Lecture12 - Thursday, May 8 Quiz #2 Homework #3 Scores are...

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1 Thursday, May 8 Quiz #2 Scores are posted Pick up Homework #3 Partial discussion in class on Tuesday Solutions will be posted Due date is changed to  Thursday (5/15) Lab #4 Sign up
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2 Thursday, May 8 Program #1 Due before midnight tomorrow Evaluation criteria are posted Notes on implementation Let the socket API and TCP/IP protocols do their jobs! Midterm #2 Thursday, May 15, in class No office hours tomorrow Engineering Expo / Industry Advisory Board
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3 Today's Topics Physical/Logical Ports Logical port numbers Internet Protocol (IP) Protocols, addressing, routing
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4 Physical/Logical Ports A physical port  is an interface to which a device  can be connected E.g., connection for network cable on host or router  hardware A logical port  is a structure used by  application/transport layer protocols
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5 Router Architecture: a little about hardware Two key router functions:   run  routing  algorithms/protocol (OSPF, BGP) forwarding  datagrams from incoming to outgoing link
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6 Physical Input Port Functions Decentralized switching Lookup : given datagram dest., lookup output port using forwarding  table in input port memory forward : forward to appropriate output port queuing : if datagrams arrive faster than forwarding rate into switch  fabric Physical layer: bit-level  reception Data link layer: e.g., Ethernet see chapter 5
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7 Physical Output Port Functions Buffering  required when datagrams arrive from fabric faster than  the transmission rate Scheduling discipline  chooses among queued datagrams for  transmission
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8 Physical  Input Port Queuing Fabric slower than input ports combined capacity  queueing may occur at input queues  Head-of-the-Line (HOL) blocking:  queued datagram at front of queue  prevents others in queue from moving forward May cause queueing delay and loss due to input port buffer overflow!
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9 Physical Output port queueing Buffering when arrival rate via switch exceeds output line speed May cause queueing delay and loss due to output port buffer  overflow!
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10 Selecting logical port numbers Communicating computers must agree on a port number  Server opens selected port and waits for incoming messages  Client selects local port and sends message to selected server port  Many common services use reserved (well-known) port numbers  Other services use  dynamically assigned  port numbers Valid range is [0 . . 65535] , but don’t use “well-know” port numbers for  special apps.
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11 Some "well-known" logical port numbers Port Name Description 7 echo
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Lecture12 - Thursday, May 8 Quiz #2 Homework #3 Scores are...

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