5400%igb0]:5400
+ addrs: {
+ lan: "[fe80::5400%igb0]:5400"
+ }
+ }
bob-airgap:
[...]
- via: [bob]
+ via: ["bob"]
+ }
+}
@end verbatim
That @ref{Configuration, configuration file} tells that we have got two
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.
-@emph{bob} can not read @emph{bob-airgap}'s packets.
+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
+@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
-proprietary JavaScript code (for spying on user activities, collect data
-on them), shamelessly exploiting the very basic human need of communication).
+@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
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.
@ref{Encrypted, encrypted} (but unfortunately lacking forward secrecy).
No filenames, mail recipients are seen.
-All communications are done with so-called @ref{Spool, spool} area:
+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
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.
+separate computer (@ref{nncp-cfgmin} command could help creating
+configuration file without private keys for that purpose).
+
+If you really want to carry your private keys, then @ref{nncp-cfgenc}
+command will be able to encrypt your configuration file. Passphrase you
+enter is strengthened with both CPU and memory hard function.
+
+@node UsecaseCaller
+@section Cheap night transfers
+
+Your Internet/telephone traffic price can vary, depending on daytime.
+Night calls/connections could be twice as cheaper. You wish to send your
+files at that time, but keep high priority email infrequently passing
+through in anytime. Also you wish to pass any kind of traffic when the
+node is available through the LAN.
+
+You can easily set your preferences in @ref{Call, call
+configurations} for @ref{nncp-caller} command used in online
+communications.
+
+@verbatim
+neigh: {
+ [...]
+ some-node: {
+ [...]
+ addrs: {
+ lan: "[fe80::be5f:f4ff:fedd:2752%igb0]:5400"
+ wan: "some-node.com:5400"
+ }
+ calls: [
+ {
+ cron: "*/1 * * * *"
+ addr: lan
+ nice: MAX
+ onlinedeadline: 3600
+ },
+ {
+ cron: "*/10 * * * *"
+ addr: wan
+ nice: PRIORITY
+ xx: rx
+ },
+ {
+ cron: "*/1 0-7 * * *"
+ addr: wan
+ nice: BULK
+ onlinedeadline: 3600
+ maxonlinetime: 3600
+ },
+ ]
+ }
+}
+@end verbatim