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Cap. 3 (Commer). 3.1 Introduccion  Reunir distintas tecnologias de red dentro de un todo coordinado.  Esquema que esconde los detalles del hardware.

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Presentation on theme: "Cap. 3 (Commer). 3.1 Introduccion  Reunir distintas tecnologias de red dentro de un todo coordinado.  Esquema que esconde los detalles del hardware."— Presentation transcript:

1 Cap. 3 (Commer)

2 3.1 Introduccion  Reunir distintas tecnologias de red dentro de un todo coordinado.  Esquema que esconde los detalles del hardware subyacentes de red a la vez que proporciona servicios universales de comunicacion.  La interconexion trata de ocultar detalles de la red.  Enfoques de Interconectividad:  Nivel Aplicación  Nivel red

3 Nivel Red en Internet  Provee transportación mejor-esfuerzo para transmitir datagramas (paquetes) de la fuente al destino. La fuente y el destino puede estar en la misma red o en diferentes redes.

4 Environment (Medio Ambiente): Enlace Datos Red: re-dirección Físico Transporte Sesión Presentación Aplicación Red: re-dirección Actualizacion de Tablas Enlace Datos Red: re-dirección Físico Transporte Sesión Presentación Aplicación Enlace Datos Físico Red: re-dirección Actualizacion de Tablas Enlace Datos Físico Red: re-dirección Actualizacion de Tablas Enlace Datos Físico Red: re-dirección Actualizacion de Tablas Enlace Datos Físico Red: re-dirección Actualizacion de Tablas Enlace Datos Físico

5 Nivel Red en Internet  A nivel red Internet es una colección de subredes, conocidos como sistemas autónomos (AS de sus siglas en inglés) conectados.  El cemento que une estas redes es el nivel red (IP internetwork Protocol).

6 Environment Backbone de USA Backbone de Europa Líneas trasatlánticas rentadas Red Regional Red Nacional Backbone de ASIA Líneas trasatlánticas rentadas Red Universitaria Red de una Companía Red Regional Red Local

7 Cap. 4 (Forouzan)

8 IP Addressing:  La dirección IP tiene 32 bits de longitud escritos como 4 octetos.  Dos dispositivo NUNCA pueden tener la misma dirección IP, pero un dispositivo puede tener MAS de una dirección IP (multihomed device).  La dirección IP representa localizaciones, NO nombres de dispositivos.  La dirección IP tiene dos partes: netid y hostid.  Una dirección IP se expresa como 4 conjuntos de 8 bits separados por un “.”  Por facilidad, se utiliza la notación “dotted-decimal” para expresar la dirección

9 Direccionamiento en IP Clase A (8,24): 256 redes y 2 24 hosts. Clase B (16,16): 32,527 redes y 32,527 hosts. Clase C (24,8): 2 24 redes y 256 hosts. Clase D (4,28) a a a a Rango de Direcc. de los hosts. Clase E (4,28) a

10 Sample Internet To the rest of the internet GG R R... x.y.z.t

11 Number of Networks and hosts in each class ClassNumber of Networks Number of Hosts A B C DNo aplica (direcciones especiales) ENo aplica(reservadas)

12 Direcciones Especiales Special Address NetidHostidComment Network address Specific All 0’s Network itself is considered an entity with an IP address. Direct Broadcast address. Specific All 1’s It used by a router to send a packet to all hosts in a specific network. Limited Broadcast address. All 1’s A host which wants to send a packet to every other host in the current network. (Actually a class E address). The router block this packet to confine the broadcasting to the local network. This Host on this network All 0’s Used by a host at bootstrap time when it does not know its IP address. At this time, the host send this address as source address and a limited Broadcast addr. as destination address. (Actually a class A address) Specific host on this network All 0’s SpecificIt used by a host to send a packet to a another host on the same network. (Actually a class A address) Loopback address 127Any It used by a host to send a packet to itself. (Actually a class A address). Used to test software.

13 Direcciones Multicast por Categoría AddressGroup Reserved All SYSTEMS on this SUBNET All Routers on this SUBNET DVPRM ROUTERS OSPFIGP all ROUTERS OSPFIGP Designeted ROUTERS ST Routers ST Hosts RIP2 Routers IGRP Routers Mobile-Agents

14 Direcciones Multicast para Conferencia AddressGroup AUDIONEWS IETF-1-LOW-AUDIO IETF-1-AUDIO IETF-1-VIDEO IETF-2-LOW-AUDIO IETF-2-AUDIO IETF-2-VIDEO MUSIC-SERVICE SEANET-TELEMETRY SEANET-IMAGE

15 Private Networks  Issues: 1. Apply for a unique address and use it without being connected to internet. 1. Advantage: Future Integration to internet without hassle. 2. Disadvantage: Almost imposible to obtain a class A o B addresses these days.. 2. Use any class address without registering it with the internet authorities.  Advantage: They can be used without permission.  Disadvantage: The address does not have to be unique. (Confusion).  Solution:  Internet authorities have reserved a block of addresses:  Advantage:  They can be used without permission.  veryboy know that these addresses are for private networks. They are unique inside of the organization.

16 Number of Networks and hosts in each class ClassNumber of NetworksTotal A B to C to

17 Exercises:  Identify the class of the following IP address: A. class A B. class B B. classC D. Class D  Identify the class of the following IP address: A. class A B. class B B. classC D. Class  Identify the class of the following IP address: A. class A B. class B B. classC D. Class D

18 Exercises:  Identify the class of the following IP address: A. class A. B. class B. B. C. class D. Class  What of the following is a source IP address: A. This host on this network. B. limited broadcast address. B. Loopback address D. specific host on this network.  Using the limited broadcast address, a ______ sends a packet to ______ on the network: A. host; all other hosts. B. router; all other routers. B. host; a specific host D. host; itself

19 Exercises :  What destination address can be used to send a packet from a host with IP address to all hosts on the network. A B B D. b and c.  A host with address needs to test internal software. What is the destination address in the packet: A B B D. all the above  A packet send form a node with IP address to all nodes on network requires a _____address. A. unicast B. multicast B. broadcast D. a or b

20 Exercise 1: Find 7 errors To the rest of the internet GG R R... x.y.z.t

21 Cap. 5 (Forouzan)

22 Subnetting and Supernetting  IP addressing works with two levels of hierachy (netid, hostid), when the two levels of hierachy are not enough, then we can use either:  Subnetting:  Network is divided into several smaller subnetworks with each subnetwork having its own subnetwork address.  The rest of the Internet is not aware of the change.  The router knows how to route packets in the subnet.  Supernettting:  Class C address are stil available.  Combination of several class C addresses to create a larger range of addresses.  The rest of the Internet is not aware of the change.

23 l1l1 l2l2 l3l3 l4l4 l5l5 l6l6 A B C D E l1l1 l2l2 l3l3 l4l4 l5l5 l6l6 a b c d Subnet: l1l1 l2l2 l3l3 l4l4 l5l5 l6l6 a b c d e F G l7l7 R1 Class B Rest of Internet Subnet

24 Subnet (Subred)  Example: Clase B (16,6,10): 32,527 redes, 62 subredes y 1,024 hosts a Rango de Direcc. de los hosts. Clase B (16,10,6): 32,527 redes, 1024 subredes y 64 hosts a Rango de Direcc. de los hosts.

25 Masking  Operation to obtain the subnettwork address from an IP address.  Mask: 32-bit number, diviedn in two parts:  The bits in the mask containing 1s defines the netid or combination of netid and subnetid.  The part of the 0s define the hostid  To get the subnet address, the router applys the bit-wise-and operation on the IP address and the mask.  Ejemplo: Si se pidieron prestados 8 bits al campo del “host”, entonces la máscara seria:

26 Special Address in Subnetting Special Address NetidHostidComment Subnetwork address Specific All 0’s Subnetwork itself is considered an entity with an IP address. Direct Broadcast address. Specific All 1’s It used by a router to send a packet to all hosts in a specific subnetwork. Limited Broadcast address. All 1’s A host which wants to send a packet to every other host in the current subnetwork. (Actually a class E address). The router block this packet to confine the broadcasting to the local subnetwork. This Host on this subnetwork All 0’s Used by a host at bootstrap time when it does not know its IP address. At this time, the host send this address as source address and a limited Broadcast addr. as destination address. (Actually a class A address) Specific host on this subnetwork All 0’s SpecificIt used by a host to send a packet to a another host on the same subnetwork. (Actually a class A address) Loopback address 127Any It used by a host to send a packet to itself. (Actually a class A address). Used to test software.

27  Example: Mask: Result:

28 l1l1 l2l2 l3l3 l4l4 l5l5 l6l6 A B C D E l1l1 l2l2 l3l3 l4l4 l5l5 l6l6 a b c d Subnet: l1l1 l2l2 l3l3 l4l4 l5l5 l6l6 a b c d e F G l7l7 R1 Supernet Rest of Internet Class C

29 Subnets  Example: Class C (22,2,8): 2 22 nets, 4 supernets y 256 hosts a Clase C (20,4,8): 2 20 nets, 16 supernet y 256 hosts a

30 Masking  Operation to obtain the subnettwork address from an IP address.  Mask: 32-bit number, divied in two parts:  The bits in the mask containing 1s defines the supernetid.  The part of the 0s define the hostid.  To get the supernet address, the router applys the bit-wise-and operation on the IP address and the mask.  Ejemplo: Si se pidieron prestados 2 bits al campo del “host”, entonces la máscara seria:

31  Example: Mask: Supernet:

32 Sample Internet To the rest of the internet G G R R... x.y.z.t

33 Exercises :  In Fig. 5.2, what is the mask for the network. A C B D. none of the above  A device has the IP address What is the subnetid? A. 1 C. 2 B. 3 D. insufficient information to answer.  Which of the followng is the defaul mask for the address: ? A C B D

34 Exercises:  What class of IP address does the subnet mask operate on? A. class A. C. class B. B. class C D. class A,B or C.  The subenet mask for a class C network is How many subnetworks are available? (Disregard special address): A. 2 C. 4 B. 8 D. 192  A supernet mask is How many class C networks were combined to make this supernet: A. 2 C. 4 B. 6 D. 8

35 Cap. 7 (Forouzan)

36 IP datagram VerHLEN Service Type Total_Length=header+Data_length PRE TOS IdentificationFlags Fragmentation Offset Time to Live=#HopsProtocol(TCP, UDP...) Header Checksum Source IP address Destination IP address Option (0-40 bytes) Data

37 Types of Service TOS bitsDescription 0000Normal (Default) 0001Minimize Cost 0010 Maximize reliability 0100 Maximize Throughput 1000Minimize Delay

38 Default TOS ProtocolTOS bitsDescription ICMP0000Normal IGP0010Maximize Reliability SNMP0010Maximize Reliability TELNET1000Minimize Delay FTP (data)0100Maximize Throughput FTP (control)1000Minimize Delay SMTP (data)0100Maximize Throughput SMTP (control)1000Minimize Delay

39 IP datagram: Fragmentation Control bits VerHLEN Service Type Total Length PRE TOS Identification Flags Fragmentation Offset DM Time to LiveProtocolHeader Checksum Source IP address Destination IP address Option Data

40 Figure 7-7

41 Figure 7-8

42 IP datagram: Options VerHLEN Service Type Total Length IdentificationFlags Fragmentation Offset Time to LiveProtocolHeader Checksum Source IP address Destination IP address Code Length (code+length+Hdata) HData CpCssNumber Data

43 Record Route Option VerHLEN Service Type Total Length IdentificationFlags Fragmentation Offset Time to LiveProtocolHeader Checksum Source IP address Destination IP address Code Length Pointer IP addresses Data

44 Figure 7-14

45 Strict Source Route Option VerHLEN Service Type Total Length IdentificationFlags Fragmentation Offset Time to LiveProtocolHeader Checksum Source IP address Destination IP address Code Length Pointer IP addresses Data

46 Figure 7-16

47 Loose Source Route Option VerHLEN Service Type Total Length IdentificationFlags Fragmentation Offset Time to LiveProtocolHeader Checksum Source IP address Destination IP address Code Length Pointer IP addresses Data

48 Timestamp Option VerHLEN Service Type Total Length IdentificationFlags Fragmentation Offset Time to LiveProtocolHeader Checksum Source IP address Destination IP address Code LengthPointerO-Flow Flags IP addresses and timestamp to be stored Data

49 Figure 7-19

50 Figure 7-20

51 Checksum VerHLEN Service Type Total Length PRE TOS IdentificationFlags Fragmentation Offset Time to LiveProtocolHeader Checksum Source IP address Destination IP address Option Data

52 Figure 7-23

53 Fragmentation  Useful when a datagram travel through different networks.  MTU (Maximum Transfer Unit) is the maximum length of data that can be encapsulated in a frame.  If a datagram is fragmented is fragment, it becomes to be a new datagram.  When a datagram is fragmented, requires part of the header to be copied by all fragments.

54 MTUs for Different Networks ProtocolMTU Hyperchannel65,535 Token Ring (16 Mbps) 17,914 Token Ring (4 Mbps) 4,464 FDDI 4,532 X PPP 296

55 No fragmentation needed. IP Datagram HeaderMTUTrailer

56 No fragmentation needed. IP Datagram H MTUT H T H T H T H T H T

57 When a host or router process a frame VerHLEN Service Type Total Length IdentificationFlags Fragmentation Offset Time to LiveProtocolHeader Checksum Source IP address Destination IP address Option Data

58 Figure 7-24

59 Figure 7-25

60 Figure 7-26

61 Cap. 6 Forouzan

62 Servicios Servicio con Confirmación Servicio sin Confirmación Servicio Orientado a Conexión Conexión Datos Desconexión Servicio NO Orientado a Conexión TCP, Ethernet, Frame Relay Ethernet UDP, IP, Ethernet X.25

63 Direct vs. Indirect Delivery

64 Routing Methods

65 Static vs. Dynamic Routing  Static Routing:  The administrator enter the route for each destination into the table manually.  Not updated automatically.  Used in small networks that do not change frequently.  Dynamic Routing:  Updated periodically using Dynamic Routing Protocols: RIP, OSPF, BGP

66 Routing Module Receive: an IP packet 1. For each entry in the routing table 1. Apply the mask to packet destination address 2. If (the mask matches the value in the destination field) 1. If (the G flag is absent) 1. Use packet destination address as next hop address 2. Send packet to fragmentation module with next hop address 3. Return 2. If no match is found, send an ICMP error message. 3. Return. Routing Table

67 Example: Routing table for router R1 MaskDestinationNext HopF.R.C.U.I U00m U00m U00m1 …………… UGH00m UG00m UG00m UG00m0

68 When R1 receives a packet for destination: MaskDestinationNext HopF.R.C.U.I U00m U00m U00m1 …………… UGH00m UG11m UG00m UG00m Address AND Mask Match? No No No No Match!! Increase by 1, if other packet with the same destination reach this router.

69 When R1 receives a packet for destination: MaskDestinationNext HopF.R.C.U.I U00m U11m U00m1 …………… UGH00m UG00m UG00m UG00m Address AND Mask Match ? No Match! Increase by 1, if other packet with the same destination reach this router.

70 When R1 receives a packet for destination: MaskDestinationNext HopF.R.C.U.I U00m U00m U00m1 …………… UGH00m UG00m UG00m UG11m Address AND Mask Match? No No No No No No Match! Increase by 1, if other packet with the same destination reach this router.

71 Chapter 8 ARP and RARP

72 Static vs. Dynamic Mapping Static Table Static Table

73 ARP (Address Resolution Protocol)

74 NL-1: Sender knows the IP address of the target. NL-2: IP ask ARP to create a request ARP message. DLL: encapsulated using broadcast address in the destination field. NL-1: recognise the IP address. NL-2: IP ask ARP to create a reply ARP message with its physical address. DLL: encapsulated using unicast address in the destination field. NL-1: Recives the destination phyisical address

75 ARP packet (Physical Address Length) (Logical Address Length) (i.e. IPv4=0800H) (i.e. Ethernet=1)

76 Encapsulation in an Ethernet frame

77 Figure 8-5, Part I

78 Figure 8-5, Part II

79 Proxy ARP

80 Figure 8-7 Sleep Pending IP_RE/srq RRP ( updates the cache table ) RRQ ( if I am not the destination, only updates table ) RRQ/srp IP_RE ( if solved in the cache )

81 Original Cache Table used for the examples State QueueAttempt Time-outProtocol Address Hardware Address R ACAE P P R ACAE32 P F R E3242ACA P

82 Example: ARP output module receive and IP datagram with address: State QueueAttempt Time-outProtocol Address Hardware Address R ACAE P P R ACAE32 P F R E3242ACA P

83 Example: ARP output module receive and IP datagram with address: State QueueAttempt Time-outProtocol Address Hardware Address R ACAE P P R ACAE32 P P F R E3242ACA P

84 Example: ARP input module receive and IP datagram with address: and Hardware Address: E ACA State QueueAttempt Time-outProtocol Address Hardware Address R ACAE P P R ACAE32 P P F R E3242ACA R E ACA

85 Example: The cache-control updates every entry. The time-out values is decremented by 60. State QueueAttempt Time-outProtocol Address Hardware Address R ACAE P F R ACAE32 P P F F R E ACA

86 RARP  Why RARP?

87 RARP

88 RARP Packet (Physical Address Length) (Logical Address Length) (i.e. IPv4=0800H) (i.e. Ethernet=1)

89 RARP in an Ethernet Frame

90 1. In a _______ protocol associates a logical address with a phyisical address. A. Static mapping C. physical mapping B. Dynamic mappingD. a and b 2. The _______ is a dynamic mapping protocol in which a logical address is found for a given physical address. A. ARPC. ICMP B. RARPD. none of the above 3. A router reads the _______ address on a packet to determine the next hop? 1. LogicalC. Source 2. PhysicalD. ARP 4. A ARP reply is_______ to _______. 1. broadcast;all hostsC. unicast; all hosts 2. multicast; all hostsD. unicast; one host

91 Chapter 9 Internet Control Message Protocol (ICMP)

92 ICMP (Internet Control Message Protocol)  Internet does not have  Error Control mechanism  Flow Control mechanism  Assistant Mechanism  ICMP compensate this two problems.

93 ICMP Position in the network layer.

94 ICMP encapsulation

95 ICMP Format

96 Types of Messages TypeMessage 3Destination Unreachable 4Source quench (“ flow Control ”) 11Time exceeded 12Parameter Problem 5Redirection TypeMessage 8 or 0Echo request or reply 13 or 14 Timestamp request or reply 17 or 18 Address mask request or reply 10 or 9 Router solicitation and advertisement

97 Types of Error Report Messages

98 Contents of data-field for the error message

99 Destination Unreachable 0Nework Unreachable8Source Host isolated 1Host Unreachable9Destination network prohibited. 2Protocol Unreachable10Destination host prohibited 3Port Unreachable11Network unreachable for the requested TOS. 4Fragmentation required12Host unreachable for the requested TOS 5Source Routing can’t be accomplished. 13Destination host filtered out. 6Destination Network Unknown14Host precedence violated. 7Destination host Unknown15IP precedence lower the network precedence level.

100 Source quenche (“flow control”)  A message is send for every datagram is discarded by a router or the destination host.

101 Time Exceeded 0Number of hops exceeded 1Final destination does not receive all the fragments.

102 Parameter Problem 0Error or ambiguity in one of the header fields 1Required part of an option I missed.

103 Redirection  A host usually start with a small routing table that is gradually augmented and updated. One of the tools to accomplish this is the redirection message.

104 Format 0Redirection for the network-specific route. 1Redirection for host-specific route. 2Redirection for network-specific route based on the specified TOS. 3Redirection for the host-specific route based on the specified TOS.

105 Types of Query Messages  Used to diagnose some network problems.

106 Echo Request and Reply  For diagnostic purposes.  Test if  there is communication at the IP level.  an intermediate router is receiving, processing and forwarding packets.  another host is reachable (ping-packet internet groper).  The identification and sequence number field are not formally defined, and can be used arbitrarily by the sender.

107 Timestamp Request and Reply  Used for:  Round-trip time  Sincronize clocks

108 Round-trip calculation

109 Example:

110 Syncronize Clocks

111 Example:

112 Address Mask Request and Reply  To identify network address, subnetwork address and host identifier.

113 Router Solicitation and Advertisement  In order that host knows the router connected to its network.  The host should know if the router is alive.

114 Router Solicitation and Advertisement Solicitatio n Advertisme nt

115 Format  Solicitation:  Advertisement:

116 Checksum

117 Figure 9-20

118 1. If a host needs to syncronise its clock with another host, it sends a _____ message. A. timestamp-request C. router-advertisement B. Source-quencheD. time-exceeded 2. The purpose of the echo request and echo reply is to _______. A. Report errors B. Check node-to-node communication C. Check packet lifetime D. Find IP address. 3. Which field is always present in a ICMP package? A. TypeC. Checksum B. CodeD. all the above 4. When the hop-count field reaches zero and the destination has not been reached, a ______ error message is sent? A. Destination addressC. Parameter problem B. Time-excedeedD. redirection 5. Error in the header or option field of an IP datagram require a _____ error message. A. Parameter-problem C. router-solicitation B. Source-quencheD. redirection

119 6. The _____ packet contains information about a router. A. Router-solicitationC. router-advertisement B. Router-InformationD. router-reply. 7. Who can send ICMP error-reporting messages? A. RoutersC. Source hosts B. Destination hostsD. a and b 8. A time-exceeded message is generated if ______? A. The round-trip time is close to zero. B. The time-to-live field has a zero value. C. Fragments of a message do not arrive within a set time D. b and c 9. In calculating the time difference between two clocks, a negative value indicates _______. 1. An invalid calculation. 2. The source clock lags behind the destination clock. 3. The destination clock lags behind the source clock. 4. The one-way time has been miscalculated.


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