FW: FW: [Malvern] Video Networking

Tue Mar 21 22:38:41 GMT 2006

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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