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 <[email protected] >> <mailto:[email protected]>> 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 >>> _______________________________________________ >>> Link mailing list >>> [email protected] <mailto:[email protected]> >>> http://mailman.anu.edu.au/mailman/listinfo/link >> > >_______________________________________________ >Link mailing list >[email protected] >http://mailman.anu.edu.au/mailman/listinfo/link -- 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:[email protected] 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 _______________________________________________ Link mailing list [email protected] http://mailman.anu.edu.au/mailman/listinfo/link
