Lecture_Network_Layer-IP Addressing.pptx
- 2. Network Layer Tasks Logical Addressing: The network layer adds a header that includes the logical addresses of the sender and receiver to the packet coming from the upper layer. Routing: When independent networks or links are connected together to create an internetwork, routers or switches route packets to their final destination. The network layer is responsible for the delivery of individual packets from the source host to the destination host
- 3. Number System • Unary • Binary • Octal • Decimal • Hexadecimal • Ex. Convert into decimal, hexadecimal and binary
- 4. Binary Number System • If n bit space is divided into k parts, then the • Total possible numbers in k parts = 2^k • Size of each part = 2^n/2^k = 2^(n-k) 1 bit 2 bits 3 bits 0 00 000 1 01 001 10 010 11 011 100 101 110 111 k n-k n bits
- 5. IP Addressing Schemes : Static Partitioning (ARPANET) 8 bits 24 bits NID HID 32 bits IPv4 address Total number of network addresses = 2^8 = 256 Total number of hosts with one network = 2^24 = 16 M (approx.)
- 6. IPv4 ADDRESSES • An IPv4 address is a 32-bit address that uniquely and universally defines the connection of a device (for example, a computer or a router) to the Internet. • The address space of IPv4 is 232 or 4,294,967,296. Dotted-decimal notation and binary notation for an IPv4 address
- 9. Q1. Change the following IPv4 addresses from binary notation to dotted-decimal notation. Solution We replace each group of 8 bits with its equivalent decimal number and add dots for separation.
- 14. Classes in binary and dotted-decimal notation • IPv4 addressing, at its inception, used the concept of classes. This architecture is called classful addressing. • In classful addressing, the address space is divided into five classes: A, B, C, D, and E. Classful addressing • In classful addressing, an IP address in class A, B, or C is divided into netid and hostid. • A mask (also called the default mask), a 32-bit number made of contiguous 1s followed by contiguous 0s.
- 16. Number of blocks and block size in classful IPv4 addressing
- 17. Default masks for classful addressing
- 19. A subnet mask is a 32-bit number used to divide an IP address into network and host portions. It helps determine which part of an IP address belongs to the network and which part belongs to the hosts (devices like PCs, routers, etc.).
- 22. Classless Addressing • In classful addressing, a large part of the available addresses were wasted. It is replaced with classless addressing. • To overcome address depletion and give more organizations access to the Internet, classless addressing was designed and implemented. • In IPv4 addressing, a block of addresses can be defined as x.y.z.t /n (Classless Inter- Domain Routing(CIDR) notation) Where x.y.z.t defines one of the addresses and the /n defines the mask.
- 23. • To simplify the handling of addresses, the Internet authorities impose, three restrictions on classless address blocks: 1. The addresses in a block must be contiguous, one after another. 2. The number of addresses in a block must be a power of 2 (I, 2, 4, 8, ... ). 3. The first address must be evenly divisible by the number of addresses. • The first address in the block can be found by setting the rightmost 32 − n bits to 0s Classless Addressing
- 24. Q2 Solution: The binary representation of the given address is 11001101 00010000 00100101 00100111 If we set 32−28 rightmost bits to 0, we get 11001101 00010000 00100101 0010000 or 205.16.37.32. The binary representation of the given address is 11001101 00010000 00100101 00100111 If we set 32 − 28 rightmost bits to 1, we get 11001101 00010000 00100101 00101111 or 205.16.37.47 A block of addresses is granted to a small organization. We know that one of the addresses is 205.16.37.39/28. What is the first and last address in the block?
- 25. A network configuration for the block 205.16.37.32/28 • The first address in a block is normally not assigned to any device; it is used as the network address that represents the organization to the rest of the world. First address is: 205.16.37.32 (Network Address) Subnet Mask:255.255.255.240 Last address is: 205.16.37.47(Broadcast Address) Total Subnet Addresses: 2^4=16 But usable is 14. usable ip: 205.16.37.33-205.16.37.46(total is 14) • A block of 16 addresses granted to a small organization •Total Addresses in Subnet: 2^(32-28) = 16 •Subnet Block Size: 256 - 240 = 16
- 28. First and Last Address: AND/OR Operations The first address can be found by ANDing the given addresses with the mask The last address can be found by ORing the given addresses with the complement of the mask.
- 30. Two-Level Hierarchy: No Subnetting • Each address in the block can be considered as a two- level hierarchical structure the leftmost n bits (prefix) define the network; the rightmost 32 − n bits define the host.
- 31. What is Subnetting? Subnetting is the process of dividing a network into multiple logical sub- networks. 1 1 2 1 2 1 2 4 3
- 34. Three-level hierarchy in an IPv4 address • If an organization was granted a large block in class A or B, it could divide the addresses into several contiguous groups and assign each group to smaller networks (called subnets) Subnetting and Supernetting • In supernetting, an organization can combine several class C blocks to create a larger range of addresses. • Supernetting decreases the number of 1s in the mask.
- 35. Subnetting Types • Fixed Length Subnet Mask (FLSM)- This strategy allows all subnet masks to be the same size. • Variable Length Subnet Mask (VLSM)- This strategy allows all subnet masks to be variable sizes.
- 36. Que. There is a requirement in a university to setup five Computer Labs (Lab1- 7 PCs; Lab2- 14 PCs; Lab3- 28 PCs; Lab4- 14 PCs; Lab5- 11 PCs ) in different departments for a Class C IPV4 address - 200.15.5.0/24, using Fixed Length Subnet Mask (FLSM). IP Address Decimal- 200.15.5.0 Binary- 11001000.00001111.00000101.00000000 Subnet Mask- 255.255.255.0 For setting up five departments, We need five subnetworks to be setup Therefore, 3 bits need to be borrowed from host bits Using 3bits, 2^3 =8 subnets can be created 11001000.00001111.00000101.00000000 New Subnet Mask- 11111111. 11111111. 11111111.11100000 or 255.255.255.224 No. of Host in each subnet= 2^5= 32 Usable IP address in each subnet= 32-2=30
- 37. IP Address Decimal- 200.15.5.0 Binary- 11001000.00001111.00000101.00000000 Subnet 1- 11001000.00001111.00000101.00000000 Subnet 2- 11001000.00001111.00000101.00100000 Subnet 3- 11001000.00001111.00000101.01000000 Subnet 4- 11001000.00001111.00000101.01100000 Subnet 5- 11001000.00001111.00000101.10000000 Subnet 8- 11001000.00001111.00000101.11100000
- 38. How Do You Get IPs? • IP address ranges controlled by IANA Internet Assigned Number Authority Roots go back to 1972, ARPANET, UCLA Today, part of ICANN IANA grants IPs to regional authorities ARIN (American Registry of Internet Numbers) may grant you a range of IPs You may then advertise routes to your new IP range There are now secondary markets, auctions, …
- 39. Classless Addressing: The Two Level Hierarchy
- 40. Classless Addressing: Class Sizes and Issues
- 42. Classless Addressing Examples 1. In a classless addressing scheme, a network has a /20 CIDR block assigned to it. What is the maximum number of useful addresses that can be assigned to a host? a. 4096 b. 4094 c. 4098 d. 2048
- 43. Solution: For a /20 CIDR block, the network portion occupies 20bits, leaving 12bits for the host portion (32−20=12). Therefore, the total number of addresses in this subnet is: 2^12=4096 (total addresses). In a typical IPv4 subnet, you lose two addresses for the network and broadcast addresses. Hence, the number of useful (assignable) host addresses is: 4096−2=4094. Thus, the correct answer is 4094.
- 44. Classless Addressing Example Consider a class B network address 130.50.0.0. The last 7 bits of the host id are allotted for host number and the remaining 9 bits are reserved for subnet number. How many usable subnets and usable number of hosts in each subnet are possible with the above addressing scheme? a. 128, 512 b. 512, 128 c. 126, 510 d. None of these
- 45. • Since a Class B network by default has 16 host bits, subdividing them into 9 bits for subnetting and 7 bits for host numbering yields: 1.Subnets: 2^9=512 possible subnets (modern practice allows using them all). 2.Hosts per Subnet: 2^7=128 total addresses per subnet → 126 usable host addresses (subtracting network and broadcast). • Hence, there are 512 usable subnets, each providing 126 host addresses
- 46. Configuration and addresses in a subnetted network suppose an organization is given the block 17.12.14.0/26, which contains 64 addresses. The organization has three offices and needs to divide the addresses into three subblocks of 32, 16, and 16 addresses. • Suppose the mask for the first subnet is n1, then 2^32- n1 must be 32, which means that n1 =27. • Suppose the mask for the second subnet is n2, then 2^32- n2 must be 16, which means that n2 = 28. • Suppose the mask for the third subnet is n3, then 2^32- n3 must be 16, which means that n3 =28.