Link layer:context datagram transferred by transportation analogy: different link protocols over trip from Princeton to Lausanne different links: limo:Princeton to JFK e.g.,WiFi on first link,Ethernet ·plane:JFK to Geneva on next link train:Geneva to Lausanne each link protocol provides ■tourist=datagram different services transport segment= e.g.,may or may not provide communication link reliable data transfer over link "transportation mode link-layer protocol travel agent routing algorithm LinkLayer:6-5Link layer: context ▪ datagram transferred by different link protocols over different links: • e.g., WiFi on first link, Ethernet on next link ▪ each link protocol provides different services • e.g., may or may not provide reliable data transfer over link transportation analogy: ▪ trip from Princeton to Lausanne • limo: Princeton to JFK • plane: JFK to Geneva • train: Geneva to Lausanne ▪ tourist = datagram ▪ transport segment = communication link ▪ transportation mode = link-layer protocol ▪ travel agent = routing algorithm Link Layer: 6-5