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Vodafone spustil 1 Gb/s internet


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Ethernet ramec (bez VLAN tagu) vcetne preambule a mezery ma celkem 1538 bytes (https://thenetworkseal.wordpress.com/general-network/data-link-layer/packet-structure-of-frame/). TCP payload (pokud TCP paket nema options) ma max. 1460 bytes, s options napr. o dalsich 8 bytes mene.

Rezie je pak 1-(1460/1538), tj. cca 5,1 %, maximalni dosazitelna rychlost v TCP speedtestech je pak 1000*(1-5,1%)=949 Mbps; pri 8 bytes TCP options by to bylo 944 Mbps.

Pro uplnost dodam, ze vypocty v predchazejicim prispevku plati pro IPv4. IPv6 ma vetsi hlavicku a uzitecny TCP payload bez options je 1440 bytes, maximalni dosazitelna rychlost TCP prenosu na 1 Gbps rozhrani je cca. 936 Mbps, s 8 byte options 931 Mbps.

A jeste pridam IPv4 TCP pres DS-Lite (IPv4 uvnitr IPv6): uzitecny payload je max. (1500-40-20-20)=1420 bez TCP options (->~923 Mbps), s 8 bytes options 1412 (->~918 Mbps).

Edited by zajdee
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