Internet Architecture

2 INTRODUCTION INTERNET developed by a community of researchers centered around the Defense Advanced Research Projects Agency (DARPA) in the mid-1970s. TCP/IP provided the many computers and devices connected to the ARPANET with a way to identify and locate each other. Based on TCP/IP - set of protocols developed to allow cooperating computers to share resources across a network equally well suited for (LAN) as well as (WAN)

A network using the TCP/IP protocol assigns a unique identifying number known as an Internet Protocol (IP) Internet suite includes not only lower-layer specifications (like TCP and IP), but also specifications for such common applications as mail, terminal emulation, and file transfer

4 INTRODUCTION TCP/IP is a layered set of protocols: an application protocol such as mail; a protocol such as TCP that provides services need by many applications; IP, which provides the basic service of getting datagrams to their destination; The IP address identifies the node and the network to which the computer is attached, so different computers can find each other and communicate.

the protocols needed to manage a specific physical medium, such as Ethernet or a point to point line. Internet Protocol was invented for the US Department of Defence Advanced Research Projects Agency (ARPA).

The goal was to create a network that would continue to function if a bomb destroyed one or more of the network’s nodes; information would get rerouted automatically so it could still reach its address. As a result of this bomb-proof design, any user on the Internet can communicate with any other user, regardless of their location

7 INTERNET ARCHITECTURE

8 INTERACTIONS BETWEEN THE LAYERS

9 Although computers process data using the binary numbering system composed of ones and zeros, IP addresses use a decimal format referred to as dotted decimal notation. Each IP address in dotted decimal notation consists of four numbers separated by a period (or dot), such as Each of the four numbers composing the address is called an octet because in binary form each number occupies eight positions. Example: – IP ADDRESSING

10 address is 32 bits in length under Internet Protocol Version 4 (IPv4). An octet can contain any value from 0 to 255 and the total number of unique values possible is 4,294,967,296 divided into either two or three parts first part designates the network address second part (if present) designates the subnet address final part designates the host address different network address classes: A, B, C, D, E: IP ADDRESSING

11 NETWORK ADDRESS CLASSES Class First bits Number of bits for Maximum Number of: Networks addressing Hosts addressing Networks Hosts of the network A = = 16,777,216 B = 16, = 65,536 C = 2,097, = 256 D = 268,435,456 E1111 Reserved for future use

Class A: large networks (begins with decimal or 0 binary) Class B: medium-sized networks (begins with decimal or 10 binary) Class C: small networks (begins with decimal or 110 binary) Class D: multicast addresses (begins with decimal or 1110 binary) Class E: experimental (begins with or 1111 binary)

The first octet in any IP address identifies its class. For example, the IP address belongs to Class C because it begins 192 Octets also determine the parts of an address that identify the network and node attached to the network. Class A IP addressing (beginning 0-127), the first octet identifies the network, while the remaining three octets identify the node.

In a Class B IP address, the first two octets identify the network and the remaining two identify the node, and in Class C IP address, the first three octets identify the network and the remaining octet identifies the node.

15 THE FUTURE OF IP IPv6 Motivation for change address space; type of services. After many proposals for IP developing, a new version of IP protocol is created - IP version 6 - IPv6.

16 IPv6 New features New address size IPv6 addresses are 128 bits using hexadecimal (16-digit) numbers. The address includes network prefix and host suffix. New header format A support of old-version headers and a new feature is introduced: header extension. Support for video and audio A flow labels and quality of services are introduced as a protocol fields.

DIFFERENCES IN IPs IPv6 addresses differ from IPv4 addresses by using colons instead of dots, and hexadecimals digits instead of decimal digits

There is IP address availability problem because of the expansion of the internet therefore the introduction of subnetting which is one of the few methods. Subnetting is the using of private IPs for intranets. Subnetting reduces the need for IP addresses because only a small percentage of IP addresses used on intranets communicate with the internet.

19 Functions: breaking up the message into segments (packets) reassembling them at the other end re-sending anything that gets lost TRANSMISSION CONTROL PROTOCOL (TCP)

20 putting things back in the right order provides full-duplex, acknowledged, and flow- controlled service to upper-layer protocols can also support numerous simultaneous upper-layer conversations TRANSMISSION CONTROL PROTOCOL (TCP)

21 Two main mechanisms to send / receive data: Stop – and – Wait Sliding Window TRANSMISSION CONTROL PROTOCOL MECHANISM

22 TCP uses positive acknowledgment with retransmission to achieve reliable data delivery Recipient sends acknowledgment control messages (ACK) to sender to verify successful receipt of data In the case of errors – the recipient sends negative acknowledge (NACK) Sender re-sends the data Finally, the recipient received the data correctly Positive acknowledge (ACK) and Negative acknowledge (NACK) are without indication of packet number No need of indication of packet number. STOP – and – WAIT

23 STOP – and – WAIT SenderRecipientSend Pack 1 ACK Pack 1 ??? ACK Pack 2 Packets processing Send Pack 2 NACK Send Pack 2

24 SLIDING WINDOW TCP uses sliding window for flow control Receiver specifies the size of the window Sender sends the data from the actual position of the window, without waiting ACK for each packet Recipient sends ACK or NACK after receiving the packet Sender analyses the missing ACK and retransmits only this packet Recipient can start to process the data, only after re-ordering the receive packets Each packet must have its number ACK or NACK must have the number of the packet

25 SLIDING WINDOW Window Size = SenderRecipientSend Pack 1 ACK 1 Send Pack 2 Send Pack 3 Pack 1 ??? Pack 3 NACK ? ACK 2 Send Pack 2 Pack 2 Packets re-ordering Packets processing ACK 2 - missing ACK 3