Computer Networks Chapter 03
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Questions and Answers

Qual es le function del de-multiplexing in le contextu del transport layer?

  • Determinar le protocol de transport a usar.
  • Assignar datagrammas IP a l'application correcte. (correct)
  • Modificar le formato de un segmento TCP.
  • Combinare segmentos de diferentes aplicaciones.

    • Quo es un aspect del connessione-less demultiplexing?

  • Le datagrammas IP non includere source IP.
  • Le socket es construite con un port local specific. (correct)
  • Le UDP segment non porta information de header.
  • Hic, le host non necessita de un address de destination.

    • Qual es le information necessaria in un datagramma IP pro le de-multiplexing?

  • Un code de controle de erro.
  • Le nombre total de datagrammas.
  • Le tamanho static del segmento.
  • Le porta de source e destination. (correct)

    • Qual es le principal differenza inter multiplexing e de-multiplexing?

    <p>Multiplexing combina diferentes aplicaciones, de-multiplexing non.</p> Signup and view all the answers

    Quo debe esser specificate quando se crea un datagramma pro un UDP socket?

    <p>Le destination IP e port.</p> Signup and view all the answers

    Qual es le principal differente inter TCP e UDP?

    <p>TCP offre delivery in ordine, enquanto UDP non lo face.</p> Signup and view all the answers

    Qual caracteristica non es supportate per le protocollo UDP?

    <p>Garantias de retardos</p> Signup and view all the answers

    Que significa multiplexing in le contesto del transport layer?

    <p>Delivery de messages a plure sockets.</p> Signup and view all the answers

    Qual es le principale responsabilitate del demultiplexing?

    <p>Utilizar information del header pro deliverar a le socket correcte.</p> Signup and view all the answers

    Qual es un service non disponibile in le protocollo UDP?

    <p>Garantias de banda</p> Signup and view all the answers

    Como se determina a qual application le message es deliverate?

    <p>Per le header information del message.</p> Signup and view all the answers

    Qual es un desvantaggio de usar UDP comparate con TCP?

    <p>UDP non provide control de congestione.</p> Signup and view all the answers

    Que protocollo usa congestion control?

    <p>TCP</p> Signup and view all the answers

    Qual es le function del transmission control protocol?

    <p>Facer delivery in ordine e reliable.</p> Signup and view all the answers

    Qual es le rol de un socket in le transport layer?

    <p>Identificar le application pro le message sendite.</p> Signup and view all the answers

    Qual es le funzione de rdt_send()?

    <p>Invia datos al livello superiur</p> Signup and view all the answers

    Qual es le principale differentia inter rdt e udt?

    <p>rdt es un protocollo reliable, udt non lo es</p> Signup and view all the answers

    Qual es le rol de deliver_data() in le protocollo rdt?

    <p>Leva datos al livello superiur</p> Signup and view all the answers

    Que tipo de transfer es considerate durante le sviluppo initial del protocollo rdt?

    <p>Transfer unidirectional de datos</p> Signup and view all the answers

    Qual es le effecto de un canale unreliable in le protocollo rdt?

    <p>Creara necessitate de um exito in communication</p> Signup and view all the answers

    In le contexto del protocollo rdt, qual es le funzione de rdt_rcv()?

    <p>Leva un pacchetto quando ille arriva al latere receiver</p> Signup and view all the answers

    Qual es le evenimento importante que occurre durante le communication entre le sender e le receiver?

    <p>Le information de control flue in ambes directiones</p> Signup and view all the answers

    Qual protocollo es primarily responsable pro le transfer de datos in le sender-side?

    <p>rdt_send()</p> Signup and view all the answers

    Qual es le tempo de transmission de un pacco de 8000 bits in un canale con una taxa de transmission de 10 bits/sec?

    <p>8 microsecs</p> Signup and view all the answers

    In le protocol rdt 3.0, como es calculato le tempo total de transmission, Usender?

    <p>RTT + L / R</p> Signup and view all the answers

    Quo es le problema principal del protocol rdt 3.0?

    <p>Le protocol limita le performance del infrastructura subjacente</p> Signup and view all the answers

    Quale modificationes es necessarie pro implementar pipelining in un protocol?

    <p>Aumentar le numero de sequencias e buffering</p> Signup and view all the answers

    Como le pipelining afecta le utilizatio del canale?

    <p>Le utilizatio incrementa per un factor de 3</p> Signup and view all the answers

    Qual es le objetivo del protocollo NAK-free rdt2.2?

    <p>Confirmar solo le ultimi packet ricevuti per medio de ACKs.</p> Signup and view all the answers

    Qual es le secuencia de eventos in un scenario de rdt 3.0?

    <p>Le primo bit de pacco es transmitte, sequite per le reception de le ACK</p> Signup and view all the answers

    Como le sender determina si un packet ha esset ricevute correctemente?

    <p>Per medio de un checksum.</p> Signup and view all the answers

    Que significa 'time to transmit packet into channel' in le contexto de transmission de datos?

    <p>Le tempo necessarie pro le packet pro viajar al recipiente</p> Signup and view all the answers

    Quo significa 'retransmit current pkt' in le contexto de duplicato ACKs?

    <p>Re-inviar le packet actuale al sender.</p> Signup and view all the answers

    In le context de pipelining, qual es le significato de 'in-flight'?

    <p>Paccos que non ha essite acknowledge</p> Signup and view all the answers

    Qual es le resultat de un errore in un packet ricevute?

    <p>Le receiver manda un NAK al sender.</p> Signup and view all the answers

    Qual es le assumption del canal in rdt3.0?

    <p>Le packets pote esser perdite.</p> Signup and view all the answers

    Qual es le consequenza de un packet con un sequenzia corrottato?

    <p>Le receiver savera que le packet non pote esser corrette.</p> Signup and view all the answers

    Qual es le rol de le checksum in le transmission de packet?

    <p>Determinar si un packet es corrottato.</p> Signup and view all the answers

    Qual es le differentia inter rdt2.1 e rdt2.2?

    <p>rdt2.1 usa solo NAKs, rdt2.2 solo ACKs.</p> Signup and view all the answers

    Quo es le function principale del checksum in UDP?

    <p>Pro detectar errores in le transmission.</p> Signup and view all the answers

    Quid ocurre si un carryout emerge durante le addition de inteiros 16-bit?

    <p>Il debe esser addite al summa resultante.</p> Signup and view all the answers

    Qual es le principal limitation del checksum internet?

    <p>Es incapace de garantir un transfert reliable de datos.</p> Signup and view all the answers

    Quid caracteriza le transport de datos reliable?

    <p>Una abstraction de service reliable pro le transfer.</p> Signup and view all the answers

    Quo determina le complexitate del protocollo de transferencia de datos reliable?

    <p>Le caracteristicas del canal unreliable.</p> Signup and view all the answers

    Quo es le statu supports del sender e receiver in le protocollo de transferencia?

    <p>Le sender e receiver non cognosce le statu del altere.</p> Signup and view all the answers

    Quo es le resultat del addition de 16-bit se le bits ha flipado ma le checksum remane identic?

    <p>Le checksums non detecta errores in stile simile.</p> Signup and view all the answers

    Quo es le resultato de un protocoll de transport non reliable?

    <p>Le transmission poterea perder, corromper o reorderar datos.</p> Signup and view all the answers

    Quo es un exemplo de multiplexing in le layer de transport?

    <p>Stabilir plures connexiones simultaneamente.</p> Signup and view all the answers

    Qual e le principale differenita inter TCP e UDP?

    <p>TCP garantisce le delivery de messages, UDP non.</p> Signup and view all the answers

    Quo necessitate le servizio reliable durante e transfer de datos?

    <p>Pro evitar le perdas o corruption de datos.</p> Signup and view all the answers

    Quo non es un characteristic del protocolo UDP?

    <p>Verifica de erres.</p> Signup and view all the answers

    Qual es le beneficio de un protocollo reliable in le transmission de datos?

    <p>Assegura que le data es recte e in ordine.</p> Signup and view all the answers

    Quale statement reflecte le razon de usar checksums?

    <p>Detection de modification accidentale in le datos.</p> Signup and view all the answers

    Study Notes

    Course Information

    • Course Title: Computer Networks
    • Course Code: CENG305
    • University: Izmir Katip Celebi University
    • Semester: Fall 2024-2025
    • Chapter: 03
    • Instructor: H. Burak Akyol, Ph.D.
    • Textbook: Computer Networking: A Top-Down Approach by Jim Kurose and Keith Ross

    Transport Layer: Overview

    • Goal: Understand principles behind transport layer services.
    • Services Include:
      • Multiplexing
      • Demultiplexing
      • Reliable data transfer
      • Flow control
      • Congestion control
    • Protocols:
      • Learn about Internet transport layer protocols.
      • UDP: Connectionless transport
      • TCP: Connection-oriented reliable transport
      • TCP congestion control

    Transport Layer: Roadmap

    • Transport-layer services
    • Multiplexing and demultiplexing
    • Connectionless transport: UDP
    • Principles of reliable data transfer
    • Connection-oriented transport: TCP
    • Principles of congestion control
    • TCP congestion control

    Transport Services and Protocols

    • Provide logical communication between application processes running on different hosts.
    • Transport protocols actions in end systems:
      • Sender: Breaks application messages into segments, passes to network layer.
      • Receiver: Reassembles segments into messages, passes to application layer.
    • Two transport protocols available to Internet applications:
      • TCP
      • UDP

    Transport vs. Network Layer Services and Protocols

    • Transport layer: Communication between processes. Relies on and enhances network layer services.
    • Network layer: Communication between hosts.

    Transport Layer Actions

    • Sender:
      • Receives an application-layer message
      • Determines segment header fields values
      • Creates segment
      • Passes segment to IP layer.
    • Receiver:
      • Receives segment from IP layer
      • Checks header values
      • Extracts application-layer message
      • Demultiplexes message up to application via socket

    Two Principal Internet Transport Protocols

    • TCP: Transmission Control Protocol
      • Reliable, in-order delivery
      • Congestion control
      • Flow control
      • Connection setup
    • UDP: User Datagram Protocol
      • Unreliable, unordered delivery
      • No-frills extension of "best-effort" IP
      • Services not available: delay guarantees, bandwidth guarantees

    Chapter 3: Roadmap

    • Transport-layer services
    • Multiplexing and demultiplexing
    • Connectionless transport: UDP
    • Principles of reliable data transfer
    • Connection-oriented transport: TCP
    • Principles of congestion control
    • TCP congestion control

    Multiplexing/Demultiplexing

    • Multiplexing (as sender): Handles data from multiple sockets, adds transport header (later used for demultiplexing)
    • Demultiplexing (as receiver): Uses header info to deliver received segments to the correct socket

    UDP: User Datagram Protocol

    • "No frills," "bare bones"
    • Internet transport protocol; "best effort" service; UDP segments may be: lost, delivered out-of-order to app.
    • Connectionless
    • No handshaking between sender and receiver
    • Each UDP segment handled independently from others

    UDP: Use Cases

    • Streaming multimedia apps (loss tolerant, rate sensitive)
    • DNS
    • SNMP (Simple Network Management Protocol)
    • HTTP/3 (if needed reliability and congestion control are added at application layer)

    UDP: User Datagram Protocol [RFC 768]

    • Protocol intended to provide a datagram mode of communication with minimal protocol mechanism. Delivery and duplicate protection are not guaranteed.
    • This protocol assumes the use of the Internet protocol (IP)
    • Format includes source port, destination port, length, and checksum fields.

    UDP: Transport Layer Actions

    • Sender Actions:
      • Passes an application-layer message to the transport layer.
      • Determines UDP segment header values.
      • Creates UDP segment.
      • Passes segment to IP layer.
    • Receiver Actions:
      • Receives segment from IP layer.
      • Checks UDP checksum header value
      • Extracts application-layer message
      • Demultiplexes message up to application via socket

    UDP Segment Header

    • Includes source port, destination port, length, and checksum.

    UDP Checksum

    • Goal: Detect errors (e.g., flipped bits) in transmitted segments.
    • Sender: Treats UDP segment contents (including header and IP addresses) as a sequence of 16-bit integers; computes checksum (one's complement sum) and puts it in UDP checksum field.
    • Receiver: Computes checksum of received segment; checks if computed checksum equals checksum field value.

    Internet Checksum

    • Goal: detect errors.
    • Sender: treats contents of UDP segment, computes the checksum, and places the checksum field into the segment.
    • Receiver: computes the checksum, checks if the computed checksum equals checksum field value.

    Principles of Reliable Data Transfer

    • Abstraction: Sending and receiving processes send data over a "reliable channel."
    • Complexity: Depends on characteristics of the unreliable channel.

    Reliable Data Transfer (RDT) Protocol: Interfaces

    • RDT functions: rdt_send(data), deliver_data(data)
    • Bi-directional communication over an unreliable channel

    Reliable Data Transfer: Getting Started

    • Incrementally develop sender and receiver sides of reliable data transfer protocol (RDT)

    RDT 1.0: Reliable Transfer over a Reliable Channel

    • Underlying channel is perfectly reliable; no bit errors or packet loss.

    RDT 2.0: Channel with Bit Errors

    • Underlying channel may flip bits in packets.
    • Receiver uses checksums to detect bit errors.

    RDT 2.0: FSM Specifications

    • Defining states and transitions for sender and receiver FSMs (Finite State Machines)

    RDT 2.0: Operations with no errors

    • Sender sends data, receiver acknowledges (ACKs) successful reception

    RDT 2.0: Corrupted Packet Scenarios

    • Sender resends data when a corrupted packet is detected
    • Receiver discards packets that are duplicates.

    RDT 2.0 has a fatal flaw

    • Sender does not know what happened at receiver if the ACK or NAK packet is corrupted
    • Possible duplicate packets

    RDT 2.1: Handling Garbled ACK/NAKs

    • Sender and receiver design include error checking and retransmission mechanisms.
    • Improved error handling by incorporating sequence numbers.

    RDT 2.2: NAK-Free Protocol

    • Achieves similar functionality to RDT 2.1 but uses only ACKs for confirmation.
    • Receiver must explicitly include the sequence number of the packet being acknowledged.

    RDT 2.2: Sender and Receiver Fragments

    • Sender and receiver implement fragments.

    RDT 3.0: Channels with Errors and Loss

    • Underlying channel may also lose packets
    • Use checksums, sequence numbers, and retransmissions

    RDT 3.0: sender waits "reasonable" amount of time for ACK

    • if ACKs are not received, retransmit

    RDT 3.0 Sender

    • includes a timer mechanism to interrupt operation after a reasonable amount of time

    RDT 3.0 in Action

    • Diagrammatic illustrations of possible scenarios (no loss, packet loss, ACK loss, etc.)

    RDT 3.0 Stop-and-Wait Operation

    • Performance analysis
    • Utilization calculations

    RDT 3.0 Pipelined Protocols Operation

    • Illustrates pipelined protocols which allow multiple unacknowledged packets to be sent and received.

    Pipelining: Increased Utilization

    • Pipelining dramatically increases the utilization level compared to stop-and-wait protocols.

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