csci5211-direct-link-lan

csci5211-direct-link-lan - S d Me and hare dia Local Are Ne...

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CSci5211: Local Area Networks 1 Shared Media and Local Area Networks Shared Media Access Problem Media access control (MAC) and LAN MAC addresses and network adaptors (NICs) MAC protocols: random access vs. controlled access Ethernet Token Ring and FDDI 802.11 Wireless LAN Readings Sections 2.6-2.7
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CSci5211: Local Area Networks 2 Multiple Access Links and LANs Two types of “links”: point-to-point, e.g., PPP for dial-up access, or over optical fibers broadcast (shared wire or medium), e.g. traditional Ethernet 802.11 wireless LAN
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CSci5211: Local Area Networks 3 Typical LAN Structure RAM RAM ROM Ethernet Processor Transmission Medium Network Interface Card (NIC) Unique MAC “physical” address
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CSci5211: Local Area Networks 4 Adaptors Communicating link layer implemented in “adaptor” (aka NIC), with “transceiver” in it Ethernet card, dial-up modem, 802.11 wireless card sending side: encapsulates packet in frame adds error checking bits, flow control, reliable data transmission, etc. receiving side looks for errors, flow control, reliable data transmission, etc extracts packet, passes to receiving node adapter is semi-autonomous data link & physical layers are closely coupled! sending node frame rcving node network packet frame adapter adapter link layer protocol
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CSci5211: Local Area Networks 5 MAC (Physical) Addresses Addressing needed in shared media MAC (media access control) or physical addresses To identify source and destination interfaces and get frames delivered from one interface to another physically-connected interface (i.e., on same physical local area network!) 48 bit MAC address (for most LANs) fixed for each adaptor, burned in the adapter ROM MAC address allocation administered by IEEE 1 st bit: 0 unicast , 1 multicast . all 1’s : broadcast MAC flat address -> portability can move LAN card from one LAN to another
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CSci5211: Local Area Networks 6 MAC (Physical, or LAN) Addresses MAC addressing operations on a LAN: each adaptor on the LAN “sees” all frames accept a frame only if dest. (unicast) MAC address matches its own MAC address accept all broadcast (MAC= all 1’s) frames accept all frames if set in “ promiscuous ” mode can configure to accept certain multicast addresses (first bit = 1)
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CSci5211: Local Area Networks 7 MAC Sub-layer Data link layer 802.3 CSMA-CD 802.5 Token Ring 802.2 Logical link control Physical layer MAC LLC 802.11 Wireless LAN Network layer Network layer Physical layer OSI IEEE 802 Various physical layers Other LANs
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Local Area Networks 8 Broadcast Links: Multiple Access Single shared communication channel Only one can send successfully at a time Two or more simultaneous transmissions interference! How to share a broadcast channel
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csci5211-direct-link-lan - S d Me and hare dia Local Are Ne...

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