* Unreliable/expensive communication link: UsecaseUnreliable.
* Slow/expensive link for high-volume data, bad QoS: UsecaseQoS.
* Extreme terrestrial environments, no link: UsecaseNoLink.
+* 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, 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
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 (@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}.
+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.
-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.
+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
@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
+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.
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 @emph{bob} node. Fire and forget!
Now this is daemon's job (or offline transfer) to send this files part
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
Assume that you send two files to @emph{bob} node. Insert USB storage
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}. Use @option{-mkdir}
option to create related directory on USB/SD storage if they are missing
@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 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. @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/Sybil-resistant networks
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
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
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).
+
+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