Date: Tue, 9 May 2000 15:01:43 +0100 From: "Gallagher, Mick" <mick.gallagher@roke.co.uk> To: "'t.pagtzis@cs.ucl.ac.uk'" <t.pagtzis@cs.ucl.ac.uk> Cc: freebsd-net@freebsd.org Subject: RE: Question on Tx queueing internals Message-ID: <D76D503DE976D1119C7E00A0C944D87501CA7F86@RSYS002A>
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As I understand, WaveLAN is based on the IEEE 802.11 standard which I think operates half duplex. (Full duplex RF kit is much more expensive to build, so the IEEE went for a half duplex standard. At least that's my reading.) HTH, Mick --- mickg@iname.com -----Original Message----- From: Theo PAGTZIS [mailto:T.Pagtzis@cs.ucl.ac.uk] Sent: 09 May 2000 12:11 To: Tan Koan-Sin Cc: freebsd-net@freebsd.org Subject: Re: Question on Tx queueing internals Tan Koan-Sin wrote: > On Tue, May 09, 2000 at 10:50:14AM +0100, Theo PAGTZIS wrote: > > I am told that on the network card there is a Tx and Rx buffer.... > > Is the output queue of an interface driver the same thing as a transmit > > buffer on the actual network card or are they two different things...ie > > when the ip_output passes the packet to the if_output function of the > > Ether interface, the if_output will add the Ether header and then put it > > on the output queue (if_snd). Is this output queue (the driver's output > > queue ) the same as what one call the Tx/Rx buffer on the network card > > or are is it a different one? > > They are different. The if_snd is a mbuf linked list in main memory. > The Tx/Rx buffers are on the card. Take the Intel 82559 (fxp) on > FreeBSD as a example, the Tx and Rx buffer on the network card are > separate 3K FIFOs. > > > Also is the Tx buffer a different piece of memory than the Rx buffer on > > the Ethernet card. I am asking that trying to understand whethe Tx and > > Rx share a single buffer on the card so that Tx buffer could starv Rx > > buffering... > > It depends the card you use. You must find the data sheet of the > chips used on your card. > > -- > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-net" in the body of the message Brill ! thanks Tan ! Would anyone have any idea what is the Tx/Rx buffs on the WavelanII 11Mbps cards? Also it has been my understanding for some time that wireless network cards are by nature half duplex...however some people argue about full duplex for which I am not at all convinced....could anyone enlighten on that? Theo To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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