| Ian McDonald | 98069ff | 2005-11-10 13:04:33 -0800 | [diff] [blame] | 1 | DCCP protocol |
| 2 | ============ |
| 3 | |
| 4 | Last updated: 10 November 2005 |
| 5 | |
| 6 | Contents |
| 7 | ======== |
| 8 | |
| 9 | - Introduction |
| 10 | - Missing features |
| 11 | - Socket options |
| 12 | - Notes |
| 13 | |
| 14 | Introduction |
| 15 | ============ |
| 16 | |
| 17 | Datagram Congestion Control Protocol (DCCP) is an unreliable, connection |
| 18 | based protocol designed to solve issues present in UDP and TCP particularly |
| 19 | for real time and multimedia traffic. |
| 20 | |
| 21 | It has a base protocol and pluggable congestion control IDs (CCIDs). |
| 22 | |
| 23 | It is at draft RFC status and the homepage for DCCP as a protocol is at: |
| 24 | http://www.icir.org/kohler/dcp/ |
| 25 | |
| 26 | Missing features |
| 27 | ================ |
| 28 | |
| 29 | The DCCP implementation does not currently have all the features that are in |
| 30 | the draft RFC. |
| 31 | |
| 32 | In particular the following are missing: |
| 33 | - CCID2 support |
| 34 | - feature negotiation |
| 35 | |
| 36 | When testing against other implementations it appears that elapsed time |
| 37 | options are not coded compliant to the specification. |
| 38 | |
| 39 | Socket options |
| 40 | ============== |
| 41 | |
| 42 | DCCP_SOCKOPT_PACKET_SIZE is used for CCID3 to set default packet size for |
| 43 | calculations. |
| 44 | |
| 45 | DCCP_SOCKOPT_SERVICE sets the service. This is compulsory as per the |
| 46 | specification. If you don't set it you will get EPROTO. |
| 47 | |
| 48 | Notes |
| 49 | ===== |
| 50 | |
| 51 | SELinux does not yet have support for DCCP. You will need to turn it off or |
| 52 | else you will get EACCES. |
| 53 | |
| 54 | DCCP does not travel through NAT successfully at present. This is because |
| 55 | the checksum covers the psuedo-header as per TCP and UDP. It should be |
| 56 | relatively trivial to add Linux NAT support for DCCP. |