Ethernet (CSMA/CD)Carriers Sense Multiple Access with Collision
DetectionXerox - EthernetIEEE 802.3
CSMA/CDWith CSMA, collision occupies medium for duration of
transmissionStations listen whilst transmitting
If medium idle, transmit, otherwise, step 2If busy, listen for
idle, then transmitIf collision detected, jam then cease
transmissionAfter jam, wait random time then start from step 1
CSMA/CDOperation
Collision DetectionOn baseband bus, collision produces much
higher signal voltage than signalCollision detected if cable signal
greater than single station signalSignal attenuated over
distanceLimit distance to 500m (10Base5) or 200m (10Base2)For
twisted pair (star-topology) activity on more than one port is
collisionSpecial collision presence signal
Gigabit Ethernet Physical1000Base-SXShort wavelength, multimode
fiber1000Base-LXLong wavelength, Multi or single mode
fiber1000Base-CXCopper jumpers
Why Change IP?Address space exhaustionTwo level addressing
(network and host) wastes spaceNetwork addresses used even if not
connected to InternetGrowth of networks and the InternetExtended
use of TCP/IPSingle address per hostRequirements for new types of
service
IPv6 Enhancements (1)Expanded address space128 bitImproved
option mechanismSeparate optional headers between IPv6 header and
transport layer headerMost are not examined by intermediate
routesImproved speed and simplified router processingEasier to
extend optionsAddress autoconfigurationDynamic assignment of
addresses
IPv6 Enhancements (2)Increased addressing flexibilityAnycast -
delivered to one of a set of nodesImproved scalability of multicast
addressesSupport for resource allocationReplaces type of
serviceLabeling of packets to particular traffic flowAllows special
handlinge.g. real time video
