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i wonder if i can learn ethernet buffer size.Almost all of us visit youtube or other video sites and if our connection limit is lower (i live in Turkey and fast internet is really )so when i want to watch a video i start video and then pause.But what is that's limit ? I know that that video is streaming to my ethernet card's cache therefore i use ifconfig command and it could not help me after that i installed System Profiler and Benchmarker GUI program and i could not understand that's network result.Finally can i learn cache size,if so how can it be ?

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Cache on ethernet cards is usually around a handful of kB, but you won't be aware of it as normal user as your video is streaming to your harddisk, so in this case it's about how much free space you have on that.

$ lspci | grep -i eth | cut -d' ' -f1 | while read d; do lspci -vvvs $d; echo; done
00:19.0 Ethernet controller: Intel Corporation 82567V-2 Gigabit Network Connection
        Subsystem: Intel Corporation Device 0028
        Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
        Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- SERR- Region 0: Memory at d0700000 (32-bit, non-prefetchable) [size=128K]
        Region 1: Memory at d0724000 (32-bit, non-prefetchable) [size=4K]
        Region 2: I/O ports at f0c0 [size=32]
        Capabilities: 
        Kernel driver in use: e1000e
        Kernel modules: e1000e

I'm guessing here as most vendors do not easily share their datasheets. Don't get your hopes up, as size=128K probably being the firmware of the card and size=4K being the its on board cache.

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That's okay,but cache is faster than harddisk so it's size is important to not lose data.In addition to this i still want to learn cache size . –  myildirim May 3 '12 at 20:27
    
A NIC (network interface card) really needs to hold a single frame, which is 1500 bytes for consumer grade networks. So low end NIC's, which most of us have on their home PC, will have maybe 10kB max. If you really want to know these details, you'll have to look into the datasheet of your specific controller. –  jippie May 3 '12 at 20:45
    
I am so thankful to help me,well how can i learn NIC strategies.Because of it has not really big memory,it must have really good strategy to control all requests and incomimng data(or result) –  myildirim May 3 '12 at 20:57
    
dmesg | grep -i eth and try to figure out which module is loaded for your network card. In many cases this will be e1000 or e1000e. Then study the kernel documentation / sources for it. –  jippie May 3 '12 at 21:07
    
Mind you, Linux has been around for a while and not just for home use, also for enterprise and supercomputer use. If one part of the kernel is heavily optimized, it will be networking. BTW: packet loss is not uncommon in Ethernets, that is why we have higher level protocols like TCP/IP which will work around that. –  jippie May 3 '12 at 21:08

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