From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eddie Kohler Date: Sat, 06 Oct 2007 21:55:06 +0000 Subject: Re: DCCP support in VLC Message-Id: <4708043A.3010005@cs.ucla.edu> List-Id: References: <200709271930.03854.rdenis@simphalempin.com> In-Reply-To: <200709271930.03854.rdenis@simphalempin.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: dccp@vger.kernel.org A quick note on half-close. The DCCP state machine has no half-closed state, but the Data Dropped option's Drop Code 1, "Application Not Listening", can be used like a TCP shutdown-for-receive. Eddie Gorry Fairhurst wrote: > Gerrit Renker wrote: >> | > When the Reset closing the connection arrives, the same shutdown >> mask is >> | > set as in TCP. What I thus think you could do as a >> | > test-for-end-of-connection is to test whether the socket >> descriptor is >> | > still read/writeable. >> | | If it works like TCP, shutdown-for-recv will make the socket >> always readable, | and will not affect writeability at all, since the >> sending half may still be | open. As such, I don't think it will >> solve the problem. >> DCCP has no half-close (RFC 4340, 4.6), so closing the socket shuts >> down both the >> read and the write end (i.e. SHUT_RDWR is set by the kernel) - you >> could test for this. >> >> | Currently, I am assuming that length = 0 means end-of-connection, >> because I | only use RTP/RTCP, so zero bytes is not a valid packet >> length. But that's a | little bit ugly. >> It would be better to use a different solution. > > > I agree. > >> There has also been discussion to use >> 0-sized packets for keep-alive or congestion messages > > (I hope that this remains talk only). >> > It's my understanding that the use of zero-length DATA packets as > transport-layer > keep alives (to probe for congestion status) was removed from the Faster > Restart proposal at the last IETF DCCP WG meeting. > This use was omitted from the latest revision of the FR draft. > > However, DCCP still does allow the application to send zero-sized DATA > from the API, just as UDP currently permits. (You may never wish to use > this if you have an application layered over RTP.) > > Gorry > - > To unsubscribe from this list: send the line "unsubscribe dccp" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html