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Tom Potts wrote: > > I'd never call 1500 bytes a big packet and The telecomms folk think anything over 48 bytes of payload is big ;) But 1500 is bigger than most of the packets floating around the Internet (not least because so many of the links use Ethernet), I'd be surprised if your Internet connection used packets as large as that - if they are just a little bit smaller that would be unsurprising. http://www.caida.org/research/traffic-analysis/pkt_size_distribution/graphs.xml Gigabit ethernet can use larger packets, indeed has to use larger packets to get the kind of data transfer rates people expect from it, but you usually have to enable it somewhere still. > I've never really understood why > VOIP is so bitty and horrible when I can get several hundred kbps HTML on the > same link - I'm fairly convinced that badly setup VOIP > (point->exchange->point) is the real problem here - and I bet Skype squeeze > free calls even further. Or perhaps VOIP and basic packet switching needs > reviewing. Even on the end of the long piece of string BT get me here I can > get many megabytes without a single error and thats a lot of wasted packet > headers. I don't think theres anything in TCP/IP that says you have to have > inefficient protocols. Much of the bad VOIP I've heard has been due to bad software (or badly configured software) at the end points, rather than networking issues. Bad sound equipment also plays a role - the number of people trying to use speakers rather than headphones and wondering about the feedback?!? But there is a huge difference between connections that provide good bandwidth, and connections that provide good characteristics for VOIP. A classic example is satellite (geostationary), with a little tweaking of TCP/IP parameters you can stuff a lot of data down a satellite connection. But the high latency means nobody sends telephone data via geostationary satellites (well not if they can help it). For VOIP you want low error rates, low latency, you don't need much bandwidth (and probably wise to assume you won't get it). A lot of consumer network kit is pretty appalling for the network characteristics you need for good VOIP. For example my router (which can do some QoS if you enable it) seems by default to operate a FIFO queue, which using ADSL saturates easily on the uplink, so I doubt would sound good if I sent a file whilst using VOIP (the Flickr upload tool in F-Spot completely stuffs my link unless I run a traffic shaper on my PC, to the point it can't get DNS responses through at all -- although I suspect a specific problem here). -- The Mailing List for the Devon & Cornwall LUG http://mailman.dclug.org.uk/listinfo/list FAQ: http://www.dcglug.org.uk/linux_adm/list-faq.html