Date: Thu, 7 Dec 2006 20:51:54 +0800 From: "maillist ifiaas" <maillist.ifiaas@gmail.com> To: "Randall Stewart" <rrs@cisco.com> Cc: freebsd-net@freebsd.org Subject: Re: Urel, a TCP option for Unreliable Streaming. Need your help. Message-ID: <161d69110612070451o6945c7c0y9cf7a7e8b6b7225d@mail.gmail.com> In-Reply-To: <4578057B.9080002@cisco.com> References: <161d69110612060709n3bf99bd4y47d94b021b8f1d02@mail.gmail.com> <m21wncv66z.wl%gnn@neville-neil.com> <4577D858.4010300@freebsd.org> <2786D1DE-E8FA-490C-AFF7-E458E262AEF7@lurchi.franken.de> <161d69110612070242p612e2318ya8d285a15a54e9fc@mail.gmail.com> <4578057B.9080002@cisco.com>
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Thanks Randall. Am I right to say that, in SCTP, the loss information is reported to the sender, instead of the receiver? Btw, TCP Urel is a option. To use it, you have to add something like, int rc = setsockopt( inSettings->mSock, IPPROTO_TCP,TCP_URE, (char*) &val, len ); to enable Urel option in TCP. I still think that partial reliability should be performed in the application layer. Although transport layer knows more about the channel condition, but they can either be reported to the application (like we did on segment loss in TCP Urel), or be infered by application (e.g. estimating the current bitrate by looking at the buffersize). As QoS is only meaningful to application, allowing flexibilty of implementing QoS (such as partial relaibility) mechenism in application layer rather than transport layer, looks much natrual to me. -gavin On 12/7/06, Randall Stewart <rrs@cisco.com> wrote: > maillist ifiaas wrote: > > Michael, > > > > In PR-SCTP where retranmission is set off, does it allows the > > applications to know which part of data is lost in the stream? > > Thanks > > Yep.. you subscribe for a notification event and SCTP will > return you the data that was not sent. > > So not only does it let you know you can actually let > SCTP hold and return the data that did not get > acknowledged.. The API also has a context so you > can attach a user defined 32 bit value to the > data.. to say bind a pointer to an object to > the actual data... for lookup or other stuff :-) > > R > > > > > > -- > Randall Stewart > NSSTG - Cisco Systems Inc. > 803-345-0369 <or> 803-317-4952 (cell) >
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