Lec7_Link(ch6).pptx - Chapter 6 The Link Layer and LANs...

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6-1 Link Layer and LANs Chapter 6: The Link Layer and LANs
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Data Link Layer 5-2
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Chapter 6: Link layer and LANs our goals: understand principles behind link layer services: error detection, correction sharing a broadcast channel: multiple access link layer addressing local area networks: Ethernet, VLANs instantiation, implementation of various link layer technologies 6-3 Link Layer and LANs
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Link layer, LAN s: outline 6.1 introduction, services 6.2 error detection, correction 6.3 multiple access protocols 6.4 LANs addressing, ARP Ethernet switches VLANS 6.7 a day in the life of a web request 6-4 Link Layer and LANs
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Link layer: introduction terminology: hosts and routers: nodes communication channels that connect adjacent nodes along communication path: links wired links wireless links LANs layer-2 packet: frame, encapsulates datagram data-link layer has responsibility of transferring datagram from one node to physically adjacent node over a link 6-5 Link Layer and LANs
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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 real data 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 6-6 Link Layer and LANs
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Link layer services framing, link access: encapsulate datagram into frame, adding header, trailer channel access if shared medium “MAC” addresses used in frame headers to identify source, destination different from IP address! reliable delivery between adjacent nodes flow control: pacing (ةعرسسس)between adjacent sending and receiving nodes 6-7 Link Layer and LANs
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Link layer: introduction 6-8 Link Layer and LANs
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error detection : errors caused by signal attenuation, noise. receiver detects presence of errors: signals sender for retransmission or drops frame error correction: receiver identifies and corrects bit error(s) without resorting to retransmission half-duplex and full-duplex with half duplex, nodes at both ends of link can transmit, but not at same time Link layer services (more) 6-9 Link Layer and LANs
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implemented?not very important in each and every host link layer implemented in “adaptor” (aka network interface card NIC) or on a chip Ethernet card, 802.11 card; Ethernet chipset implements link, physical layer attaches into host’s system buses combination of hardware, software controller physical transmission cpu memory host bus (e.g., PCI) network adapter card application transport network link link physical 6-10 Link Layer and LANs
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Adaptors communicating sending side: encapsulates datagram in frame
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  • Fall '19
  • ARP,  hosts, 802.1q protocol,  trip,  travel agentLink

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