Ch-4: Ethernet Communications

Networking Basics
1. uses MAC address to communicate on a LAN from host to host
2. Uses name resolution
  1. broadcasts asking for info (all f's for MAC)
Ethernet Basics
1. def=contention based media access method that allows all host on a network to share the same bandwith of a link
2. collision domain=area of network where collision events are possible-where every host must pay attention
3. broadcast domain=area of network where a broadcast would reach-normally delineated by switches, hubs, etc.
4. CSMA/CD=carrier sense multiple access collision detection=a protocol for avoiding packet collisions=
  1. monitor segment, if collision event, then all hosts stop transmitting for a while, then free-for-all to transmit
5. half-duplex=one pair of wires for transmitting or receiving. 30-40% efficient
6. full-duplex=two pairs of wire, supposed to be 100% efficient, uses point-to-point communication, requires dedicated switch port
  1. switch to host, switch to switch, host to host (using crossover)
Physical Layer
1. EIA/TIA required ethernet use RJ-45 connection
2. inherent attenuation measured in decibals
3. crosstalk
4. 802.3=ethernet LAN
  1. 802.3u=FastEthernet
    1. 802.3ab=Gigabit Ethernet on Cat 5+
      1. 802.3ae=Gigabit over fiber/coax
5. 10Base2=10Mbps, coax, thinnet, 185m, BNC connector
  1. 10Base5=10Mbps, coax, thicknet, 500m
    1. 10BaseT=10Mbps, Cat3, 100m, phys star logic bus
      1. 100BaseTX=FastEthernet, 100Mbps, Cat3+, 100m
        100BaseFX=mm fiber, 100Mbps,
        1000BaseCX=twinax (double coax), 1Gbps, 25m
        1000BaseT=Cat 5 UTP, 4 pair, 100m, 1Gbps
        1000BaseSX=mm fiber, 1Gbps, max 550m
        1000BaseLX=sm fiber, max 10km, 1Gbps
        10GBaseT=10Gbps, Cat 5e+, economical
        10GBaseSR=mmfiber, 300m, 10Gbps
        10GBaseLR=smfiber, 10km, 10Gbps
        10GBaseER=smfiber, 40km, 10Gbps
        10GBaseSW=mmfiber, used with SONET, 300m
        10GBaseLW=smfiber, 10km, SONET
        10GBaseEW=40km, smfiber, SONET
Data Link Layer
1. responsible for hardware addressing and framing packets in prep for transmission
2. binary number=byte of 1's and 0's. values are 128,64,32,16,8,4,2,1 with value being adding all of the enabled spots.. decimal=regular numbers. hex=0-9 are regular, a=10, b=11,c=12,d=13,e=14,f=15, hex number is 0x or h then two values. convert from binary to hex by dividing into nibbles and changing value of nibble to hex value
3. MAC address=burned into NIC
  1. first 24 bits are OUI (organizationally unique id) second 24 bits are vendor specific
    1. of OUI,1st bit=I/G(individual group), if 0 it's a device, if 1 it's an ethernet broadcast. 2nd bit=G/L(global/local), if 0 it's globally admin'd, if 1 it's locally admin'd.
4. Ethernet stations pass data frames between each other using a group of bits known as a MAC FRAME FORMAT. This provides error detection from a cyclic redundancy check (CRC)
5. Channel bonding is a computer-networking arrangement where two or more network interfaces on a host are combined for redundancy and/or increased throughput
  1. aka Link Aggregation or Cisco=EtherChannel
  2. switch to server, switch to switch, or switch/router to ISP

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Ch-4: Ethernet Communications

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