21 - Ethernet address and ARP

21 - Ethernet address and ARP - Last Lecture: Data Link...

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Last Lecture: Data Link Layer 1. Design goals and issues 2. (More on) Error Control and Detection 3. Multiple Access Control (MAC) 4. Ethernet, LAN Addresses and ARP 5. Hubs, Bridges, Switches 6. Wireless LANs 7. WLAN Security 8. Mobile Networking SUNY at Buffalo; CSE 489/589 – Modern Networking Concepts; Fall 2010; Instructor: Hung Q. Ngo 1
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This Lecture: Data Link Layer 1. Design goals and issues 2. (More on) Error Control and Detection 3. Multiple Access Control (MAC) 4. Ethernet, LAN Addresses and ARP 5. Hubs, Bridges, Switches 6. Wireless LANs 7. WLAN Security 8. Mobile Networking SUNY at Buffalo; CSE 489/589 – Modern Networking Concepts; Fall 2010; Instructor: Hung Q. Ngo 2
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Ethernet “Dominant” LAN technology: Cheap $20 for 100Mbs! First widely used LAN technology Simpler, cheaper than token LANs and ATM Kept up with speed race: 10Mbps -- 10 Gbps SUNY at Buffalo; CSE 489/589 – Modern Networking Concepts; Fall 2010; Instructor: Hung Q. Ngo 3 Metcalfe’s Ethernet sketch
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Ethernet Frame Structure Sending adapter encapsulates IP datagram (or other network layer protocol packet) in Ethernet frame Preamble: 7 bytes with pattern 10101010 followed by one byte with pattern 10101011 used to synchronize receiver, sender clock rates SUNY at Buffalo; CSE 489/589 – Modern Networking Concepts; Fall 2010; Instructor: Hung Q. Ngo 4
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Ethernet Frame Structure (more) Addresses : 6 bytes if adapter receives frame with matching destination address, or with broadcast address (eg ARP packet), it passes data in frame to net-layer protocol otherwise, adapter discards frame Type : indicates the higher layer protocol, mostly IP but others may be supported such as Novell IPX and AppleTalk) CRC : if error detected, frame is simply dropped SUNY at Buffalo; CSE 489/589 – Modern Networking Concepts; Fall 2010; Instructor: Hung Q. Ngo 5
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Connectionless: No handshaking between sending and receiving NICs Unreliable: receiving NIC doesn’t send ACKs or NACKs to sending NIC Stream of datagrams passed to network layer can have gaps (missing datagrams) Gaps will be filled if app is using TCP Otherwise, app will see gaps Ethernet’s MAC protocol Half-duplex: unslotted CSMA/CD Full-duplex: no protocol, small gap between frames SUNY at Buffalo; CSE 489/589 – Modern Networking Concepts; Fall 2010; Instructor: Hung Q. Ngo 6
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Ethernet CSMA/CD algorithm SUNY at Buffalo; CSE 489/589 – Modern Networking Concepts; Fall 2010; Instructor: Hung Q. Ngo 7 1. NIC receives datagram from network layer, creates frame 2. If NIC senses channel idle (for 96 bit times ), starts frame transmission. If NIC senses channel busy, waits until channel idle (for 96 bit times), then transmits 3. If NIC transmits entire frame without detecting another transmission, NIC is done with frame! 4. If NIC
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21 - Ethernet address and ARP - Last Lecture: Data Link...

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