Link layer:context ▣ Datagram transferred by transportation analogy different link protocols trip from Princeton to over different links: Lausanne o limo:Princeton to JFK o e.g.,Ethernet on first link, frame relay on o plane:JFK to Geneva intermediate links,802.11 o train:Geneva to Lausanne on last link tourist datagram ▣Each link protocol ▣transport segment= provides different communication link services transportation mode o e.g.,may or may not provide rdt over link link layer protocol travel agent routing algorithm 5:DataLink Layer 5-55: DataLink Layer 5-5 Link layer: context  Datagram transferred by different link protocols over different links:  e.g., Ethernet on first link, frame relay on intermediate links, 802.11 on last link  Each link protocol provides different services  e.g., may or may not provide rdt 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