PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 221Internet Addresses (You should read Chapter 4 in Forouzan)IP Address is 32 Bits LongConceptually the address is the pair (NETID, HOSTID)Addresses are assigned by the internet company for assignment of names and numbersICANNICANN:Protocol Support Organization (PSO)Domain Name Supporting Organization (DNSO)Address Supporting Organization (ASO)Regional Internet RegistriesAmerican Registry for Internet Numbers (ARIN)http://www.arin.net/registration/fee_schedule.htmlwww.arin.netwww.icann.orgReference “ IP Fundamentals ” Chapter 1 and 2 by Maufer2Formats for IP addresses: (classful addressing)Class A0101101110Network (7 bits) Host (24 bits)Network (14 bits)Network (21 bits)Host (16 bits)Host (8 bits)Multicast address (28 bits)( There is a class E reserved for future use)Historically a class A address was assigned to networks with > 216 (65, 536) hostsClass B to networks with 28 (256) to 216 hostsClass C to networks with < 28 hostsClass BClass CClass D3Internet Addresses Cont.For Humans easier to deal with decimal so dotted decimal notation is used.Group 8 bits.8 bits.8 bits.8 bits and use decimal numbersExample 10000000 00001010 00000010 00011110 => 128.10.2.30Class Lowest Address Highest Address A 1.0.0.0 126.0.0.0 B 128.1.0.0 191.254.00 C 192. 0.1.0 223.255.254.0 D 224.0.0.0 239.255.255.255Some addresses are reservedExample 127.0.0.0 is reserved for loop back4IP version 4 uses 32 bit address 2 4.3 billion addresses32and six billion live on earth at presentClassless inter-domain routing (CIDR) discussed later slowed down addressexhaustion.Scaling Issues: 1. Eventual exhaustion of the IPV4 address space. 2. Ability to route traffic between ever increasing number of networks that comprise the internet.5IP addresses cont.Class A all 0’s network number is used to represent the “ default” route ( 0.0.0.0)this is a routing table entry which means any destination not matching any other table entry should be sent to the default route. (more later)Class A all 1’s network number is loopback. 127.0.0.1 usually means “ This samemachine” all 127.anything.anything.anything is loopback.There are a total of 27 -2 = 126 class A networks.There are 214 - 2 = 16, 382 class B networks (again all 0’s & all 1’s network addresses reserved)There are 221-2 = 2,097,150 class C networks.There are 228 = 268, 435, 456 class D multicast addresses.6Notation:Class A has 8 bit network prefix this is called a slash 8’s /8 can write 127.0.0.0 as 127/8 or 127.0.0.0/8/ 8 prefixes ( class A)Classfull addressing allows using only the first 1,2,3 or 4 bits to determine the class. (I.E. if MSB = 0 => class A/ 8 address block has 231 out of 232 total IP addresses => / 8 takes up 50% total IPV4 addresses / 16 prefixes ( class B) 230total addresses => 25% total IPV4 addresses / 24 prefixes ( class C ) 229out of 232 => 12.5% total IPV4 addresses Class D with 1110 most significant bits used for multicastClass E with 1111 most significant bits and are reserved for experimental use7In the Beginning- IP addresses assigned based on request, not need- 32 bit address was thought to be plenty- classful addresses easy to understand and implement but not efficient / 24 supports 254 hosts too small / 16 supports 65,534 too large8IP RoutingFor a host IP routing is simple:If destination is directly connected to host then IP datagram is sent directly to the destination.otherwise host sends datagram to a default routerThe IP layer can be configured to act as a router in addition to acting as a hostA host never forwards datagrams from one of its interfaces to another, while a router forwards datagramsIP Layer has a routing table in memory that it searches each time it receives a a datagram to sendEach entry in routing table contains: - Destination IP address - IP address of a next hop router or IP address of a directly connected network - Flags (specify if network or host address) - Specification of which network interface the datagram should go to for transmission9IP Routing Performs The Following Actions:1. Search routing table for entry that matches complete destination IP address2. Search table for match of destination network IP. This check must take into account a possible “ Subnet Mask ” ( Defined Later ).3. Search for default entry.4. If none of the above discard and send host unreachable or network unreachable error back.Note: Hop by hop nature of this process.10Classical Subnetting Reference “ IP Fundamentals ” Chapter 3 Extended-Network-PrefixNetwork - Prefix Host - NumberNetwork - Prefix Subnet - Number Host - NumberBefore :After :Subnetting attacks the expanded routing table problem by making the subnetstructure of a network invisible outside the organization’s private network.External Internet Does Not Need To Know Internal Subnet Structure11Example : 172. 27. 0.0. / 16Subnet 1R AR CSubnet 2R BR DInternetSubnet 5Subnet 4Subnet 3R BR AInternet seesI need 5 subnets so I use 3 bits in the subnet - number field12This means I haveSubnet Number Binary representationof least-significant two bytesAvailable host addresseswithin each subnet0 172.27.0.0 00000000.00000000 0.1- 31. 2541 172.27.32.0 00100000.00000000 32.1- 63.2542 172.27.64.0 01000000.00000000 64.1- 95.2543 172.27.96.0 01100000.00000000 96.1-127.2544 172.27.128.0 10000000.00000000 128.1-159.2545 172.27.160.0 10100000.00000000 160.1-191.2546 172.27.192.0 11000000.00000000 192.1-223.2547 172.27.224.0 11100000.00000000 224.1-255.254Need a method to know how many bits are used for subnet-number=> subnet mask In this example the subnet mask is 255.255.224.0 11111111.11111111.11100000.0000000013Subnet MaskAt boot time a machine gets its own IP address ( stored on disk for example )Host also needs to be told how many bits are to be used for subnet ID and how manyfor host ID. This is the subnet mask.Subnet mask is 32 bit value containing “one bits” for the network ID and subnet ID,“zero