Transportlayer)and)UDP) · Chapter)3)outline) 3.1)Transportlayer) services 3.2)Mul:plexing)and)...

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Transport layer and UDP Computer Networking: A Top Down Approach 6 th edition Jim Kurose, Keith Ross Addison-Wesley Some materials copyright 1996-2012 J.F Kurose and K.W. Ross, All Rights Reserved ”www.cnn.com?” “12.3.4.15”

Transcript of Transportlayer)and)UDP) · Chapter)3)outline) 3.1)Transportlayer) services 3.2)Mul:plexing)and)...

Page 1: Transportlayer)and)UDP) · Chapter)3)outline) 3.1)Transportlayer) services 3.2)Mul:plexing)and) demulplexing ) 3.3Conneconless transport:)UDP) 3.4)Principles)of)reliable) datatransfer)

Transport  layer  and  UDP  

Computer Networking: A Top Down Approach 6th edition Jim Kurose, Keith Ross Addison-Wesley  

Some materials copyright 1996-2012 J.F Kurose and K.W. Ross, All Rights Reserved

”www.cnn.com?”

“12.3.4.15”

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Overview  

2  

•  Principles  underlying  transport  layer  – Mul:plexing/demul:plexing  –  Detec:ng  errors  –  Reliable  delivery  –  Flow  control  –  Conges:on  control  

•  Major  transport  layer  protocols:  –  User  Datagram  Protocol  (UDP)  

•  Simple  unreliable  message  delivery  

–  Transmission  Control  Protocol  (TCP)  •  Reliable  bidirec:onal  stream  of  bytes  

transport

application

physical

link

network

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Chapter  3:  Transport  Layer  Goals:  •  Understand  principles  behind  transport  layer  services:  – Mul:plexing,  demul:plexing  

–  Reliable  data  transfer  

–  Flow  control  –  Conges:on  control  

•  Learn  about  Internet  transport  layer  protocols:  –  UDP:  connec:onless  transport  

–  TCP:  connec:on-­‐oriented  reliable  transport  

–  TCP  conges:on  control  

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Chapter  3  outline  3.1  Transport-­‐layer  

services  3.2  Mul:plexing  and  

demul:plexing  3.3  Connec:onless  

transport:  UDP  3.4  Principles  of  reliable  

data  transfer  

3.5  Connec:on-­‐oriented  transport:  TCP  –  Segment  structure  –  Reliable  data  transfer  –  Flow  control  –  Connec:on  management  

3.6  Principles  of  conges:on  control  

3.7  TCP  conges:on  control  

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Transport  services  and  protocols  •  Provide  logical  communica+on  

between  app  processes  running  on  different  hosts  

•  Transport  protocols  run  in  end  systems    –  Send  side:  breaks  app  messages  into  segments,  passes  to    network  layer  

–  Recv  side:  reassembles  segments  into  messages,  passes  to  app  layer  

•  More  than  one  transport  protocol  available  to  apps  –  Internet:  TCP  and  UDP  

applica:on  transport  network  data  link  physical  

applica:on  transport  network  data  link  physical  

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Segments  •  Segment  

– Message  sent  from  one  transport  en:ty  to  another  transport  en:ty  

– Term  used  by  TCP,  UDP,  other  Internet  protocols  – aka  TPDU  (Transport  Protocol  Data  Unit)  

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Internet  layering  model  

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HTTP  

TCP  

IP  

Ethernet  interface  

HTTP  

TCP  

IP  

Ethernet  interface  

IP   IP  

Ethernet  interface  

Ethernet  interface  

SONET  interface  

SONET  interface  

host   host  

router   router  

HTTP  message  

TCP  segment  

IP  packet   IP  packet  IP  packet  

frame   frame  frame  

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Transport  layer  challenges  •  Running  on  best-­‐effort  network:  

– Messages  may  be  dropped  – Messages  may  be  reordered  – Duplicate  messages  may  be  delivered  – Messages  have  some  finite  size  – Messages  may  arrive  a\er  long  delay  

•  Sender  must  not  overrun  receiver  •  Network  may  be  congested  •  Hosts  must  support  mul:ple  applica:ons  

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Internet  transport-­‐layer  protocols  •  Reliable,  in-­‐order  delivery:  TCP  –  Conges:on  control    –  Flow  control  –  Connec:on  setup  

•  Unreliable,  unordered  delivery:  UDP  –  No-­‐frills  extension  of  "best-­‐effort"  IP  

•  Services  not  available:    –  Delay  guarantees  –  Bandwidth  guarantees  

applica:on  transport  network  data  link  physical  

applica:on  transport  network  data  link  physical  

 network  data  link  physical    

network  data  link  physical  

 network  data  link  physical  

 network  data  link  physical    

network  data  link  physical    

network  data  link  physical    

network  data  link  physical  

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Transport  layer  •  Goal:  End-­‐to-­‐end  data  transfer  

–  Just  gebng  to  host  machine  isn't  enough  – Deliver  data  from  process  on  sending  host  to  correct  process  on  receiving  host  

•  Solu:on:  OS  demul:plexes  to  correct  process  – Port  number,  an  abstract  locater  – OS  demuxes  combining  with  other  info    

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UDP    <port,  host>  TCP      <source  port,  source  IP,  dest  port,  dest  IP>  

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Mul:plexing/demul:plexing  

process  

socket  

Use  header  info  to  deliver  received  segments  to  correct    socket  

Demul+plexing  at  receiver:  Handle  data  from  mul:ple  sockets,  add  transport  header  (later  used  for  demul:plexing)  

Mul+plexing  at  sender:  

transport  

applica:on  

physical  

link  

network  

P2  P1  

transport  

applica:on  

physical  

link  

network  

P4  

transport  

applica:on  

physical  

link  

network  

P3  

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How  demul:plexing  works  •  Host  receives  IP  datagrams  

–  Each  datagram  has  source  IP  address,  des:na:on  IP  address  

–  Each  datagram  carries  one  transport-­‐layer  segment  

–  Each  segment  has  source,  des:na:on  port  number    

•  Host  uses  IP  addresses  &  port  numbers  to  direct  segment  to  appropriate  socket  

source  port  #   dest  port  #  32  bits  

applica:on  data    (payload)  

other  header  fields  

TCP/UDP  segment  format  

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Connec:onless  demul:plexing  •  Recall:  created  socket  can  specify  host-­‐local  port  #:  

DatagramSocket  mySocket1                =  new  DatagramSocket(12534);  

   

•  When  host  receives  UDP  segment:  –  Checks  des:na:on  port  #  in  segment  

–  Directs  UDP  segment  to  socket  with  that  port  #  

IP  datagrams  with  same  des+na+on  port  #,  but  different  source  IP  addresses  and/or  source  port  numbers  will  be  directed  to  same  socket  at  des:na:on  

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•  Recall:  when  crea:ng  datagram  to  sent  into  UDP  socket,  must  specify:  –  Des:na:on  IP  –  Des:na:on  port  #  

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Connec:onless  demux:  example  

DatagramSocket  serverSocket  =  new  DatagramSocket  (6428);  

transport

application

physical

link

network

P3 transport

application

physical

link

network

P1

transport

application

physical

link

network

P4

DatagramSocket  mySocket1  =  new  DatagramSocket  (5775);  

DatagramSocket  mySocket2  =  new  DatagramSocket  (9157);    

source port: 9157 dest port: 6428

source port: 6428 dest port: 9157

source port: ? dest port: ?

source port: ? dest port: ?

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Connec:on-­‐oriented  demux  •  TCP  socket  iden:fied  by  4-­‐tuple:    –  Source  IP  address  –  Source  port  number  –  Dest  IP  address  –  Dest  port  number  

•  Demux:  receiver  uses  all  four  values  to  direct  segment  to  appropriate  socket  

•  Server  host  may  support  many  simultaneous  TCP  sockets:  –  Each  socket  iden:fied  by  its  own  4-­‐tuple  

•  Web  servers  have  different  sockets  for  each  connec:ng  client  –  Non-­‐persistent  HTTP  will  have  different  socket  for  each  request  

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Connec:on-­‐oriented  demux:  example  

transport  

applica:on  

physical  

link  

network  

P3  transport  

applica:on  

physical  

link  

P4  

transport  

applica:on  

physical  

link  

network  

P2  

source  IP,port:  A,9157  dest  IP,  port:  B,80  

source  IP,port:  B,80  dest  IP,port:  A,9157  

host:  IP  address  A  

host:  IP  address  C  

network  

P6  P5  P3  

source  IP,port:  C,5775  dest  IP,port:  B,80  

source  IP,port:  C,9157  dest  IP,port:  B,80  

Three  segments,  all  des:ned  to  IP  address:  B,    dest  port:  80  are  demul:plexed  to  different  sockets  

server:  IP  address  B  

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Connec:on-­‐oriented  demux:  example  

transport  

applica:on  

physical  

link  

network  

P3  transport  

applica:on  

physical  

link  

transport  

applica:on  

physical  

link  

network  

P2  

source  IP,port:  A,9157  dest  IP,  port:  B,80  

source  IP,port:  B,80  dest  IP,port:  A,9157  

host:  IP  address  A  

host:  IP  address  C  

server:  IP  address  B  

network  

P3  

source  IP,port:  C,5775  dest  IP,port:  B,80  

source  IP,port:  C,9157  dest  IP,port:  B,80  

P4  

threaded  server  

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Why  use  UDP?  •  Provides:  

–  Lightweight  communica:on  between  processes  –  Avoid  overhead  and  delays  of  ordered,  reliable  delivery  –  Precise  control  of  when  data  is  sent  

•  As  soon  as  app  writes  to  socket,  UDP  packages  and  sends  –  No  delay  establishing  a  connec:on  –  No  connec:on  state,  scales  to  more  clients  –  Small  packet  overhead,  header  only  8  bytes  long  

•  Does  not  provide:  –  Flow  control  –  Conges:on  control  –  Retransmission  on  error  

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UDP  checksum  

Sender:  •  Treat  segment  contents,  

including  header  fields,    as  sequence  of  16-­‐bit  integers  

•  Checksum:  addi:on  (one’s  complement  sum)  of  segment  contents  

•  Sender  puts  checksum  value  into  UDP  checksum  field  

 

Receiver:  •  Compute  checksum  of  

received  segment  •  Check  if  computed  

checksum  equals  checksum  field  value:  –  NO  -­‐  error  detected  –  YES  -­‐  no  error  detected.  But  maybe  errors  nonetheless?  More  later  ….  

Goal:  detect  errors  (e.g.  flipped  bits)  in  transmiped  segment  

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Internet  checksum:  example  

Example:  add  two  16-­‐bit  integers  

1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 1 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 0 0 1 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

wraparound  

sum  checksum  

Note:  when  adding  numbers,  a  carryout  from  the  most  significant  bit  needs  to  be  added  to  the  result    

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Internet  checksum:  example  

Receiver,  check  by  adding  data  and  checksum:  

1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 1 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 1 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 1

checksum  

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data  2  data  1  

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

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UDP  checksums  •  UDP  checksum  

– Add  up  16-­‐bit  words  in  one's  complement  – Take  one's  complement  of  the  sum  – Done  on  UDP  header,  data,  IP  pseudo-­‐header  

•  Helps  detect  misdelivered  packets  •  Violates  layers,  looking  into  network  layer  

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UDP  header   IP  pseudo-­‐header  

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Type  of  UDP  apps,  part  1/3  •  Simple  query  protocols    

– Overhead  of  connec:on  establishment  is  overkill  – Easier  to  have  applica:on  retransmit  if  needed  – e.g.  DNS,  UDP  port  53  

– e.g.  DHCP,  UDP  port  67/68  

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”www.cnn.com?”

“12.3.4.15”

DHCPDISCOVER

“192.168.1.30”

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Type  of  UDP  apps,  part  2/3  •  Request/reply  style  interac:on  

– Client  sends  request  to  server  •  Blocks  while  wai:ng  for  reply  

– Server  responds  with  reply  – Must  deal  with:  

•  Iden:fy  process  that  can  handle  request  

•  Possible  loss  of  request  or  reply  •  Correlate  request  with  reply  

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Request/reply  example  •  Remote  Procedure  Call  (RPC)  

– Request/reply  paradigm  over  UDP  – Allow  programs  to  call  procedures  located  on  a  remote  host  

–  Invisible  to  the  applica:on  programmer  •  Client  code  blocks  while  request  made  and  response  waited  for  from  remote  host  

– Object-­‐oriented  languages:  •   Remote  Method  Invoca:on(RMI),  e.g.  Java  RMI  

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Type  of  UDP  apps,  part  3/3  •  Mul:media  streaming  

– e.g.  Voice  over  IP,  video  conferencing  – Time  is  of  the  essence  

•  By  :me  packet  is  retransmiped,  it's  too  late!  •  Interac:ve  applica:ons:  

–  Human-­‐to-­‐human  interac:on  –  e.g.  conference,  first-­‐person  shooters  

•  Streaming  applica:ons:  –  Computer-­‐to-­‐human  interac:on    –  Video,  audio  streaming    

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Summary  •  Transport  layer  

– Providing  end-­‐to-­‐end  process  communica:on  •  Port  numbers  allow  mul:ple  processes  per  host  

– Provide  reliable  transport  on  best-­‐effort  network  •  User  Datagram  Protocol  (UDP)  

– Lightweight  protocol  running  on  top  of  IP  – Three  typical  classes  of  applica:ons:  

•  Simple  queries  (DNS,  DHCP)  •  Request/reply  seman:cs  (RPC)  •  Real-­‐:me  data  (Skype)  

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Oligozoospermia kc001 udp

Oligozoospermia kc001 udp

Udp Programming

Udp Programming

Chap 11 udp

Chap 11 udp

Chapter 3 Transport Layer - Land · Transport Layer 3-3 Chapter 3 outline 3.1 Transportlayer services 3.2 Multiplexing and demultiplexing 3.3 Connectionless transport: UDP 3.4 Principles

Chapter 3 Transport Layer - Land · Transport Layer 3-3 Chapter 3 outline 3.1 Transportlayer services 3.2 Multiplexing and demultiplexing 3.3 Connectionless transport: UDP 3.4 Principles

UDP & TCP Where would we be without them!. UDP User Datagram Protocol.

UDP & TCP Where would we be without them!. UDP User Datagram Protocol.

UM1713 User manual - st.com · 6.1.3 UDP echo client ... 6.1.5 UDP TCP echo server based on netconn AP ... • UDP (User Datagram Protocol)

UM1713 User manual - st.com · 6.1.3 UDP echo client ... 6.1.5 UDP TCP echo server based on netconn AP ... • UDP (User Datagram Protocol)

udp glcnac

udp glcnac

UDP Sockets Chap 8, 14, 22. Elementary UDP Sockets Chap 8.

UDP Sockets Chap 8, 14, 22. Elementary UDP Sockets Chap 8.

€TCP/UDP Port Numberspsanchez/Distro_2012... · 19 tcp, udp chargen Character Generator; alias=ttytst source 20 tcp, udp ftp-data File Transfer [Default Data] 21 tcp, udp ftp File

€TCP/UDP Port Numberspsanchez/Distro_2012... · 19 tcp, udp chargen Character Generator; alias=ttytst source 20 tcp, udp ftp-data File Transfer [Default Data] 21 tcp, udp ftp File

DataStorageManagementinCloudEnvironments: … · DataStorageManagementinCloudEnvironments: Taxonomy,Survey,andFutureDirections ... Document-based ... •Transportlayer ...

DataStorageManagementinCloudEnvironments: … · DataStorageManagementinCloudEnvironments: Taxonomy,Survey,andFutureDirections ... Document-based ... •Transportlayer ...

Transport Layer (UDP)

Transport Layer (UDP)

31. Performance Comparison of transport protocols, UDP and UDP

31. Performance Comparison of transport protocols, UDP and UDP

Introducingan almost reliable UDP protocol: TheKeyed UDP · Introducingan almost reliable UDP protocol: TheKeyed UDP Nuno M. Garcia, PhD Coordinator of Assisted Living Computing and

Introducingan almost reliable UDP protocol: TheKeyed UDP · Introducingan almost reliable UDP protocol: TheKeyed UDP Nuno M. Garcia, PhD Coordinator of Assisted Living Computing and

UDP Server

UDP Server

Tcp Udp Notes

Tcp Udp Notes

Integrating Bulk-DataTransfer into the Aurora Distributed ...paullu/Aurora/Papers/bulk-data.jpdc... · Communication mechanisms (shared memory, MPI, UDP sockets) Table 1: Layered

Integrating Bulk-DataTransfer into the Aurora Distributed ...paullu/Aurora/Papers/bulk-data.jpdc... · Communication mechanisms (shared memory, MPI, UDP sockets) Table 1: Layered

TransportLayer TCP UDP

TransportLayer TCP UDP

FindingClusteringConfigurationstoAccurately ... · FindingClusteringConfigurationstoAccurately InferPacketStructuresfromNetworkData ... transportlayer ,networklayer and ... rd Annual

FindingClusteringConfigurationstoAccurately ... · FindingClusteringConfigurationstoAccurately InferPacketStructuresfromNetworkData ... transportlayer ,networklayer and ... rd Annual

UDP Programme

UDP Programme

layertechniques transport UDP-Lite a · A. TransportLayer: UDP-Lite ... However, the UDPLite document mandates the use ofpartial header checksum by the link. Unequal Error Protection

layertechniques transport UDP-Lite a · A. TransportLayer: UDP-Lite ... However, the UDPLite document mandates the use ofpartial header checksum by the link. Unequal Error Protection