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CCN-lite is a reduced and lightweight -- yet functionally interoperable -- implementation of the CCNx and NDN protocols. It covers:

• PARC's Content Centric Networking Protocol, both the old (v0.8) and new (v1.0) variant,
• the Named-Data Networking project,
• the Named-Function Networking project,
• an experimental and compact encoding for IoT environments

CCN-lite supports multiple platforms, including:

• Linux and OS X user space
• Linux kernel
• Android
• Arduino and RFduino
• OMNeT++

CCN-lite is meant as a code base for class room work, experimental extensions and simulation experiments. The ISC license makes it an excellent starting point for commercial products.

CCN-lite has been included in the RIOT operating system for the Internet of Things (IoT): http://www.riot-os.org/

Table of Contents

1. Getting started
2. Rationale for CCN-lite
3. Extensions
4. CCN-lite supported platforms
5. Command line tools
6. Useful links
7. Tentative roadmap
8. Changelog
9. Credits

1. Getting started

To start right now with CCN-lite visit the tutorial. It covers installation on Unix and basic functionality of CCN-lite.

For more information about CCN-lite supported platforms and how to build, see CCN-lite supported platforms. The source code of CCN-lite is available on GitHub, either the master branch or dev-master. If you found a bug or want to report a problem with CCN-lite, feel free to create an issue on GitHub - we appreciate it!

2. Rationale for CCN-lite

The original motivation in 2011 for creating CCN-lite was that PARC's CCNx router software had grown huge. CCN-lite provides a lean alternative for educational purposes and as a stepping stone. It's for those who want a simple piece of software for experimentation or own development, but who do not need all features of the full thing.

This brings the interesting question of interoperability: What minimum functionality is necessary in order to participate in a CCNx network? With CCN-lite, we have made a first attempt at identifying that set, but we are aware that this set might be incomplete, or may change depending on how CCNx evolves. We consider this question of "sufficient CCNx functionality" to be of engineering and academic interest of its own and welcome contributions from everybody.

Hence, with CCN-lite, we did a race-to-the-bottom and strived for a kind of "Level-0" interoperability. Level-0, as we understood it, covers:

• ccnb encoding of messages (or any other encoding flavor, including the TLV variants)
• PIT and FIB, basic CCN data structures
• longest and exact prefix matching for basic CCN operations, including minsuffixcomp und maxsuffixcomp handling
• matching of publisher's public key to fight cache poisoning
• nonce and/or hop limit tracking to avoid loops as a minimal safeguard

As an interoperability goal we set for ourselves the threshold that the CCN-lite software must be able to route at the CCN level between fully fledged CCNx forwarders. Of course, this is a moving target, but we regularly use our tools to interface with the NDN testbed, for example.

We deliberately do not cover in our CCN-lite code:

• sophisticated data structures for performance optimizations
• exclusion filtering in interests
• all TCP connectivity and the old CCNx cmd line utilities that have TCP hardwired into them
• crypto functionality which is not our prime concern (yet)
• repository functionality, SYNC server, ...

A second reason to create CCN-lite was the software license (the original CCNx project picked GNU, but NDN also has chosen this path) where we prefer a Berkeley Software Distribution style of "do whatever you want" as we believe that this will help adopting CCN technology. Therefore, CCN-lite is released under the ISC license. We have learned that several companies have picked up CCN-lite for their internal experiments, so we think our license choice was right.

What you get with CCN-lite is:

• a tiny CCNx core (1000-2000 lines of C suffice)
• multiple platform support
• partially interoperable management protocol implementation
• a simple HTTP server to display the relay's internal configuration
• plus some interesting extensions of our own, see the next section.

3. Extensions

In several selected areas we have started our own contributions that are now part of CCN-lite:

• Named functions for letting clients express results instead of accessing only raw data. See also the use of Scala to host function execution and to interface to a NFN network.

• Experimental RPC functionality for letting neighbors mutually invoke functions, which could be the starting point both for network management functionality and for data marshalling (of interests and data objects) using the TLV encoding.

• Clean packet scheduler support at chunk level as well as packet or fragment level (symbol USE_SCHEDULER)

• Packet fragmentation and lost packet detection support for running the CCNx protocol natively over Ethernet (symbol USE_FRAG). This is somehow outdated and waits for protocol specs to emerge.

Other features that you can switch on and off at compile time are:

Featue	Description
USE_CCNxDIGEST	Enable digest component, requires crypto lib.
USE_CHEMFLOW	Experimental scheduler based on chemical networking, source not included.
USE_DEBUG	Basic data structure dumping.
USE_DEBUG_MALLOC	Compile with memory armoring.
USE_DUP_CHECK	Check for duplicate nonces.
USE_ECHO	Enable an echo prefix, returning the current time.
USE_LINKLAYER	Talk to Ethernet, W-LAN, 802.15.4 devices, raw frames.
USE_FRAG	Enable fragments, to run CCNx over Ethernet.
USE_HMAC256	Enables hash-based authentification codes.
USE_HTTP_STATUS	Provide status info for web browsers.
USE_IPV4	Enable IP support.
USE_LOGGING	Enable log messages.
USE_KITE	Routing along the return path, not yet supported.
USE_MGMT	React to CCNx management protocol messages.
USE_NACK	NACK support for NFN.
USE_NFN	Enable named function networking.
USE_NFN_NSTRANS	Namespace translation for NFN.
USE_NFN_MONITOR	Message logging for nfn-scala.
USE_SCHEDULER	Rate control at CCNx msg and fragment level.
USE_SIGNATURES	Authenticate management messages.
USE_STATS	Enable statistics.
USE_SUITE_*	Enable a specific protocol: CCNB, NDN2013, CCNx2014, IOT2014, LOCALRPC or CISCO2015.
USE_UNIXSOCKET	Add UNIX IPC to the set of interfaces.

The approach for these extensions is that one can tailor a CCN forwarder to including only those features really necessary. We have strived to make these choices as orthogonal as possible and invite you to attempt the same for your additions.

4. CCN-lite supported platforms and how to compile

CCN-lite currently supports five platforms. To find out how to install and use CCN-lite on each individual platform, refer to the platform-specific readme files:

• Unix
• Linux kernel
• Android
• Arduino and RFduino
• OMNeT++

Additionally, CCN-lite has a pre-built Dockerfile to enable the usage of Docker with CCN-lite. See the Docker-specific readme file for more information.

Named function support

If you want named function support (NFN), define an environment variable at the shell level before invoking make:

export USE_NFN=1
make clean all

If you want both NFN and NACK support, define an additional environment variable before invoking make:

export USE_NFN=1
export USE_NACK=1
make clean all

CCN-lite-minimalrelay

As an exercise in writing the least C code possible in order to get a working NDN forwarder, CCN-lite includes ccn-lite-minimalrelay.c. It has all extra features disabled and only provides UDP connectivity. But hey, it works! And it really is lean, looking at the lines of C code:

 435 ccn-lite-minimalrelay.c
1010 ccnl-core.c
 701 ccnl-core-fwd.c    // only partially needed
1090 ccnl-core-util.c
 647 ccnl-pkt-ndntlv.c  // only partially needed

 316 ccnl-core.h
 197 ccnl-defs.h
 104 ccnl-pkt-ndntlv.h

5. Command line tools

The main command line tools and their corresponding source file that are shipped with CCN-lite are the following:

Tool	Description
ccn-lite-relay.c	CCN-lite forwarder: user space. This file is compiled into three executables, depending on compile time environment flags: ccn-lite-relay ccn-nfn-relay ccn-nfn-relay-nack
ccn-lite-lnxkernel.c	CCN-lite forwarder: Linux kernel module
util/ccn-lite-ctrl.c	Command line program running the CCNx management protocol (over Unix sockets). Used for configuring a running relay either running in user space or as a kernel module.
util/ccn-lite-ccnb2xml.c	Simple CCNB packet parser
util/ccn-lite-cryptoserver.c	Used by the kernel module to carry out compute intensive crypto operations in user instead of kernel space.
util/ccn-lite-fetch.c	Fetches both a single chunk content or a series of chunks for larger named data. Only the content is returned without any protocol bytes.
util/ccn-lite-mkC.c	Simple content composer, to stdout, without crypto.
util/ccn-lite-mkF.c	Simple tool to split a large file into a fragment series.
util/ccn-lite-mkI.c	Simple interest composer, to stdout.
util/ccn-lite-peek.c	Simple interest injector waiting for a content chunk, can also be used to request named-function results.
util/ccn-lite-pktdump.c	Powerful packet dumper for all known packet formats. Output is in hexdump style, XML or content only.
util/ccn-lite-produce.c	Creates a series of chunks for data that does not fit into a single PDU.
util/ccn-lite-rpc.c	Send an RPC request and return the reply.
util/ccn-lite-simplenfn.c	Simplified interface to request named-function results.
util/ccn-lite-valid.c	Demo application for validating a packet's signature.

6. Links:

• Source code repository: https://github.com/cn-uofbasel/ccn-lite
• CCN-lite web site: http://www.ccn-lite.net/
• CCNx site: http://www.ccnx.org/
• NDN site: http://named-data.net/
• NFN site: http://named-function.net/

7. Tentative roadmap

Work has started for the next release 0.4 (Dec 2015?), where the focus should be on the following areas:

• Manifests
• Security (key management, signed computations and trust schematas)
• Data access control
• Better selector support for NDN
• RIOT re-integration

8. Changelog

Release 0.3.0 (Jul 2015)

• Demonstrated interoperability with now-stabilized CCNx1.0, which can run side-by-side with NDN in a single CCN-lite relay
• OMNeT++ integration is back, as it has been requested many times
• New platforms and transport:
  • Arduino and RFduino
  • Android and Bluetooth Low Energy
• New functionality: "begin-end" fragmentation for CCNx1.0 and NDN
• Improved build quality for Ubuntu and OSX
• Improved READMEs all over the release, easy tutorials
• Named Function Networking (NFN) over NDN now has Python bindings to make the publishing of named functions easier.

9. Credits

Release 0.3.0 (Jul 2015)

Code contributions:

Lukas Beck
Christopher Scherb
Manolis Sifalakis
Christian F. Tschudin

Feedback and other contributions:

Fateh Al-Mufti
Frederik Brix
Patrick Buder
Daniel Federau
Ilir Fetai
Nenad Kokeza
David Kordsmeier
Dima Mansour
Marc Mosko
Mihai Daniel Rapcea
Fabian Rauschenbach
Yanick Salzmann
Maarten Schenk
Urs Schnurrenberger
Marco Suter
Marc-Andrea Tarnutzer
Marco Dieter Vogt
Akan Yilmaz

Release 0.2.0 (Dec 2014)

Code contributions:

Basil Kohler
Christian Mehlis
Massimo Monti
Christopher Scherb
Manolis Sifalakis
Christian F. Tschudin

Code and documentation feedback:

Samuel Bader
Christoph Betschart
Nore Derguti
Ralph Droms
Wilson A. Eghonghon
Daniel Federau
Ralph Gasser
Cedric Geissmann
Rasa Liebfried
Dario Maggi
Frank Müller
Marko Obradovic
Michaja Pressmar
Mihai D. Rapcea
Urs Schnurrenberger
Thomas Simonsen
Alexander Stiemer
Ziba Tavassoli
Simon Wang
Mario Weber

Release 0.1.0 (Jul 2013)

Code contributions:

Stefan Braun
Pierre Imai
Basil Kohler
Thomas Meyer
Massimo Monti
Christopher Scherb
Manolis Sifalakis
Christian F. Tschudin