[LINK] FTTP soon normal

Tue Apr 29 13:45:07 AEST 2014

G'day Rog,

Actually I meant CSMA/CA ... which whilst it creates more efficient data transfers than the /CD variant and is more amenable/efficient/effective for Wifi use, still presents a performance hit for the network (from memory the the /CD variant was a spec that related to 10Base T and earlier Ethernet). 

And yeah, I should take more care with my acronyms ... but what the hell, I've been 6 years retired, and therefore out of the technical side of things ... and am enjoying not having to keep up-to-date literature, dictionaries and encyclopaedias of technical terms and acronyms, technology and the like just to keep on top of things. Nowadays I just concentrate on what works for me.

That said, thanks for the correction.

								Regards,

On 29 Apr 2014, at 12:41 pm, Roger Clarke <Roger.Clarke at xamax.com.au> wrote:

> At 23:32 +1000 28/4/14, Hamish Moffatt wrote:
>> There's no CDMA on a switched network...
> 
> C'mon Hamish.  You know he meant CSMA/CD.    (:-)}
> 
> Lots of us have had that slip of the tongue.
> 
> ____________________________________________
> 
> 
>> On 28/04/14 19:29, Frank O'Connor wrote:
>>> Sorry,
>>> 
>>> I meant CDMA ... collision detection. Error correction, as Hamish said
>>> ... is a level 3 Feature.
>>> 
>>> Again ... just my 2 cents worth ...
>>> ---
>>> On 28 Apr 2014, at 6:39 pm, Hamish Moffatt <hamish at cloud.net.au
>>> <mailto:hamish at cloud.net.au>> wrote:
>>> 
>>>> On 28/04/14 18:22, Frank O'Connor wrote:
>>>>> Well, yeah ... but:
>>>>> 
>>>>> 1. ANY form of networking causes 'slow-downs' simply by its very
>>>>> nature, irrespective of what the data interface is capable of.
>>>>> 
>>>>> 1Gbs hard wired Ethernet? Sure ... if you only have 2 devices
>>>>> connected, are running a single networked application ... and even
>>>>> then all you'll get is 300-500Mbs max due to error correction (huge
>>>>> overhead in Ethernet which increases logarithmically as nodes
>>>>> activate), data scheduling problems and lots of negotiations
>>>>> (e.g.ACK/NACKS, non-data packets ... ICMP for example, and other
>>>>> high level protocols inherent in TCP/IP) between the devices.
>>>>> 
>>>>> It doesn't much matter what network architecture you use ... the
>>>>> overheads persist (as they were designed to do by the network
>>>>> protocol inventors) and slow traffic way below the optimum. With
>>>>> networks its important that little numbers like error detection and
>>>>> recovery work ... especially in non-tolerant applications and devices.
>>>> 
>>>> I think you're getting your layers pretty mixed up here.
>>>> 1000base-T/802.3ab (Gigabit Ethernet) has no error correction (it has
>>>> error detection), and given that's it's almost always switched won't
>>>> have problems scaling as you add more devices and applications unless
>>>> your switch is completely hopeless. Of course it has overheads that mean
>>>> you won't actually get 1000Mbit/sec of user data (HTTP or whatever) but
>>>> the performance is pretty predictable and quite close to the theoretical
>>>> with modern computers.
>>>> 
>>>> TCP/IP adds overheads to get its work done but there's no interference
>>>> between nodes and applications there either.
>>>> 
>>>>> 
>>>>> 2. Bottom line: WiFi is no more or less efficient than hard wired
>>>>> network protocols. Indeed, low level WiFi protocols are typically
>>>>> Ethernet protocols ... and hence subject to the SAME efficiency and
>>>>> effectiveness limitations as the wired protocols they emulate. The
>>>>> difference is that with WiFi you can overlay channels more easily
>>>>> than you can on an Ethernet connection ... which doesn't handle
>>>>> packet crowding very well at all.
>>>> 
>>>> WiFi of course is working on a shared channel, while switched ethernet
>>>> effectively has a separate channel for each connection.
>>>> 
>>>> 
>>>> 
>>>> Hamish
>>>> _______________________________________________
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>>>> http://mailman.anu.edu.au/mailman/listinfo/link
>>> 
>> 
>> _______________________________________________
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> 
> -- 
> Roger Clarke                                 http://www.rogerclarke.com/
> 
> Xamax Consultancy Pty Ltd      78 Sidaway St, Chapman ACT 2611 AUSTRALIA
> Tel: +61 2 6288 6916                        http://about.me/roger.clarke
> mailto:Roger.Clarke at xamax.com.au                http://www.xamax.com.au/
> 
> Visiting Professor in the Faculty of Law            University of N.S.W.
> Visiting Professor in Computer Science    Australian National University
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