[DCCP]: Create Documentation/networking/dccp.txt

DCCP protocol

============

Last updated: 10 November 2005

Contents

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- Introduction

- Missing features

- Socket options

- Notes

Introduction

============

Datagram Congestion Control Protocol (DCCP) is an unreliable, connection

based protocol designed to solve issues present in UDP and TCP particularly

for real time and multimedia traffic.

It has a base protocol and pluggable congestion control IDs (CCIDs).

It is at draft RFC status and the homepage for DCCP as a protocol is at:

	http://www.icir.org/kohler/dcp/

Missing features

================

The DCCP implementation does not currently have all the features that are in

the draft RFC.

In particular the following are missing:

- CCID2 support

- feature negotiation

When testing against other implementations it appears that elapsed time

options are not coded compliant to the specification.

Socket options

==============

DCCP_SOCKOPT_PACKET_SIZE is used for CCID3 to set default packet size for

calculations.

DCCP_SOCKOPT_SERVICE sets the service. This is compulsory as per the

specification. If you don't set it you will get EPROTO.

Notes

=====

SELinux does not yet have support for DCCP. You will need to turn it off or

else you will get EACCES.

DCCP does not travel through NAT successfully at present. This is because

the checksum covers the psuedo-header as per TCP and UDP. It should be

relatively trivial to add Linux NAT support for DCCP.