1 TCP/IP Internetting. 2 3 4 ä Subnet layer ä Links stations on same subnet ä Often IEEE LAN standards ä PPP for telephone connections ä TCP/IP specifies

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TCP/IP InternettingTCP/IP Internetting

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Subnet layerSubnet layer Links stations on same subnetLinks stations on same subnet

Often IEEE LAN standardsOften IEEE LAN standards

PPP for telephone connectionsPPP for telephone connections

TCP/IP specifies almost any subnet standardTCP/IP specifies almost any subnet standard

For LANs, etc., specifies OSIFor LANs, etc., specifies OSI

OSI further subdivides into Physical, Data LinkOSI further subdivides into Physical, Data Link

ApplicationApplication

TransportTransport

InternetInternet

SubnetSubnetData LinkData Link

PhysicalPhysical

TCP/IPTCP/IP OSIOSI

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Internet layer:Internet layer: Links stations across internetsLinks stations across internets

Main standard is the Internet Protocol (IP)Main standard is the Internet Protocol (IP)

Dominant protocol for routersDominant protocol for routers


TransportTransport

InternetInternet

SubnetSubnet

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Transport layer:Transport layer: Links computers, even if different platformsLinks computers, even if different platforms

Main standards are Transmission Control Protocol Main standards are Transmission Control Protocol (TCP) and User Datagram Protocol (UDP)(TCP) and User Datagram Protocol (UDP)

Application layer:Application layer: Links application programs even if from different Links application programs even if from different

vendorsvendors

Many standards, because many applicationsMany standards, because many applications

SMTP for e-mail; HTTP for the WWW, etcSMTP for e-mail; HTTP for the WWW, etc..


TransportTransport

InternetInternet

SubnetSubnet

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Universal AddressingUniversal Addressing

Each host has a unique IP NumberEach host has a unique IP Number 32-bit binary number32-bit binary number

Goes in the IP header’s source and destination fieldsGoes in the IP header’s source and destination fields

1000000010101011000100010000110110000000101010110001000100001101

Impossible to rememberImpossible to remember

DestinationDestinationSourceSource

IP PacketIP Packet 4 Bytes4 Bytes 4 Bytes4 Bytes

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99

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Subnet MaskSubnet Mask

Problem: IP numbers do not include subnettingProblem: IP numbers do not include subnetting

Solution: Create a second number: a Subnet MaskSolution: Create a second number: a Subnet Mask

Define which bits of the IP address refer to subnets Define which bits of the IP address refer to subnets vs. hosts on subnetvs. hosts on subnet

Subnet mask is 32 bits long, in dot quad formatSubnet mask is 32 bits long, in dot quad format

See the class meeting on See the class meeting on Windows TCP/IP Windows TCP/IP for for basic IP and Subnet Mask concepts.basic IP and Subnet Mask concepts.

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RoutersRouters

Routers also get IP addressesRouters also get IP addresses So packets can be sent to them for routingSo packets can be sent to them for routing Has network ID of the network on which it sitsHas network ID of the network on which it sits Must be assigned a host IDMust be assigned a host ID Example: 128.171.17.1Example: 128.171.17.1

DefaultRouter

IP Packetfor Delivery

Another Router

128.171.17.1128.171.17.1

128.171.17.104128.171.17.104

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RoutersRouters

Subnets can have Multiple RoutersSubnets can have Multiple Routers There is usually a default router for packet deliveryThere is usually a default router for packet delivery Default router is used if no router is specifiedDefault router is used if no router is specified Routers are sometimes called gateways in TCP/IPRouters are sometimes called gateways in TCP/IP

DefaultRouter

IP Packetfor Delivery

Other Router

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Routing Protocols

There are no “master” routers.

Each router works independently to do routing.

This requires each router to build a “routing table” thatcontains information about the locations of other routers.

There are no “master” routers.

Each router works independently to do routing.

This requires each router to build a “routing table” thatcontains information about the locations of other routers.

RoutingTable

RoutingTable

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Routing Protocols

Routing protocols allowrouters to exchangeinformation in theirrouting tables.

Routing protocols allowrouters to exchangeinformation in theirrouting tables.

RoutingTable

RoutingTable

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Peer Control Among RoutersPeer Control Among Routers

Routers Communicate Among ThemselvesRouters Communicate Among Themselves To coordinate their actions without central controlTo coordinate their actions without central control Share knowledge of network connectivityShare knowledge of network connectivity Common standards are RIP, OSPF, BGPCommon standards are RIP, OSPF, BGP

RouterCoordination

Message

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Routing ProtocolsRouting Protocols

RIP - RIP - Router Information ProtocolRouter Information Protocol High overhead, but simple and OK for small networksHigh overhead, but simple and OK for small networks

OSPF - OSPF - Open Shortest Path FirstOpen Shortest Path First Optimizes routing, but complexOptimizes routing, but complex

BGP - BGP - Border Gateway (Router) ProtocolBorder Gateway (Router) Protocol Used in Used in Internet BackboneInternet Backbone Routers Routers

Read Cisco routers for an overviewRead Cisco routers for an overview

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Autonomous Systems

AutonomousRouter

Border Router

RIPor

OSPF

RIPor

OSPF

BPG

Border Router

Organization can select anyrouting protocol to synchronizeits autonomous (internal)routers. RIP and OSPF arecommon.

Border routers that linkautonomous systems normallyuse BPG.

Autonomous System

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Error HandlingError Handling

TCP/IP a comprehensive set of error TCP/IP a comprehensive set of error handling processeshandling processes The Internet Control Message Protocol (ICMP) is used The Internet Control Message Protocol (ICMP) is used

to send error messages.to send error messages.

Hosts, Routers send ICMP messages to one another if a Hosts, Routers send ICMP messages to one another if a problem occursproblem occurs

““Host not found” is a common ICMP error message.Host not found” is a common ICMP error message.

Host

Router

ICMP Error Message

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Internet Control Message Protocol (ICMP)

The Internet Control Message Protocol (ICMP)is for delivering supervisory messagesamong hosts and routers

The Internet Control Message Protocol (ICMP)is for delivering supervisory messagesamong hosts and routers

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“Host Unreachable”

Error MessagesError Messages

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SourceQuench

Flow Control

“Source Quench” tells hostto reduce transmission rate.

Flow Control

“Source Quench” tells hostto reduce transmission rate.

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“EchoRequest”

“EchoResponse”

Source host can ask questions of destination hosts.

“Echo Request” asks if the other hostis reachable.

Destination host sends back “Echo Response.”

Usually implemented with “PingPing”program.

Source host can ask questions of destination hosts.

“Echo Request” asks if the other hostis reachable.

Destination host sends back “Echo Response.”

Usually implemented with “PingPing”program.

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AutoconfigurationAutoconfiguration

Autoconfiguration Server has a bank of addressesAutoconfiguration Server has a bank of addresses When a PC “logs in,” it gets a temporary IP numberWhen a PC “logs in,” it gets a temporary IP number..

Popular standards are DHCP (in Windows NT) and RARPPopular standards are DHCP (in Windows NT) and RARP

Large stations receive permanent addressesLarge stations receive permanent addresses

DHCP Request for Address

DHCP Response:Your Temporary Address is

127.171.17.35

DHCPServer

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Autoconfiguration Protocol

SourceHost

Auto-Configuration

Host

Source host sends Autoconfigutation RequestMessage to the autoconfiguration host

“My 48-bit MAC subnet address is X.Please give me a 32-bit IP host address.”

Autoconfiguration Request Message

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Autoconfiguration Protocol

SourceHost

Auto-Configuration

Host

Autoconfiguration host sends back aAutoconfiguration response message.

“Computer at MAC Address X,your 32-bit IP host number is ‘110100…’.”

Autoconfiguration Response Message

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Autoconfiguration ProtocolsAutoconfiguration Protocols

RARP: Reverse Address Resolution ProtocolRARP: Reverse Address Resolution Protocol Older autoconfiguration protocolOlder autoconfiguration protocol

BootpBootp Another older protocolAnother older protocol

DHCPDHCP Dynamic Host Configuration ProtocolDynamic Host Configuration Protocol

Built into Windows NT ServerBuilt into Windows NT Server

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Domain Name ServiceDomain Name Service

Hosts also have IP host namesHosts also have IP host names Voyager.cba.hawaii.eduVoyager.cba.hawaii.edu

Like nicknamesLike nicknames

IP packets require formal IP numbers to put in their IP packets require formal IP numbers to put in their source and destination fieldssource and destination fields

If tell your software the IP host name, it must look up If tell your software the IP host name, it must look up the IP numberthe IP number

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Domain Name ServiceDomain Name Service

Program knowing a host name sends Program knowing a host name sends request to Domain Name Service (DNS) request to Domain Name Service (DNS) Server; receives IP NumberServer; receives IP Number

DNS Request forVoyager.cba.hawaii.edu

DNS Response: 128.171.17.13

DNSServer

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Domain Name System (DNS)

SourceHost

DNSHostDNS Request Message

Source host sends DNS Request Message to DNS host.“I need the 32-bit IP host number for the host namedvoyager.cba.hawaii.edu.”

Source host sends DNS Request Message to DNS host.“I need the 32-bit IP host number for the host namedvoyager.cba.hawaii.edu.”

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SourceHost

DNSHost

DNSHost

DNS Response Message

DNS host returns a DNS Reply Message.“The 32-bit host number is 128.171.44.53”.

DNS host returns a DNS Reply Message.“The 32-bit host number is 128.171.44.53”.

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SourceHost

DNSHost

DNSHost

Each network has a DNS host May also have a secondary DNS host Network DNS host may only know theIP names and numbers of local hosts onthe network For other IP names, contacts anotherDNS host, especially root DNS hosts,which should have extensive information

Each network has a DNS host May also have a secondary DNS host Network DNS host may only know theIP names and numbers of local hosts onthe network For other IP names, contacts anotherDNS host, especially root DNS hosts,which should have extensive information

Documents

1 TCP/IP Internetting. 2 3 4 ä Subnet layer ä Links stations on same subnet ä Often IEEE LAN standards ä PPP for telephone connections ä TCP/IP specifies