Ethernet dominant"LAN technology 口 cheap$20for100Mbs! o first wildey used LAn technology O Simpler, cheaper than token LANs and ATM o Kept up with speed race: 10, 100, 1000 Mbps TRANSCENVER STATION TAP XI NTERFACE CABLE Metcalfe's Etheret INTERFACEU COTELER sketch 正MARR THE ETHER A 5: DataLink Layer 5a-11
5: DataLink Layer 5a-11 Ethernet “dominant” LAN technology: cheap $20 for 100Mbs! first wildey used LAN technology Simpler, cheaper than token LANs and ATM Kept up with speed race: 10, 100, 1000 Mbps Metcalfe’s Etheret sketch
Ethernet Frame Structure Sending adapter encapsulates IP datagram(or other network layer protocol packet)in Ethernet frame Preamble Dest. Source Address Address Data Preamble o 7 bytes with pattern 10101010 followed by one byte with pattern 10101011 o used to synchronize receiver sender clock rates 5: Datalink layer 5a-12
5: DataLink Layer 5a-12 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
Ethernet frame Structure (more O Addresses: 6 bytes frame is received by al adapters on a Lan and dropped if address does not match o Type: indicates the higher layer protocol, mostly IP but others may be supported such as Novell IPX and Apple Talk D CRC: checked at receiver if error is detected the frame is simply dropped Dest. Source Preamble Data Address Address CRIE ype 5: Datalink layer 5a-13
5: DataLink Layer 5a-13 Ethernet Frame Structure (more) Addresses: 6 bytes, frame is received by all adapters on a LAN and dropped if address does not match Type: indicates the higher layer protocol, mostly IP but others may be supported such as Novell IPX and AppleTalk) CRC: checked at receiver, if error is detected, the frame is simply dropped
Ethernet: useS CSMA/CD A: sense channel, if idle then i transmit and monitor the channel if detect another transmission then abort and send iam signal update #t collisions delay as required by exponential backoff algorithm; goto A else done with the frame; set collisions to zero] else wait until ongoing transmission is over and goto A] 5: DataLink Layer 5a-14
5: DataLink Layer 5a-14 Ethernet: uses CSMA/CD A: sense channel, if idle then { transmit and monitor the channel; If detect another transmission then { abort and send jam signal; update # collisions; delay as required by exponential backoff algorithm; goto A } else {done with the frame; set collisions to zero} } else {wait until ongoing transmission is over and goto A}