no slide titlebill/cnds2003_2004/cnds_unit06... · 2003-11-05 · data packet addresses converting...

Author: W.Buchanan. IP – The Address (1)

Unit 6


TTL=255

TTL=200

TTL=190TTL=170

TTL=50

TTL=25

TTL=12

TTL stops thedata packet from transversingthe Internet forever.

TTL=255

TTL=200

TTL=190TTL=170

TTL=50

TTL=25

TTL=12


IP


Mobile Networks (Unit 10)

Switches/VLANs (Unit 5)

IP Addressing/Subnets (Unit 6) TCP/Socket Programming (Unit 7)

Router Programming (Unit 8) Routing Protocols (Unit 9)

Introduction (Unit 1)

Net Elements (Unit 2) Net Types (Unit 3) Net Design (Unit 4)


Application program

makes contact with network

application for e-mail

Application program

makes contact with network

application for e-mail

Application

Convert data into a form

which can be transmitted

Convert data into a form

which can be transmitted

Presentation

Contact remote system and request a transmission

Contact remote system and request a transmission

Session

Negotiate data transfer and

split data into segments

Negotiate data transfer and

split data into segments

Add source and

destination addresses

Transport

Add source and

destination addressesData packet

converting into a form which can be transmitted

over the network

Network

Data packet converting into a form which can be transmitted

over the network

Data link

The data frame is converted into

binary form and transmitted over a

physical connection

The data frame is converted into

binary form and transmitted over a

physical connection

Physical

E-mail application program

E-mail application program

Hello.Fred.

To: FredFrom: BertHello.Fred.

HELO sys.comFOR FredTo: FredFrom: BertHello.Fred.

Seg 1Seg 2Seg 3

Seg 1Addr

Seg 2Addr

Seg 3Addr

Seg 1AddrStart End

Data encapsulation

Seg 2AddrStart EndSeg 3AddrStart End


Network address

Edinburgh Castle,10 Princes Street,EdinburghEH1 1LZ

Physicaladdress

OS Grid Co-ordinate:03434, 75321

CityStreetPlace


Name:MyBookChapter: 1


Name:MyBookChapter: n

Address: 1 High St

Address: 1 High St

Address: 1 High St

I’m sending it,now.

I’m sending it,now.

What’s the maximumsize of the documentsthat can besent?Document is

split into chapters

Analogy

Sess

ion

Tran

spor

tN

etw

ork


SortingOffice

SortingOffice

SortingOffice

SortingOfficeSorting

OfficeSortingOffice

Network (Logical address)

Network

Data link

Physical

Throughout the networkaddress stays the same,but the physical addresschanges

Actual (Physical address)


Postal NetworkPostal Network SortingOffice

SortingOffice

SortingOffice

SortingOffice

The actual physical address is finallyresolved

Only at the end does the physical address and the logical address have to be resolved.





Address: 1 High St

Address: 1 High St

Address: 1 High St

Document is reassembled

Analogy

Thanks. I’ve received it.

Thanks. I’ve received it.Se

ssio

nTr

ansp

ort

Net

wor

k


InternetInternet

Only at the end does the physical address and the logical address have to be resolved.

Data segments (TCP)

Data packets (IP)

1 2

Ethernet

Analogy

The actual physical address is finallyresolved


IP and MAC Addresses

IP Src: IP1IP Dest: IP8MAC Src: MAC1MAC Dest: MAC2

MAC2, IP2

MAC5, IP5MAC6, IP6

MAC8, IP8

MAC1,IP1

MAC3, IP3

MAC4, IP4 MAC7, IP7




The IP addresses stay thesame but the MAC addresschanges


IP and MAC Addresses

MAC2, IP2

MAC5, IP5MAC6, IP6

MAC8, IP8

MAC1,IP1

[Gateway is the port of the router]

MAC3, IP3

MAC4, IP4 MAC7, IP7

ARP broadcasts

Each network segmentdetermines MAC addressesof gateways by sendingand ARP broadcast.


IP and TCP

NetworkNetwork

Data LinkData Link

PhysicalPhysical A router routes with the network address (such as the IP address)

IP address is used toroute data around the Internet

TCP part allows applications to communicate over the network


IP header

IPIP TCPTCP Higher-level protocol/dataHigher-level protocol/data Data Packet

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

32

32

16

VersionVersion Header lengthHeader length Type of serviceType of service

Total lengthTotal length

IdentificationIdentification

00 DD MM Fragment OffsetFragment Offset

Time-to-LiveTime-to-Live ProtocolProtocol

Header ChecksumHeader Checksum

Source IP AddressSource IP Address

Destination IP AddressDestination IP Address

Source IP address

Routersroute withthe destinationaddress

Destination IP address


IP header

IPIP TCPTCP Higher-level protocol/dataHigher-level protocol/data Data Packet (IPv4)

The firstthing that isread is theversion.

IPv4 usesa 32-bit address.

IPv6 usesa 32-bit address.









1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16


IP header


A datagram could propagate through the internet indefinitely. To prevent this, the 8-bit time-to-live value is set to the maximum transit time in seconds and is set initially by the source IP. Each gateway then decrements this value by a defined amount. When it becomes zero the datagram is discarded. It also defines the maximum amount of time that a destination IP node should wait for the next datagram fragment.









1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16


Time-to-live field

TTL=255

TTL=200

TTL=190TTL=170

TTL=50

TTL=25

TTL=12



IP header










Protocol (8 bits). Different transport protocols can be used on the datagram. The 8-bit protocol field defines the type to be used. E.g. 1 – ICMP and 6 – TCP.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16


IP can support many different upper-layer protocols

InternetInternet

Voice overIP

TCPUDP

NetBIOSover IP

ICMP(ping,tracert)

IPX/SPXover IP

The Internet can supportmany different higher-layer protocols, not just TCP


IP header

IPIP TCPTCP Higher-level protocol/dataHigher-level protocol/data Data Packet (IPv4)


Total lengthTotal lengthVery basicChecksum.

Thus, thereIs very littleerror checking/verification.







1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16


IP header










IPv4 addressIs 32 bits long.

- which onlyGives up to4 billion addresses (232)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16


32 bits

Network Host

1010101010101010 0101010101010101 0011001100110011 1100110011001100

8 bits

170170 8585 5151 204204Dottednotation(W.X.Y.Z)

Binarynotation

NET(0–127)NET(0–127) HOSTHOST HOSTHOST HOSTHOST

NET (128 – 191)NET (128 – 191) NETNET HOSTHOST HOSTHOST

NET (192 – 223)NET (192 – 223) NETNET NETNET HOSTHOST

Class A

Class B

Class C

IP address classifications


TCP/IP Intranet

PLUTO

OBERONDIONE

VENUS

Network B

MOON

JUPITERMERCURY

MARS

Network A

VAX01VAX02

ETHER C

RouterResponsible for examining IP address to determine if the TCP/IP packet must be routed out of the network, and the main network. Router must have two IP addresses as it is part of two network segments

RouterResponsible for examining IP address to determine if the TCP/IP packet must be routed out of the network, and the main network. Router must have two IP addresses as it is part of two network segments


IP Address Types

IP Address RangesNetwork Host

Class A: 1-126 0.0.1 to 255.255.254(127 networks) (16,711,680 hosts)

Class B: 128.1 to 191.254 0.1 to 255.254(16,320 networks) (65,024 hosts)

Class C: 192.0.1 to 223.255.254 1 to 254(2,088,960 networks) (255 hosts)





00

11 00

11 11 00

Network (7 bits) Node (24 bits)



Class A

Class B

Class C


TCP/IP Intranet

Network A[Network Number]


Network C[Network Number]

Network C[Network Number]

Network B[Network Number]


Network NumberNetwork Number Host NumberHost Number

IP address

w.x

w.x.y.z

GlobalnetworkGlobalnetwork

[Host Number]


TCP/IP Intranet with Subnets


Network A[Network Number] Network B

[Network Number]


Network NumberNetwork Number

IP address (Type B) PC419: 146.176.151.130

[Host Number]

Lab Block: 146.176.151Subnet A

[Subnet Number]

Subnet A[Subnet Number]

Subnet B[SubnetNumber]

Subnet B[SubnetNumber]

Subnet Number

Subnet Number

Host NumberHost

Number

Computing mainblock: 146.176.160

Napier: 146.176





W.X

W.X.Y

W.X.Y.Z

Typical Subnet masksClass A: 255.0.0.0Class B: 255.255.0.0Class C: 255.255.255.0

Typical Subnet masksClass A: 255.0.0.0Class B: 255.255.0.0Class C: 255.255.255.0

GlobalnetworkGlobalnetwork


Class A IP Address

Network 1Network 2

Network 3Network

NetworkNetwork

Class ANetwork: 1 - 126Host: 0.0.1 - 255.255.254

Few networks, and many hosts

1 16,711,680

Net. 127

Networks: Few

Networks: Many

InternetInternet










Class B IP Address

Network 1Network 2

Network 3Network

NetworkNetwork

Net. 16,320

Class BNetwork: 128.1 - 191.254Host: 0.1 - 255.254

Large number of networks, large number of host (althoughnot as many as Class A)

1 65,024

Networks: Average

Networks: Average

InternetInternet










Class C IP Address

Network 1Network 2

Network 3Network

NetworkNetwork

Net. 2,088,960

Class CNetwork: 192.0.1 - 223.255.254Host: 1 - 254

Large number of networks, and few hosts

1 255

Networks: Many

Networks: Few

InternetInternet










Network addresses, and broadcasting

32.0.0.0 (Class A network address).146.176.0.0 (Class B network address).199.20.30.0 (Class C network address).

32.255.255.255 (Class A broadcast into 32.0.0.0).146.176.255.255 (Class A broadcast into 146.176.0.0).199.20.30.255 (Class C broadcast into 199.20.30.0).

Network Addresses – The address used to represent the whole of a network

NetW.Z.0.0 Broadcast Addresses – All nodes on the

addressed network will listen to the transmission

NetW.Z.0.0

NetW.Z.Y.0

NetW.Z.Y.0

NetW.0.0.0

NetW.0.0.0

NetW.Z.0.0

NetW.Z.0.0


Subnetting masks for Class B addresses

Subnet address Dotted not. Max sub. Max hosts (/subnet)11111111.11111111.11000000.00000000 255.255.192.0 2 16382 11111111.11111111.11100000.00000000 255.255.224.0 6 819011111111.11111111.11110000.00000000 255.255.240.0 14 409411111111.11111111.11111000.00000000 255.255.248.0 30 204611111111.11111111.11111100.00000000 255.255.252.0 62 102211111111.11111111.11111110.00000000 255.255.254.0 126 51011111111.11111111.11111111.00000000 255.255.255.0 254 25411111111.11111111.11111111.10000000 255.255.255.128 510 12611111111.11111111.11111111.11000000 255.255.255.192 1022 6211111111.11111111.11111111.11100000 255.255.255.224 2046 3011111111.11111111.11111111.11110000 255.255.255.240 4094 1411111111.11111111.11111111.11111000 255.255.255.248 8190 611111111.11111111.11111111.11111100 255.255.255.252 16382 2

For example, if the network address is 144.32.0.0 andthe five bits are used for the subnet mask then:

The network 144.32.{00001} 000.0000 0000 is the first subnet – 144.32.8.0(node range 144.32.8.1 to 144.32.15.254)and 144.32.{11110} 000.0000 0000 is the last subnet – 144.32.240.0(node range 144.32.240.1 to 144.32.255.254)


Example Domain Naming Structure

salessalesresreswwwwww

necnecsonysonyintelintel

pc01pc01wwwwwwsun01sun01

mmsemmsedcsdcseeceeece

hwhwnapiernapiereded

orgorgacaccoco

www.sony.com

pc01pc01

pc01.eece.napier.ac.uk

frfrukukdedemilmilgovgovcomcomeduedu Primary domain

Example DNS mappingsDomain name IP addressweb.nec.com 143.101.15.6www.sony.com 198.83.178.11www.intel.com 134.134.214.1www.ieee.com 140.98.1.1

Example DNS mappingsDomain name IP addressweb.nec.com 143.101.15.6www.sony.com 198.83.178.11www.intel.com 134.134.214.1www.ieee.com 140.98.1.1


Domain name server

InternetInternetInternetInternet

Once WWW browser has theIP address of the destination,it can then access it

DNS returns back theIP address of thedomain name

WWW browser asksThe DNS for the IPaddress of the domainname

Domain nameserver

DNS may interrogateOther DNS’s toDetermine IP addresses


Allocating IP addresses

• Limiting access to the Internet. IP addresses can be mapped to MAC addresses. A node which requires an IP address will ask the IP granting server for an IP address. The server then checks the host’s MAC address to determine if it is allowed to access the Internet. If it is not, the server does not return an IP address. The system administrator can thus set up a table which only includes the hosts which are required to connect to the Internet.

• Authenticating nodes. A typical hacking method is to steal an IP address and use it for the time of a connection. This can be overcome by making all of the nodes on the network ask the IP granting server for their IP address. It is thus not possible to steal an address, as the IP granting server will check the MAC address of the host.

• Allocating from a pool of IP addresses. An organization may be granted a limited range of IP addresses which is not enough to allocate to all the nodes in the organization. The IP granting server can thus be set up to allocate IP addresses to nodes as they require them. When all the IP addresses have been allocated, no more IP addresses can be given out. When a node is finished with its IP address, the IP address that was granted to it can be put back in the pool when it is finished with it.

• Centralized configuration of IP addresses. The system manager can easily setup IP addresses to nodes from the central IP granting server.

• Barring computers from connecting to a network. Some networks are set up so that they must get a valid IP address before they can connect to the network (typically in Unix-type networks). The IP granting server will check the MAC address of the requester, if it is not allowed the server will not grant it an IP address.


University Network

ComputerStudiesRouter

146.176.160.1

ComputerStudiesRouter

146.176.160.1

MechanicalDepartment

Router146.176.129.1

MechanicalDepartment

Router146.176.129.1

ElectricalDepartment

Router146.176.151.254

ElectricalDepartment

Router146.176.151.254

146.176.160

Gateway146.176.1.3

Gateway146.176.1.3

InternetInternet

146.176.144146.176.145146.176.146146.176.150146.176.151


Example network

146.176.144

pc2 pc3

Dione

SaturnMercury

Earth

Pluto

Venus

Titan

Io

Phobos

Neptune

Ariel

Rhea

+Demos+Uranus

Oberon

Moon

Mimas

HP

VAX

Miranda

Triton

Vega(X)

Rigel(X)

Mwave

Intel

Leda

Castor

Pollux

Spica

Token Ring networks

PC Ethernetnetwork

146.176.151

146.176.150

146.176.146

146.176.145 146.176.147

eepc02eepc01

WorkstationEthernet network


MAC1,IP1

[IP address][Subnet mask][Gateway is the port of the router]

[IP address][Subnet mask]

[IP address][Subnet mask]


IPCONFIG /ALL

Ethernet adapter Local Area Connection 3:

Connection-specific DNS Suffix . : myuni.ac.ukDescription . . . . . . . . . . . : Realtek RTL8139/810x Family Physical Address. . . . . . . . . : 00-0A-E4-01-2C-F1Dhcp Enabled. . . . . . . . . . . : YesAutoconfiguration Enabled . . . . : YesIP Address. . . . . . . . . . . . : 192.168.0.13Subnet Mask . . . . . . . . . . . : 255.255.255.0Default Gateway . . . . . . . . . : 192.168.0.254DHCP Server . . . . . . . . . . . : 146.176.2.205DNS Servers . . . . . . . . . . . : 146.176.1.5

212.4.208.100Primary WINS Server . . . . . . . : 146.176.2.205Secondary WINS Server . . . . . . : 146.176.2.204Lease Obtained. . . . . . . . . . : 05 November 2003 09:19:35Lease Expires . . . . . . . . . . : 08 November 2003 09:19:35


DHCPserver

Here’s my MAC address.What’s my IP address?

Here it is…

DNSserver

What’s the IP address forthis site?

Here it is…

WINSserver

Here’s my Windows name.Can I have an IP address?

Here it is…


Network address translation

NATRouterNAT

Router

IP Src: 192.168.10.12

IP Dest: 11.22.33.44

IP Src: 192.168.10.12

IP Dest: 11.22.33.44

Outgoing dataOutgoing data

IP Src: 168.10.34.21

IP Dest: 11.22.33.44

IP Src: 168.10.34.21

IP Dest: 11.22.33.44

Outgoing dataOutgoing data

IP Src: 11.22.33.44

IP Dest: 168.10.34.21

IP Src: 11.22.33.44

IP Dest: 168.10.34.21

Incoming dataIncoming data

IP Src: 11.22.33.44

IP Dest: 192.168.10.12

IP Src: 11.22.33.44

IP Dest: 192.168.10.12

Incoming dataIncoming data

PAT (Port address translation) – Maps many addresses to one global address.


NAT – The advantages

• Increases range of address.• Hides the network address of the network.• Allow easy creation of subnetworks.

Network can use their own network addresses, such as10.10.0.1, 10.10.0.2,and so on.

Network can use their own network addresses, such as10.10.0.1, 10.10.0.2,and so on. NATNAT

Globaladdresses(which areunique on theInternet)


Borrowing addresses for some links

RouterA

RouterA S0 S0

E0

E1

E0

E1

IP addressunnumbered borrowsaddresses from anotherport

RouterB

RouterB

no slide titlebill/cnds2003_2004/cnds_unit06... · 2003-11-05 · data packet addresses converting...

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