FW: FW: [Malvern] Video Networking

Wed Mar 22 00:52:18 GMT 2006

A switch is better than a hub because it keeps track of which
interfaces are down which paths so that it can just send the packet
down the one route instead of all of them as a hub does with every
single packet.  It does this by looking at the actual traffic meaning
that for the first packets it will be no better than a hub, but
subsequent ones will.

With the wifi the actual wireless bit doesn't have multiple ports in
the same way that a switch does so there is not a similar
optimization.  At the wired end it could be anything, quite often just
a cheap hub.

On 3/21/06, Ian Pascoe <ianpascoe at btinternet.com> wrote:
> Hmm, interesting Andy.
>
> So what you are saying is that although the Base T type of network is the
> most popular, and to be honest in the dedicated press (see Geoff's comments
> from an earlier posting) the one they always steer home users towards, you
> don't actually get what's written on the box.
>
> Now lets see if I can get techy and actually understand it.
>
> When a router sends out a package into the LAN it won't because of the way
> the cables are daisy chained together, be able to send it directly to the
> required destination, therefore it has to broadcast it out to all and
> sundry.  I presume therefore that the router has to wait until it then
> receives notification from that the receipiant has got the package
> successfully before sending out the next.
>
> Following this from the router into the LAN, I know that a switch is better
> to have than a hub - is this because the switch knows what is connected to
> it and therefore does not need to further broadcast these packages, or is it
> just the way it handles the traffic?
>
> And taking a sidestep, does a wi-fi Tx act as a hub or a switch or something
> else entirely different?
>
> When is the techy evening on networks Phil - I need help!
>
> Ian
>
> -----Original Message-----
> From: malvern-bounces at mailman.lug.org.uk
> [mailto:malvern-bounces at mailman.lug.org.uk]On Behalf Of Andy Morris
> Sent: 19 March 2006 09:20
> To: Malvern at mailman.lug.org.uk
> Subject: Re: FW: [Malvern] Video Networking
>
>
> Ian,
>
> There is the added restriction of network efficiency and utilization.
>  From experience, a NetAdmin who found more than 30% continuous
> bandwidth use on a LAN would be panicking at the risk of data loss. It
> may say 100Mb, but actually getting it is another matter - because a LAN
> is "open-broadcast" not point-to-point. To do what you want to do would
> need a 1Gb LAN, at least, or change to a more efficient network type
> (such as ATM).
>
> Andy
>
>
> Ian Pascoe wrote:
> > Chris / Rik
> >
> > Thanks for your replies guys.
> >
> > OK, so looking at a 10 base T network running at 10mb, to get a fully
> > un-compressed data stream from a DVD file would totally engulf the network
> > at one extreme, or looking at the average data rate still only allow one
> > data stream to be viewed; ie average rate of 6-7 Mb would require a
> minimum
> > bandwidth of 12Mb to view 2 data streams.  Or am I missing something
> > fundemental in the way networks work?
> >
> > Taking it to the next level of a 100 base T network with a bandwidth of
> > 100Mb this would give the potential of about 15 data simultaneous streams
> > with a bit of bandwidth left over.  In this case if everything was sourced
> > from one server and one HD would you then run into problems with the
> amount
> > of data that could be read off the HD to provide these data streams.  I
> know
> > that for instance you could get around this by dumping the file into
> memory
> > and streaming it from there but keeping it simple with the assumption that
> > what comes off of the HD goes straight out into the network.
> >
> > Sorry about keeping on with this but it niggles!
> >
> > Ian
> >
> > -----Original Message-----
> > From: malvern-bounces at mailman.lug.org.uk
> > [mailto:malvern-bounces at mailman.lug.org.uk]On Behalf Of Chris Eilbeck
> > Sent: 17 March 2006 23:46
> > To: malvern at mailman.lug.org.uk
> > Subject: Re: [Malvern] Video Networking
> >
> >
> > On Fri, Mar 17, 2006 at 09:33:37PM -0000, Ian Pascoe wrote:
> >> Evening all
> >>
> >> Following on from the conversations at Geoff's on Wednesday - apple cake
> > and
> >> quiche very much up to standard thanks Geoff.
> >>
> >> A question for those of you involved with networks.
> >>
> >> If you have a LAN with a server and a number of PCs off of it, what is
> the
> >> limitation to how many people could view the same video source if stored
> > on
> >> the servers HD?  Would this be limited by the server's hardware, network
> >> bandwidth or something completely different.  The source would be fall
> > blown
> >> DVD material.
> >
> > You'd have trouble doing this over most cheap networking technologies.
> > You'd definitely have to have a switch rather than a hub.
> >
> >> I presume that within any network the Tx and Rx have a small buffer on
> the
> >> network cards that once filled is downloaded into the PC?
> >
> > Yep.
> >
> >> Does anyone know what the transfer rate is for data coming off of a DVD
> > data
> >> file?  ie CD Audio is something like 128k/bps.
> >
> > CD audio is 1.5mbps.  DVD video can be upto 10mbps but is usually around
> > 6-7mbps.
> >
> >> Why am I asking - for no other reason than would it work at home - ie you
> >> load your DVD onto a HD and you can take your laptop / PC in which ever
> > room
> >> to watch your favorite film whilst someelse is doing the same in another
> > and
> >> so on.
> >
> > That'd be cool.  Have a look at http://www.videolan.org/
> >
> > Chris
> > --
> > Chris Eilbeck
> > MARS Flight Crew                              http://www.mars.org.uk/
> > UKRA #1108 Level 2                                                UYB
> > Tripoli UK Member #9527                                          LSMR
> >
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