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Unformatted text preview: Layer: Establishes connecKon among hosts, duplex, half- duplex, graceful connecKon terminaKon, combinaKon of streams •  PresentaKon Layer: NegoKaKon of format of data exchanged between hosts •  ApplicaKon layer: ApplicaKon services such as FTP, X.400 (mail), HTTP 11 The Internet Architecture FTP HTTP TFTP TCP DNS UDP IP Net 1 Ethernet Net 1 FDDI TCP: Transmission Control Protocol FTP: File Transfer Protocol HTTP: Hypertext Transport Protocol UDP: User Datagram Protocol TFTP: Trivial File Transfer Protocol IP: Internet Protocol DNS: Domain Name System 12 Comparison of the two architectures 13 Main Driving Goals of IP (In Order) •  CommunicaKon should conKnue despite failures –  Survive equipment failure or physical agack –  Traffic between two hosts conKnue on another path •  Support mulKple types of communicaKon services –  Differing requirements for speed, latency, & reliability –  BidirecKonal reliable delivery vs. message service •  Accommodate a variety of networks –  Both military and commercial faciliKes –  Minimize assumpKons about the underlying network 14 Other Driving Goals, Somewhat Met •  Permit distributed management of resources –  Nodes managed by different insKtuKons –  … though this is sKll rather challenging •  Cost- effecKveness –  StaKsKcal mulKplexing through packet switching –  … though packet headers and retransmissions wasteful •  Ease of agaching new hosts –  Standard implementaKons of end- host protocols –  … though sKll need a fair amount of end- host soNware •  Accountability for use of resources –  Monitoring funcKons in the nodes –  … though this is sKll fairly limited and immature 15 Network Performance Metrics •  Bandwidth –  Amount of data transmiged per unit of Kme –  Per link, or end- to- end –  Units 1KB = 210 bytes, 1Mbps = 106 bits per sec •  Throughput –  Data that the link or network is able to deliver –  Per link or end- to- end, same units as Bandwidth 16 Latency or delay •  Time for sending data from host A to B •  Per link or end- to- end –  Usually consist of •  Transmission delay •  PropagaKon delay •  Queuing delay •  Round Trip Time (RTT) : Kme to send a message from A to B and back –  Important for flow control mechanisms...
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