Table of Contents Contents Datagram Congestion Control Protocol ethereal/wireshark support GStreamer support TODO & testing 1 Datagram Congestion Control Protocol 1.1 DCCP stack for Linux 1.1.1 Experimental Work 1.2 Choosing and initialising your CCID 1.3 Applications 1.3.1 tcpdump support 1.3.2 ethereal/wireshark support 1.3.3 iperf support 1.3.4 DCCP Plugin for GStreamer 1.3.5 D-ITG 1.3.6 netcat support 1.3.7 Python support 1.3.8 Ruby support 1.3.9 PHP 1.3.10 C Application Programming Interface to DCCP 1.3.9.1 Some Important Details 1.3.11 Other applications 1.4 TIMEWAIT sockets 1.5 Mailing List Archives 1.6 TODO & testing 1.7 FAQ 1.8 IRC .nz/DCCP but this is now the master site for the DCCP implementation for Linux.DCCP is a transport level protocol (like TCP and UDP) which aims to solve many different congestion issues.This is useful for applications that don't need the data reliability/re-transmission of TCP, but want a session and want congestion control unlike UDP.

DCCP is currently at proposed standard RFC status (4340-4342).The main reference page on the web for DCCP.There is also a writeup at LWN.DCCP stack for Linux There is a GPL version of DCCP in the Linux Kernel.This is being maintained by Arnaldo C. Melo at present.The history of this is that it draws from the code of Patrick McManus, Lulea and the WAND group that Ian McDonald is part of.The core DCCP stack was written by Arnaldo C. Melo using the Linux TCP implementation as a model, with DCCP being used as a way to identify code in the TCP implementation that could be made generic and shared with other INET transport level implementations.This resulted in the generalisation of code related to the minisockets representing both TCP_SYN_RECV/DCCP_RESPOND and TCP_TIME_WAIT/DCCP_TIME_WAIT status, code related to established/timewait/listen sockets (inet_lookup, inet_lookup_established, etc), the interface to get sock information (tcp_diag), and many other functions and data structures, with more expected to be generalised and eventually used by SCTP and any other INET transport protocols that may be introduced in the future.

The CCID 3 code was drawn from the WAND group, that in turn got it initially from the Lulea FreeBSD codebase and made it work in the core DCCP stack written by Patrick McManus.Ian McDonald got it relicensed from BSD license to GPL by getting written permission via email from the original Lulea authors of the code.It was modified by Arnaldo C. Melo to fit Linux standards wrt list handling and several other aspects.Since then Gerrit Renker and Ian McDonald have spent a lot of time improving CCID 3.The CCID 4 code was drawn from the Embedded Laboratory, by Leandro Melo de Sales, Ivo Calado and Erivaldo Xavier, that in turn got it initially from the CCID 3 and made it work in the core DCCP stack, adding the differences for CCID4 available in the RFC 5622.The CCID 4 can be considered to be a working in progress implementation, while now Gerrit Renker has been also provide efforts on the implementation of CCID 4.The  CCID 5/249 code was drawn from the Embedded Laboratory, by Ivo Calado and Leandro Melo de Sales.

This CCID implements the Cubic congestion control in a attempt to achieve similar performance of TCP Cubic in long fat network.The code is based on a mix of TCP-Cubic and CCID-2 implementations.The CCID 5/249 can be considered to be a working in progress implementation.The CCID modular infrastructure was written to fit the CCID 3 existing interface, but will probably be changed in the near future in the effort to have a generic CA (Congestion Avoidance) infrastructure shared with TCP | CCID (and others, who knows), continuing work on the existing TCP | CCID CA infrastructure put in place by Stephen Hemminger.bitcoin bar graphTo have a look at the theoretical performance of CCID 3 see xcalc spreadsheet - the codebase currently assumes s=256, unless you override with an option.bitcoin reuters codeThere is a mailing list for DCCP work which is dccp at vger dot kernel dot org.ethereum trillion

Discussion also occurs on the main Linux networking mailing list - netdev at vger dot kernel dot org.Experimental Work Andrea Bittau is experimenting with wiring the TCP plugabble congestion control to DCCP, graphs can be seen here.Gerrit Renker is fixing up the CCID3 implementation and his notes can be found here At present Gerrit's tree has a substantial number of improvements and is where most work should be done.bitcoin zukunft 2015Details of using this can be found at DCCP_Testing#Experimental_DCCP_source_tree Choosing and initialising your CCID To use CCID2 do something like: To use CCID3 do something like: The seq_window increases the sequence window validation from the default of 100 which can cause problems.bitcoin buena inversionsend_ackvec sets the appropriate setting for the CCID.litecoin wallet android app

This should be fixed so it defaults correctly really.Applications tcpdump support tcpdump now has DCCP support in the tree.There is tcpdump support available at here for older versions.This applies to many versions and at least the weekly build from CVS of tcpdump dated 22nd August 2005.This is in the process of being tidied up for submission to tcpdump maintainers.Remember to run tcpdump(8) with a -s0 parameter to capture all data (or some other value) as the default size gets the base DCCP header, but not the options, in many cases.ethereum javascript walletAlso, if you want to capture only DCCP traffic, you can use the primitive ip[9] == 33 in the filter expression.bitcoin build osxSee here Latest version of Wireshark seems to work just fine with DCCP.ethereal tool linux

iperf support There is a patch for DCCP available on the iperf page.GStreamer is a library for constructing graphs of media-handling components.The applications it supports range from simple Ogg/Vorbis playback, audio/video streaming to complex audio (mixing) and video (non-linear editing) processing.Applications can take advantage of advances in codec and filter technology transparently.Developers can add new codecs and filters by writing a simple plugin with a clean, generic interface.For more about gstreamer go to GStreamer.net Documentation about DCCP on GStreamer Article: DCCP Plugin for GStreamer @ Linux Magazine D-ITG D-ITG supports DCCP.It is available on the D-ITG page.netcat support A patch for netcat is available here or here.The version of netcat that this is used against is 0.71 and was used on 8th September for, what we believe to be, the first public transmission of DCCP over the Internet.The above patch doesn't handle service codes and Guillaume Teissier has modified the patch to do this.

plete.patch Python support Python's low level socket library is transparent enough to support DCCP without even knowing it!Here is an adaptation of the http://wand.net.nz/~iam4/dccp/dccp-cs-0.01.tar.bz2 example code: Ruby support Ruby's low level socket library is also able to support DCCP.Here is the corresponding Ruby code to the previous Python script : PHP PHP's low level socket library is also able to support DCCP.Here is the corresponding Python and Ruby code of the previous scripts: Server: Client: C Application Programming Interface to DCCP DCCP's implementation on Linux is based on the TCP implementation.The API provided is through the linux //socket// library and so, much of the code looks similar to initialization/send/receive code of a regular TCP socket.The server initializes a socket, binds it to a port, and waits to accept clients to connect.The client initializes a socket and connects to the server.Note that although the connection setup of DCCP is like TCP, transmission of data is unreliable like UDP.

Here's how to get started: There are some general #includes and #defines needed by both client and server.These are: A DCCP server is much like a TCP server.The code for initializing, binding and accepting sockets is shown below.Note that the code for getting the local IP is not shown.Read Brief Socket Tutorial for linux socket basics.A DCCP client is also much like a TCP client in that in connects to a remote server.Once the connection has been set up (client successfully connected to server and server got a valid socket for the client), they can exchange data.Take a look at the send routine and notice the checking for errno.This is because DCCP's congestion control can refuse to send a packet.The receive routine is simple.How do you know which congestion control algorithm is being used?By default, it should be CCID2 which is a TCP-like congestion control but you can make sure by typing this in a console: This should give you something like: which means that both the outgoing and incoming congestion control mechanisms are CCID2 2.

What if I want to change the congestion control algorithm to CCID3?See Choosing and initialising your CCID above.Newer revisions of DCCP allow for setting of CCID through setsockop() functions of socket.Current implementation of DCCP on linux does NOT support packet fragmentation This means that if the packet you are sending over DCCP is greater than your Maximum Transmission Unit (MTU) it will not be sent!For example, if you call the send() routine with a size of 30000, chances are the packet will not be sent So you must take care to packetize your packets in sizes that are smaller than the MTU and still leave room for IP header (20 bytes) and DCCP header (32 bytes).packet size of about 1400 bytes is recommended BR Other applications More info on apps can be found at Gerrit's page or Ian's page.TIMEWAIT sockets TIMEWAIT sockets are finally implemented and we have initial support for iproute2, so just enable INET_DIAG and if enabled as a module make sure it is load prior to using the iproute2 utilities, like ss.

The latest iproute2 version now includes DCCP support directly.Then use it: The above listing was with the ttcp test.Mailing List Archives DCCP@IETF - A discussion of the DCCP protocol by the IETF - a discussion of the Linux implementation of DCCP - Another archive for the DCCP@vger mailing list There is a TODO list also which tracks the issues needing working on.There is a DCCP Testing page which also talks about how to test in DCCP Testing .FAQ Q: Why do I get an errno 13 (EACCES) or permission denied?A: You are running SELinux that does not have DCCP support.Disable SELinux or upgrade to a newer version of the kernel.Q: Why do I get an errno 90 (EMSGSIZE) or Message too long?A: The packet size used is bigger than the PMTU.The initial idea was to set the packet size option, similar to the example below, but this option became deprecated.Instead, you can get the current PMTU value, as shown below, and in your application you implement your sending mechanism filling the packets considering the mpu size: Then use the dccp_get_mtu_size function to retrieve the mtu size and implement your sending mechanism considering this value.