60-Transporte

8/9/2019 60-Transporte

1/55

3-1

El Servicio de TransporteEl Servicio de Transporte

Servicios Brindados a las Capas

superiores Primitivas del Servicio de Transporte

Berkeley Sockets


2/55

3-2

Servicios Brindados a lasCapas superiores

Servicios Brindados a lasCapas superiores


3/55

3-3

PrimitivasPrimitivas


4/55

3-4

ENCAPSULADOENCAPSULADO


5/55

3-5

Primitivas (2)Primitivas (2)

Las lneas llenas representan la secuencia de estados decleinte. Las punteadas las secuencias de estados del server.


6/55

3-6

Berkeley Sockets para TCPBerkeley Sockets para TCP


7/55

3-7

Elementos de Protocolos deTransporte

Elementos de Protocolos deTransporte

Direccionamiento Establecimiento de Conexin

Liberacin de conexin Control de Flujo y Buffering

Multiplexing

Recuperacin de Caidas


8/55

3-8

Protocolo de TransporteProtocolo de Transporte

(a) Ambiente de capa data link

(b) Ambiente de capa de transporte.


9/55

3-9

DireccionamientoDireccionamiento

TSAPs, NSAPs y conexiones de transporte.


10/55


11/55

3-11

(a) TPDUs no pueden entrar en la regin prohibida.

(b) El problema de la resincronizacin

Establecimiento de la ConexinEstablecimiento de la Conexin


12/55

3-12

Establecimiento de la Conexin(3)Establecimiento de la Conexin(3)

Three protocol scenarios for establishing a connection using a three-wayhandshake. CR denotes CONNECTION REQUEST.(a) Normal operation,(b) Old CONNECTION REQUEST appearing out of nowhere.

(c) Duplicate CONNECTION REQUEST and duplicate ACK.


13/55

3-13

Liberacin de la ConexinLiberacin de la Conexin

Desconexin abripta con perdida de datos.


14/55

3-14

Connection Release (2)Connection Release (2)

The two-army problem.


15/55

3-15

Cuatro escenarios de protocolo para liberacin de conexin.(a) Caso normal ( three-way handshake.)(b) Prdida de ACK .

6-14, a, b



16/55

3-16

(c) Respuesta perdida. ( d) Respuestaperdida y prdida de DRs .

6-14, c,d



17/55

3-17

Control de Flujo y BufferingControl de Flujo y Buffering

(a) Chained fixed-size buffers. (b) Chained variable-sized buffers.(c) One large circular buffer per connection.


18/55

3-18Dynamic buffer allocation. The arrows show the direction oftransmission. An ellipsis () indicates a lost TPDU.

Control de Flujo y BufferingControl de Flujo y Buffering


19/55

3-19

MultiplexingMultiplexing

(a) Upward multiplexing.

(b) Downward multiplexing.


20/55

3-20

Crash RecoveryCrash Recovery

Diferentes combinaciones de estrategia de server y cliente


21/55

3-21

A Simple Transport ProtocolA Simple Transport Protocol

The Example Service Primitives

The Example Transport Entity

The Example as a Finite State

Machine


22/55

3-22

The Example Transport EntityThe Example Transport Entity


23/55

3-23

The Example Transport Entity(2)

The Example Transport Entity(2)

Each connection is in one of seven states: Idle Connection not established yet.

Waiting CONNECT has been executed, CALL REQUEST sent.

Queued A CALL REQUEST has arrived; no LISTEN yet.

Established The connection has been established.

Sending The user is waiting for permission to send a packet.

Receiving A RECEIVE has been done.

DISCONNECTING a DISCONNECT has been done locally.


24/55

3-24

The Example as a Finite StateMachine

The Example as a Finite StateMachine

The example protocol as afinite state machine. Eachentry has an optionalpredicate, an optionalaction, and the new state.

The tilde indicates that nomajor action is taken. Anoverbar above a predicateindicate the negation of the

predicate. Blank entriescorrespond to impossibleor invalid events.


25/55

3-25

The Example as a Finite StateMachine (2)

The Example as a Finite State

Machine (2)


26/55

3-26

The Internet TransportProtocols: UDP

The Internet TransportProtocols: UDP

Introduction to UDP

Remote Procedure Call The Real-Time Transport

Protocol


27/55

3-27

Introduction to UDPIntroduction to UDP

El Encabezado UDP.


28/55

3-28

Remote Procedure CallRemote Procedure Call

Steps in making a remote procedure call.The stubs are shaded.


29/55

3-29

The Real-Time TransportProtocol

The Real-Time TransportProtocol

(a) La posicion de RTP en el stack de protocolos .

(b) Packet nesting.


30/55

3-30

The Real-Time TransportProtocol (2)

The Real-Time TransportProtocol (2)

The RTP header.


31/55

3-31

The Internet TransportProtocols: TCP

The Internet Transport

Protocols: TCP Introduction to TCP

The TCP Service Model The TCP Protocol The TCP Segment Header TCP Connection Establishment TCP Connection Release TCP Connection Management Modeling TCP Transmission Policy

TCP Congestion Control TCP Timer Management Wireless TCP and UDP Transactional TCP


32/55

3-32

The TCP Service ModelThe TCP Service Model

Port Protocol Use21 FTP File transfer23 Telnet Remote login

25 SMTP E-mail

69 TFTP Trivial File Transfer Protocol

79 Finger Lookup info about a user

80 HTTP World Wide Web

110 POP-3 Remote e-mail access119 NNTP USENET news


33/55

3-33

The TCP Service Model (2)The TCP Service Model (2)

(a) Four 512-byte segments sent as separate IP datagrams.

(b) The 2048 bytes of data delivered to the application in asingle READ CALL.


34/55

3-34

The TCP Segment HeaderThe TCP Segment Header

TCP Header.


35/55

3-35

The TCP Segment Header (2)The TCP Segment Header (2)

The pseudoheader included in the TCP checksum.


36/55

3-36

TCP Connection EstablishmentTCP Connection Establishment

(a) TCP connection establishment in the normal case.

(b) Call collision.

6-31


37/55


38/55

3-38

TCP Connection Management

Modeling (2)

TCP Connection Management

Modeling (2)TCP connectionmanagement finite

state machine.The heavy solidline is the normalpath for a client.The heavy dashed

line is the normalpath for a server.The light lines areunusual events.Each transition is

labeled by theevent causing itand the actionresulting from it,separated by a

slash.


39/55

3-39

TCP Transmission PolicyTCP Transmission Policy

Window management in TCP.


40/55

3-40

TCP Transmission Policy (2)TCP Transmission Policy (2)

Silly window syndrome.


41/55

3-41

TCP Congestion ControlTCP Congestion Control

(a) A fast network feeding a low capacity receiver.

(b) A slow network feeding a high-capacity receiver.


42/55

3-42

TCP Congestion Control (2)TCP Congestion Control (2)

An example of the Internet congestion algorithm.


43/55

3-43

TCP Timer ManagementTCP Timer Management

(a) Probability density of ACK arrival times in the data link layer.

(b) Probability density of ACK arrival times for TCP.


44/55

3-44

Wireless TCP and UDPWireless TCP and UDP

Splitting a TCP connection into two connections.


45/55

3-45

Transitional TCPTransitional TCP

(a) RPC using normal TPC.

(b) RPC using T/TCP.


46/55

3-46

Performance IssuesPerformance Issues

Performance Problems in ComputerNetworks

Network Performance Measurement System Design for Better Performance

Fast TPDU Processing Protocols for Gigabit Networks

Performance Problems in ComputerPerformance Problems in Computer


47/55

3-47

Performance Problems in Computer

Networks

Performance Problems in Computer

Networks

The state of transmitting one megabit from San Diego toBoston

(a) At t = 0, (b) After 500 sec, (c) After 20 msec, (d) after40 msec.

Network PerformanceNetwork Performance


48/55

3-48

Network Performance

Measurement

Network Performance

Measurement

The basic loop for improving networkperformance.

Measure relevant network parameters,performance.

Try to understand what is going on.

Change one parameter.

System Design for BetterSystem Design for Better


49/55

3-49

System Design for Better

Performance


PerformanceRules:

CPU speed is more important than network speed. Reduce packet count to reduce software overhead.

Minimize context switches.

Minimize copying.

You can buy more bandwidth but not lower delay.

Avoiding congestion is better than recovering fromit.

Avoid timeouts.



50/55

3-50


Performance (2)


Performance (2)

Response as a function of load.



51/55

3-51


Performance (3)


Performance (3)

Four context switches to handle one packet

with a user-space network manager.

F TPDU P i


52/55

3-52

Fast TPDU ProcessingFast TPDU Processing

The fast path from sender to receiver is shown with a heavy line.

The processing steps on this path are shaded.

F TPDU P i (2)F TPDU P i (2)


53/55

3-53

Fast TPDU Processing (2)Fast TPDU Processing (2)

(a) TCP header. (b) IP header. In both cases, the shadedfields are taken from the prototype without change.

F TPDU P i (3)F TPDU P i (3)


54/55

3-54

Fast TPDU Processing (3)Fast TPDU Processing (3)

A timing wheel.

P t l f Gi bit N t kP t l f Gi bit N t k


55/55

3-55

Protocols for Gigabit NetworksProtocols for Gigabit Networks

Time to transfer and acknowledge a 1-megabit file over a4000-km line.

60-Transporte

Documents

Transcript of 60-Transporte