[LINK] FTTP soon normal

[Hamish Moffatt]

There's no CDMA on a switched network...


Hamish

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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>