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