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Internet Protocol (IP) : 

Internet Protocol (IP) Part of TCP/IP Used by the Internet Specifies interface with higher layer e.g. TCP Specifies protocol format and mechanisms

IP Protocol : 

IP Protocol

IP Services : 

IP Services Primitives Functions to be performed Form of primitive implementation dependent e.g. subroutine call Send Request transmission of data unit Deliver Notify user of arrival of data unit Parameters Used to pass data and control info

Parameters (1) : 

Parameters (1) Source address Destination address Protocol Recipient e.g. TCP Type of Service Specify treatment of data unit during transmission through networks Identification Source, destination address and user protocol Uniquely identifies PDU Needed for re-assembly and error reporting Send only

Parameters (2) : 

Parameters (2) Don’t fragment indicator Can IP fragment data If not, may not be possible to deliver Send only Time to live Send only Data length Option data User data

Type of Service : 

Type of Service Precedence 8 levels Reliability Normal or high Delay Normal or low Throughput Normal or high

Options : 

Options Security Source routing Route recording Timestamping

Header Fields (1) : 

Header Fields (1) Version Currently 4 IP v6 - see later Internet header length In 32 bit words Including options Type of service Total length Of datagram, in octets

Header Fields (2) : 

Header Fields (2) Identification Sequence number Used with addresses and user protocol to identify datagram uniquely Flags More bit Don’t fragment Fragmentation offset Time to live Protocol Next higher layer to receive data field at destn

Header Fields (3) : 

Header Fields (3) Header checksum Reverified and recomputed at each router 16 bit ones complement sum of all 16 bit words in header Set to zero during calculation Source address Destination address Options Padding To fill to multiple of 32 bits long

Data Field : 

Data Field Carries user data from next layer up Integer multiple of 8 bits long (octet) Max length of datagram (header plus data) 65,535 octets

IP Addresses : 

IP Addresses The IP addresses are unique and universal. An IP address is a 32-bit address.

Slide 13: 

Example Change the following IP addresses from binary notation to dotted-decimal notation. a. 10000001 00001011 00001011 11101111 b. 11111001 10011011 11111011 00001111 Solution We replace each group of 8 bits with its equivalent decimal number (see Appendix B) and add dots for separation: a. b.

Slide 14: 

Example Change the following IP addresses from dotted-decimal notation to binary notation. a. b. Solution We replace each decimal number with its binary equivalent (see Appendix B): a. 01101111 00111000 00101101 01001110 b. 01001011 00101101 00100010 01001110

Slide 15: 

In classful addressing, the address space is divided into five classes: A, B, C, D, and E.

Slide 16: 

Finding the class in binary notation

Slide 17: 

Finding the address class

Slide 18: 

Example Find the class of each address: a. 00000001 00001011 00001011 11101111 b. 11110011 10011011 11111011 00001111 Solution See the procedure in Figure 19.11. a. The first bit is 0; this is a class A address. b. The first 4 bits are 1s; this is a class E address.

Slide 19: 

Finding the class in decimal notation

Slide 20: 

Netid and hostid

IP Addresses - Class A : 

IP Addresses - Class A 32 bit global internet address Network part and host part Class A Start with binary 0 All 0 reserved 01111111 (127) reserved for loopback Range 1.x.x.x to 126.x.x.x All allocated

IP Addresses - Class B : 

IP Addresses - Class B Start 10 Range 128.x.x.x to 191.x.x.x Second Octet also included in network address 214 = 16,384 class B addresses All allocated

IP Addresses - Class C : 

IP Addresses - Class C Start 110 Range 192.x.x.x to 223.x.x.x Second and third octet also part of network address 221 = 2,097,152 addresses Nearly all allocated See IPv6

Slide 24: 

Example Find the class of each address: a. b. c. Solution a. The first byte is 227 (between 224 and 239); the class is D. b. The first byte is 252 (between 240 and 255); the class is E. c. The first byte is 134 (between 128 and 191); the class is B.

Slide 25: 

Blocks in class A Millions of class A addresses are wasted.

Slide 26: 

Blocks in class B Many class B addresses are wasted.

Slide 27: 

The number of addresses in class C is smaller than the needs of most organizations. Blocks in class C

Slide 28: 

Network address In classful addressing, the network address is the one that is assigned to the organization.

Slide 29: 

Given the address, find the network address. The class is A. Only the first byte defines the netid. We can find the network address by replacing the hostid bytes (56.7.91) with 0s. Therefore, the network address is A network address is different from a netid. A network address has both netid and hostid,with 0s for the hostid.

Slide 30: 

Example Given the address, find the network address. Solution The class is B. The first 2 bytes defines the netid. We can find the network address by replacing the hostid bytes (17.85) with 0s. Therefore, the network address is Given the network address, find the class. Example The class is A because the netid is only 1 byte.

Slide 31: 

A network with two levels of hierarchy IP addresses are designed with two levels of hierarchy.

Slide 32: 

A network with three levels of hierarchy (subnetted)

Subnets and Subnet Masks : 

Subnets and Subnet Masks Allow arbitrary complexity of internetworked LANs within organization Insulate overall internet from growth of network numbers and routing complexity Site looks to rest of internet like single network Each LAN assigned subnet number Host portion of address partitioned into subnet number and host number Local routers route within subnetted network Subnet mask indicates which bits are subnet number and which are host number

Slide 34: 

Addresses in a network with and without subnetting

Slide 35: 

Default masks The network address can be foundby applying the default mask to anyaddress in the block (including itself).It retains the netid of the block and sets the hostid to 0s.

Slide 36: 

Example A router outside the organization receives a packet with destination address Show how it finds the network address to route the packet. Solution The router follows three steps: The router looks at the first byte of the address to find the class. It is class B. The default mask for class B is The router ANDs this mask with the address to get The router looks in its routing table to find out how to route the packet to this destination.

Slide 37: 

Subnet mask

Slide 38: 

Example A router inside the organization receives the same packet with destination address Show how it finds the subnetwork address to route the packet. Solution The router follows three steps: The router must know the mask. We assume it is /19, as shown in Figure 19.23. The router applies the mask to the address, The subnet address is The router looks in its routing table to find how to route the packet to this destination

Classless Addressing : 

Classless Addressing Classful address created problems ISP came into prominence  an organization providing Internet access to individuals, small business that do not want to create a site and use the services of the Internet. In 1996 a new architecture called classless addressing was announced.

Slide 40: 

Variable-Block Length Idea is to have variable length blocks not belonging to any class Block could be of 2,4,128 addresses or so on The whole address space (232) is divided into different block sizes. One condition  no. of addresses should be power of 2 Beginning address must be evenly divisible by the number of addresses. If block of 4 address then start address evenly divisible by 4

Slide 41: 

Mask An organization is given the first address and the mask Both together define the whole block Finding the Network Address AND the mask and the address to find the first address Subnetting Can create subnets to meet its needs

CIDR-Classless Interdomain Routing : 

CIDR-Classless Interdomain Routing Dynamic Address Configuration Information required IP address Subnet mask IP address of a router IP address of a name server Stored in config file ( what if diskless, boot for first time or moved to different subnet) Use DHCP (Dynamic Host Configuration Protocol)


DHCP Client-Server Program Two databases First  binds physical address to IP address Second  makes DHCP dynamic A request for a temp IP address makes the server go to the pool of available IP address and assigns the IP address for a temp period

CIDR – Classless InterDomain Routing : 

CIDR – Classless InterDomain Routing A set of IP address assignments.

Slide 45: 

DHCP transition diagram

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Slide 47: 

Address translation

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Slide 49: 

Five-column translation table

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