| DCCP protocol |
| ============ |
| |
| |
| Contents |
| ======== |
| |
| - 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. The specification mandates use of |
| service codes (RFC 4340, sec. 8.1.2); if this socket option is not set, |
| the socket will fall back to 0 (which means that no meaningful service code |
| is present). Connecting sockets set at most one service option; for |
| listening sockets, multiple service codes can be specified. |
| |
| 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. |