Tài liệu Protocols and Transmission Theory pptx

Protocols Explained • Protocol History • Signalling – Frequency vs Bit Rate Transmission and Protocol Theory Protocol History • Ethernet conception • StarLAN • Token Ring • Cell vs Packets – ATM vs Ethernet • Ethernet comes of age Transmission and Protocol Theory Protocol History • Born from the original Aloha Network in 1972 • Xerox, who pioneered the first PC with a GUI commission Bob Metcalfe to develop networking from their ALTO computers to Arpanet • The breakthrough was a device that could listen before transmitting, which allowed for full utilization of the bandwidth speed (2.94Mbps) • In 1977 they were issued the patent on CSMA/CD (Carrier-Sense Multiple Access with Collision Detection) Transmission and Protocol Theory Protocol History • The key principle behind Ethernets success was not it’s speed early on or the way it transmitted within a network, but Metcalfe’s vision to have a standardized platform that WAS NOT proprietary • This was pushed further by joint efforts between Intel, DEC and Xerox in the late 70’s through to the early 80’s • Simultaneously the IEEE began working on standardizing protocol developments, starting with Ethernet, as Xerox continued to turn it’s patents over to them in an effort to drive global adoption with a standard platform Transmission and Protocol Theory Protocol History • Metcalfe and others broke off on their own to form 3COM in 1979 • They released their first TCP/IP transceivers for UNIX a full 18 Months before the IEEE standard • The 3C100 Transceivers were being produced for DEC, Intel and Sun Microsystems • Both Apple and IBM were approached in an effort to push networking for the developing PC market • Apple said yes, but IBM said no because of their own Token Ring developments Transmission and Protocol Theory Protocol History • 3COM, without the cooperation of IBM, decided to produce the highly successful ISA EtherLink adaptors for IBM PC’s • This was highly cost effective at the time ($950 USD) and gained large acceptance • Demand was driven not by “Personal” computing, but rather by businesses adopting the PC • Of course with so many computers within companies the need to network grew • 3COM met these demands and become the NIC champion in the mid 80’s Transmission and Protocol Theory Protocol History • Ethernet networks were first connected using Coax cables • 10Base5, running on RG-8 cable was capable of distances up to 500m • 10Base2, running on RG-58 cable was capable of distances of 185m • Although the distances were reduced using 10Base2, acceptance was better due to reduced costs in cabling infrastructure, as well as active hardware • It was quickly realized that LAN connections did not require 500m distances in the horizontal Transmission and Protocol Theory Protocol History – Thick vs Thin Vampire Terminator Clamp Clamp Ethernet cable Transceptor Dispositive Connection Terminator Vampire RG Coax Connectors Transceptor NIC 10Base5 Cable AUI Dispositive Connection NIC 10Base2 RG Coax Ethernet cable Terminator BNC Connector Terminator BNC Connector Transmission and Protocol Theory Protocol History - StarLAN vs Thick/Thin Bus • Thin Ethernet had advantages over regular (thick) Ethernet, in that the cables were cheaper and the electronics were all located within the NIC Both still had drawbacks with their Bus architecture MAC’s were difficult Cables could not be severed or the entire network would go down Termination at both ends was a must! • Intel and AT&T saw this as an opportunity to change the architecture to a “Star” configuration Transmission and Protocol Theory Protocol History StarLAN - Bus vs Star Centralized Controller Bus Topology Star Topology Transmission and Protocol Theory 10 ... gaps for timing •The packet relies on Best-Effort Transmission and does not offer true QoS and has a 98% efficiency Transmission and Protocol Theory 15 Protocol History - Packets are just like... real-time application and increased bandwidth requirements of the time • QoS has been addressed through sheer pipe size and prioritized packeting Transmission and Protocol Theory 19 Protocol History... within companies the need to network grew • 3COM met these demands and become the NIC champion in the mid 80’s Transmission and Protocol Theory Protocol History • Ethernet networks were first connected