From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gerrit Renker Date: Fri, 22 Sep 2006 17:51:31 +0000 Subject: Re: [PATCH 7/7] [DCCP]: Remove socket option Message-Id: <200609221851.31561@strip-the-willow> List-Id: References: <200609221433.48612.ian.mcdonald@jandi.co.nz> In-Reply-To: <200609221433.48612.ian.mcdonald@jandi.co.nz> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: dccp@vger.kernel.org | Hi, a bit of re-clarification: CCIDs 2 and 3 are *not* meant for apps that | NEVER vary their packet size. Rather, they are meant for apps that very | packet size *for application reasons* (such as codec output), but *not* in | response to congestion. CCIDs 2 and 3 expect to reduce application RATES in | response to congestion. My understanding is that there is very little wisdom currently regarding applications which vary their packet sizes due to application reasons; I have copied the quotes I am referring to below. The work-in-progress draft-ietf-dccp-tfrc-voip-05.txt is not very outspoken about what happens if the application changes its packet size. [RFC 4341, sec. 5.3]: "CCID 2 is optimized for applications that generally use a fixed packet size and vary their sending rate in packets per second in response to congestion." [RFC 4342, sec. 5.3]: "CCID 3 is intended for applications that use a fixed packet size, and that vary their sending rate in packets per second in response to congestion." If we allow applications to violate these premises then I don't know how to fix this in the code. | In summary, in the longer-term deriving 's' from observations would work, but | I don't see any objection to this socket option in the short term or the long | term. It allows the application to explicitly state its intent, which is | usually useful. I would like to suggest a compromise: retaining an experimental patch which allows this socket option and can be used for people interested in experimenting with these ideas, to gain new insights; and to leave the main kernel API as simple as it can possibly be made. --Gerrit