The transport layer breaks a message down into

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Unformatted text preview: way, packets pass through routers. A router examines a packet’s des=na=on (in the header) and, taking into account, e.g., traffic volumes, forwards the packet. The packet is forwarded to a router that is closer to the des=na=on and on the way to which there seems to be a lightly ­loaded route. Routers, therefore, are crucial in avoiding conges=on due to compe==on between very, very many sources for a route to one target (or just a few). The SoKware Stack over the Fabric 16 application transport internet link physical Protocol Layers 17           The Internet can be understood as having four main protocol layers. The applica(on layer is the one that only deals with messages in the form that the applica=on sends and receives. The transport layer breaks a message down into packets and wraps it with control informa=on. The internet layer may break data further in order to fulfill its main task, i.e., to route packets forward to their des=na=on. The link layer oversees the working of the physical fabric and may request and send confirma=on of error ­free transmission. Example Protocols at Each Layer 18 application http transport tcp internet ip link mac physical 802.11b Packet Encapsula=on at each Layer 19 http data udp header ip header frame header frame udp data udp ip ip data data frame footer mac Protocol Instances (1) 20           Each protocol layer can be instan=ated by many dis=nct, specific protocols. The best known applica=on layer prot...
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